Springer Handbook of Mechanical Engineering

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Springer

Handbook of Mechanical Engineering Grote, Antonsson (Eds.) With DVD-ROM, 1822 Figures and 402 Tables

13

Editors: Professor Dr.-Ing. Karl-Heinrich Grote Department of Mechanical Engineering Otto-von-Guericke University Magdeburg Universitätsplatz 2 39106 Magdeburg, Germany [email protected] Professor Erik K. Antonsson Department of Mechanical Engineering California Institute of Technology (CALTEC) 1200 East California Boulevard Pasadena, CA 91125, USA [email protected]

Library of Congress Control Number:

ISBN: 978-3-540-49131-6

2008934575

e-ISBN: 978-3-540-30738-9

All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science+Business Media, LLC New York, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. The use of designations, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Product liability: The publisher cannot guarantee the accuracy of any information about dosage and application contained in this book. In every individual case the user must check such information by consulting the relevant literature. Production and typesetting: le-tex publishing services oHG, Leipzig Senior Manager Springer Handbook: Dr. W. Skolaut, Heidelberg Illustrations: schreiberVIS, Seeheim and Hippmann GbR, Schwarzenbruck Cover design: eStudio Calamar Steinen, Barcelona Cover production: WMXDesign GmbH, Heidelberg Printing and binding: Stürtz GmbH, Würzburg Printed on acid free paper SPIN 10934364

60/3180/YL

543210

V

Preface

Mechanical engineering is a broad and complex field within the world of engineering and has close relations to many other fields. It is an important economic factor for all industrialized countries and the global market allows for wide international competition for products and processes in this field. To stay up to date with scientific findings and to apply existing knowledge in mechanical engineering it is important to renew and continuously update existing information. The editors of this Springer Handbook on Mechanical Engineering have worked successfully with 92 authors worldwide to include chapters about all relevant mechanical engineering topics. However, this Handbook cannot claim to cover every aspect or detail of the mechanical engineering areas or fields included, and where mechanical engineers are currently present and contributing their expertise and knowledge towards the challenges of a better world. However, this Handbook will be a valuable guide for all who design, develop, manufacture, operate, and use mechanical artefacts. We also hope to spark interest in the field of mechanical engineering from others. In this Handbook, high-school students can get a first glance at the options in this field and possible career moves. We, the editors, would like to express our gratitude and thanks to all of the authors of this Handbook, who

have devoted a considerable amount of time towards this project. We would like to thank them for their patience and cooperation, and we hope for a long-lasting partnership in this ambitious project. We would also most sincerely like to thank our managers and friends at Springer and le-tex. The executives at Springer–Verlag were always most cooperative and supportive of this Handbook. Without Dr. Skolaut’s continuous help and encouragement and Ms. Moebes’ and Mr. Wieczorek’s almost daily requests for corrections, improvements, and progress reports it would have taken another few years – if ever – to publish this Handbook. Stürtz has done a fantastic job in printing and binding. Finally we would like to thank all the people we work with in our departments and universities, who tolerated the time and effort spent on this book. Finally, we know that there is always room for improvement – with this Handbook as with most engineering products and approaches. We, as well as the authors welcome your fair hints, comments, and criticism. Through this Handbook and with the authors’ efforts, we would also like to draw your attention to what has been accomplished for the benefit of the engineering world and society. Berlin, Fall 2008 Pasadena, Fall 2008

Karl-Heinrich Grote Erik K. Antonsson

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About the Editors

Dr. Karl-Heinrich Grote is a Professor and Chair of the Department of Mechanical Engineering – Engineering Design at the Otto-von-Guericke University in Magdeburg, Germany. He earned his “Diploma in Mechanical Engineering” (Masters of Science in Mechanical Engineering) in 1979 and his “Dr.-Ing.” (Ph.D. in Engineering) in 1984, both from the Technical University in Berlin, Germany. After a post doctoral stay in the USA he joined an automotive supplier as manager of the engineering design department. In 1990 he followed a call to become full professor at the Mechanical Engineering Department at the California State University, Long Beach, USA. In 1992 he received the TRW Outstanding Faculty award and in 1993 the VDI "Ring of Honor" for his research on Engineering Design and Methodology. In 1995 he was named chair of the Engineering Design Department at the Otto-von-Guericke University in Magdeburg, where he is now Dean of the College of Mechanical Engineering. From October 2002 to September 2004 he was Visiting Professor of Mechanical Engineering at the California Institute of Technology (Caltech) USA. Since 1995 he is Editor of the DUBBEL (Taschenbuch für den Maschinenbau) and author of several books. Dr. Erik Antonsson is a Professor of Mechanical Engineering at the California Institute of Technology in Pasadena, where he organized the Engineering Design Research Laboratory and has conducted research and taught since 1984. He earned a Bachelor of Science in Mechanical Engineering from Cornell University in 1976, and a PhD in Mechanical Engineering from the Massachusetts Institute of Technology, Cambridge in 1982. In 1984 he joined the Mechanical Engineering Faculty at the California Institute of Technology, where he served as the Executive Officer (Chair) from 1998 to 2002. From September, 2002 through January, 2006, Dr. Antonsson was on leave from Caltech and served as the Chief Technologist at NASA’s Jet Propulsion Laboratory (JPL). He was an NSF Presidential Young Investigator (1986-1992), won the 1995 Richard P. Feynman Prize for Excellence in Teaching, and was a co-winner of the 2001 TRW Distinguished Patent Award. Dr. Antonsson is a Fellow of the ASME, and a member of the IEEE, AIAA, SME, ACM, and ASEE. He has published over 110 scholarly papers in the field of engineering design research, has edited two books, and holds eight U.S. patents.

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List of Authors

Gritt Ahrens Daimler AG X944 Systems Integration and Comfort Electric 71059 Sindelfingen, Germany e-mail: [email protected]

Seddik Bacha Université Joseph Fourier Grénoble Electrical Engineering Laboratory Saint Martin d’Hères 38402 Grenoble, France e-mail: [email protected]

Stanley Baksi TRW Automotive, Lucas Varity GmbH Carl Spaeter Str. 8 56070 Koblenz, Germany e-mail: [email protected]

Thomas Böllinghaus Federal Institute for Materials Research and Testing (BAM) Unter den Eichen 87 12205 Berlin, Germany e-mail: [email protected]

Gerry Byrne University College Dublin School of Electrical, Electronic and Mechanical Engineering Belfield, Dublin 4, Ireland e-mail: [email protected] Boris Ilich Cherpakov (deceased) Edward Chlebus Wrocław University of Technology Centre for Advanced Manufacturing Technologies Lukasiewicza 5 50-371 Wrocław, Poland e-mail: [email protected] Mirosław Chłosta IMBiGS – Institute for Mechanized Construction and Rock Mining (IMBiGS) ul. Racjonalizacji 6/8 02-673 Warsaw, Poland e-mail: [email protected] Norge I. Coello Machado Universidad Central “Marta Abreu” de Las Villas Faculty of Mechanical Engineering Santa Clara, 54830, Cuba e-mail: [email protected]

Alois Breiing Eidgenössische Technische Hochschule Zürich (ETH) Institut für mechanische Systeme (IMES) Zentrum für Produkt-Entwicklung (ZPE) ETH Zentrum, CLA E 17.1, Tannenstrasse 3 8092 Zurich, Switzerland e-mail: [email protected]

Francesco Costanzo Alenia Aeronautica Procurement/Sourcing Management Department Viale dell’Aeronautica Pomigliano (NA), Italy e-mail: [email protected]

Eugeniusz Budny Institute of Mechanized Construction and Rock Mining Racjonalizacji 6/8 02-673 Warsaw, Poland e-mail: [email protected]

Carl E. Cross Federal Institute for Materials Research and Testing (BAM) Joining Technology Unter den Eichen 87 12200 Berlin, Germany e-mail: [email protected]

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List of Authors

Frank Dammel Technical University Department of Mechanical Engineering/Institute of Technical Thermodynamics Petersenstr. 30 64287 Darmstadt, Germany e-mail: [email protected] Jaime De La Ree Virginia Tech Electrical and Computer Engineering Department 340 Whittemore Hall Blacksburg, VA 24061, USA e-mail: [email protected] Torsten Dellmann RWTH Aachen University Department of Rail Vehicles and Materials-Handling Technology Seffenter Weg 8 52074 Aachen, Germany e-mail: [email protected] Berend Denkena Leibniz University Hannover IFW – Institute of Production Engineering and Machine Tools An der Universität 2 30823 Garbsen, Germany e-mail: [email protected] Ludger Deters Otto-von-Guericke University Institute of Machine Design Universitätsplatz 2 39016 Magdeburg, Germany e-mail: [email protected] Ulrich Dilthey RWTH Aachen University ISF Welding and Joining Institute Pontstr. 49 52062 Aachen, Germany e-mail: [email protected]

Frank Engelmann University of Applied Sciences Jena Department of Industrial Engineering Carl-Zeiss-Promenade 2 07745 Jena, Germany e-mail: [email protected]

Ramin S. Esfandiari California State University Department of Mechanical & Aerospace Engineering Long Beach, CA 90840, USA e-mail: [email protected]

Jens Freudenberger Leibniz-Institute for Solid State and Materials Research Dresden Department for Metal Physics P.O. Box 270116 01171 Dresden, Germany e-mail: [email protected]

Stefan Gies RWTH Aachen University Institute for Automotive Engineering Steinbachstr. 7 52074 Aachen, Germany e-mail: [email protected]

Joachim Göllner Otto-von-Guericke University Institute of Materials and Joining Technology Department of Mechanical Engineering Universitätsplatz 2 39016 Magdeburg, Germany e-mail: [email protected]

Timothy Gutowski Massachusetts Institute of Technology Department of Mechanical Engineering Cambridge, MA 02139, USA e-mail: [email protected]

List of Authors

Takeshi Hatsuzawa Tokyo Institute of Technology Precision and Intelligence Laboratory 4259-R2-6, Nagatsuta-cho 226-8503 Yokohama, Japan e-mail: [email protected] Markus Hecht Berlin University of Technology Institute of Land and Sea Transport Systems Department of Rail Vehicles Salzufer 17–19 10587 Berlin, Germany e-mail: [email protected] Hamid Hefazi California State University Mechanical and Aerospace Engineering Department of Mechanical and Aerospace Engineering 1250 Bellflower Boulevard Long Beach, CA 90840, USA e-mail: [email protected] Martin Heilmaier Technical University Department of Physical Metallurgy Petersenstr. 23 64287 Darmstadt, Germany e-mail: [email protected] Rolf Henke RWTH Aachen University Institute of Aeronautics and Astronautics Wuellnerstr. 7 52062 Aachen, Germany e-mail: [email protected] Klaus Herfurth Industrial Advisor Am Wiesengrund 34 40764 Langenfeld, Germany e-mail: [email protected] Horst Herold (deceased)

Chris Oliver Heyde Otto-von-Guericke University Electric Power Networks and Renewable Energy Sources Universitätsplatz 2 39106 Magdeburg, Germany e-mail: [email protected]

Andrew Kaldos AKM Engineering Consultants 31 Tudorville Road Bebington, Wirral CH632 HT, UK e-mail: [email protected]

Yuichi Kanda Toyo University Department of Mechanical Engineering Advanced Manufacturing Engineering Laboratory 2100 Kujirai 350-8585 Kawagoe-City, Japan e-mail: [email protected]

Thomas Kannengiesser Federal Institute for Materials Research and Testing (BAM) Joining Technology Unter den Eichen 87 12200 Berlin, Germany e-mail: [email protected]

Michail Karpenko New Zealand Welding Centre Heavy Engineering Research Association (HERA) 17–19 Gladding Place Manukau City, New Zealand e-mail: [email protected]

Bernhard Karpuschewski Otto-von-Guericke University Department of Manufacturing Engineering Universitätsplatz 2 39106 Magdeburg, Germany e-mail: [email protected]

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List of Authors

Toshiaki Kimura Japan Society for the Promotion of Machine Industry (JSPMI) Production Engineering Department Technical Research Institute 1-1-12, Hachiman-cho 203-0042 Tokyo, Japan e-mail: [email protected] Dwarkadas Kothari VIT University School of Electrical Sciences Vellore, TN 632 014, India e-mail: [email protected] Hermann Kühnle Otto-von-Guericke University Institute of Ergonomics Factory Operations and Automation Universitätsplatz 2 39106 Magdeburg, Germany e-mail: [email protected] Oleg P. Lelikov Bauman Moscow State Technical University 2-nd Baumanskaya, 5 Moscow, 105005, Russia Andreas Lindemann Otto-von-Guericke University Institute for Power Electronics Universitätsplatz 2 39106 Magdeburg, Germany e-mail: [email protected] Bruno Lisanti AST Via Dante Alighieri 57 Lonate Pozzolo (VA), Italy e-mail: [email protected] Manuel Marya Schlumberger Reservoir Completions Material Engineering 14910 Airline Road Rosharon, TX 77583, USA e-mail: [email protected]

Surendar K. Marya GeM-UMR CNRS 6183, Ecole Centrale Nantes Institut de Recherche en Génie Civil et Mécanique 1 Rue de la Noë 44321 Nantes, France e-mail: [email protected] Ajay Mathur Simon India Limited Plant Engineering Devika Tower, 6 Nehru Place New Delhi, India e-mail: [email protected] Klaus-Jürgen Matthes Chemnitz University of Technology Institute for Manufacturing/Welding Technology Reichenhainer Str. 70 09126 Chemnitz, Germany e-mail: [email protected] Henning Jürgen Meyer Technische Universität Berlin Berlin Institute of Technology Konstruktion von Maschinensystemen Straße des 17. Juni 144 10623 Berlin, Germany e-mail: [email protected] Klaus Middeldorf DVS – German Welding Society Düsseldorf, Germany e-mail: [email protected] Gerhard Mook Otto-von-Guericke University Department of Mechanical Engineering Institute of Materials and Joining Technology and Materials Testing Universitätsplatz 2 39016 Magdeburg, Germany e-mail: [email protected] Jay M. Ochterbeck Clemson University Department of Mechanical Engineering Clemson, SC 29634-0921, USA e-mail: [email protected]

List of Authors

Joao Fernando G. Oliveira University of São Paulo Department of Production Engineering Av. Trabalhador Sãocarlense, 400 São Carlos, SP 13566-590, Brazil e-mail: [email protected], [email protected]

Holger Saage University of Applied Sciences of Landshut Faculty of Mechanical Engineering Am Lurzenhof 1 84036 Landshut, Germany e-mail: [email protected]

Antje G. Orths Energinet.dk Electricity System Development Tonne Kjærsvej 65 7000 Fredericia, Denmark e-mail: [email protected]

Shuichi Sakamoto Niigata University Department of Mechanical and Production Engineering Ikarashi 2-8050 950 2181 Niigata, Japan e-mail: [email protected]

Vince Piacenti Robert Bosch LLC System Engineering, Diesel Fuel Systems 38000 Hills Tech Drive Farmington Hills, MI 48331, USA e-mail: [email protected] Jörg Pieschel Otto-von-Guericke University Institute of Materials and Joining Technology Universitätsplatz 2 39106 Magdeburg, Germany e-mail: [email protected]

Roger Schaufele California State University 1250 Bellflower Boulevard Long Beach, CA 90840, USA e-mail: [email protected] Markus Schleser RWTH Aachen University Welding and Joining Institute Pontstr. 49 52062 Aachen, Germany e-mail: [email protected]

Stefan Pischinger RWTH Aachen University Institute for Combustion Engines Schinkelstr. 8 52062 Aachen, Germany e-mail: [email protected]

Meinhard T. Schobeiri Texas A&M University Department of Mechanical Engineering College Station, TX 77843-3123, USA e-mail: [email protected]

Didier M. Priem École Centrale Nantes Department of Materials 1 Rue de la Noë, GEM UMR CNRS 6183 44321 Nantes, France e-mail: [email protected]

Miroslaw J. Skibniewski University of Maryland Department of Civil and Environmental Engineering 1188 Glenn L. Martin Hall College Park, MD 20742-3021, USA e-mail: [email protected]

Frank Riedel Fraunhofer-Institute for Machine Tools and Forming Technology (IWU) Department of Joining Technology Reichenhainer Str. 88 09126 Chemnitz, Germany e-mail: [email protected]

Jagjit Singh Srai University of Cambridge Centre for International Manufacturing Institute for Manufacturing Cambridge, CB2 1 RX, UK e-mail: [email protected]

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List of Authors

Vivek Srivastava Corporate Technology Strategy Services Aditya Birla Management Corporation MIDC Taloja, Panvel Navi Mumbai, India e-mail: [email protected]

Peter Stephan Technical University Darmstadt Institute of Technical Thermodynamics Department of Mechanical Engineering Petersenstr. 30 64287 Darmstadt, Germany e-mail: [email protected]

Zbigniew A. Styczynski Otto-von-Guericke University Electric Power Networks and Renewable Energy Sources Universitätsplatz 2 39106 Magdeburg, Germany e-mail: [email protected] or [email protected]

P.M.V. Subbarao Indian Institute of Technology Mechanical Engineering Department HAUS KHAS New Delhi, 110 016, India e-mail: [email protected]

Oliver Tegel Dr.-Ing. h.c. F. Porsche AG R&D, IS-Management Porschestr. 71287 Weissach, Germany e-mail: [email protected]

A. Erman Tekkaya ATILIM University Department of Manufacturing Engineering Incek Ankara, 06836, Turkey e-mail: [email protected]

Klaus-Dieter Thoben University of Bremen Bremen Institute for Production and Logistics GmbH Department of ICT Applications in Production Hochschulring 20 28359 Bremen, Germany e-mail: [email protected] Marcel Todtermuschke Fraunhofer-Institute for Machine Tools and Forming Technology Department of Assembling Techniques Reichenhainer Str. 88 09126 Chemnitz, Germany e-mail: [email protected] Helmut Tschoeke Otto-von-Guericke University Institute of Mobile Systems Universitätsplatz 2 39106 Magdeburg, Germany e-mail: [email protected] Jon H. Van Gerpen University of Idaho Department of Biological and Agricultural Engineering Moscow, ID, USA e-mail: [email protected] Anatole Vereschaka Moscow State University of Technology “STANKIN” Department of Mechanical Engineering Technology and Institute of Design and Technological Informatics Laboratory of Surface Nanosystems Russian Academy of Science Vadkovsky pereulok 1 Moscow, 101472, Russia e-mail: [email protected] Detlef von Hofe Hohen Dyk 106 47803 Krefeld, Germany e-mail: [email protected]

List of Authors

Nikolaus Wagner RWTH Aachen University ISF Welding and Joining Institute Pontstr. 49 52062 Aachen, Germany e-mail: [email protected] Jacek G. Wankowicz Institute of Power Engineering ul. Mory 8 01-330 Warsaw, Poland Ulrich Wendt Otto-von-Guericke University Department of Materials and Joining Technology Universitätsplatz 2 39106 Magdeburg, Germany e-mail: [email protected] Steffen Wengler Otto-von-Guericke University Faculty of Mechanical Engineering Institute of Manufacturing Technology and Quality Management Universitätsplatz 2 39106 Magdeburg, Germany e-mail: [email protected]

Lutz Wisweh Otto-von-Guericke University Faculty of Mechanical Engineering Institute of Manufacturing Technology and Quality Management Universitätsplatz 2 39106 Magdeburg, Germany e-mail: [email protected] Johannes Wodara Schweißtechnik-Consult Hegelstr. 38 39104 Magdeburg, Germany e-mail: [email protected] Klaus Woeste RWTH Aachen University ISF Welding and Joining Institute Pontstr. 49 52062 Aachen, Germany e-mail: [email protected] Hen-Geul Yeh California State University Department of Electrical Engineering 1250 Bellflower Boulevard Long Beach, CA 90840-8303, USA e-mail: [email protected]

Bernd Wilhelm Volkswagen AG Sitech Sitztechnik GmbH Stellfelder Str. 46 38442 Wolfsburg, Germany e-mail: [email protected]

Hsien-Yang Yeh California State University Long Beach Department of Mechanical and Aerospace Engineering 1250 Bellflower Boulevard Long Beach, CA 90840, USA e-mail: [email protected]

Patrick M. Williams Assystem UK 1 The Brooms, Emersons Green Bristol, BS16 7FD, UK e-mail: [email protected]

Shouwen Yu Tsinghua University School of Aerospace Beijing, 100084, P.R. China e-mail: [email protected]

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XVII

Contents

List of Abbreviations .................................................................................

XXIII

Part A Fundamentals of Mechanical Engineering 1 Introduction to Mathematics for Mechanical Engineering Ramin S. Esfandiari ................................................................................. 1.1 Complex Analysis........................................................................... 1.2 Differential Equations.................................................................... 1.3 Laplace Transformation ................................................................. 1.4 Fourier Analysis ............................................................................. 1.5 Linear Algebra ............................................................................... References ..............................................................................................

3 4 9 15 24 26 33

2 Mechanics Hen-Geul Yeh, Hsien-Yang Yeh, Shouwen Yu ............................................ 2.1 Statics of Rigid Bodies ................................................................... 2.2 Dynamics ...................................................................................... References ..............................................................................................

35 36 52 71

Part B Applications in Mechanical Engineering 3 Materials Science and Engineering Jens Freudenberger, Joachim Göllner, Martin Heilmaier, Gerhard Mook, Holger Saage, Vivek Srivastava, Ulrich Wendt ............................................ 3.1 Atomic Structure and Microstructure............................................... 3.2 Microstructure Characterization ...................................................... 3.3 Mechanical Properties ................................................................... 3.4 Physical Properties ........................................................................ 3.5 Nondestructive Inspection (NDI) ..................................................... 3.6 Corrosion ...................................................................................... 3.7 Materials in Mechanical Engineering .............................................. References ..............................................................................................

75 77 98 108 122 126 141 157 218

4 Thermodynamics Frank Dammel, Jay M. Ochterbeck, Peter Stephan ...................................... 4.1 Scope of Thermodynamics. Definitions ........................................... 4.2 Temperatures. Equilibria ............................................................... 4.3 First Law of Thermodynamics ......................................................... 4.4 Second Law of Thermodynamics ..................................................... 4.5 Exergy and Anergy.........................................................................

223 223 225 228 231 233

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Contents

4.6 Thermodynamics of Substances...................................................... 4.7 Changes of State of Gases and Vapors............................................. 4.8 Thermodynamic Processes ............................................................. 4.9 Ideal Gas Mixtures ......................................................................... 4.10 Heat Transfer ................................................................................ References ..............................................................................................

235 256 262 274 280 293

5 Tribology Ludger Deters .......................................................................................... 5.1 Tribology....................................................................................... References ..............................................................................................

295 295 326

6 Design of Machine Elements Oleg P. Lelikov ......................................................................................... 6.1 Mechanical Drives ......................................................................... 6.2 Gearings ....................................................................................... 6.3 Cylindrical Gearings ....................................................................... 6.4 Bevel Gearings .............................................................................. 6.5 Worm Gearings.............................................................................. 6.6 Design of Gear Wheels, Worm Wheels, and Worms .......................... 6.7 Planetary Gears ............................................................................. 6.8 Wave Gears ................................................................................... 6.9 Shafts and Axles ............................................................................ 6.10 Shaft–Hub Connections ................................................................. 6.11 Rolling Bearings ............................................................................ 6.12 Design of Bearing Units ................................................................. 6.A Appendix A ................................................................................... 6.B Appendix B ................................................................................... References ..............................................................................................

327 329 334 348 364 372 388 399 412 426 449 460 483 516 518 519

7 Manufacturing Engineering Thomas Böllinghaus, Gerry Byrne, Boris Ilich Cherpakov (deceased), Edward Chlebus, Carl E. Cross, Berend Denkena, Ulrich Dilthey, Takeshi Hatsuzawa, Klaus Herfurth, Horst Herold (deceased), Andrew Kaldos, Thomas Kannengiesser, Michail Karpenko, Bernhard Karpuschewski, Manuel Marya, Surendar K. Marya, Klaus-Jürgen Matthes, Klaus Middeldorf, Joao Fernando G. Oliveira, Jörg Pieschel, Didier M. Priem, Frank Riedel, Markus Schleser, A. Erman Tekkaya, Marcel Todtermuschke, Anatole Vereschaka, Detlef von Hofe, Nikolaus Wagner, Johannes Wodara, Klaus Woeste ........... 7.1 Casting ......................................................................................... 7.2 Metal Forming............................................................................... 7.3 Machining Processes...................................................................... 7.4 Assembly, Disassembly, Joining Techniques .................................... 7.5 Rapid Prototyping and Advanced Manufacturing ............................ 7.6 Precision Machinery Using MEMS Technology................................... References ..............................................................................................

523 525 554 606 656 733 768 773

Contents

8 Measuring and Quality Control Norge I. Coello Machado, Shuichi Sakamoto, Steffen Wengler, Lutz Wisweh 8.1 Quality Management ..................................................................... 8.2 Manufacturing Measurement Technology........................................ 8.3 Measuring Uncertainty and Traceability .......................................... 8.4 Inspection Planning ...................................................................... 8.5 Further Reading ............................................................................

787 787 793 816 817 818

9 Engineering Design Alois Breiing, Frank Engelmann, Timothy Gutowski ................................... 9.1 Design Theory ............................................................................... 9.2 Basics ........................................................................................... 9.3 Precisely Defining the Task............................................................. 9.4 Conceptual Design ......................................................................... 9.5 Design .......................................................................................... 9.6 Design and Manufacturing for the Environment.............................. 9.7 Failure Mode and Effect Analysis for Capital Goods .......................... References ..............................................................................................

819 819 842 843 845 848 853 867 875

10 Piston Machines Vince Piacenti, Helmut Tschoeke, Jon H. Van Gerpen .................................. 10.1 Foundations of Piston Machines..................................................... 10.2 Positive Displacement Pumps......................................................... 10.3 Compressors .................................................................................. 10.4 Internal Combustion Engines ......................................................... References ..............................................................................................

879 879 893 910 913 944

11 Pressure Vessels and Heat Exchangers Ajay Mathur ............................................................................................ 11.1 Pressure Vessel – General Design Concepts ..................................... 11.2 Design of Tall Towers ..................................................................... 11.3 Testing Requirement ..................................................................... 11.4 Design Codes for Pressure Vessels ................................................... 11.5 Heat Exchangers............................................................................ 11.6 Material of Construction ................................................................ References ..............................................................................................

947 947 952 953 954 958 959 966

12 Turbomachinery Meinhard T. Schobeiri .............................................................................. 967 12.1 Theory of Turbomachinery Stages ................................................... 967 12.2 Gas Turbine Engines: Design and Dynamic Performance .................. 981 References .............................................................................................. 1009 13 Transport Systems Gritt Ahrens, Torsten Dellmann, Stefan Gies, Markus Hecht, Hamid Hefazi, Rolf Henke, Stefan Pischinger, Roger Schaufele, Oliver Tegel ...................... 1011 13.1 Overview....................................................................................... 1012

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13.2 Automotive Engineering ................................................................ 13.3 Railway Systems – Railway Engineering ......................................... 13.4 Aerospace Engineering .................................................................. References ..............................................................................................

1026 1070 1096 1144

14 Construction Machinery Eugeniusz Budny, Mirosław Chłosta, Henning Jürgen Meyer, Mirosław J. Skibniewski ........................................................................... 14.1 Basics ........................................................................................... 14.2 Earthmoving, Road Construction, and Farming Equipment .............. 14.3 Machinery for Concrete Works ........................................................ 14.4 Site Lifts........................................................................................ 14.5 Access Machinery and Equipment .................................................. 14.6 Cranes .......................................................................................... 14.7 Equipment for Finishing Work........................................................ 14.8 Automation and Robotics in Construction ....................................... References ..............................................................................................

1149 1150 1155 1175 1191 1200 1213 1228 1238 1264

15 Enterprise Organization and Operation Francesco Costanzo, Yuichi Kanda, Toshiaki Kimura, Hermann Kühnle, Bruno Lisanti, Jagjit Singh Srai, Klaus-Dieter Thoben, Bernd Wilhelm, Patrick M. Williams .................................................................................. 15.1 Overview....................................................................................... 15.2 Organizational Structures ............................................................... 15.3 Process Organization, Capabilities, and Supply Networks ................. 15.4 Modeling and Data Structures ........................................................ 15.5 Enterprise Resource Planning (ERP) ................................................ 15.6 Manufacturing Execution Systems (MES).......................................... 15.7 Advanced Organization Concepts .................................................... 15.8 Interorganizational Structures........................................................ 15.9 Organization and Communication .................................................. 15.10 Enterprise Collaboration and Logistics ............................................ References ..............................................................................................

1267 1268 1271 1279 1290 1303 1307 1314 1321 1330 1337 1354

Part C Complementary Material for Mechanical Engineers 16 Power Generation Dwarkadas Kothari, P.M.V. Subbarao ....................................................... 16.1 Principles of Energy Supply ............................................................ 16.2 Primary Energies ........................................................................... 16.3 Fuels ............................................................................................ 16.4 Transformation of Primary Energy into Useful Energy ...................... 16.5 Various Energy Systems and Their Conversion ................................. 16.6 Direct Combustion System .............................................................. 16.7 Internal Combustion Engines ......................................................... 16.8 Fuel Cells ......................................................................................

1363 1365 1367 1367 1368 1368 1371 1372 1372

Contents

16.9 Nuclear Power Stations .................................................................. 16.10 Combined Power Station................................................................ 16.11 Integrated Gasification Combined Cycle (IGCC) System...................... 16.12 Magnetohydrodynamic (MHD) Power Generation ............................ 16.13 Total-Energy Systems for Heat and Power Generation ..................... 16.14 Transformation of Regenerative Energies ........................................ 16.15 Solar Power Stations ...................................................................... 16.16 Heat Pump.................................................................................... 16.17 Energy Storage and Distribution ..................................................... 16.18 Furnaces ....................................................................................... 16.19 Fluidized-Bed Combustion System ................................................. 16.20 Liquid-Fuel Furnace ...................................................................... 16.21 Burners......................................................................................... 16.22 General Furnace Accessories........................................................... 16.23 Environmental Control Technology ................................................. 16.24 Steam Generators .......................................................................... 16.25 Parts and Components of Steam Generator ..................................... 16.26 Energy Balance Analysis of a Furnace/Combustion System ............... 16.27 Performance of Steam Generator ................................................... 16.28 Furnace Design ............................................................................. 16.29 Strength Calculations ..................................................................... 16.30 Heat Transfer Calculation ............................................................... 16.31 Nuclear Reactors ........................................................................... 16.32 Future Prospects and Conclusion .................................................... References ..............................................................................................

1373 1374 1375 1378 1379 1381 1382 1385 1385 1386 1390 1392 1392 1394 1396 1398 1402 1406 1409 1409 1412 1414 1414 1418 1418

17 Electrical Engineering Seddik Bacha, Jaime De La Ree, Chris Oliver Heyde, Andreas Lindemann, Antje G. Orths, Zbigniew A. Styczynski, Jacek G. Wankowicz ....................... 17.1 Fundamentals ............................................................................... 17.2 Transformers ................................................................................. 17.3 Rotating Electrical Machines .......................................................... 17.4 Power Electronics .......................................................................... 17.5 Electric Drives................................................................................ 17.6 Electric Power Transmission and Distribution .................................. 17.7 Electric Heating ............................................................................. References ..............................................................................................

1421 1422 1442 1448 1461 1478 1487 1504 1509

18 General Tables Stanley Baksi ........................................................................................... 1511

Acknowledgements ................................................................................... About the Authors ..................................................................................... Detailed Contents...................................................................................... Subject Index.............................................................................................

1521 1523 1539 1561

XXI

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List of Abbreviations

3DP

3-D printing

A ABCS ABS ACCS ACFM ADAS ADI ADI AFM AGR API ARIS AS ASC ASME ATC ATS ATZ AWJ

automated building construction systems acrylonitrile-butadiene-styrene automatic cutter control system actual cubic feet per minute advanced driver-assistance system austempered cast iron austempered ductile cast iron atomic force microscope advanced gas-cooled reactor application programming interface architecture of integrated information systems active sum automatic stability control American Society of Mechanical Engineers automatic tool change air transport system Automobiltechnische Zeitschrift abrasive waterjet

B bcc bct BDC bdd BHN BHS BHW BiW BM BMEP BMS BOM BOO BOSC BPM BPR BSE BVP BWB BWR

body-centered cubic body-centered tetragonal bottom dead center block definition diagram Brinell hardness Brinell hardness Brinell hardness body-in-white beam machining break mean effective pressure bionic manufacturing system bill of materials bill of operations built-to-order supply chain ballistic particle manufacturing business process reengineering backscattered electrons boundary-value problem blended wing body boiling-water reactor

C CAD CAES CAM CAM-LEM CAN CAPP CAS CAS CBN CC CCD CCGT CCT ccw CD CD CDC CDP CDP CE CFC CFD CFRP CGI CHP CI CI CIFI CIM CIMOSA CIP CLFM CMCV CMM CMP CMU CNC CNG CODAP CPFR CPM CPT CR CRM CRP

computer-aided design compressed air energy storage computer-aided manufacturing computer-aided manufacturing of laminated engineering material controller area network computer-aided process planning computer-aided styling calibrated airspeed cubic boron nitride contour crafting charge-coupled device combined cycle gas turbines continuous cooling transition counterclockwise compact disc continuous dressing crank dead center car development process car development project concurrent engineering chlorofluorocarbons computational fluid dynamics carbon fiber reinforced plastic compacted graphite iron combined heat and power compression ignition corporate identity cylinder-individual fuel injection computer-integrated manufacturing computer-integrated manufacturing open system architecture continuous improvement process constitutional liquid film migration charge motion control valve coordinate measuring machine chemical-mechanical planarization cooperative manufacturing unit computer numerical control compressed natural gas code francais de construction des appareils a pression collaborative planning, forecasting, and replenishment critical-path method critical pitting temperature common rail customer relationship management continuous replenishment planning

XXIV

List of Abbreviations

CRSS CRT CSLP CVD CVN

critical resolved shear stress cathode ray tube capacitated lot-sizing lead-time problem chemical vapor deposition charpy V-notch

D DBTT DC DfC DFE DFIG DfRC DIC DI DIN DIO DIS DLF DLM DMD DMLS DMU DNC DPH DSC DVS D/W

ductile to brittle transition direct current design for construction design for the environment double-fed induction generator design for robotic construction differential interference contrast direct injection Deutsches Institut für Normung digital input output Draft International Standard direct laser fabrication direct laser fabrication direct metal deposition direct metal laser sintering digital mock-up direct numerical control diamond-pyramid hardness number differential scanning calorimetry Verband für Schweißen und verwandte Verfahren e.V. depth-to-width

E E2 EAS EBM EBSD ECDD ECDM ECG ECM ECM ECR ECU EDG EDM EDM EDP EDS EDX EELS EFFBD EGR EIS EJMA

extended enterprises equivalent airspeed electron beam machining electron backscatter diffraction evanescent coupling display device electrochemical-discharge machining electrochemical grinding electrochemical machining electronic control module efficient customer response electronic control unit electro-discharge grinding electro-discharge machining engineering data management electronic data processing energy-dispersive x-ray spectroscopy energy dispersive x-ray spectrometer electron energy loss spectroscopy enhanced functional flow block diagram exhaust gas recirculation entry into service Expansion Joint Manufacturer’s Association

ELID EMC EPA EPC EP EPDM EPMA ERP ESCA ESP ESP

electrolytic in-process dressing electromagnetic compatibility Environmental Protection Agency event-driven process chains extreme pressure ethylene propylene diene monomer electron probe microanalysis enterprise resource planning electron spectroscopy for chemical analysis electrostatic precipitator electronic stability program

F FAR FBC FBR fcc FD FDM FE FEGT FEM FEPA FFT FGD FKA FIB FLD FMEA FPM FPO

federal air regulations fluidized-bed combustion fast breeder reactor face-centered cubic forced draught fused deposition modeling flap-extended furnace exit gas temperature finite element modeling Federation of European Producers of Abrasíves fast Fourier transform flue gas desulphurization Forschunggesellschaft Kraftfahrwesen mbH Aachen focused ion beam forming limit diagram failure mode and effect analysis freeform powder molding future project office

G GA GERAM GHG GIM GJL GMA GoM GPS G/R GTAW

general arrangement generalized enterprise reference model architecture and methodology greenhouse gas GRAI integrated methodology lamellar graphite cast iron gas metal arc guidelines of modeling global positioning system gradient/growth rate gas tungsten arc welding

H HAZ HC HCP hcp

heat-affected zone hydrocarbons hexagonal closed packed hexagonal closed packed

List of Abbreviations

HDC HDPE HEM HFID HHV HIL HIP HMS HP HPCC HPT HRC HRSG HSC HSLA HSM HSS HTA HVDC

head dead center high-density polyethylene high-efficiency machining heated flame ionization detector higher heating value hardware-in-the-loop hot isostatic pressing holonic manufacturing systems high pressure high-pressure combustion chamber high-pressure turbine Rockwell hardness heat recovery steam generator high-speed cutting high-strength low-alloy high-speed machining high-speed steel heavier than air high-voltage direct-current

I IAARC IAS IBD IBM ICAO ICDD ICE ICE IC ICT IDD IDI ID ID IEEE IE IFAC IFIP IGBT IGC IGES IIE IISE ILT IMP IP ISB ISARC

International Association for Automation and Robotics in Construction indicated airspeed internal block diagram ion beam machining International Civil Aviation Organization International Center for Diffraction Data internal combustion engines intercity express integrated circuits information and communication technology interferometric display device indirect diesel injection induced draught inside diameter Institute of Electrical and Electronics Engineers Erichson index International Federation for Automatic Control International Federation for Information Processing insulated gate bipolar transistor intergranular corrosion test initial graphics exchange specification information-interoperable environment ion-induced secondary electrons Fraunhofer Institut für Lasertechnik International Marketing and Purchasing intermediate pressure interact system B International Symposia on Automation and Robotics in Construction

ISO IT IVP

International Standards Organization information technology initial-value problem

J JIT JiT

Java intelligent network just-in-time

L LAM LB LBM LCA LCI LC LDV LENS LHV LMJ LM LNG LOM LP LPCC LPG LPT LRO LTA LYS

laser-assisted machining laser beam laser beam machining life cycle analysis life cycle inventory laser cutting light duty vehicles laser engineered net shaping lower heating value micro-jet procedure layer manufacturing liquefied natural gas laminated object manufacturing low pressure low-pressure combustion chamber petroleum gas low-pressure turbine long-range order lighter than air lower yield stress

M MAM MAP MAS MCD MDT MEMS MEP MESA MES MHD MIC MIPS MLW MMC MOSFET MPI MPM MPW MRI

motorized air cycle machine main air pipe multi-agent systems monocrystalline diamond mean down time microelectromechanical system mean effective pressure Manufacturing Enterprise Solutions Association manufacturing execution systems magnetohydrodynamics microbiologically influenced corrosion microprocessor without interlocked pipeline stages maximum landing weight metal-matrix composites metal oxide semiconductor field effect transistor magnetic particle inspection metra potential method magnetic pulse welding magnetic resonance imaging

XXV

XXVI

List of Abbreviations

MRP MRP M/T MTBE MTBF MWE MZFW

manufacturing resources planning materials requirement planning machine tool methyl t-butyl ether mean time between failure manufacturers weight empty maximum zero fuel weight

N NACE NC NCE NDE NDI NDIR ND NDT NEDC NEMS NLGI NTP NV-EBW NVH

National Association of Corrosion Engineers numerically controlled numerically controlled equipment nondestructive evaluation nondestructive inspection nondispersive infrared normal direction nondestructive testing New European Driving Cycle nanoelectromechanical systems National Association of Lubricating Grease Institute normal temperature and pressure nonvacuum electron-beam welding noise–vibration–harshness

O OBJ ODE OECD OFA OFW OIM OLE OMT OOSE OPC ORiN OWE

polygon mesh ordinary differential equation Organisation for Economic Co-operation and Development over fire air oblique flying wing orientation imaging microscopy object linking and embedding object-modeling technique object-orientes software engineering open connectivity via open standards open robot interface for the network operating weight empty

P PABADIS PAM PBM PBMR PC PC PC PCBN PCD PCM

plant automation based on distributed systems plasma arc machining plasma beam machining pebble-bed reactor pulverized coal polycrystalline personal computer polycrystalline cubic boron nitride polycrystalline diamond powertrain control module

PDE PDF PDM PEMFC PERA PERT PET PHE PLC PLS PM PMZ PPC ppm PQR PROSA PSB PSD PSLX PS p.t.o. PVC PVD PV PWB PWHT PWR

partial differential equations powder diffraction file product data management polymer electrolyte fuel cell purdue enterprise reference architecture project evaluation and review technique polyethylene terephthalate plate heat exchanger programmable logic controller pre-lining support powder metallurgy partially melted zone production planning and control parts per million procedure qualification record product–resource–order–staff architecture persistent slip bands power spectral densities planning and scheduling language on XML specifications passive sum power take-off polyvinyl chloride physical vapor deposition pressure valve printed wiring board post-weld heat treatment pressurized-water reactor

Q QA QCC QFD QMS

quality assurance quality control charts quality function deployment quality management systems

R RAC RAMS RAO RaoSQL RAP RBV RD RE RF RFID RIE RISC RK RM RP RPI rpm

robot action command reliability, availability, maintainability, safety robot access object robot access object SQL reclaimed asphalt pavements resource-based view rolling direction reverse engineering radiofrequency radiofrequency identification reactive ion etching reduced-instruction-set computer Runge–Kutta method rapid manufacturing rapid prototyping Rensselaer Polytechnic Institute revolutions per minute

List of Abbreviations

RPZ RRD RT RT RTM RT rms RUP

risk priority number robot resource definition radiographic testing reheat turbine resin transfer molding room temperature root mean square rational unified process

S SAES SBR SC SC SCADA SCF SCF SCM SCOR SC SCTR SDM SEDM SEFI SEM SE SFC SGC SHE SHM SI SI SI SI SIC SIMS SLA SLCA SLPL SLS SMART SMAW SMD SME SMM SNCR SNG SN SoA SOF SOHC SOP SPC SPV

scanning Auger electron spectroscopy polystyrene-butadien-rubber supply chain supercritical supervisory control and data aquisition steel-frame buildings super construction factory supply chain management supply-chain operations reference supply chain solidification cracking temperature range shape deposition manufacturing spark electro-discharge machining sequential fuel injection scanning electron microscopy secondary electrons specific fuel consumption solid ground curing standard hydrogen electrode structural health monitoring spark ignition secondary ions spark-ignited system international statistical inventory control secondary-ion mass spectroscopy stereolithography streamlined life cycle analysis space limit payload selective laser sintering Shimizu manufacturing system by advanced robotics technology shielded metal arc welding surface mounted device small and medium-sized enterprises Sanders model maker selective noncatalytic reduction systems synthetic natural gas supply network space of activity soluble organic fraction single overhead camshaft start of production statistical process control simple pressure vessel

SQL SRO STL SUV SysML

structured query language short-range order stereolithography language sports utility vehicle systems modelling language

T TCL TCT TDC TD TEMA TEM TGV TIG TLAR TMAH TMC TOR TPM TPS TQM TRIAC TSF TTS TTT

total accumulated crack length time compression technology top dead center transversal direction Tubular Exchanger Manufacturer’s Association transmission electron microscopy train à grande vitesse gas tungsten arc welding top-level aircraft requirements tetramethyl ammonium hydroxide traffic message channel top of rail total productive maintenance Toyota production system total quality management triode alternating current switch topographic shell fabrication tribotechnical system time–temperature transition

U UCAV UHC UHCA UHEGT UIC ULEV UNS UPS UPV US USC USM UTS UT UYS

unmanned combat air vehicle unburned hydrocarbon ultra-high-capacity aircraft ultra high efficiency gas turbine technology Union International des Chemins de Fer ultralow-emission vehicle unified numbering system uninterruptible power supply unifired pressure vessel ultrasonic ultra-supercritical steam ultrasonic machining ultimate tensile strength ultrasonic testing upper yield stress

V VC VDI VHN VICS

vacuum casting Verein Deutscher Ingenieure (Association of German Engineers) Vickers hardness number Voluntary Interindustry Commerce Standard Association

XXVII

XXVIII

List of Abbreviations

VI VLCT VOC VOF VO VPN VR VTOL

viscosity index very large commercial transport volatile organic compound volatile organic fraction virtual organizations virtual private network virtual-reality vertical take-off and landing

weld procedure specification wheel-slide protection world wide web water/cement

X XPS XRD

x-ray-exited photoelectron spectroscopy x-ray diffraction

Y

W WBS WDS WDX WEDM WLT

WPS WSP WWW W/C

work breakdown structure wavelength dispersive x-ray spectroscopy wavelength dispersive x-ray spectroscopy wire electro-discharge machining white light triangulation

YPE

yield point elongation

Z ZEV

zero-emission vehicle

1

Part A

Fundame Part A Fundamentals of Mechanical Engineering

1 Introduction to Mathematics for Mechanical Engineering Ramin S. Esfandiari, Long Beach, USA 2 Mechanics Hen-Geul Yeh, Long Beach, USA Hsien-Yang Yeh, Long Beach, USA Shouwen Yu, Beijing, P.R. China

3

Ramin S. Esfandiari

This chapter is concerned with fundamental mathematical concepts and methods pertaining to mechanical engineering. The topics covered include complex analysis, differential equations, Laplace transformation, Fourier analysis, and linear algebra. These basic concepts essentially act as tools that facilitate the understanding of various ideas, and implementation of many techniques, involved in different branches of mechanical engineering. Complex analysis, which refers to the study of complex numbers, variables and functions, plays an important role in a wide range of areas from frequency response to potential theory. The significance of ordinary differential equations (ODEs) is observed in situations involving the rate of change of a quantity with respect to another. A particular area that requires a thorough knowledge of ODEs is the modeling, analysis, and control of dynamic systems. Partial differential equations (PDEs) arise when dealing with quantities that are functions of two or more variables; for instance, equations of motions of beams and plates. Higher-order differential equations are generally difficult to solve. To that end, the Laplace transformation is used to transform the data from the time domain to the so-called s-domain, where equations are algebraic and hence easy to treat. The solution of the differential equation is ultimately obtained when information is transformed back to time domain. Fourier analysis is comprised of Fourier series and Fourier transformation. Fourier series are a specific trigonometric series representation of a periodic signal, and frequently arise in areas such as system response analysis. Fourier

1.1

Complex Analysis .................................. 1.1.1 Complex Numbers ........................ 1.1.2 Complex Variables and Functions ...

4 4 7

1.2

Differential Equations ........................... 1.2.1 First-Order Ordinary Differential Equations ................... 1.2.2 Numerical Solution of First-Order Ordinary Differential Equations ...... 1.2.3 Second- and Higher-Order, Ordinary Differential Equations ......

9

1.3

9 10 11

Laplace Transformation......................... 1.3.1 Inverse Laplace Transform ............. 1.3.2 Special Functions ......................... 1.3.3 Laplace Transform of Derivatives and Integrals ............................... 1.3.4 Inverse Laplace Transformation...... 1.3.5 Periodic Functions ........................

15 16 18

1.4

Fourier Analysis .................................... 1.4.1 Fourier Series............................... 1.4.2 Fourier Transformation .................

24 24 25

1.5

Linear Algebra...................................... 1.5.1 Vectors and Matrices..................... 1.5.2 Eigenvalues and Eigenvectors ........ 1.5.3 Numerical Solution of Higher-Order Systems of ODEs ....

26 27 30

References ..................................................

33

21 22 23

32

transformation maps information from the time to the frequency domain, and its extension leads to the Laplace transformation. Linear algebra refers to the study of vectors and matrices, and plays a central role in the analysis of systems with large numbers of degrees of freedom.

Part A 1

Introduction 1. Introduction to Mathematics for Mechanical Engineering

Introduction to Mathematics for Mechanical Engineering

1.2 Differential Equations

Mathematical models of dynamic systems – mechanical, electrical, electromechanical, liquid-level, etc. – are represented by differential equations [1.3]. Therefore, it is imperative to have a thorough knowledge of their basic properties and solution techniques. In this section we will discuss the fundamentals of differential equations, specifically, ordinary differential equations (ODEs), and present analytical and numerical methods to solve them. Differential equations are divided into two general categories: ordinary differential equations and partial differential equations (PDEs). An equation involving an unknown function and one or more of its derivatives is called a differential equation. When there is only one independent variable, the equation is called an ordinary differential equation (ODE). For example, y + 2y = ex is an ODE involving the unknown function y(x), its first derivative y = dy/ dx, as well as a given function ex . Similarly, xy − yy = sin x is an ODE relating y(x) and its first and second derivatives with respect to x, as well as the function sin x. While dealing with time-varying functions – as in many physical applications – the independent variable x will be replaced by t, representing time. In that case, the rate of change of the quantity y = y(t) with respect to the independent variable t is denoted by y˙ = dy/ dt. If the unknown function is a function of more than one independent variable, e.g., u(x, y), the equation is referred to as a partial differential equation. The derivative of the highest order of the unknown function y(x) with respect to x is the order of the ODE; for instance, y + 2y = ex is of order one and xy − yy = sin x is of order two. Consider an nth-order ordinary differential equation in the form an y

(n)

+ an−1 y

(n−1)



+ · · · + a1 y + a0 y = g(x) , (1.25)

Part A 1.2

1.2 Differential Equations 1.2.1 First-Order Ordinary Differential Equations First-order ODEs generally appear in the implicit form F(x, y, y ) = 0 .

(1.26)

For example, y + y2 = cos x can be expressed in the above form with F(x, y, y ) = y + y2 − cos x. In other cases, the equation may be written explicitly as y = f (x, y) .

(1.27)

An example would be y + 2y = ex where f (x, y) = ex − 2y. A function y = s(x) is a solution of the firstorder ODE in (1.26) on a specified (open) interval if it has a derivative y = s (x) and satisfies (1.26) for all values of x in the given interval. If the solution is in the form y = s(x), then it is called an explicit solution. Otherwise, it is in the form S(x, y) = 0, which is known as an implicit solution. For example, y = 4 e−x/2 is an explicit solution of 2y + y = 0. It turns out that a single formula y = k e−x/2 involving a constant k = 0 generates all solutions of this ODE. Such formula is referred to as a general solution, and the constant is known as the parameter. When a specific value is assigned to the parameter, a particular solution is obtained. Initial-Value Problem (IVP) A first-order initial-value problem (IVP) appears in the form

y = f (x, y) ,

y(x0 ) = y0 ,

(1.28)

where y(x0 ) = y0 , is called the initial condition.

where y = y(x) and y(n) = dn y/ dx n . If all coefficients a0 , a1 , · · · , an are either constants or functions of the independent variable x, then the ODE is linear. Otherwise, the ODE is nonlinear. Based on this, y + 2y = ex describes a linear ODE, while xy − yy = sin x is nonlinear.

Example 1.8: IVP Solve the initial-value problem

Example 1.7: Order and linearity

y = k e−x/2 . Applying the initial condition, we obtain

3y − (2x + 1)y + y

= Since the derivaConsider tive of the highest order is three, the ODE is third order. Comparison with (1.25) reveals that n = 3, and a3 = 3, a2 = −(2x + 1), a1 = 0, a0 = 1, and g(x) = ex . Thus, the ODE is linear. ex .

2y + y = 0 ,

y(2) = 3 .

Solution. As mentioned earlier, a general solution is

y(2) = k e−1 = 3

Solve for k

⇒

9

k = 3e .

Therefore, the particular solution is y = 3 e · e−x/2 = 3 e1−x/2 .

10

Part A

Fundamentals of Mechanical Engineering

Part A 1.2

Separable First-Order Ordinary Differential Equations A first-order ODE is referred to as separable if it can be written as

f (y)y = g(x) .

(1.29)

Using y = dy/ dx in (1.29), we have f (y)

dy = g(x) ⇒ f (y) dy = g(x) dx . dx

(1.30)

f (x) ≡ 0, then the ODE is called homogeneous, otherwise it is called nonhomogeneous. Solution of Linear First-Order ODEs The general solution of (1.31) can be expressed as [1.1, 4]   eh(x) f (x) dx + c , y(x) = e−h(x) (1.32) where h(x) = g(x) dx .

Integrating the two sides of (1.30) separately, yields f (y) dy = g(x) dx + c , c = const.

Note that the constant of integration in the calculation of h is omitted because c accounts for all constants.

Example 1.9: Separable ODE

Solve the initial-value problem ex y = y2 , y(0) = 1.

Example 1.10: Linear first-order ODE Find the particular solution to the initial-value problem 2 y˙ + y = 4 e2t , y(0) = 1.

Solution. The ODE is separable and treated as

Solution. Noting that t is now the independent vari-

able, we first rewrite the ODE to agree with the form of (1.31), as

dy = y2 dx 1 1 dy = dx 2 ex y 1 − = − e−x + c y (c = const.) 1 y(x) = −x , e −c ex

Provided that y  = 0

⇒

⇒ Solve for y

⇒

which is the general solution to the original differential equation. The specific value of c is determined via the given initial condition, as ⎫Initial condition y(0) = 1 ⎪ ⎬ 1 ⇒ =1⇒c=0. ⎪ 1 − c 1 ⎭ y(0) = 1−c By gen. solution Substitution into the general solution yields the particular solution y(x) = ex . Linear First-Order Ordinary Differential Equations A differential equation that can be expressed in the form

y + g(x)y = f (x) ,

(1.31)

where g and f are given functions of x, is called a linear first-order ordinary ODE. This of course agrees with what was discussed in (1.25) with slight changes in notation. If f (x) = 0 for every x in the interval under consideration, that is, if f is identically zero, denoted

1 y˙ + y = 2 e2t 2 so that 1 g = , f = 2 e2t . 2   With h = g(t) dt = 12 dt = 12 t, the general solution is given by (1.32),   −t/2 t/2 2t e · 2 e dt + c y(t) = e   4 = e−t/2 2 e5t/2 dt + c = e2t + c e−t/2 . 5 Applying the initial condition, we find y(0) = 45 + c = 1 ⇒ c = 15 . The particular solution is y(t) = 45 e2t + 1 −t/2 . 5e

1.2.2 Numerical Solution of First-Order Ordinary Differential Equations Recall that a first-order ODE can appear in an implicit form F(x, y, y ) = 0 or an explicit form y = f (x, y). We will consider the latter, and assume that it is subject to a prescribed initial condition, that is, y = f (x, y) ,

y(x0 ) = y0 ,

x0 ≤ x ≤ x N . (1.33)

If finding a closed-form solution of (1.33) is difficult or impossible, we resort to a numerical solution. What

Introduction to Mathematics for Mechanical Engineering

x1 = x0 + h , x2 = x0 + 2h · · · xn = x0 + nh , · · · , x N = x0 + Nh known as mesh points, where h is called the step size. Note that the mesh points are equally spaced. Among many numerical methods to solve (1.33), the fourthorder Runge–Kutta method is most commonly used in practice. The difference equation for the fourth-order Runge–Kutta method (RK4) is derived as [1.5, 6] 1 (1.34) yn+1 = yn + (q1 + 2q2 + 2q3 + q4 ) , 6 n = 0, 1, · · · , N − 1 , where q1 = h f (xn , yn )   h q1 q2 = h f xn + , yn + , 2 2   h q2 q3 = h f xn + , yn + , 2 2 q4 = h f (xn + h, yn + q3 ) . Example 1.11: Fourth-order Runge–Kutta method

Apply RK4 with step size h = 0.1 to solve y + y= 2x 2 , y(0) = 3, 0 ≤ x ≤ 1.

Solution. Knowing that f (x n , yn ) = −yn + 2x n2 , the

four function evaluations/step of the RK4 are   q1 = h − yn + 2xn2 ,     1  1 2 , q2 = h − yn + q1 + 2 xn + h 2 2     1  1 2 q3 = h − yn + q2 + 2 xn + h , 2 2   q4 = h − (yn + q3 ) + 2(xn + h)2 . Upon completion of each step, yn+1 is calculated by (1.34). So, we start with n = 0, corresponding to x0 = 0 and y0 = 3, and continue the process up to n = 10. Numerical results are generated as y(0) = 3 , y(0.1) = 2.7152 , y(0.2) = 2.4613 , y(0.3) = 2.2392 , · · · , y(0.9) = 1.6134 , y(1) = 1.6321 .

Further inspection reveals that RK4 produces the exact values (at least to five-decimal place accuracy) of the solution at the mesh points.

1.2.3 Second- and Higher-Order, Ordinary Differential Equations The application of basic laws such as Newton’s second law and Kirchhoff’s voltage law (KVL) leads to mathematical models that are described by second-order ODEs [1.3]. Although it is quite possible that the system models contain nonlinear elements, in this section we will mainly focus on linear second-order differential equations. Nonlinear systems may be treated via numerical techniques such as the fourth-order Runge– Kutta method (Sect. 1.2), or via linearization [1.3]. In agreement with (1.25), a second-order ODE is said to be linear if it can be expressed in the form y + g(x)y + h(x)y = f (x) ,

(1.35)

where f , g, and h are given functions of x. Otherwise, it is called nonlinear. Homogeneous Linear Second-Order ODEs If y1 and y2 are two solutions of the homogeneous linear ODE

y + g(x)y + h(x)y = 0

(1.36)

on some open interval, their linear combination y = c1 y1 + c2 y2 (c1 , c2 constants) is also a solution on the same interval. This is known as the principle of superposition. General Solution of Linear Second-Order ODEs – Linear Independence A general solution of (1.36) is based on the idea of linear independence of functions, which involves what is known as the Wronskian. We first mention that a 2 × 2 determinant (Sect. 1.5.1) is evaluated as     p q  = ps − qr .  r s

If each of the functions y1 (x) and y2 (x) has at least a first derivative, then their Wronskian is denoted by W(y1 , y2 ) and is defined as the 2 × 2 determinant      y1 y2  W(y1 , y2 ) =     = y1 y2 − y2 y1 . (1.37)  y1 y2  If there exists a point x ∗ ∈ (a, b) where W = 0, then y1 and y2 are linearly independent on the entire interval (a, b).

11

Part A 1.2

this means is that we find approximate values for the solution y(x) at several points

1.2 Differential Equations

12

Part A

Fundamentals of Mechanical Engineering

Part A 1.2

Example 1.12: Independent solutions – the Wronskian The functions y1 = e2x and y2 = e−3x are linearly independent for all x because their Wronskian is         e−3x   y1 y2   e2x W(y1 , y2 ) =     =  2x   y1 y2   2 e −3 e−3x 

= −5 e−x = 0

Since eλx = 0 for any finite values of x and λ, then λ 2 + a1 λ + a2 = 0 Solve the

1 2

λ2 =

1 2

⇒

characteristic equation

for all x.



  − a1 + a12 − 4a2



  − a1 − a12 − 4a2

.

(1.40)

If y1 and y2 are two linearly independent solutions of (1.36) on the interval (a, b), they form a basis of solutions for (1.36) on (a, b). A general solution of (1.36) on (a, b) is a linear combination of the basis elements, that is, y = c1 y1 + c2 y2

λ1 =

(c1 , c2 constants) .

(1.38)

Example 1.13: General solution, basis

It can be easily verified that y1 = e2x and y2 = e−3x are solutions of y + y − 6y = 0 for all x. They are also linearly independent by Example 1.12. Consequently, y1 = e2x and y2 = e−3x form a basis of solutions for the ODE at hand, and a general solution for this ODE is y = c1 e2x + c2 e−3x (c1 , c2 constants).

The solutions λ1 and λ2 of the characteristic equation are the characteristic values. The assumption was y = eλx , hence the solutions of (1.39) are y1 = eλ1 x and y2 = eλ2 x . To find a general solution of (1.39), the two independent solutions must be identified. But this depends on the nature of the characteristic values λ1 and λ2 , as discussed below. ` ´ Case 1: Two Distinct Real Roots a21 − 4a2 > 0‚λ1  = λ2 .

In this case, the solutions y1 = eλ1 x and y2 = eλ2 x are linearly independent, as may easily be verified. Thus, they form a basis of solution for (1.39). Therefore, a general solution is y(x) =

Example 1.14: Unique solution of an IVP

Find the particular solution of y + y − 6y = 0, y(0) = −1, y (0) = 8.

Solution. By Example 1.13, a general solution is y =

c1 e2x + c2 e−3x . Differentiating and applying the initial conditions, we have y(0) = c1 + c2 = −1 y (0) = 2c1 − 3c2 = 8

Solve the system

⇒

c1 = 1 . c2 = −2

Therefore, the unique solution of the IVP is obtained as y = e2x − 2 e−3x . Homogeneous Second-Order Differential Equations with Constant Coefficients Consider a homogeneous linear second-order ODE with constant coefficients,

y + a1 y + a2 y = 0 (a1 , a2 constants)

(1.39)

and assume that its solution is in the form y = eλx , where λ, known as the characteristic value, is to be determined. Substitution into (1.39), yields λ2 eλx + a1 λ eλx + a2 eλx = 0   ⇒ eλx λ2 + a1 λ + a2 = 0 .

c1 eλ1 x + c2 eλ2 x General solution — λ1 =λ2 , real

.

(1.41)

` Case 2:´ Double (Real) Root a21 − 4a2 = 0‚ λ1 = λ2 = − 21 a1 . It can be shown [1.1] that the two lin-

early independent solutions are y1 = e−a1 x/2 and y2 = x e−a1 x/2 . Therefore, 1

1

y(x) = c1 e− 2 a1 x + c2 x e− 2 a1 x =

1

(c1 + c2 x) e− 2 a1 x

General solution — λ1 =λ2 , real

.

(1.42)

` ´ ¯2 . Case 3: Complex Conjugate Pair a21 − 4a2 < 0‚λ1 = λ 1 The  characteristic values are given as λ1,2 = 2 (−a1 ± a12 − 4a2 ). Since a12 − 4a2 < 0, we write

     1 −a1 ± − 4a2 − a12 2   √  1 = −a1 ± −1 4a2 − a12 2    1 2 = −a1 ± i 4a2 − a1 = −σ ± iω , 2 √ (i = −1)

λ1,2 =

Introduction to Mathematics for Mechanical Engineering

1 σ = a1 , 2 1 4a2 − a12 . (1.43) ω= 2 The two independent solutions are y1 = e−σ x cos ωx and y2 = e−σ x sin ωx, and a general solution of (1.39) is obtained as y(x) =

e−σ x (c1 cos ωx + c2 sin ωx)

General solution — λ1 =λ¯ 2 , complex conjugates

.

Nonhomogeneous Linear Second-Order ODEs Nonhomogeneous second-order ODEs appear in the form

y + g(x)y + h(x)y = f (x) , f (x) ≡ 0 .

(1.46)

A general solution for this equation is then obtained as y(x) =

+ yp (x) . yh (x) Homogeneous solution Particular solution

(1.47)

(1.44)

Homogeneous Solution yh (x). yh (x) is a general solution of the homogeneous equation (1.36), and as previously discussed, it is given by

Example 1.15: Case (3)

Solve y + 2y + 2y = 0, y(0) = 1, y (0) = 0. Solution. We first find the characteristic equation and

the corresponding characteristic values, as

Complex conjugate pair, Case (3) By (1.43), we identify σ = 1 and ω = 1, so that the general solution by (1.44) is y(x) = e−x (c1 cos x + c2 sin x) . Next, we differentiate this to obtain + e−x (−c1 sin x + c2 cos x) Finally, by the initial conditions,

1 + c2

=0

⇒

c1 = 1 c2 = 1

y + a1 y + a2 y = f (x)

and the solution is y(x) = e−x (cos x + sin x). Boundary-Value Problems (BVP). In certain appli-

cations involving second-order differential equations, a pair of information is provided at the boundary points of an open interval (a, b) on which the ODE is to be solved. This pair is referred to as the boundary conditions, and the problem y + a1 y + a2 y = 0 , y(a) = A , y(b) = B    Boundary conditions

is called a boundary-value problem (BVP).

Particular Solution yp (x). yp (x) is a particular solution of (1.46), and does not involve any arbitrary constants. The nature of yp (x) depends on the nature of f (x), as well as its relation to the independent solutions y1 and y2 of the homogeneous equation.

Method of Undetermined Coefficients When (1.46) happens to have constant coefficients and the function f (x) is of a special type – polynomial, exponential, sine and/or cosine or a combination of them – then the particular solution can be obtained by the method of undetermined coefficients as follows. Consider

y (x) = − e−x (c1 cos x + c2 sin x)

y (0) = −c

(c1 , c2 constants)

where y1 and y2 are linearly independent and form a basis of solutions for (1.36). Note that the homogeneous solution involves two arbitrary constants.

λ2 + 2λ + 2 = 0 ⇒λ1,2 = −1 ± i .

y(0) = c1 = 1

yh = c1 y1 + c2 y2 ,

(1.45)

(a1 , a2 constants) . (1.48)

Since the coefficients are constants, the homogeneous solution yh is found as before. So all we need to do is to find the particular solution yp . We will make a proper selection for yp based on the nature of f (x) and with the Table 1.1 Selection of particular solution – the method of undetermined coefficients Term in f (x)

Proper choice of yp

an x n + . . . + a1 x + a0 A eax A sin ωx or A cos ωx A eσ x sin ωx or A eσ x cos ωx

Kn xn + . . . + K1 x + K0 K eax K 1 cos ωx + K 2 sin ωx eσ x (K 1 cos ωx + K 2 sin ωx)

13

Part A 1.2

where

1.2 Differential Equations

14

Part A

Fundamentals of Mechanical Engineering

Part A 1.2

aid of Table 1.1. This choice involves unknown coefficients, which will be determined by substituting yp and its derivatives into (1.48). The details, as well as special cases that may occur, are given below. Procedure. Step 1: Homogeneous Solution yh (x). Solve the homo-

geneous equation y + a1 y + a2 y = 0 to find the two independent solutions y1 and y2 , and the general solution yh (x) = c1 y1 (x) + c2 y2 (x).

a homogeneous solution associated with a double root. Therefore, by special case II the modified choice is Kx 2 e−x . Consequently, the particular solution is in the form yp (x) = K 1 x + K 0 + K x 2 e−x . First term

Second term

Substitution of yp and its derivatives into the nonhomogeneous ODE, and collecting terms, results in 2K e−x + K 1 x + K 0 + 2K 1 = x + 1 + 3 e−x . Equating the coefficients of like terms, we have

Step 2: Particular Solution yp (x). For each term in f (x)

choose a proper yp as suggested by Table 1.1. For instance, if f (x) = x + 2 ex then pick yp = K 1 x + K 2 + K ex . Note that, if instead of x we had 3x − 2, for example, the choice of yp would still be the same because they both represent first-degree polynomials. We then substitute our choice of yp , along with its derivatives, into the original ODE to find the undetermined coefficients. Special cases.

I. Suppose a term in our choice of yp coincides with a solution (y1 or y2 ) of the homogeneous equation, and that this solution is associated with a simple (i. e., nonrepeated) characteristic value. Then, make the modification by multiplying yp by x. II. If a term in the choice of yp coincides with a solution of the homogeneous equation, and that this solution is associated with a repeated characteristic value, modify by multiplying yp by x 2 . Example 1.16: Special case II

Solve y + 2y + y = x + 1 + 3 e−x ,

y(0) = 1 , y (0) = 0 .

Step 1: Homogeneous Solution. The characteristic

equation (λ + 1)2 = 0 yields a double root λ = −1. This means y1 = e−x and y2 = x e−x , so that the homogeneous solution is yh (x) = (c1 + c2 x) e−x .

Step 2: Particular Solution. The right-hand side of the

ODE consists of two functions, x +1

First-degree polynomial

and

e−x .

The first term, x + 1, does not coincide with either y1 or y2 , so the proper choice by Table 1.1 is K 1 x + K 0 . The second term involves e−x , which happens to be

K = 32 2K = 3 ⇒ K1 = 1 K1 = 1 K 0 + 2K 1 = 1 K 0 = −1 3 ⇒ yp (x) = x − 1 + x 2 e−x . 2 Step 3: General Solution. The general solution is then

found as 3 y(x) = (c1 + c2 x) e−x + x − 1 + x 2 e−x . 2 Step 4: Initial Conditions. Applying the initial conditions, we obtain c1 = 2 and c2 = 1. Finally, the solution to the IVP is 3 y(x) = (2 + x) e−x + x − 1 + x 2 e−x . 2

Higher-Order Ordinary Differential Equations Many of the techniques for the treatment of differential equations of order three or higher are merely extensions of those applied to second-order equations. Here we will only discuss nth-order, linear nonhomogeneous ODEs with constant coefficients, that is,

y(n) + an−1 y(n−1) + · · · + a1 y + a0 y = f (x) , (1.49)

where a0 , a1 , · · · , an−1 are constants. As in the case of second-order ODEs, a general solution consists of the homogeneous solution and the particular solution. For cases when f (x) is of a special type, the particular solution is obtained via the method of undetermined coefficients. Method of Undetermined Coefficients. The idea introduced for second-order ODEs is now extended to find yp for (1.49). As before, a proper choice of yp is made assuming that f (x) consists of terms that are listed in Table 1.1. If none of the terms in f (x) happens to be

Introduction to Mathematics for Mechanical Engineering

Special Cases.

1. If a term in our choice of yp coincides with a homogeneous solution, which corresponds to a simple (nonrepeated) characteristic value, then we make the modification by multiplying yp by x. 2. If a term in yp coincides with a solution of the homogeneous equation, and this solution is associated with a characteristic value of multiplicity m, we modify by multiplying yp by x m . Example 1.17: Special case II

is a first-degree polynomial, we pick yp = K 1 x + K 0 . But x happens to be a homogeneous solution associated with a double root (λ = 0). Hence, the modification is yp = (K 1 x + K 0 )x 2 . Substituting this and its derivatives into the original ODE, and simplifying, we arrive at (6K 1 − 8K 0 ) − 24K 1 x = 1 + 12x K = − 12 6K 1 − 8K 0 = 1 ⇒ 1 −24K 1 = 12 K 0 = − 12 1 ⇒ yp = − (x + 1)x 2 2 ⇒

Step 3: General Solution. Combination of yh and yp

gives a general solution y = c1 + c2 x + c3 e4x − 12 (x + 1)x 2 .

Solve y − 4y = 1 + 12x , y(0) = 0 , y (0) = 4 ,

Step 2: Particular Solution. Noting that f (x) = 1 + 12x

y (0) = 15 .

Solution. Step 1: Homogeneous Solution. Characteristic equa-

tion: λ3 − 4λ2 = λ2 (λ − 4) = 0 ⇒ λ = 0, 0, 4 . Therefore yh = c1 + c2 x + c3 e4x .

Step 4: Initial Conditions. Applying the initial conditions to the general solution and its derivatives, we obtain

c1 = −1 y(0) = c1 + c3 = 0  ⇒ y (0) = c2 + 4c3 = 4 c2 = 0 y (0) = 16c3 − 1 = 15 c3 = 1 1 1 ⇒ y(x) = −1 + e4x − x 3 − x 2 . 2 2

1.3 Laplace Transformation In Sect. 1.2 we mainly learned to solve linear timeinvariant (LTI) ODEs without ever leaving the time domain. In this section we introduce a systematic approach to solve such ODEs in a more-expedient manner. The primary advantage gained here is that the arbitrary constants in the general solution need not be found separately. The idea is simple: in order to solve an ODE and corresponding initial-value problem (IVP) or boundaryvalue problem (BVP), transform the problem to the so-called s domain, in which the transformed problem is an algebraic one. This algebraic problem is then treated properly, and the data is ultimately transformed back to time domain to find the solution of the original problem. The transform function is a function of a complex vari-

able, denoted by s. If a function f (t) is defined for all t ≥ 0, then its Laplace transform is defined by F(s)

Notation

=

L[ f (t)] ∞ Definition = e−st f (t) dt

(1.50)

0

provided that the integral exists. The complex variable s is the Laplace variable, and L is the Laplace transform operator. It is common practice to denote a time-dependent function by a lower-case letter, say, f (t), and its Laplace transform by the same letter in upper case, F(s).

15

Part A 1.3

an independent homogeneous solution, then no modification is necessary. Otherwise, the following special cases need be taken into account.

1.3 Laplace Transformation

18

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Fundamentals of Mechanical Engineering

Part A 1.3

we assume that f (t) is such that F(s) = L[ f (t)] is either known directly from Table 1.2 or can be determined by other means. Either way, once F(s) is available, the two transforms labeled (1) and (2) will be obtained in terms of the derivative and integral of F(s), respectively. Before presenting two key results pertaining to these situations we make the following definition. If a transform function is in the form F(s) = N(s)/D(s), then each value of s for which D(s) = 0 is called a pole of F(s). A pole with a multiplicity (number of occurrences) of one is known as a simple pole.

Example 1.23: Theorem 1.3

Show that   s sin ωt = cot−1 . L t ω Solution. Comparing with (1.58), f (t) = sin ωt so that

F(s) = ω/(s2 + ω2 ). Subsequently,  L

 ∞ ω sin ωt dσ = t σ 2 + ω2 s

∞

1 dσ 1 + (σ /ω)2 ω s  σ ∞ = tan−1 ω σ=s s s π = − tan−1 = cot−1 . 2 ω ω

Theorem 1.2: Differentiation of Laplace Transforms.

=

If L[ f (t)] = F(s) exists, then at any point except at the poles of F(s), we have L[t f (t)] = −

d F(s) = −F  (s) ds

(1.55)

or alternatively, t f (t) = −L−1 [F  (s)] .

(1.56)

The general form of (1.55) for n = 1, 2, 3, · · · is given by L[t n f (t)] = (−1)n

dn dsn

F(s) = (−1)n F (n) (s) . (1.57)

Example 1.22: Differentiation of F(s) Find L[t sin 3t]. Solution. Comparing with the left side of (1.55), we

have f (t) = sin 3t so that F(s) = 3/(s2 + 9). Therefore,   3 d L[t sin 3t] = − ds s2 + 9 6s = 2 (s + 9)2

Theorem 1.3: Integration of Laplace transforms. If L[ f (t)/t] exists, and the order of integration can be interchanged, then

 L

 ∞ f (t) = F(σ) dσ . t ⎡

f (t) = tL−1 ⎣

Much can be learned about the characteristics of a system based on its response to specific external disturbances. To perform the response analysis, these disturbances must first be mathematically modeled, which is where special functions play an important role. In this section we will introduce the step, ramp, pulse, and impulse functions, as well as their Laplace transforms. Unit Step u(t) The unit-step function (Fig. 1.11) is analytically defined as ⎧ ⎪ if t > 0 ⎪ ⎨1 (1.60) u(t) = 0 if t < 0 . ⎪ ⎪ ⎩ undefined (finite) if t = 0

This may be physically realized as a constant signal (of magnitude 1) suddenly applied to the system at time t = 0. By the definition of the Laplace transform, we find

(1.58)

s

Alternatively,

1.3.2 Special Functions

L[u(t)] ∞ s

Notation

=

∞ U(s) = 0

⎤ F(σ) dσ ⎦ .

e−st u(t) dt

∞ (1.59)

= 0

e−st dt =

1 . s

(1.61)

22

Part A

Fundamentals of Mechanical Engineering

Part A 1.3

Case 1: Linear Factor s − pi . Each typical linear factor

Finally,

s − pi of D(s) is associated with a fraction in the form A , s − pi where A = const. is to be determined appropriately. We note that s = pi is called a simple pole of X(s).

x(t) = L−1 [X(s)] = e−t + 2t e−t = (2t + 1) e−t .

1.3.4 Inverse Laplace Transformation Inverse Laplace transformation clearly plays a vital role in completing the procedure for solving differential equations. In this section we will learn a systematic technique, using partial fractions, to treat a wide range of inverse Laplace transforms. We will also introduce the convolution method, which is quite important from a physical standpoint. Partial Fractions Method When solving an ODE in terms of x(t) through Laplace transformation, the very last step involves finding L−1 [X(s)]. And we almost always find ourselves looking for the inverse Laplace transform of functions in the form of

X(s) =

N(s) Polynomial of degree m = , m 0 ,a > 0 ⎩0 otherwise ⎧ ⎨ eat t < 0 ,a > 0 ⎩0 otherwise ⎧ ⎨ eat b < t < b 1 2 ⎩0 otherwise e−a|t| , a > 0 ⎧ ⎨− e−at t < 0 ,a < 0 ⎩ eat t>0 ⎧ ⎨ eiat −b < t < b ⎩0 otherwise ⎧ ⎨ eiat b < t < b 1 2 ⎩0 otherwise 1 a2 +t 2

,a > 0

⎧ ⎨t 0 < t < b ⎩0 otherwise ⎧ ⎪ 0 0

ˆf (ω) 

2 sin bω π ω

−ib1 ω − e−ib2 ω √1 e iω 2π

1 √1 2π a+iω

formation with this type of property is known as an integral transformation. The obvious similarities between the Laplace and Fourier transforms are credited to the Laplace transformation being an integral transformation itself. Fourier transforms of several functions are listed in Table 1.3. Example 1.29: Fourier transform Find the Fourier transform of ⎧ ⎨0 if t < 0 (a > 0) . f (t) = ⎩ e−at if t > 0

1 √1 2π a−iω

(a−iω)b2 − e(a−iω)b1 √1 e a−iω 2π

 



a 2 π ω2 +a2 2 −iω π ω2 +a2

2 sin(ω−a)b π ω−a

i(a−ω)b1 − ei(a−ω)b2 √i e a−ω 2π

π 2

e−a|ω| a

−ibω (1+ibω) √1 −1+ e 2π ω2

ibω − e−2ibω √1 −1+2 e 2π ω2

2 √1 e−ω /(4a) 2a √ −aω2

2a e

Solution. By (1.83),

1 fˆ(ω) = √ 2π 1 =√ 2π

∞ −∞ ∞

f (τ) e−iωτ dτ

e−aτ e−iωτ dτ

0

−1  −(a+iω)τ ∞ 1 =√ e 0 2π a + iω 1 1 =√ . 2π a + iω Using fˆ(ω) above in (1.84), we find 1 f (t) = √ 2π =

1 2π

∞ −∞

∞ −∞

1 1 eiωt dω √ 2π a + iω

1 eiωt dω . a + iω

This is known as the complex Fourier integral representation of the function under consideration.

1.5 Linear Algebra In this section we present the fundamentals of linear algebra, specifically, vectors and matrices, and their relation to linear systems of algebraic and differential equations. The methods of linear algebra are mainly useful in the treatment of systems of equations that are heavily coupled, that is, when a large number of

equations in the system involve many of the unknown variables. In these cases, techniques such as direct substitution and elimination are no longer suitable due to their lack of computational efficiency. We focus on algebraic systems first, then extend the ideas to systems of differential equations.

28

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Fundamentals of Mechanical Engineering

Part A 1.5

B, the product is undefined. If the product is defined, then to get the (i, j) entry of C, we proceed as follows: the ith row of A is clearly a 1 × n vector. The jth column of B is an n × 1 vector, hence these two vectors have the same number of components, n. In these two vectors, multiply the first components, the second components, etc., up to the nth components. Then add the individual products together. The result is cij .

Example 1.31: Special matrices

Matrices U, L, and D are upper triangular, lower triangular, and diagonal, respectively: ⎛ ⎞ ⎛ ⎞ −2 1 2 1 0 0 ⎜ ⎟ ⎜ ⎟ U=⎝ 0 5 0⎠ , L=⎝2 0 0⎠ , ⎛

# AB =

⎛

⎞ −2 −1 4 1 −2 3 ⎜ ⎟ . ⎝ 1 2 0⎠ 0 1 4 2×3 3 5 1 3×3 $

Solution. We first note that the operation is valid be-

cause A has three columns and B has three rows. And, AB will be 2 × 3. Following the strategy outlined above, we find the product as  1·(−1)+(−2)·2+3·5 AB = 1·(−2)+(−2)·1+3·3 0·(−2)+1·1+4·3 0·(−1)+1·2+4·5  1·4+(−2)·0+3·1 0·4+1·0+4·1

# =

$

5 10 7 13 22 4

.

(1.86)

(kA) = kA ,

(1.87)

T

T

(AB)T = BT AT .

Determinant The determinant of a square matrix A = [aij ]n×n is a real scalar denoted by |A| or det(A). For the most trivial case of n = 1, A = [a11 ], and we define the determinant simply as |A| = a11 . For n ≥ 2, the determinant is defined as using the i-th row

|A| =

(A + B)T = AT + BT scalar k

(1.88)

Special Matrices A square matrix A is symmetric if AT = A and skewsymmetric if AT = −A. A square matrix An×n = [aij ] is called upper-triangular if aij = 0 for all i > j, that is, every entry below the main diagonal is zero, lowertriangular if aij = 0 for all i < j, that is, all elements above the main diagonal are zeros, and diagonal if aij = 0 for all i = j. The n × n identity matrix is a diagonal matrix whose diagonal entries are all equal to 1, and is denoted by I.

4 7 −1

Note that in U and L zeros are allowed along the main diagonal. In fact, the main diagonal may consist of all zeros. On the other hand, D may have one or more zero diagonal elements, as long as they are not all zeros. In the event that all entries of an n × n matrix are zeros, it is called the n × n zero matrix 0n×n .

2×3

Matrix Transpose Given an m × n matrix A, its transpose, denoted by AT , is an n × m matrix with the property that its first row is the first column of A, its second row is the second column of A, and so on. Given that all matrix operations are valid,

⎞

3 0 0 ⎟ ⎜ D = ⎝ 0 −4 0 ⎠ . 0 0 1

Example 1.30: Matrix Multiplication

Find

0 0 3

n "

aik (−1)i+k Mik , i = 1, 2, · · · , n

(1.89)

k=1

or using the j-th column |A| =

n "

ak j (−1)k+ j Mk j , j = 1, 2, · · · , n (1.90)

k=1

Here Mik is the minor of the entry aik , defined as the determinant of the (n − 1) × (n − 1) submatrix of A obtained by deleting the ith row and the kth column of A. The quantity (−1)i+k Mik is known as the cofactor of aik and is denoted by Cik . Also note that (−1)i+k is responsible for whether a term is multiplied by +1 or −1. Equations (1.89) and (1.90) suggest that the determinant of a square matrix can be calculated using any row or any column of the matrix. However, for all practical purposes, it is wise to use the row (or column) containing the most number of zeros, or if none, the one with the smallest entries. A square matrix with a nonzero determinant is known as a nonsingular matrix. Otherwise, it is called singular. The rank of any matrix A, denoted by rank(A), is the size of the largest nonsingular submatrix of A. If |An×n | = 0, we conclude that rank (A) < n.

30

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Fundamentals of Mechanical Engineering

Part A 1.5

Inverse via the Adjoint Matrix. The inverse of an invert-

ible matrix A = [aij ]n×n is determined using the adjoint of A, denoted by adj(A) and defined as [1.1]

the original matrix. The inverse of an upper-triangular matrix is upper-triangular. The diagonal elements of the inverse are the reciprocals of the diagonal entries of the original matrix, while the off-diagonal entries do not obey any pattern. A similar result holds for lower-triangular matrices. Furthermore, it turns out that a block-diagonal matrix and its inverse have exactly the same structure.

adj(A) ⎞ ⎛ (−1)1+1 M11 (−1)2+1 M21 · · · (−1)n+1 Mn1 ⎟ ⎜ ⎜ (−1)1+2 M12 (−1)2+2 M22 · · · (−1)n+2 Mn2 ⎟ ⎟ =⎜ .. .. .. ⎟ ⎜ ⎠ ⎝ . . . Properties of Inverse. Some important properties of the (−1)1+n M1n (−1)2+n M2n · · · (−1)n+n Mnn ⎞ ⎛ inverse [1.1, 8] are given below. The assumption is that C11 C21 · · · Cn1 all listed inverses exist. ⎟ ⎜ ⎜ C12 C22 · · · Cn2 ⎟ −1 −1 =⎜ (1.92) • (A ) = A. .. .. ⎟ ⎟. ⎜ .. • (AB)−1 = B−1 A−1 . ⎝ . . . ⎠ • (AT )−1 = (A−1 )T . C1n C2n · · · Cnn • The inverse of a symmetric matrix is symmetric. Note that each minor Mij (or cofactor Cij ) occupies the • (A p )−1 = (A−1 ) p , where p is a positive integer. ( j, i) position in the adjoint matrix, the opposite of what • det(A−1 ) = 1/ det(A). one would normally expect. Then, the inverse of A is simply defined by

1.5.2 Eigenvalues and Eigenvectors

A

−1

1 = adj(A) . |A|

(1.93)

Example 1.33: Formula for the inverse of a 2 × 2 matrix

Find a formula for the inverse of $ # a11 a12 . A= a21 a22 Solution. Following the procedure outlined above, we

find

The fundamentals of linear algebra are now extended to treat systems of differential equations, which are of particular importance to us since they represent the mathematical models of dynamic systems. In the analysis of such systems, one frequently encounters the eigenvalue problem, solutions of which are eigenvalues and eigenvectors. This knowledge enables the analyst to determine the natural frequencies and responses of systems. Let A be an n × n matrix, v a nonzero n × 1 vector, and λ a number (complex in general). Consider Av = λv

M11 = a22 , M12 = a21 , M21 = a12 , M22 = a11 , Then, A

−1

1 = |A|

#

C11 = a22 , C12 = −a21 , C21 = −a12 , C22 = a11 .

a22 −a12 −a21 a11

$ ,

(1.94)

which is a useful formula for 2 × 2 matrices, allowing us to omit the intermediate steps. Inverses of Special Matrices. If the main diagonal entries are all nonzero, the inverse of a diagonal matrix is again diagonal. The diagonal elements of the inverse are simply the reciprocals of the diagonal elements of

(1.95)

A number λ for which (1.95) has a nontrivial solution (v = 0n×1 ) is called an eigenvalue or characteristic value of matrix A. The corresponding solution v = 0 of (1.95) is the eigenvector or characteristic vector of A corresponding to λ. Eigenvalues, together with eigenvectors form the eigensystem of A. The problem of determining eigenvalues and the corresponding eigenvectors of A, described by (1.95), is called an eigenvalue problem. The trace of a square matrix A = [aij ]n×n , denoted by tr(A), is defined as the sum of the eigenvalues of A. It turns out that tr(A) is also the sum of the diagonal elements of A. A matrix and its transpose have the same eigenvalues. Solving the Eigenvalue Problem Let us consider (1.95), Av = λv. Because equations in this form involve scalars, vectors, and matrices, it is im-

Introduction to Mathematics for Mechanical Engineering

Av − λv = 0n×1 ⇒ (A − λI)v = 0 ,

(1.96)

where we note that every term here is an n × 1 vector. The identity matrix I = In has been inserted so that the two terms in parentheses are compatible; otherwise we would have A − λ, which is meaningless. This equation has a nontrivial solution (v = 0) if and only if the coefficient matrix, A − λI, is singular. That means |A − λI| = 0 .

(1.97)

This is called the characteristic equation of A. The determinant |A − λI| is an nth-degree polynomial in λ and is known as the characteristic polynomial of A whose roots are precisely the eigenvalues of A. Once the eigenvalues have been identified, each eigenvector corresponding to each of the eigenvalues is determined by solving (1.96). Example 1.34: Eigenvalues and eigenvectors

Find the eigenvalues and eigenvectors of # $ −1 −3 A= . 0 2 Solution. To find the eigenvalues of A, we solve the

characteristic equation, |A − λI| = 0      −1 − λ −3  ⇒ =0  0 2−λ  ⇒ (λ + 1)(λ − 2) = 0 ⇒ λ1,2 = −1, 2 . Without losing any information, let us assign λ1 = −1. To find the eigenvector, solve (1.96) with λ = λ1 = −1, λ =−1

1 (A − λ1 I)v1 = 0 ⇒ (A + I)v1 = 0 ,

we apply suitable elementary row operations [1.1] to the augmented matrix to reduce it to # $ 0 1 0 . 0 0 0 The second row suggests that there is a free variable, implying that the two equations contained in (1.99) are linearly dependent. From the first row, we have v21 = 0 so that v21 cannot be the free variable, so v11 must be. In this example, since we already have v21 = 0, then v11 = 0 because otherwise v1 = 0, which is not valid. For simplicity, # $ let v11 = 1, so 1 . 0 Similarly, the eigenvector corresponding to λ2 = 2 can be shown to be v2 = [−1 1]T . The set (v1 , v2 ) is the basis of all eigenvectors of matrix A. v1 =

Special Matrices The eigenvalues of triangular and diagonal matrices are the diagonal entries. The eigenvalues of blocktriangular and diagonal matrices are the eigenvalues of the block matrices along the main diagonal. All eigenvalues of a symmetric matrix are real, while those of a skew-symmetric matrix are either zero or pure imaginary. Generalized Eigenvectors If λk is an eigenvalue of A occurring m k times, then m k is the algebraic multiplicity of λk , denoted by AM(λk ). The maximum number of linearly independent eigenvectors associated with λk is called the geometric multiplicity of λk , GM(λk ). In general, GM(λk ) ≤ AM(λk ). In Example 1.34 the AM and GM of each of the two eigenvalues was 1. When GM(λk ) 0 but, in contrast to the eutectic system, the G(x) curves for the two solid solutions α1 and α2 are shifted to one side of composition relative to the liquid phase L. As for the eutectic system one common tangent line can be applied to the G(x) curves of all three phases at TP and the peritectic reaction is (3.37) α1 → L + α2 ,

which quite naturally explains why peritectic systems likely emerge when two components with substantially different melting points are alloyed. Systems with Intermetallic Phases The opposite type of effect arises when ΔHM < 0 and the atoms like each other within a certain composition range. In such systems (Fig. 3.34) melting will be more difficult in the α2 phase because of its very deep G(x) curve and a maximum melting point may appear. If the attraction between the unlike atoms is very strong and the α2 phase extends as far as the liquid, it may be called an ordered intermetallic phase.

3.2 Microstructure Characterization 3.2.1 Basics The primary characteristic of a material is its integral and percentual chemical composition, that is, e.g., for metals, the chemical elements, for polymer materials the types of polymers and possible reinforcements, and for ceramics the oxides, nitrides or carbides. Starting with the chemical composition, a specific microstructure [3.18] will be generated during the solidification of a melt, the mixing of polymeric components, heat treatment, the manufacturing process (rolling, milling, deep drawing, welding), or during usage (aging, corrosion). As pointed out in detail in Sect. 3.1.2 the (usually three-dimensional) microstructure of materials can consist of several constituents, for example, grains (or crystallites) with different crystallographic orientation (which are separated from each other by grain boundaries, Fig. 3.26) or precipitates, impurities (slags, oxides, sulfides), pores, reinforcement particles, fibres, and others. The constituents of a microstructure are visualized by material-specific preparation and imaging methods. However, for complete characterization of a microstructure (materialography, or more specifically metallography, plastography, ceramography) more methods than microscopic imaging are often necessary. For the interpretation and understanding of a microstructure the knowledge of the presence and nature of crystallinity of the constituting phases is essential. This information is obtained by X-ray diffraction, which is a nonmicroscopic integral method. The information on the local chemical composition, the local crystal structure, and characteristic geometric parameters of the constituents

is investigated by microscopic methods which differ in their generated signals, optical resolution, and contrast mechanism.

3.2.2 Crystal Structure by X-ray Diffraction The first goal in microstructure characterization is to learn which crystalline phases are present in a material. This is achieved mainly by X-ray diffraction (XRD) [3.19, 20], which gives information on the crystal structure of constituents in a microstructure. This is possible by their crystallographic parameters: type of crystal lattice, crystal symmetry, and unit cell dimension (Sect. 3.1). Moreover, information on the perfection of the crystal lattice (number of dislocations), and from this on the degree of plastic deformation, and on the external and residual stresses acting on the lattice are also obtainable. The theory of X-ray diffraction is based on Bragg’s law, which describes how electromagnetic waves of a certain wavelength λ interfere with a regular lattice. At certain angles of incidence (θ) with regard to a set of parallel crystal planes, which are therefore called reflectors, constructive interaction takes place according to nλ = 2dhkl sin θ ,

(3.38)

where n is a positive integer and dhkl represents the interplanar spacing between the crystal planes that cause constructive interaction; λ is the known wavelength of the incident X-ray beam. In XRD the specimen is irradiated by a monochromatic X-ray beam, Cu-KAα or Cr-Kα , which is

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X-ray beam. In this way the orientation distribution of a single reflection, and thus for a single lattice plane, is determined [3.24].

3.2.3 Materialography Materialography is the investigation of the microstructure of materials [3.25]. It includes specimen preparation and imaging of the microstructure, the quantification of the constituents (content, arrangement, size, shape, and orientation), as well as the local chemical and crystallographic characterization of the constituents, if necessary. Specimen Preparation The three-dimensional microstructure of a material is usually deduced from two-dimensional images, which are obtained by sectioning the sample. The resulting specimen is either in bulk form or thin and transparent, depending on the type of material and the goal of investigation. The whole process of specimen preparation, starting with cutting small parts from larger pieces, has to be performed without disturbing the microstructure by mechanical or thermal influences. Small specimens (wire, cross sections of sheet metal) are mounted in a resin using pans which can easily be handled and have the right size for grinding machines. Bulk samples are prepared by grinding and polishing using metallographic machines with rotating wheels. A large number of material-specific abrasives and lubricants are available [3.26]. The selection of the most suitable ones is based on the material’s composition and on the mechanical properties of its constituents. Mechanical polishing is performed using a rotating wheel covered with cloth and small particle abrasives (for final polishing steps with grain size < 1 μm), such as powders of diamond or aluminum oxide, or colloidal silicon dioxide. For further smoothing of the surface electrolytic polishing can be applied, especially for homogeneous, i. e., single phase, materials. The prerequisite of microscopic imaging is a sufficient optical contrast, meaning that neighboring regions must show a certain difference of brightness or color. The contrast (C) is defined as the ratio of intensities I , which can be the intensity of white light (gray values) or the intensities of colors (red, green, and blue)

C=

I1 − I2 , I1

(3.39)

where I2 < I1 . Contrast can already be present after polishing the samples, e.g., if black graphite is present in

50 μm

Fig. 3.36 Grain-boundary etching of an austenitic CrNi

steel; the large number of twins is due to severe plastic deformation; light optical micrograph

a bright matrix of grey cast iron, colored grains in copper alloys and mineralic materials, and contours due to different abrasion of constituents. In most cases, however, the contrast has to be developed by means of chemical or physical etching [3.27]. Chemical etchings

20 μm

Fig. 3.37 Microstructure of a carbon steel (0.35% C),

etched with 3% HNO3 ; light microscopy of a polished and etched metallographic cross-section

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5 mm 5 μm

Fig. 3.38 Microstructure of a welding; macroscopy of an etched specimen

are water-based acidic or basic solutions or complex solutions of salts, sometimes containing organic substances. Grain boundary etching is usually applied to microstructures consisting only of one constituent (Fig. 3.36), where the etching agent reacts preferentially with the more reactive grain boundaries. Large differences in the etching rate of the constituents of a microstructure generate slopes at the grain boundaries between different constituents, which gives also a grain boundary contrast. For some etching agents the ablation depends on the crystallographic orientation of the grains and as a result topographies with different light-scattering capability are developed. If a grain consists of two phases, such as pearlite (consisting of ferrite and cementite), one of them can be selectively etched, leaving a light-scattering topography of pearlite grains, which are dark under the microscope, as compared with the brighter ferrite grains in a carbon steel (Fig. 3.37, compare also Fig. 3.39). Physical etching methods are based on a selective ablation of constituents by a plasma generated in a glow discharge apparatus or by ion beam bombardment, for example in a focused ion beam (FIB) instrument (see later). For light microscopy of polymer materials, transparent specimens are prepared by cutting lamellae, using a microtome with a glass or diamond knife, from the sample. The specimens are some micrometers thick and are positioned between a glass microscope slide and

Fig. 3.39 Scanning electron microscopy (SEM) image of

pearlite in plain carbon steel; secondary electron (SE) image

a cover glass by adding a drop of immersion oil to keep off air bubbles and to increase the refractive index of the interspace. Easily plastic deformable polymers, such as polyethylene, are cut at low temperatures (at −70 ◦ C or lower) with a cryomicrotome. From polymer matrix composites thin transparent specimens are obtained by grinding and polishing small pieces which are glued to a glass strip. Microscopy of the Microstructure For some metallographic samples it is sufficient to image the specimen with no or only little magnification. This macrometallography is used, e.g., for the inspection of the microstructure of welds (Fig. 3.38). In most cases, however, microscopy is necessary to visualize the microstructure. The most commonly used method is reflection light microscopy of bulk specimen. The contrast, as mentioned above, is based on the different reflection capability or color intensities of the constituents. If sufficient contrast cannot be obtained by specimen preparation, other imaging modes can be used, such as light microscopy with polarized light for aluminum and magnesium alloys, or differential interference contrast microscopy (DIC) for refractory metals (Mo, W, V). Inverted microscopes are used for bulk metallographic samples, because they allow easy positioning of the specimen on the microscope stage with the viewed

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surface exactly perpendicular to the optical axis. This is a basic requirement to have all parts of the viewed area in focus. Images are captured by a charge-coupled device (CCD) camera and a computer whereby easy-tohandle software is useful, and should allow calibration, setting scale markers (micron bar), and some interactive distance measurements. Patterns of microscope calibration standards are imaged for the calibration of the magnification of a selected microscope configuration. As a calibration value the pixel size, as micrometer per edge length of square pixels, is stored with the image. A micron bar can be placed permanently into the image if necessary, but one has to be careful if the micrograph is used for automatic image analysis afterwards. In some cases dark-field microscopy, in which the diffuse reflected light is detected instead of the directly reflected light, gives better visibility of small objects. The lateral resolution of light microscopy is 0.25 μm at best (due to the wavelength of visible light). Best values are obtained when a substance with a large refractive index (immersion oil) is placed between the specimen and the objective. For higher resolutions (and magnifications) than are possible with light optical methods electron microscopy is a method widely applied in metallography. In addition, it allows complementary information on the local chemical composition and the crystal structure to be obtained. Scanning electron microscopy (SEM) is used for imaging metallographically prepared surfaces of bulk samples, and transmission electron microscopy (TEM) is used for imaging thin foils which are transparent to electrons. In both instruments, the electrons are emitted from an electron gun, accelerated in an electric field (0.5–25 kV in SEM, and 80–400 kV – in some cases over 1 MV – in TEM) towards the anode and then formed to a small beam (with a diameter of a few nanometer) by means of an electron optical system. High vacuum is necessary all along the electron path to prevent collisions of the electrons with gas molecules. In an SEM [3.28, 29] the specimen, mounted on a multi-axis stage in the specimen chamber, is scanned with the focused electron beam. The emitted secondary electrons (SE) and backscattered electrons (BSE) are registered by detectors which are mounted above the specimen and the signal intensities are stored as digital grey value images. The SE detector is a scintillator– photomultiplier system and for BSE a scintillator or a semiconductor detector can be used. The best resolution is achievable with the SE signal, and can be as good as 1 nm for suitable instrument parameters and specimen constitution. The information

depth is some tens of nanometers for the SE mode. For imaging of very small particles or thin layers, especially if they consist of low-atomic-number elements, the emission depth can be lowered by applying a lower accelerating voltage. With SE, a topography contrast is generated, which is based on the dependency of the SE intensity on the incident angle between the electron beam and the imaged surface area (Fig. 3.39). With BSE a composition contrast image can be obtained, because the intensity of the BSE emission is related to the atomic number of the material. Regions containing higher-atomic-number elements are brighter than those composed of lower-atomic-number elements (Fig. 3.40). Even atomic number differences smaller then unity can result in a contrast, which is in many cases good enough for imaging the microstructure of polished, but unetched, specimens. SEM samples have to be stable under high-vacuum conditions. This is not the case if they contain water or other liquids which can evaporate. Therefore, in some SEMs, fitted with special vacuum devices and detectors, imaging at a pressure of up to 25 mbar is possible by the injection of water into the specimen chamber; this is known as variable-pressure SEM (VPSEM) or environmental SEM (ESEM). The resulting water partial pressure prevents the evaporation of water from the specimen and an alteration of its structure. Cooling the specimen with the aid of a cooling stage to a temper-

10 μm

Fig. 3.40 Atomic number contrast in a SEM BSE image of brass; Pb particles are bright due to their higher atomic number as compared with Cu and Zn

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is protected by a Pt strip, which is deposited before the milling by ion-induced decomposition of a metalorganic Pt compound fed into the specimen chamber through a small tube. Imaging is possible in a FIB by means of secondary ions (SI) and the ion-induced secondary electrons (iiSE), respectively. The latter give both topographical and compositional contrast. Some crystalline materials show good orientation contrast due to the channeling effect [3.32] and the microstructure is visible without etching (Fig. 3.42). Modern instruments combine the functions of SEM and FIB. The SEM mode is used for conventional imaging with electrons, even during ion milling steps, and for charge neutralization. An energy dispersive X-ray spectrometer (EDX) and a camera for electron backscatter diffraction (EBSD) imaging (see later) can be additionally fitted to such an instrument. Thus, the real three-dimensional chemical composition, crystal structure, and microstructure of a sample can be obtained by slice-milling the wall of a cross section in small steps (50 nm to a few microns) and subsequent reconstruction of the microstructure from the resulting EDS and EBSD image series. TEM [3.33] is used for the investigation of microstructural constituents smaller than about 50 nm in the conventional mode (CTEM) or the scanning mode (STEM), whereby a resolution of 0.1 nm can be achieved with dedicated instruments. The specimen has to be electron transparent with a thickness of 20–1000 nm, depending on the electron energy and

Fig. 3.41 Cross-section prepared using a focused ion beam (FIB); Al alloy, edge protected by a Pt strip, iiSE image

Fig. 3.42 Crystal orientation contrast due to the ion chan-

neling effect in Cu; FIB iiSE image

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ature just above the freezing point supports this effect. Imaging electrically nonconductive materials, such as polymers, ceramics, oxides, and mounting resins, is possible in different ways. Either they are coated with a conductive layer (Au, C, Pt, or Cr) by sputtering or evaporation, or a low accelerating voltage is applied (< 2 kV), or imaging is performed under low-vacuum conditions (at least 1 mbar), whereby ions that are generated by collision of electrons with gas atoms prevent the specimen surface from being charged. Cross sections are commonly prepared for microstructural investigation of subsurface regions and of thin surface layers. The edge of the specimen has to be preserved to prevent its rounding and the ablation of thin layers during grinding and polishing. Often resins filled with hard particles are used, or a metal is plated on the sample surface before mounting; chemical deposition of Ni is preferred. A good alternative for the inspection of subsurface regions is cross sectioning with ion beams. Larger areas (up to some millimeters edge length) are cut with broad beams of Ar [3.30]. Target preparation of cross sections is performed using focused ion beam (FIB) instruments [3.31], in which a Ga+ ion beam (0.5–30 kV accelerating voltage, 7 nm diameter) is scanned over the specimen. The ion bombardment results in a milling effect. Preparation is possible at any region of interest at the specimen surface by milling a stair-shaped trench, typically 20 μm wide and deep. The cross section is imaged after the specimen is tilted (Fig. 3.41). The edge of the trench

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Chemical Analysis of Thin Layers Methods suitable for the chemical analysis of thin layers (in the nanometer thickness range), for measuring the concentration profile within such layers, and for interface layers must possess a very small information depth. Layers of interest are, e.g., sputtered or plasma-assisted coatings, corrosion layers, tribological reaction layers, and grain boundaries. Methods most used for the analysis of engineering materials are scanning Auger electron spectroscopy (SAM), X-ray-exited photoelectron spectroscopy (XPS)/ electron spectroscopy for chemical analysis (ESCA), and secondary-ion mass spectroscopy (SIMS) [3.35]. The lateral resolution ranges from some nanometers (SAM, SIMS) to some microns (XPS). Concentration–depth profiles are available during spectroscopy with a resolution of a few nanometers by simultaneous sputtering of the specimen with accelerated ions (O+ , Ar+ , Ga+ , etc.).

with respect to the rolling direction of sheet metal, can influence many properties significantly, such as deformation behavior, corrosion, electrical conductivity, etc. The local crystal structure is obtained by electron diffraction with different resolutions in a TEM (< 1 nm) or SEM (> 20 nm) by applying Bragg’s law (3.38). In a TEM electron diffraction of a single grain gives rise to a point pattern (Fig. 3.46) from which the relevant crystal parameters (crystal structure, symmetry, unit cell dimensions) can be deduced. It is noteworthy here that TEM has the implication that only a few grains or particles can be investigated and that sample preparation may become a difficult and tedious task. In an SEM electron backscatter diffraction (EBSD) [3.37, 38] patterns are registered by a combination of a phosphor screen and a CCD camera fitted to the specimen chamber. In the pattern (Fig. 3.47) each of the so-called Kikuchi bands represents a pair of lattice planes with their width corresponding to the lattice plane spacing. From the EBSD pattern the crystal structure, symmetry, and the crystallographic orientation of a single grain can be calculated using commercial software. This method is also known as orientation imaging microscopy (OIM) [3.38]. Note, that image quality (sharpness) is deteriorated with an increasing number of dislocations within a grain, in other words with the de-

Local Measurement of the Crystal Structure Knowing the crystal structure locally in a microstructure, for example, of a single grain or a specific precipitate is of interest for the following reasons:

1. In cases when the EDX analysis is not able to discriminate between chemically similar phases, determining the crystal structure may support phase identification. 2. Crystallographic orientation of single grains with respect to the specimen coordinates, for example,

Fig. 3.46 Electron diffraction pattern of a Ni alloy obtained in a TEM at 200 kV; the small spots are superlattice peaks stemming from coherent and ordered precipitates embedded in a disordered fcc matrix

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dow) is registered and from that the concentration of this chemical element can be determined along a preselected line. Extending this method to an area of interest yields so-called element mapping (Fig. 3.45). Typically, EDX measurements in a SEM have a lateral and a depth resolution of 0.5 μm for high-atomicnumber elements, and up to 10 μm for low-atomicnumber elements (graphite, polymers), respectively, and relative errors of 3–8%. Better resolution can be obtained if the analysis is performed on thin specimens (≈ 100 nm thick) in both a SEM or a TEM. Elements can be analyzed qualitatively starting with the atomic number of 5 B whereas quantitative results can be obtained for elements starting from 11 Na. Wavelengthdispersive X-ray spectroscopy (WDS, WDX), using one or more crystal spectrometers attached to a SEM, allows the quantification of low-atomic-number elements (B, C, N, and O) and the analysis of trace elements. Because WDX cannot be used in a TEM, EELS is the alternative method of interest here.

3.2 Microstructure Characterization

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pact tension or cylindrical disc (Fig. 3.72). Load line displacement is recorded as a function of applied load. A fatigue precracked test specimen is loaded in tension or bending to induce either: 1. Unstable crack extension (or fracture instability) or 2. Stable crack extension (or stable tearing) The first method is used to determine the value of fracture toughness at the point of instability, while the second method results in a continuous relationship for fracture toughness versus crack extension (called the

R-curve, Fig. 3.73). For R-curve determination, crack extension is also recorded simultaneously by optical or electrical means. The recorded data is then used to evaluate K Ic , JIc or the J–R curve using standard relations. K Ic is independent of the specimen geometry only under plain-strain conditions and this criterion should be assessed carefully. Similar crack growth tests may also be used to evaluate the performance of a material under creep and/or fatigue. Table 3.3 summarizes standards for mechanical testing of materials according to ASTM [3.58].

3.4 Physical Properties While the prime design criterion in most applications in mechanical engineering is mechanical properties (Sect. 3.3), physical properties are instead decisive for most applications as functional materials. As some of these materials are of paramount importance in fields related to mechanical engineering such as microelectronics, mechatronics, and the production, conversion, and distribution of electric power, we will briefly discuss in this section selected properties such as electrical and thermal conductivity with respect to materials in mechanical engineering, i. e., metals, ceramics, glasses, and polymers, as described in more detail in Sect. 3.6. Particularly, a discussion of the broad and still emerging fields of magnetism and superconductivity and semiconducting materials must be omitted here. For in-depth information, the interested reader is referred to the recent version of the Encyclopedia of Magnetic and Superconducting Materials [3.59] and to the Springer Handbook of Condensed Matter and Materials Data [3.1].

3.4.1 Electrical Properties Ohm’s Law and Electrical Conductivity The relation between the voltage U (in Volts, V) and the current I (in Ampères, A) in an electric conductor (often in the form of a wire) is given by (the macroscopic) form of Ohm’s law as U (3.68) R= , I where R is the resistance (in Ohms, Ω) of the material to the current flow and depends critically on the geometry and (intrinsic) properties of the material, therefore

R=ρ

l l = , A σA

(3.69)

where l is the length and A is the cross-section of the conductor; ρ (Ω m) and σ (Ω−1 m−1 ) are the electrical resistivity and electrical conductivity, respectively, being specific for the material under consideration. Combining (3.68) and (3.69) yields j=

V I = σ = σE , A l

(3.70)

with the current density j (A/m2 ) and the electric field strength E (V/m). Alternatively, j is given by the product of the number of charge carriers n, the charge of each carrier q, and the average drift velocity v of the carriers, thus j = nqv .

(3.71)

Setting (3.70) and (3.71) equal yields the microscopic form of Ohm’s law, which is more relevant for materials engineers σ = nq

v = nqμ . E

(3.72)

The term v/E is called the mobility μ (m2 V−1 s−1 ) of the charge carriers. While the charge q of the carriers of the electric current is a constant, one may readily recall from (3.72) that the electrical conductivity of materials can be controlled essentially by two factors, namely: 1. The number of charge carriers n 2. Their mobility μ While electrons are the charge carriers in conductors (metals), semiconductors, and many insulators, ions carry the charge in ionic compounds. Therefore, in pure materials the mobility μ depends critically on the bonding strength and – in addition in ionic compounds – on

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striking similarity between k and the diffusion coefficient D in mass transfer (3.14), where the heat flux Q/A is analogous to the flux of atoms jD . A schematic experimental setup for measuring k is shown in Fig. 3.77, where heat is introduced on one side of a bar- or discshaped sample through a heat source and the change of temperature on the other side is measured as a function of time. The commonly employed technique is called the laser flash method. Values for the thermal conductivity k of selected materials are listed in Table 3.7. A comparison yields that the k values of metals and alloys are usually much larger than those of ceramics, glasses, and polymers. This is due to the fact that in metals and alloys thermal energy is transferred through the movement of (loosely bonded) valence electrons which can be excited with little thermal energy into the conduction band. This leads to a relationship between thermal and electrical conductivity in many metals of the form k = L = 2.3 × 10−8 W Ω K−2 , σT

(3.79)

where L is the Lorentz constant.

In contrast, the prime energy transfer mechanism in ceramics, glasses, and polymers is vibration of lattices and (silicate or molecular polymeric) chains, respectively. Since the electronic contribution is absent, the thermal conductivity in these material classes is usually much lower than that in metals and alloys. An exception to the rule is carbon in its covalently bonded form as diamond, which has the highest k value and therefore commonly serves as a heat sink material. The situation is reversed when the temperature of the materials is increased: the greater lattice and chain vibrations usually lead to an increase of the thermal conductivity in ceramics, glasses, and polymers. In metals and alloys the same mechanism applies in principle, however, the electronic contribution will be lowered, even though the number of carriers is increased, as their mobility is more strongly reduced due to increasing scattering effects. Therefore, thermal conductivity in metals and alloys usually decreases with increasing temperature. Like the electrical conductivity, thermal conductivity in metals and alloys also decreases with increasing number of lattice defects of various dimensionality (Sect. 3.7.2), introduced into the microstructure due to the increased electron scattering.

3.5 Nondestructive Inspection (NDI) Nondestructive inspection (NDI) includes all methods to characterize a material without indenting, extracting samples, reducing its service capabilities or even destroying it. NDI includes defect detection and quantification, called nondestructive testing (NDT), and the assessment of material properties, called nondestructive evaluation (NDE). NDI is an integral part of component design, manufacturing, maintenance, and recycling of components. More and more components are designed following the rule of fitness-for-service. This concept assumes the presence of a maximum undetectable-by-NDI defect. The design has to make sure that this defect does not become critical during a well-defined service period. To keep the safety coefficient at a predefined level the component will be larger or heavier than it should be without the defect. With increasing capabilities of NDI this maximum undetectable defect decreases, allowing the designer to reduce the component weight while keeping the safety coefficient at the same level. In manufacturing, NDI enables the inspection of the whole output while destructive methods rely on a more

or less satisfying quantity of samples being more or less representative for the current party. Besides suitability, the inspection speed is the deciding criterion for NDI application. In maintenance there is no alternative to NDI. According to considerations of fracture mechanics the concept of damage tolerance requires the detection and characterization of all defects starting from an individually defined level. Depending on the findings of NDI the next service period may be shorter or longer. The typical requirement for inspection is a high probability of defect detection accompanied by a tolerable rate of false indications. Modern maintenance concepts include online monitoring of the structural health of a component or the whole construction. All industrial branches use NDI, the best known being flying structures. However, pipelines, heat exchangers, vessels, bridges, and car components are also inspected nondestructively. We will focus on the most important and widely used methods in mechanical engineering but also touch on the promising field of structural health monitoring (SHM).

Materials Science and Engineering

Comparative vacuum monitoring offers an effective method for in situ real-time monitoring of crack initiation and/or propagation. This method measures the differential pressure between fine galleries containing a low vacuum alternating with galleries at atmosphere in a simple manifold (Fig. 3.105). Comparative vacuum monitoring enables the monitoring of the external surfaces of materials for crack initiation, propagation, and corrosion. The galleries can also be embedded between components or within material compounds such as composite fiber. Fiber Bragg gratings measure either the tensile or compressive strain applied along the grating length of an optical fiber (Fig. 3.106). The grating consists of a periodic variation of the index of refraction and provides a linear relationship between the change in wavelength of the reflected light and the strain in the fiber caused by externally applied loads or thermal expansion. To operate multiple sensors along a single optical fiber, the various Bragg gratings should have different Bragg wavelengths in order to differentiate between them.

3.6 Corrosion 3.6.1 Background In general, corrosion is understood to refer to material degradation through reaction with its environment. This has led to a common tendency to assess it in terms of the corrosion products which are formed, i. e., concentrating on the phenomenon rather than its cause. Recent developments in observing and measuring corrosion are increasingly changing this picture. As a result, it is necessary to give up commonly held assumptions in order to understand the nature of corrosion. Among other things, the order of standard potentials of the elements has been overemphasized for some time in terms of its relevance. In contrast to the other topics described in this Chapter, it is hardly possible to describe the corrosion behavior of technical equipment and structural components by means of formulae, tables or guidelines. The reason for this is that their corrosion resistance, and thus corrosion itself, is not just a property of the material, but rather of the system as a whole. The actual corrosion behavior is dependent in equal measure on the metal (as a technical material, taking into account all its properties), the environment (i. e., the concentration,

temperature, flow rate, etc. of the corrosive medium), and the equipment design. In this context, design has to be understood in a broader sense to encompass everything from microscopically small surface roughness, methods of joining parts together, combinations of materials (including crevices resulting from the design) right through to the equipment construction as a whole. As a result, a large number of influencing factors are involved and the possible variations become difficult to comprehend. Thus corrosion behavior always has to be assessed in terms of the character of the complete system, and a so-called corrosion atlas is of little help. Even if the appearance of material damage is similar in more than one case, this does not mean that the causes are the same. In practice, the cumulative experience gained from failures, one’s own technical knowledge, and the corrosion data to be found in the literature always possess validity only over a narrow range of situations. Small deviations in particular parameters (locally reduced concentration of oxygen with stainless steels, shifts in the pH value with aluminum, attainment of a critical temperature level, etc.) can have dramatic consequences. A number of physical factors, such as

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Impedance spectroscopy uses either a single piezoelectric element or a transmitter–receiver combination (Fig. 3.104). The excitation oscillates in a predefined frequency band and the measurement is either the impedance or the complex voltage at the receiver. The frequency-dependent behavior of the measurement indicates defects on or close to the piezoelectric element [3.90]. Both, acousto-ultrasonic and impedance spectroscopy can be used to inspect polymer matrix composites, metal matrix composites, ceramic matrix composites, and even monolithic metallic materials. Eddy-current foil sensors are an alternative technology to the classical eddy-current technique (Sect. 3.5.5) for the detection of surface or hidden cracks. In this method, a copper winding is printed onto a plastic substrate, just like an electronic track. Due to their thin geometry, they can be mounted onto interfaces between structural parts, around bolts, in corners, and hardly accessible regions. Periodic reading of these coils can provide information on structural health.

3.6 Corrosion

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Table 3.8 Energy required to produce metals from the compound state and the standard potential E 0 at 25 ◦ C within the order of potentials of individual elements (SHE = standard hydrogen electrode), see also [3.95] Metal

Metal oxide

Energy required for production (kJ/kg) (kJ/mol)

Standard potential (mV) (SHE, 25 ◦ C)

Al Cr Fe Ni Pb Cu Ag Au

Al2 O3 Cr2 O3 Fe2 O3 NiO PbO Cu2 O Ag2 O Au2 O3

29 200 10 260 6600 3650 920 1180 60 −180

−1660 −740 −440 −250 −130 +340 +790 +1500

mechanical stresses or the uptake of solvents leading to swelling of plastics, also have a strong influence on corrosion behavior. This virtually unlimited spectrum of influencing factors and conditions cannot be accommodated within rigid guidelines. Instead, it is important to become acquainted with the nature of corrosion itself (and with its apparent contradictions) in order to be in a position to assess the risk in a concrete situation, or to clarify specific aspects in cooperation with experts, sometimes by carrying out appropriate experiments. Corrosion can be divided into two main types: 1. Electrochemical corrosion (the atmospheric corrosion of steels, often equated with rusting, is an important example here) 2. Chemical corrosion (high-temperature corrosion, leading to scale formation on steels, is a key area here, but the corrosion of glass, ceramics, and concrete is also primarily chemical in nature)

3.6.2 Electrochemical Corrosion Fundamentals In order to understand corrosion, it is vital first to consider its ultimate cause, i. e., the driving force. Most common metals are produced under the expenditure of large amounts of energy from their compounds, mostly oxides; for example, 6600 kJ/kg are required to produce iron from Fe2 O3 and as much as 29 200 kJ/kg to produce aluminum from Al2 O3 . Further examples are given in Table 3.8. The durability of metals is thus limited by nature, since the material always attempts to attain a condition of lower energy. In general, the conversion back to this state occurs more quickly, and the tendency for this to happen is higher, the further away the metal is from the energetically stable condition. Hu-

788 534 367 213 191 75 6 −37

man efforts to prevent this are limited to influencing the kinetics of the reconversion and delaying the attainment of the thermodynamically stable, nonmetallic state. This can be achieved over an appropriate period of time by means of various measures, the use of coatings being one such example. If a metallic surface comes into contact with water, the process of metal dissolution begins spontaneously. During this process, the metal goes into solution as an ion (Mez+ ) and, depending upon its valence (z), one or more electrons (ze) are set free and remain within the metal. The release of electrons is also known as oxidation. Note, however, that oxidation is not necessarily associated with oxide formation. The originally neutral metal becomes negatively charged via the electrons left behind during this process and thus the dissolution can be described electrically by means of Faraday’s law MIt (3.80) (g) . Δm = zF In (3.80), Δm is the loss of mass, M is the molarity, I is the flow of electrons (current amplitude) as a result of metal dissolution, t is time, and F is Faraday’s constant. If the electrons are not consumed, charge separation rapidly leads to an increase in electrostatic forces, which then prevents further metal dissolution. Thus a so-called dynamic equilibrium is attained, in which the same number of metal ions undergo dissolution as are returned to the metallic state Me ↔ Mez+ + ze− .

(3.81)

In analogy to a plate condenser, the charge in the metal (free electrons) is opposed by an equivalent level of positive charge within the electrolyte (Fig. 3.107). This electrolytic double layer is the location of the potential difference between the metal and the electrolyte, i. e., the electrode potential E. This potential can

Materials Science and Engineering

Erosion Corrosion. If the corrosion of metallic materials is stimulated by erosion processes at the metal surface, the damage mechanism is referred to as erosion corrosion or cavitation. Erosion corrosion can be observed in equipment containing flowing water, or steam, as a result of high flow rates and the presence of solid particles in the medium. The latter damage the microstructure by impacting the metal surface and thus input mechanical energy, which favors corrosion. Cavitation corrosion refers to the situation when gas contained in water is abruptly released, or transformed into steam. The collapse of the resulting bubbles damages the metal surface by releasing soft or brittle components from the microstructure, thus stimulating the corrosion process. Cavitation corrosion is observed, particularly in steam boilers, degassing equipment, pumps, turbines, and valves. Galvanic Corrosion. In practice, an attempt is often

made to explain all corrosion phenomena by reference to the list of standard electrode potentials. However, the theory of galvanic corrosion elements derived from this has been unacceptable scientifically since the investigations of Wagner and Traut in 1938 [3.109]. It should be regarded only as a special case of the more universal theory of mixed potentials. So-called galvanic corrosion occurs, in addition to normal corrosion, if two metals with different electrochemical potentials are connected together electrically. In this case, metal dissolution is accelerated at the less noble material (anode) and the consumption of electrons is favored at the more noble material (cathode). It is impossible to say what will be more or less noble just from the list of standard electrode potentials, since the addition of alloying elements and the formation of protective surface layers result in an entirely different order.

Table 3.11 Influence of area ratio on the corrosion rate of

shiny nickel in contact with chromium in simulated rainwater of pH 2.5 (the less noble chromium, according to the list of standard potentials, forms the cathode here and is nobler than nickel as a result of passive film formation) [3.96] Area ratio Cr/Ni for constant chromium area of 6.3 cm2

Anodic current density of nickel dissolution (mA/cm2 )

Rate of nickel metal loss (mm/year)

1:1 1 : 0.1 1 : 0.01 1 : 0.001 1 : 0.0001 1 : 0.00005

0.0015 0.015 0.15 1.3 6.8 17

0.016 0.16 1.6 13.9 72.8 182

In practice, the contact resistances and the conductivity of the electrolyte are often more important than the potential difference. The area ratio of anode to cathode is also of great importance. Table 3.11 shows the effect of area on the current density using, as an example, passive chromium as the cathode and active nickel as the anode. From this it can be seen that the anode should be as large as possible and the cathode as small as possible. In practice, aluminum sheets (large anode) can be joined together with Monel rivets (70% Ni, 30% Cu) without leading to problems of galvanic corrosion. If one were to join copper sheets with aluminum rivets (small anode), however, the results would be catastrophic. Microbiologically Influenced Corrosion. Corrosion

caused by bacteria has increased in importance over recent years. Thus, damage to materials in the Earth (e.g., pipes and cables) has occurred as a result of the effects of micro-organisms (microbiologically influenced corrosion, MIC). One such example involves corrosion processes as a result of sulfate-reducing bacteria: in the presence of water, these can reduce sulfates and simultaneously lower the pH value with the formation of sulfuric acid. Traces of water are contained even in fuels such as oil and p.t.o., so that microbes can develop and disturb the electrochemical equilibrium. The resulting electrochemical reaction releases oxygen and thus permits electron consumption, leading to notch-like defects at the surface of the material. Although the suspicion is often raised that the bacteria themselves are directly active (iron eaters), this is not true. Instead, the attack is related to digestive products (e.g., acids), as well as to hindered access of the oxygen necessary for repassivation resulting from the formation of microbe colonies

153

Part B 3.6

A corrosive environment leads to the absence of a true fatigue endurance limit. Instead, the fatigue strength can only be stated as a function of time (and accumulated loading cycles). The initial process of crack formation is comparable to that occurring in a noncorrosive environment: elements of the lattice structure become separated from the surface at slip bands as a result of localized plastic deformation. This results in the formation of microscopic notches, leading to stress concentrations, and later to cracks. In a corrosive environment, however, the cracks propagate more quickly. As a rule, they are transgranular in nature. All materials are basically affected and no specific corrosive medium is required. The damage results from the slip processes that are initiated by cyclic loading.

3.6 Corrosion

154

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Applications in Mechanical Engineering

Part B 3.6

Table 3.12 Influence of prior surface preparation on the

lifetime of an alkaline-epoxy-based coating (consisting of one primer, two intermediate, and one final layers) exposed outdoors [3.96] Prior surface and manner of surface preparation

Average lifetime of the coating system

Rust Converted or stabilized rust Scale (firmly adherent) Manual derusting Prepared with mechanical tools Flame descaled Pickled Blasted

1 –2 years 1 –3 years 3 years 4 years 5 years 5 years 8 –10 years 9 –12 years

at the surface of the material. Clarification of the exact corrosion mechanism in an individual case can be complicated, since one is dealing with a living system and the local conditions can vary considerably (aerobic or anaerobic bacteria). Corrosion under Coatings. The corrosion mechanism

under coatings is still somewhat unclear and research is still needed into the effects of a series of influencing factors. As a rule, coatings are hydrophobic, i. e., water droplets do not wet the surface. This is only valid, however, for liquid water, where thousands of molecules band together to form small clusters. Although invisible, water vapor (not to be confused with steam, which also contains clusters) consists of separate molecules and determines the relative air humidity. Such water molecules can diffuse relatively easily through a coating, as can oxygen, carbon dioxide, and sulfur dioxide. If the coating adhesion is poor, cavities (or even rust particles) can exist between the metal surface and the coating and these permit local condensation of water and concentration of metal ions. Together with the water, the oxygen which diffuses into such cavities initiates the electron-consuming process with the formation of OH− ions. These combine with the iron ions which have gone into solution to form rust. Since porous rust has a volume which is six to eight times greater than that of the corroded amount of metal, the coating is pushed away from the surface (formation of blisters). Larger amounts of water then collect in the resulting cavities and accelerate the processes already described. Table 3.12 illustrates the life expectancy as a function of the preparation of the surface prior to coating. This makes it clear that the lifetime can be very different, even for the same coating system. With a firmly

adhering coating, the water molecules still obtain access to the surface very quickly, but the locations at which they can condense remain so small that changes only become visible to the naked eye much later.

3.6.3 Corrosion (Chemical) Basic Principles With chemical corrosion, the material and the medium react directly with one another as a result of an overlap being formed between the electron paths of each of the partners. No increase in free electrons occurs in the metal. The products formed determine the continued evolution of the corrosion. The formation of protective layers is also desirable here, since these layers act as effective barriers to diffusion processes and, thus, hinder further reactions. The extent of corrosion can be determined either gravimetrically (weight change) or metallographically. In contrast to the above, electrochemical corrosion leads to processes which take place in parallel at separate locations. Corrosion products (rust) are formed via secondary reactions, i. e., after the actual corrosion has occurred. The free electrons which are generated offer the possibility of direct measurement of the corrosion processes involved. High-Temperature Corrosion At high temperatures, the corrosion resistance of metallic materials decreases as a result of reactions with gases. The reaction product here is referred to as scale. It is a solid corrosion product which grows at the metal surface and forms a barrier to the reaction partners metal and gas. In order for this layer to grow, at least one of the partners must be mobile within the layer. Many oxides and sulfides contain cavities and vacancies within their microstructure and these locations permit metal cations to be transported towards the outside. Scale formation is particularly important in practice with steels which are exposed to oxygen from the air, or to mixtures of common technical gases with steam or carbon dioxide. At low temperatures (200–400 ◦ C), the initially high rate of reaction rapidly falls to very low values and growth of the protective layer versus time can be described by a logarithmic equation. In general, the resulting thin films (< 0.1 μm), which are often described as tarnish layers, do not represent any significant damage to the material. They can, however, be detrimental upon subsequent exposure to water, i. e., in connection with electrochemical corrosion. At higher temperatures, the initial chemical reaction involves the

158

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Part B 3.7

Applications in Mechanical Engineering

Table 3.13 Properties of some widely used metallic materials, carbon fiber, and high-density polyethylene (HDPE). Note that some of the values given in the table are prone to variation (data compiled from different sources [3.115–117]) Metal

Melting point (◦ C) base metal

Density (g/cm3 )

Yield strength (MPa)

High-carbon steels Stainless steels Cast irons Aluminum 2000 series Titanium alloys Copper alloys Superalloys Magnesium alloys Carbon fiber High-density polyethylene (HDPE)

1536 1536 1147 (eutectic) 660

7.8 7.8 7.4 2.8

350– 1600 150– 500 50– 400 200– 500

45– 205 19– 64 7 – 54 71– 179

210 193 150 70

200 2700 160 1430

1668 1083 1453 650

4.5 8.9 7.9 1.75

400– 1100 75– 520 800 300

89– 244 8 – 58 101 171

100 135 180 45

6020 1330 6500 2800

3650 ∼ 250

1.75 0.95

3500– 5500 26– 33

2000– 3140 27– 35

expansion, cost, and last but not least recyclability. For structural applications in mechanical engineering metallic materials [3.113, 114] are still the most widely used group of materials; their order of importance is Fe, Al, Cu, Ni, and Ti. While the physical properties of materials belonging to different classes are given in Sect. 3.3, in Table 3.13 a comparison of the mechanical properties of some important metals and alloys, carbon fiber, and a polymer is shown.

3.7.1 Iron-Based Materials Iron-based materials are the most widely used metallic materials, mainly because of their relatively inexpensive manufacturing and their enormous flexibility. Accordingly, the properties of Fe-based materials can be varied to a great extent, allowing precise adaptation to specific application requirements ranging from high-strength, high-temperature, and wear-resistant alloys for tools to soft or hard ferromagnetic alloys for applications in the electrical industries. Pure iron, however, is only of minor importance in structural applications since its mechanical properties are simply inadequate. Alloying with carbon leads to the most important groups of constructional alloys, namely: 1. Steels with a carbon content of up to about 2.06% carbon (if not stated otherwise all compositions are giving in wt. %) 2. Cast iron, which practically contains 2.5–5% carbon

Specific yield strength (MPa cm3 /g)

Young’s modulus (GPa)

230– 400 0.7

Cost (US$/t)

30 000 1000

These Fe−C alloys exhibit outstanding properties, including widely variable mechanical properties: yield strengths ranging from 200 MPa to values exceeding 2000 MPa, hot and cold rolling ability, weldability, chip-removing workability, high toughness, high wear resistance, high corrosion resistance, heat resistance, high-temperature resistance, high Young’s modulus, nearly 100% recyclability, and many more. In the following sections the characteristic phases, microstructures, compositions, and applications of iron–carbon alloys are treated with emphasis on the fundamental background. For further reading, references such as [3.1, 118–122] and the online database [3.123] are recommended. The Iron–Carbon Phase Diagram and Relevant Microstructures Fe−C-based materials, in general, can be classified into two main categories:

1. Steels or steel castings, which are forgeable iron– carbon alloys with up to about 2.06% C 2. Gray iron or pig iron with more then 2.06% C (in practice 2.5–5%), which cannot be forged and are brought into final form only by casting These two groups of Fe–C alloys divide the iron– carbon diagram (Fig. 3.126) into two parts, namely an eutectoid (steel) part and an eutectic (cast iron) part. In the thermally stable condition carbon prevails in the

170

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Applications in Mechanical Engineering

Part B 3.7

Table 3.15 SAE–AISI system of designation for carbon

and alloy steels [3.123] Nummerals and digits

Type of steel and nominal alloy content (%)

Carbon steels 10xx a Plain carbon 11xx Resulfurized 12xx Resulfurized and rephosphorized 15xx Plain carbon (max. Mn range 1.00–1.65) Manganese steels 13xx Mn 1.75 Nickel steels 23xx Ni 3.50 25xx Ni 5.00 Nickel–chromium steels 31xx Ni 1.25; CR 0.65 and 0.80 32xx Ni 1.75; Cr 1.07 33xx Ni 3.50; Cr 1.50 and 1.57 34xx Ni 3.00; Cr 0.77 Molybdenum steels 40xx Mo 0.20 and 0.25 44xx Mo 0.40 and 0.52 Chromium–molybdenum steels 41xx CR 0.50, 0.80 and 0.95; Mo 0.12, 0.20, 0.25 and 0.30 Nickel–chromium–molybdenum steels 43xx Ni 1.82; Cr 0.50 and 0.80; Mo 0.25 43BVxx Ni 1.82; Cr 0.50; Mo 0.12 and 0.25; V 0.03 min 47xx Ni 1.05; Cr 0.45; Mo 0.20 and 0.35 81xx Ni 0.30; Cr 0.40; Mo 0.120 86xx Ni 0.55; Cr 0.50; Mo 0.20 87xx Ni 0.55; Cr 0.50; Mo 0.25 88xx Ni 0.55; Cr 0.50; Mo 0.35 93xx Ni 3.25; Cr 1.20; Mo 0.12 94xx Ni 0.45; Cr 0.40; Mo 0.12 97xx Ni 0.55; Cr 0.20; Mo 0.20 98xx Ni 1.00; Cr 0.80; Mo 0.25 Nickel–molybdenum steels 46xx Ni 0.85 and 1.82; Mo 0.20 and 0.25 48xx Ni 3.50; Mo 0.25 Chromium steels 50xx Cr 0.27, 0.40, 0.50 and 0.65 51xx Cr 0.80, 0.87, 0.92, 0.95, 1.00 and 1.05 50xx Cr 0.50; C 1.00 min 51xx Cr 1.02; C 1.00 min 52xx Cr 1.45; C 1.00 min

Table 3.15 (cont.) Nummerals and digits

Type of steel and nominal alloy content (%)

Chomium–vanadium steels 61xx CR 0.60, 0.80 and 0.95 V 0.10 and 0.15 min Tungsten–chromium steels 72xx W 1.75; Cr 0.75 Silicon–manganese steels 92xx Si 1.40 and 2.00; Mn 0.65, 0.82 and 0.85; Cr 0 and 0.65 Boron steels xxBxx B denotes boron steel Leaded steels xxLxx L denotes leaded steel Vanadium steels xxVxx V denotes vanadium steel a The xx in the last two digits of these designations indicates that the carbon content (in hundredths of a percent) is to be inserted

•

carbides are quite stable, they may not dissolve in austenite and can therefore have adverse effects on hardenability. It is used as a stabilizer in corrosionresistant steels. Class 4. These elements contract the γ -phase field. This is observed when carbide-forming elements such as tantalum, niobium, and zirconium are present. Boron also belongs to this class of alloying additions. Zirconium is primary used in so-called high-strength low-alloy (HSLA) steels to improve their hot-rolling properties.

Classification and Designations. A variety of steel classification systems are in use; they subdivide, for example, with regard to chemical composition, application area, required strength level, microstructure, manufacturing methods, finishing method or the product form (a comprehensive comparison of steels standards is given in [3.127, 128]). Chemical composition is, however, by far the most widely used basis for classification and/or designation of steels. The most commonly used system of designation is those of the American Iron and Steel Institute (AISI) and the Society of Automotive Engineers (SAE), which are based upon a four- or five-digit number, where the first two digits refer to the main alloying elements and the latter two or three digits give the carbon content in wt. %.

Materials Science and Engineering

3.7 Materials in Mechanical Engineering

D00001 – D99999 F00001 – F99999 G00001 – G99999 H00001 – H99999 J00001 – J99999 K00001 – K99999 S00001 – S99999 T00001 – T99999

Steels with specified mechanical properties Cast irons AISI and SAE carbon and alloy steels (except tool steels) AISI and SAE H-steels Cast steels (except tool steels) Miscellaneous steels and ferrous alloys Heat- and corrosion-resistant steels (stainless), valve steels, iron-based superalloys Tool steels, wrought and cast

The designation 1020 according SEA–AISI is used, for example, for a carbon steel with nominally 0.2 wt. % C, and the steel 10120 according to SEA– AISI contains 1.2 wt. % C. The various grades of carbon and alloy steels are given in Table 3.15. The unified numbering system (UNS) for metals and alloys is being used with increasing frequency. It has been developed by ASTM and SAE and other technical societies, trade associations, individual users and producers of metals and alloys, and US government agencies. The system helps to avoid confusion, preventing the use of more than one identification number for the same metal or alloy. Each UNS designation consists of a single-letter prefix followed by five digits. The prefix usually indicates the family class of metals: for example, T for tool steel, S for stainless steel, and F for cast irons, while G is used for carbon and alloy steels. Existing designation systems, such as the AISI– SAE system were incorporated into the UNS system wherever feasible. More information on the UNS system and an in-depth description can be found in SAE J1086 and ASTM E 527. Table 3.16 gives an overview of the main groups of UNS designations for iron-based materials. The American Society for Testing and Materials (ASTM) standard contains full specifications of specific products, such as A 574 for alloy steel socket-head cap screws, and is oriented towards the performance of the fabricated end product. Theses commonly used steels are not initially included in the SAE–AISI designations. From a user’s viewpoint steels may generally be divided into two main categories, namely standard steels and tool steels. It is useful to further subdivide standard steels according to their chemical composition into three major groups: 1. Carbon steels 2. Alloy steels 3. Stainless steels

Carbon Steels. Carbon steels contain less than 1.65%

manganese, 0.6% silicon, and 0.6% copper. According to the SAE standard J142 General Characteristics and Heat Treatments of Steels plain carbon steels of the 10xx and 15xx series in Table 3.15 are divided into four groups [3.125]:

•

•

•

•

Group I steels with a carbon content of less than 0.15% provide enhanced cold formability and drawability. These steels are therefore used as coldrolled sheets in automobile panels and appliances and are suitable for welding and brazing. It should however be noted that these alloys are susceptible to grain growth upon annealing after cold working and, as a consequence, exhibit a tendency to embrittlement (strain age-embrittlement). Group II steels with carbon contents of 0.15–0.3% show increased strength and hardness and are less suitable for cold forming. The steels are applicable for carburizing or case hardening. As shown above, increasing manganese content supports the hardenability of the core and case, and intermediate manganese levels (0.6–1.0%) are preferential for machining. Carburized plain carbon steels are used for parts which require a hard wear-resistant surface and a soft core, for example, small shafts, plungers, and lightly loaded gears. Group III steels with medium carbon content of 0.3% to nearly 0.55% can be directly hardened by induction or flame hardening or by cold working. These steels are found in automotive applications and can be used for forgings and for parts which are machined from bar stock. Group IV steels with high carbon levels of 0.55% to nearly 1.0% offer improved wear characteristics and high yield strengths and are generally heat treated before use. Since cold-forming methods are not practical for this group of alloys, application parts such as flat stampings and springs are coiled from small-diameter wire. With their good wearing

Part B 3.7

Table 3.16 Main groups of UNS designations for iron-based materials

171

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Applications in Mechanical Engineering

Table 3.17 Chemical composition and mechanical properties in the as-rolled, normalized, annealed, and quenched-and-tempered condition of some carbon steels [3.125] SAE –AISI number

Cast or heat chemical ranges and limits (wt.%) C

Mn

Pmax

Smax

1020

0.17 –0.23

0.3–0.6

0.04

1040

0.36 –0.44

0.6–0.9

0.04

1095

1137

0.9 – 1.04

0.32 –0.39

0.3–0.5

1.35–1.65

0.04

0.04

Treatment

Austenitizing/ tempering temperature (◦ C)

0.05

As rolled Normalized Annealed

– 870 870

0.05

As rolled Normalized Annealed

0.05

0.08 –0.13

Yield strength (MPa)

Elongation (%)

448.2 441.3 394.7

330.9 346.5 294.8

36.0 35.8 36.5

– 900 790

620.5 589.5 518.8

413.7 374.0 353.4

25.0 28.0 30.2

Quenched + Tempered

205 650

779 634

593 434

19 29

As rolled Normalized Annealed

– 900 790

965.3 1013.5 656.7

572.3 499.9 379.2

9.0 9.5 13.0

Quenched + Tempered

205 650

1289 896

827 552

10 21

As rolled Normalized Annealed

– 900 790

379.2 396.4 344.7

28.0 22.5 26.8

Quenched + Tempered

205 650

938 483

5 28

properties typical applications are found in the farm implement industry as plow beams, plow shares, scraper blades, discs, mower knives, and harrow teeth. The so-called free-machining grades are either resulferized (group 11xx steels) or resulferized and rephosphorized carbon steels (group 12xx). These additives enhance their machining characteristics and lower machining costs. Chemical compositions as well as the mechanical properties of some carbon steels are given in Table 3.17. Alloy Steels. Alloy steels constitute a category of fer-

rous metals that exceed the element limits for carbon steels. They contain elements not found in carbon steels such as nickel, molybdenum, chromium (up to 3.99%), cobalt, etc.. The primary function of the alloying elements is to increase the hardenability and to optimize the mechanical properties such as toughness after the final heat treatment. Table 3.18 summarizes the mechanical properties of selected alloy steels in the normalized, annealed, and quenched-and-tempered condition. In the following the alloy steels are divided

Tensile strength (MPa)

627.4 668.8 584.7 1082 655

into five major groups according to their application area [3.125]. Structural steels according to the SAE–AISI system include carburized steel grades, through-hardening grades, and nitriding grades. Carburizing grades with low alloying combinations such as SAE–AISI 4023 or 4118 have better core properties than plain carbon steels and are hardenable in oil in small cross-sections, resulting in less distortion compared with water-quenched alloys. These alloys are applied as cam shafts, wrist pins, clutch fingers, and other automotive parts. For applications requiring higher core and case hardness such as for automotive gears, universal joints, small hand tools, piston pins, bearings, etc. higher-alloy carburizing steels such as Ni−Mo (SAE–AISI 4620), plain Cr (SAE–AISI 5120) or Ni−Cr−Mo (SAE–AISI 8620) steels are used. Aircraft engine parts, truck transmissions and differentials, rotary rock-bit cutters, and large antifriction bearings are made from high-alloy steels as SAE–AISI 4820 and 9310. Through-hardening grades in principle contain higher carbon levels than carburized grades. In this group the lower-alloy steels are used for applications

3.7 Materials in Mechanical Engineering

173

Table 3.18 Mechanical properties of selected alloy steels in the normalized, annealed and quenched-and-tempered condi-

Part B 3.7

Materials Science and Engineering

tion [3.125] SAE–AISI number

Treatment

Austenitizing temperature (◦ C)

Tempering temperature (◦ C)

1340

Normalized Annealed

870 800

– –

Quenched + Tempered

– –

205 650

Normalized Annealed

870 815

– –

Quenched + Tempered

– –

– –

Normalized Annealed

870 865

– –

Quenched + Tempered

– –

Normalized Annealed

3140

4130 (w)

4140

4150

4320

4340

4620

4820

5046

Tensile strength (MPa)

Yield strength (MPa)

Elongation (%)

836 703

558 436

22 26

1806 800

1593 621

11 22

892 690

600 423

20 24

– –

– –

– –

669 560

436 361

26 28

205 650

1627 814

1462 703

10 22

870 815

– –

1020 655

655 417

18 26

Quenched + Tempered

– –

205 650

1772 758

1641 655

8 22

Normalized Annealed

870 815

– –

1155 730

734 379

12 20

Quenched + Tempered

– –

205 650

1931 958

1724 841

10 19

Normalized Annealed

895 850

– –

793 579

464 610

21 29

Quenched + Tempered

– –

– –

– –

Normalized Annealed

870 810

– –

1279 745

862 472

12 22

Quenched + Tempered

– –

205 650

1875 965

1675 855

10 19

Normalized Annealed

900 855

– –

574 512

366 372

29 31

Quenched + Tempered

– –

– –

Normalized Annealed

860 815

– –

Quenched + Tempered

– –

– –

– –

– –

– –

Normalized Annealed

– –

– –

– –

– –

– –

Quenched + Tempered

– –

205 650

1744 786

1407 655

9 24

– –

– –

– – 750 681

485 464

– –

– – 24 22

174

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Part B 3.7

Applications in Mechanical Engineering

Table 3.18 (cont.) SAE–AISI number

Treatment

Austenitizing temperature (◦ C)

Tempering temperature (◦ C)

Tensile strength (MPa)

Yield strength (MPa)

Elongation (%)

5140

Normalized Annealed Quenched + Tempered

870 830 – –

– – 205 650

793 572 1793 758

472 293 1641 662

22.7 29 9 25

5160

Normalized Annealed

855 815

– –

957 723

531 276

18 17

Quenched + Tempered

– –

205 650

2220 896

1793 800

4 20

Normalized Annealed

870 815

– –

940 667

616 412

22 23

Quenched + Tempered

– –

205 650

1931 945

1689 841

8 17

Normalized Annealed

870 845

– –

650 564

430 372

Quenched + Tempered

– –

205 650

1641 772

1503 689

9 23

Normalized Annealed

870 815

– –

929 695

607 416

16 22

Quenched + Tempered

– –

205 650

1999 986

1655 903

10 20

Normalized Annealed

900 845

– –

933 774

579 486

20 22

Quenched + Tempered

– –

205 650

2103 993

2048 814

1 20

Normalized Annealed

890 845

– –

907 820

571 440

19 17

Quenched + Tempered

– –

– –

6150

8630

8740

9255

9310

in small sections or in larger sections that may not have optimal properties but allow weight savings due to the higher strength of the alloys. Typical examples are manganese steels (SAE–AISI 1330–45), which are used for high-strength bolts, molybdenum steels (SAE–AISI 4037–4047), and chromium steels (SAE–AISI 5130– 50), which are used for automotive steering parts, and low-Ni−Cr−Mo steels (SAE–AISI 8630–50), which are used for small machinery axles and shafts. Heavy aircraft or truck parts or ordnance materials require higher-alloy structural steels, such as SAE–AISI 3430 or 86B45. There are several constructional alloy steels which are used for specialized applications; for example, SAE–AISI 52100 steels are used almost exclusively for ball-bearing applications and the chromium steels

– –

– –

24 29.0

– –

SAE–AISI 5150 and 5160 were developed for spring steel applications. Steels that belong to the nitriding grades are in most cases either medium-carbon and chromium-containing low-alloy steels, which are covered by the SAE–AISI (for example, 4100, 4300, 5100, 6100, 8600, 9300, and 9800 group) or Al-containing (up to 1%) low-alloy steels, which are not described by SAE–AISI designations but have simple names such as “Nitralloy”. Typical applications for nitride grades include gears designed for low contact stresses, spindles, seal rings, and pins. Low-carbon quenched-and-tempered steels typically contain less than 0.25% C and less than 5% alloy additions. Economical points of view have driven the

Materials Science and Engineering

3.7 Materials in Mechanical Engineering

ASTM specification a A 242

Title

Alloying elements b

Available mill forms

Special characteristics

Intended uses

High-strength Cr, Cu, N, Plate, bar, and shapes Atmospheric-corrosion Structural members in low-alloy Ni, Si, Ti, V, ≤ 100 mm in thickness resistance four times welted, bolted or riveted structural steel Zr of carbon steel construction A 572 High-strength Nb, V, N Plate, bar, and sheet piling Yield strength of 290 to Welded, bolded, or low-alloy ≤ 150 mm in thickness 450 MPa in six grades riveted structures, but niobiummany bolted or riveted vanadium steels bridges and buildings of structural quality A 588 High-strength Nb, V, Cr, Plate, bar, and shapes Atmospheric-corrosion Welded, bolded, or riveted low-alloy strucNi, Mo, Cu, ≤ 200 mm in thickness resistance four times of structures, but primarily tural steel with Si, Ti, Zr carbon steel; nine grades welded bridges and build345 MPa miniof similar strength ings in which weight mum yield point savings or added durability ≤ 100 mm in is important thickness A 606 Steel sheet Not specified Hot-rolled and cold-rolled Atmospheric-corrosion Structural and miscellaand strip hotsheet and strip twice that of carbon steel neous purposes for which rolled steel and (type 2) or four times of weight savings or added cold-rolled, carbon steel (type 4) durability is important high-strength low-alloy with improved corrosion resistance A 607 Steel sheet and Nb, V, N, Cu Hot-rolled and cold-rolled Atmospheric-corrosion Structural and miscellastrip hot-rolled sheet and strip twice that of carbon steel, neous purposes for which steel and coldbut only when copper greater strength or weight rolled, highcontent is specified; yield savings are important strength lowstrength of 310 to 485 MPa alloy niobium in six grades and/or vanadium A 618 Hot formed Nb, V, Si, Cu Square, rectangular round Three grades of similar General structural purwelded and seamand special-shape struc- yield strength; may be pur- poses include welded, less high-strength tural welded or seamless chased with atmospheric- bolted or riveted bridges low-alloy structubing corrosion resistance twice and buildings tural tubing that of carbon steel A 633 Normalized Nb, V, Cr, Plate, bar, and shapes Enhanced notch tough- Welded, bolted or reveted high-strength Ni, Mo, Cu, ≤ 150 mm in thickness ness; yield strenth of 290 structures for service at low-alloy N, Si to temperatures at or above structural steel 415 MPa in five grades −45 ◦ C A 656 High-strength V, Al, N, Ti, Plate, normally ≤ 16 mm Yield strength of 552 MPa Truck frames, brackets, low-alloy, hot Si in thickness crane booms, mill cars rolled structural and other applications for vanadiumwhich weight savings are alluminumimportant nitrogen and titaniumaluminum steels a For grades and mechanical properties b In addition to carbon manganese, phosphorus, and sulfur. A given grade may contain one or more of the listed elements, but not necessarily all of them; for specified compositional limits c Obtained by producing killed steel, made to fine-grain practice, and with microalloying elements such as niobium, vanadium, titanium, and zirconium in the composition

Part B 3.7

Table 3.19 Characteristics and uses of HSLA steels according to ASTM standards [3.125]

175

176

Part B

Part B 3.7

Applications in Mechanical Engineering

Table 3.19 (cont.) ASTM specification a

Title

Alloying elements b

Available mill forms

Special characteristics

Intended uses

A 690

High-strength low-alloy steel H-piles and sheet piling

Ni, Cu, Si

Structural-quality H-pills and sheet piling

A 709, grade 50 and 50 W

Structural steel

V, Nb, N, Cr, Ni, Mo

All structural shape groups and plate ≤ 100 mm thickness Pipe with nominal pipesize diameters of 13 to 660 mm

Corrosion resistance two to three times greater than that of carbon steel in the splash zone of marine structures Minimum yield strength of 345 MPa, grade 50 W is a weathering steel Minimum yield strength of ≤ 345 MPa and corrosion resistance two or four times that of carbon steel Improved formability c compared to a A 606 and A 607; yield strength of 345 to 550 MPa in four grades

Dock walls sea walls Bulkheads, excavation and similar structures exposed to seawater Bridges

A 714

High-strength V, Ni, Cr, Piping low-alloy welded Mo, Cu, Nb and seamless steel pipe A 715 Steel sheet and Nb, V, Cr, Hot-rolled sheet and strip Structural and miscelstrip hot-rolled, Mo, N, Ti, laneous applications for high-strength low Zr, B which high strength, alloy with imweight savings, improved proved formabilformability and good ity weldability are important A 808 High-strength V, Nb Hot-rolled plate ≤ 65 mm Charpy V-noth impact Railway tank cars low-alloy steel in thickness energies of 40– 60 J with improved (40– 60 ft lfb) at −45 ◦ C notch toughness A 812 High-strength V, Nb Steel sheet in coil form Yield strength of Welded layered pressure low-alloy steel 450–550 MPa vessels A 841 Plate produced by V, Nb, Cr, Plates ≤ 100 mm in thickYield strength of Welded pressure vessels thermomechanMo, Ni ness 310–345 MPa ical controlled processes A 847 Cold-formed, Cu, Cr, Ni, Welded rubbing with Minimum yield strength Round, square, or spewelded and seam- Si, V, Ti, Zr, maximum periphery of ≤ 345 MPa with cially shaped structural less high-strength Nb 1625 mm and wall thickatmospheric-corrosion tubing for welded, riveted low-alloy strucness of 16 mm or seamless twice that of carbon steel or bolted construction of tural rubbing with tubing with maximum pebridges and buildings improved atmosriphery of 810 mm and pheric corrosion wall thickness of 13 mm resistance A 860 High-strength Cu, Cr, Ni, Normalized or quenchedMinimum yield strength High-pressure gas and oil butt-welding fitMo, V, Nb, and-tempered wrought fit≤ 485 MPa transmission lines tings of wrought Ti tings high-strength low-alloy steel A 871 High-strength V, Nb, Ti, As-rolled plate ≤ 35 mm Atmospheric-corrosion re- Tubular structures low-alloy steel Cu, Mo, Cr thickness sistance four times that of and poles with atmospheric carbon structural steel corrosion resistance a For grades and mechanical properties b In addition to carbon manganese, phosphorus, and sulfur. A given grade may contain one or more of the listed elements, but not necessarily all of them; for specified compositional limits c Obtained by producing killed steel, made to fine-grain practice, and with microalloying elements such as niobium, vanadium, titanium, and zirconium in the composition

development of these steels and the choice of alloying additions accordingly. With their low carbon content

these steels have high ductility and notch toughness and are suitable for welding while still offering high

Materials Science and Engineering

3.7 Materials in Mechanical Engineering

AISI–SAE grade

Nominal composition (wt.%) C Cr Ni

Austenitic grades 201 0.15 304 0.08

17 19

5 10

304L 0.03 316 0.08 321 0.08 347 0.08 Ferritic grades 430 0.12 442 0.12 Martensitic grades 416 0.15

19 17 18 18

10 12 10 11

431

0.2

16

440C

1.1

17

Condition Others 6.5%Mn

2.5%Mo 0.4%Ti 0.8%Nb

17 20 13

0.6%Mo 2

Nonstandard (precipitation-hardened) grades 17– 4 0.07 17 4 17– 7 0.09 17 7

0.7%Mo

0.4%Nb 1.0%Al

yield strengths (approximately 340–900 MPa). In addition, they have two to six times higher corrosion resistance than that of plain carbon steels. Depending on the final treatment these steels could be either martensitic, bainitic, and, in some compositions, ferritic. These steels are not covered by SAE–AISI designations but most of them can, however, be find in ASTM specifications such as A514, A517, and A543. Thanks to the high strength and toughness values these steels can be applied at lower final costs than plain carbon steels, which leads to a wide variety of applications. They are used as major members of large steel constructions, pressure valves, earth-moving, and mining equipment. Ultrahigh-strength steels are a group of alloy steels with yield strengths in excess of 1300 MPa; some have plain-strain fracture toughness levels exceeding √ 100 MPa m. Some of these steels are included in the SAE–AISI designation system and have medium carbon contents with low-alloy additions. Examples are steels in the SAE–AISI 4130 series, the higher-strength 4140, and the deeper hardening higher-strength 4340 steels. Starting form the 4340 alloy series numerous modifications have been developed. Addition of silicon, for example, reduces the sensitivity to embrittlement on

Yield strength (MPa)

Tensile strength (MPa)

Elongation (%)

Annealed Annealed Cold-worked Annealed Annealed Annealed Annealed

310 205 965 205 205 240 240

650 520 1275 520 520 585 620

40 30 9 30 30 55 50

Annealed Annealed

205 275

450 520

22 20

Quenched and tempered Quenched and tempered Quenched and tempered

965

1240

18

1035

1380

16

1895

1965

2

1170 1585

1310 1650

10 6

Age-hardened Age-hardened

tempering at low temperatures (required to keep high strength levels). Addition of vanadium leads to grain refinement, which improves the strength and toughness of the material. Medium-carbon alloys can be welded in the annealed or normalized condition, requiring a further heat treatment to retrieve the desired strength. If high fracture toughness as well as high strength is specifically desired, as for aircraft structural components, pressure vessels, rotor shafts for metal-forming equipment, drop hammer rods, and high-strength shockabsorbing automotive parts, high nickel (7–10.5%) and Co (4.25–14.50%) contents are used as primary alloying elements. While √ offering a plane-strain fracture toughness of 100 MPa m the HP-9-4-30 steel can have a tensile strength as high as 1650 MPa. Furthermore, the steel can be hardened to martensite in sections up to 150 mm thick. The AF 1410 steel (developed by the US Air Force) has an ultimate tensile strength (UTS) of √ 1615 MPa and a K IC value of 154 MPa m. The group of alloy steels for elevated- or lowtemperature applications includes two different alloying systems. For high-temperature applications chromium–molybdenum steels offer a good combination of oxidation and corrosion resistance (provided by

Part B 3.7

Table 3.20 Compositions and properties of some widely used stainless steels [3.129]

177

178

Part B

Applications in Mechanical Engineering

Part B 3.7

the chromium content of up to 9%) on the one hand and high strength at elevated temperatures (provided by the molybdenum content of 0.5–1.0%) on the other. These steels can be applied at temperatures up to 650 ◦ C for pressure vessels and piping in the oil and gas industries and in fossil-fuel and nuclear power plants. In lowtemperature service applications such as storage tanks for liquid hydrocarbon gases and structures and machinery design for use in cold regions, ferritic steels with high nickel content (approximately 2–9%) are typically used. Another important category of alloy steels are the high-strength low-alloy steels (HSLA). HSLA steels, or microalloyed steels, are designed to meet specific mechanical properties rather than a chemical composition. So the chemical composition can vary for different end-product thicknesses with still retaining specific mechanical properties. The low carbon content of these steels (0.05–0.25%) allows good formability and excellent weldability. Further alloying elements are added to meet the application requirements (Table 3.19), resulting in a division into six categories, as follows:

• •

• • • •

Weathering steels, where small amounts of copper and phosphorous are added to improve atmospheric corrosion resistance Microalloyed ferritic–pearlitic steels, with small amounts (less than 0.1%) of carbide-forming elements such as niobium, vanadium or titanium which enable precipitation strengthening and grain refinement As-rolled pearlitic steels, with high strength, toughness, formability, and weldability, which have carbon, manganese, and further additions Acicular ferrite (low-carbon bainite) steels (less than 0.08% C), which offer an excellent combination of high yield strength, weldability, formability, and good toughness Dual-phase steels, with martensitic portions finely dispersed in a ferritic matrix. These steels have high tensile strength and sufficient toughness Inclusion-shape-controlled steels, in which the shape of sulfide is changed from elongated stringers to small, dispersed, near-spherical globules to improve ductility and toughness; elements which are suitable are, e.g., Ca, Zr, and Ti

The allocation to a specific group is not rigorous; many of these steels have properties which would also allow allocation to other groups mentioned.

Stainless steels. Stainless steels in general contain at

least 12% chromium, which forms a thin protection layer at the surface (Cr−Fe−oxide) when exposed to air [3.129]. As shown above, chromium stabilizes the ferrite to remain stable up to the melting point, presuming, however, a low carbon content. Stainless steels can be differentiated depending on their crystal structure or the acting strengthening mechanisms according to Table 3.20. Ferritic stainless steels are relatively inexpensive and contain as much as 30% chromium with typically less than 0.12% C. They show good strength and intermediate ductility. Martensitic stainless steels typically contain less than 17% chromium to contract the austenitic region not too strongly but have a higher C content of up to 1.0%. These alloys are used for high-quality knifes, ball bearings or fittings. Austenitic stainless steels are formed by the addition of nickel, offer high ductility, and are intrinsically not ferromagnetic. These alloys are well suited for hightemperature applications because of their high creep resistance and, thanks to their high toughness at low temperatures, for cryogenic service as well. Precipitation-strengthened stainless steels contain additions such as Al, Nb or Ta, which form precipitates such as Ni3 Al during heat treatment and can have very high strength levels. Stainless steels with duplex microstructure consist of about 50% ferrite and austenite each. They show an ideal combination of strength, toughness, corrosion resistance, formability, and weldability, which no other stainless steel can supply. Tool steels. Tool steels are made to meet special quality requirements, primarily due to their use in manufacturing processes as well as for machining metals, woods, and plastics [3.130]. Some examples are cutting tools, dies for casting or forming, and gages for dimensional tolerance measurements. Tool steels are very clean ingot-cast wrought products with medium (minimum 0.35%) to high carbon content and high alloy (up to 25%) contents, making them extremely expensive. They must withstand temperatures up to 600 ◦ C and should in addition have the following properties:

• • •

Generally a high hardness to resist deformation. Resistance to wear for economical tool life, which depends directly on hardness; this can be increased by alloying with carbide-forming elements such as W and Cr. Dimensional stability. Dimensional changes of tools can be caused by microstructural alteration, by

0.26–0.36 0.25–0.45

0.65-0.8 1.5–1.6

0.78–0.88 0.78–0.88 1.0–1.1 0.84–0.94

Tungsten high-speed steels H21 T20821 H23 T20823

Tungsten high-speed steels T1 T12001 T15 T12015

Molybdenum high-speed steels M1 T11301 T11302 M2 M3 T11313 M10 T11310

3.5 – 4.0 3.75– 4.5 3.75– 4.5 3.75– 4.5

3.75–4.5 3.75–5

3.0 – 3.75 11.0 – 12.75

4.75– 5.5 4.75– 5.5 4.0 – 4.75

0.30–0.45 0.32–0.45 0.32–0.45

Chromium hot-work steels H12 T20812 H13 T20813 H19 T20819

0.15– 0.5 0.15– 0.4

11– 13 11– 13 11– 13

0.4 – 0.6 0.5 max

1.00–1.80

High carbon high-chromium cold-work steels D2 T30402 1.40–1.60 D3 T30403 2.00–2.35 D4 T30404 2.05–2.40

0.8 – 1.2 0.8 – 1.2 0.2 – 0.5

0.15– 1.2 0.9 – 1.2

4.75– 5.5 0.9 – 1.2

1.0–1.4 1.4–1.8

0.1 – 0.4 0.3 – 0.5

Air-hardening medium-alloy cold-work tool steels A2 T30102 0.95–1.05 1.00 max A6 T30106 0.65–0.75 1.8–2.5

Shock-resisting tool steels S1 T41901 0.4–0.55 S2 T41902 0.4–0.55 Oil-hardening cold-work tool steels O1 T31501 0.85–1.00 T31502 0.85–0.95 O2

0.7–1.5 0.85–1.5

1 – 1.35 1.75 –2.2 2.25 –2.75 1.8 – 2.2

0.9 – 1.3 4.5 – 5.25

0.3 – 0.6 0.75 –1.25

0.5 max 0.8 – 1.2 1.75 –2.2

1.1 max 1.0 max 1.0 max

0.1 max 0.15– 0.35

1.4 – 2.1 5.5 – 6.75 5.5 – 6.75

17.25–18.75 11.75–13.0

8.5 – 10.0 11 –12.75

4.0 – 5.25

1.0 – 1.7

0.9 – 1.4 0.9 – 1.4

0.4 – 0.6

1.50–3.00

8.2–9.2 4.5–5.5 4.75–6.5 7.75–8.5

1.0 max

1.25– 1.75 1.1 – 1.75 0.3 – 0.55

0.7 – 1.2

0.7 – 1.2

0.5 max 0.30–0.60

Composition in % (with emphasis to show differences between steels belonging to each group) C Mn Si Cr V W Mo

4.75– 5.25

4.0 – 4.5

Co

Lower cost than T-type tools

Original highspeed cutting steel, most wear-resistant grade

Hot extrusion dies for brass, nickel, and steel, hotforging dies

Al or Mg extrusion dies, die-casting dies, mandrels, hot shears, forging dies

Uses under 482 ◦ C, gages, long-run forming and blanking dies

Thread rolling and slitting dies, intricate die shapes

Short-run coldforming dies, cutting tools

Chisels, hammers, rivet sets, etc.

Cold-heading dies, woodworking tools, etc.

Typical uses

3.7 Materials in Mechanical Engineering

Table 3.21 Chemical composition and usage of selected tool steels [3.129]

Part B 3.7

Designation AISI-SAE UNS no. Water-hardening grades W1 T72301 W2 T72302

Materials Science and Engineering 179

182

Part B

Applications in Mechanical Engineering

Part B 3.7

Table 3.22 Mechanical properties of forged steel, pearlitic ductile iron, and ADI [3.134] Mechanical property

Forged steel

Material Pearlitic ductile iron

Grade 150/100/7 ADI

Tensile strength (MPa) Yield strength (MPa) Elongation (%) Brinnel hardness Impact strength (ft-lb) (J)

790 520 10 262 130

690 480 3 262 40

1100 830 10 286 120

the material has a lower strength compared with the pearlitic gray cast iron. Depending on the cooling rate a mixture of ferrite (surrounding the graphite flakes) and pearlite may be formed as well. The flake-type shape of the graphite in gray cast iron leads to generally brittle behavior. Furthermore, the impact strength of gray cast iron is low and it does not have a distinct yield point. On the other hand, excellent damping against vibrations, excellent wear resistance, and acceptable fatigue resistance are desirable properties of gray cast iron. Typical applications are engine blocks, gears, flywheels, brake discs and drums, and machine bases. In ductile iron the form of the graphite is nodular or spheroidal instead of flake type. This is achieved by the addition of trace amounts of Mg and/or Ce which react with sulfur and oxygen. However, in ductile iron the impurity level has to be controlled more precisely than in gray cast iron since it affects nodule formation. Ductile cast iron exhibits improved stiffness and shock resistance. It has good machinability and fatigue strength as well as high modulus of elasticity, yield strength, wear resistance, and ductility. Damping capacity and thermal conductivity are lower than in gray iron. By weight, ductile gray iron castings are more expensive than gray iron. Ductile iron is used in applications such as valve and pump bodies, crankshafts, in heavy-duty gears or automobile door hinges, and nowadays with increasing frequency also as engine blocks. Austempered ductile cast iron (ADI) is a subgroup of the ductile iron family but could be treated as a separate class of engineering materials. In contrast to the former, the matrix of this spheroidal graphite cast iron is bainitic (not pearlitic). This microstructure is obtained by isothermal transformation of austenite at temperatures below that at which pearlite forms. In terms of properties, the bainitic matrix has almost twice the strength of pearlitic ductile iron while retaining high elongation and toughness. While exhibiting superior wear resistance and fatigue strength the castability of ADI is not very different from that of other ductile irons, but heat treatment is a critical issue to fully exploit its

beneficial properties. For example, the yield strength of ADI is more than three times that of the best cast or forged aluminum. In addition ADI castings weigh only 2.4 times more than Al alloys and are 2.3 times stiffer. ADI is also 10% less dense than steel. Furthermore, for a typical component, ADI costs 20% less per unit weight than steel and half that of Al. A comparison of forged steel, pearlitic ductile iron, and ADI is shown in Table 3.22. White cast irons are formed trough fast cooling and consist of Fe3 C and pearlite. The origin of this designation is the white-appearing crystalline fracture surface. While having an excellent wear resistance and high compressive strength the principal disadvantage of white cast iron is its catastrophic brittleness. Therefore in most applications white cast iron is only formed on the surface of cast parts, while the core consists of either grey cast iron or ductile iron. Examples of the application of white cast iron are mill liners and shot-blasting nozzles as well as railroad brake shoes, rolling-mill rolls, and clay-mixing and brick-making equipment, crushers, and pulverizers. Compacted graphite iron (CGI), also known as vermicular iron, can be considered as an intermediate between gray and ductile iron, and possesses many of the favorable properties of each. CGI is difficult to produce successfully on a commercial scale because the alloy additions must be kept within very tight limits. The advantages of CGI compared with gray cast iron are its higher fatigue resistance and ductility, which are at the same level as those of ductile iron. Machinability, however, is superior to that of ductile iron and its damping capacity is almost as good as that of gray iron. This combination and the high thermal conductivity of CGI suggest applications in engine blocks, brake drums, and exhaust manifolds of vehicles. Malleable iron is white iron that has been converted by a two-stage heat treatment to a condition in which most of its carbon content is in the form of irregularly shaped nodules of graphite, called temper carbon. In contrast to white iron it is malleable

184

Part B

Applications in Mechanical Engineering

Part B 3.7

Table 3.23 The various degrees of purity of pure aluminum [3.135] Aluminum (%)

Examples (ISO)

Examples (AA)

Designation

99.5000 to 99.7900 99.80000 to 99.9490 99.9500 to 99.9959 99.9960 to 99.9990 > 99.9990

A 199.5–A 199.8 A 199.8–A 199.95R A 199.95R–A 199.99R A 199.99R –

1050–1080, 1145 1080–1090, 1185 1098, 1199 – –

Commercial purity High purity Super purity Extreme purity Ultra purity

Table 3.24 Constitution of aluminum alloys Wrought alloys 1xxx Commercial pure Al (> 99% Al)

Not aged

2xxx Al−Cu 3xxx Al−Mn

Age hardenable Not aged

4xxx Al−Si and Al−Mg−Si

Age hardenable if Mg is present

5xxx Al−Mg

Not aged

6xxx Al−Mg−Zn

Age hardenable

7xxx Al−Mg−Zn 8xxx Other elements (for example Al−Li)

Age hardenable Depends on additions

Casting alloys 1xx.x Commercial pure Al 2xx.x Al−Cu

Not aged Age hardenable

3xx.x Al−Si−Cu or Al−Mg−Si

Some are age hardenable

4xx.x Al−Si 5xx.x Al−Mg

Not aged Not aged

7xx.x Al−Mg−Zn

Age hardenable

8xx.x Al−Sn 9xx.x (Other elements)

Age hardenable Depends on additions

Pure Aluminum Commercial-purity aluminum, mainly manufactured by modified Hall–Héroult electrolysis, usually reaches a purity of 99.5–99.8%. On further electrolytic refinement (the three-layer method [3.135]) of commercially pure aluminum or secondary aluminum, superpurity aluminum (99.95–99.99%) can be prepared. Finally, for special purposes, aluminum can be further purified by zone melting to result in extreme purity aluminum of up to 99.99995%. Classification of pure aluminum is given in Table 3.23 of [3.135]. In the annealed condition aluminum possesses only low strength at room temperature. By cold deformation, however, it is possible to improve its strength significantly, whereas the elongation is reduced considerably (Fig. 3.143).

Traditionally, pure aluminum is used in wrought condition for electrical conductors (EC-aluminum). Further important applications of aluminum are as foils for the food processing industries and in packaging practice (alloy 1145), as case components, boxes in tool-building, in the building industry as well as claddings, and to improve resistance to corrosion with heat-treatable Al alloys. Aluminum Alloys The major alloying elements of aluminum are copper, manganese, magnesium, silicon, and zinc. Depending on the production route to its final form, aluminum alloys may in principle be divided into wrought alloys and cast alloys. The wrought alloys can be classified into two main groups:

1. Age-hardenable alloys 2. Non-age-hardenable alloys The nomenclature used for wrought alloys consists of four digits 2xxx-8xxx where the last two digits are the alloy identifier (Table 3.24). The second digit indicates certain alloy modifications (0 stands for the original alloy). A second designation is usually used, and describes the final temper treatment (Table 3.25). Aluminum responds readily to strengthening mechanisms (Sect. 3.1) such as age hardening, solution hardening, and strain hardening, resulting in 2–30 times higher strength compared with pure aluminum (Table 3.26). Age hardening is the most effective hardening mechanism. It is based on the fact that the solubility of certain elements increases on increasing temperature. In the case of Cu as the alloying element, maximum solubility is reached at about 550 ◦ C (Fig. 3.144). For age hardening the material is solution annealed in the single-phase region, quenched to room or low temperature, and finally age hardened at higher temperatures (100–200 ◦ C) to facilitate the formation of small precipitates. On further age hardening the precipitates continue to grow, resulting in overaging (Fig. 3.144), which is accompanied by a loss in material strength.

Materials Science and Engineering

3.7 Materials in Mechanical Engineering

F O H

W T

As-fabricated (hot worked, forged, cast, etc.) Annealed (in the softest possible condition) Cold worked H1x – cold worked only (“x” referes to the amount of cold work and strengthening) H-12 – cold work that gives a tensile strength midway between the O and H14 tempers H-14 – cold work that gives a tensile strength midway between the O and H18 tempers H-16 – cold work that gives a tensile strength midway between the H14 and H18 tempers H-18 – cold work that gives about 75% reduction H-19 – cold work that gives a tensile strength greater than 2000 psi of that obtained by the H18 temper H2x – cold worked and partly annealed H3x – cold worked and stabilized at a low temperature to prevent age hardening of the structure Solution treated Age hardened T1 – cooled from the fabrication temperature and naturally aged T2 – cooled from the fabrication temperature, cold worked, and naturally aged T3 – solution treated, cold worked, and naturally aged T4 – solution treated and naturally aged T5 – cooled from the fabrication temperature and artifically aged T6 – solution treated and artifically aged T7 – solution treated and stabilized by overaging T8 – solution treated, cold worked, and artifically aged T9 – solution treated, artifically aged, and cold worked T10 – cooled from the fabrication temperature, cold worked, and artifically aged

The strength increase Δσ is inversely proportional to the separation distance l of the precipitates and is giving in the peak aged condition (Fig. 3.145) by Δσ ∼ 2Gb/l (G – shear modulus; b – Burger vector). However, on further annealing the precipitates can grow by Ostwald ripening, i. e., small precipitates are consumed and larger particles grow continuously at their expense. This process results in severe strength

decrease when the material is exposed to high temperatures during service (Fig. 3.146). Depending on the alloying additions, different strengthening mechanisms are activated:

•

2xxx: Precipitation of Cu-rich phases allows the formation of high-strength alloys at the expense of weldability. Precipitation from the α-solid so-

Table 3.26 Effect of strengthening mechanisms on the mechanical properties of aluminum alloys (after data in [3.137]) Material Pure annealed Al (99.999% Al) Commercially pure Al (annealed, 99% Al)

Tensile

Yield

strength (MPa)

strength (MPa)

(%) Elongation

Yield strength (alloy) Yield strength (pure)

45

17

60

90

34

45

2.0

Solid solution strengthened (1.2% Mn)

110

41

35

2.4

75% cold worked pure Al

165

152

15

8.8

Dispersion strengthened (5% Mg)

290

152

35

8.8

Age hardened (5.6% Zn–2.5% Mg)

570

503

11

29.2

Part B 3.7

Table 3.25 Heat treatments of aluminum alloys

185

188

Part B

Applications in Mechanical Engineering

Part B 3.7

Table 3.28 Selected cast aluminum alloys and their mechanical properties (after data in [3.140], see also [3.137]) Alloy

Chemical composition

Tensile strength (MPa)

Yield strength (MPa)

Elongation (%)

Casting process

201-T6 319-F

4.5% Cu 6% Si 3.5% Cu

356-T6

7% Si 0.3% Mg

380-F 384-F 390-F 443-F

8.5% Si 3.5% Cu 11.2% Si 4.5% Cu 0.6% Mg 17% Si 4.5% Cu 0.6% Mg 5.2% Si

413-F 518-F 713-T5 850-T5

12% Si 8% Mg 7.5% Zn 0.7% Cu 0.35% Mg 6.2% Sn 1% Ni 1% Cu

483 186 234 228 262 317 331 283 131 159 228 296 310 207 159

434 124 131 165 186 156 165 241 55 62 110 145 193 152 76

7 2 2.5 3.5 5 3.5 2.5 1 8 10 9 2.5 7 4 10

Sand Sand Permanent mold Sand Permanent mold Permanent mold Permanent mold Die casting Sand Permanent mold Die casting Die casting Sand Sand Sand

3.7.3 Magnesium and Its Alloys General Properties Magnesium is the lightest structural metal with a density close to that of polymers (plastics). It is therefore not surprising that Mg alloys are especially found in applications where the weight of a workpiece is of paramount importance, as generally is the case in the transportation industry. In recent years magnesium cast alloys have particularly becoming increasingly important and have partly replaced well-established Al-based alloys. The main reason is the excellent die-filling characteristics of magnesium, which allows large, thinwalled, and unusually complex castings to be produced economically. Magnesium can be cast with thinner walls (1–1.5 mm) than plastics (2–3 mm) or aluminum (2–2.5 mm) and, by designing appropriately located ribs, the stiffness disadvantage of magnesium versus aluminum can be compensated without increasing the wall thickness of an overall magnesium part. Further positive properties to be noted are the excellent machinability, high thermal conductivity

(Sect. 3.4), and the good weldability. However, Mg alloys suffer from poor corrosion resistance and the manufacturing costs are comparatively high. With its hexagonal close-packed crystal structure the roomtemperature deformation behavior of Mg alloys is moderate, resulting in poor cold workability. Thus, all current applications are manufactured through casting. Furthermore, Mg is a very reactive metal and readily oxidizes when exposed to air. Since pure Mg is only of minor importance for structural applications it appears almost always in the alloyed condition with additions such as Al and Zn. A comprehensive treatment of Mg and its alloys is given in [3.141]. Magnesium Alloys Major alloying elements of Mg are Al, Zn, and Mn, while elements such as Sn, Zr, Ce, Th, and B are occasionally of importance. Impurities in Mg alloys are commonly Cu, Fe, and Ni. Mg designation is based on the main alloying elements (such as AZ for aluminum and zinc) followed by the amount of additives and a letter that indicates the amount of variations with

Table 3.29 Designation of Mg alloys 1. 2. 3. 4.

Two letters which indicate the major alloying additions A−Al; Z−Zn; M−Mn; K−Zr; T−Sn; Q−Ag; C−Cu; W−Y; E–rare earths Two or three numbers which indicate the nominal amounts of alloying elements (rounded off to the nearest percent) A letter which describes variation to the normal alloy If needed, the temper treatment according to Table 3.30

Materials Science and Engineering

3.7 Materials in Mechanical Engineering

Part B 3.7

Table 3.30 Temper designations (after [3.1]) General designations F O H T W Subdivisions of H H1, Plus one or more digits H2, Plus one or more digits H3, Plus one or more digits

As fabricated Annealed. recrystallized (wrought products only). Strain-hardened Thermally threated to produce stable tempers other than F, O, or H. Solution heat-treated (unstable temper). Subdivisions of T Strain only T2 Strain-hardened T3 and then partially annealed Strein-hardened T4 and then stabilized T5 T6 T7 T8 T9 T10

Annealed (cast products only) Solution heat-treated and cold worked Solution heat-treated Artificial aged only Solution heat-treated and artificial aged Solution heat-treated and stabilized Solution heat-treated, cold worked, and artificial aged Solution heat-treated, artificial aged, and cold worked Artificial aged and cold worked

Table 3.31 General effects of alloying elements in magnesium materials (after [3.1], see also [3.141–143]) Series AZ

Alloying elements Al, Zn

QE

Ag, rare earths

AM

Al, Mn

AE

Al, rare earth

AS

Al, Si

WE

Y, rare earths

Melting and casting behavior

Mechanical and technological properties

Improve castability; tendency to microproporosity; increase fluidity of the melt; refine weak grain Improve castability; reduce microporosity

Solid-solution hardener; precipitation hardening at low temperatures (< 120 ◦ C); improve strength at ambient temperatures; tendency to brittleness and hot shortness unless Zr is refinded Solid-solution and precipitation hardening at ambient and elevated temperatures; improve elevated-temperature tensile and creep properties in the presence of rare-earth metals Solid-solution hardener; precipitation hardening at low temperatures (< 120 ◦ C); increase creep resistivity Solid-solution and precipitation hardening at ambient and elevated temperatures; improve elevated-temperature tensile and creep properties; increase creep resistivity Solid-solution hardener, precipitation hardening at low temperatures (< 120 ◦ C); improves creep properties

Improve castability; tendency to microporosity; control of Fe content by precipitating Fe − Mn compound; refinement of precipitates Improve castability; reduce microporosity

Tendency to microporosity; decreased castability; formation of stable silicide alloying elements; compatible with Al, Zn, and Ag; refine week grain Grain refining effect; reduce microporosity

respect to the normal alloy (Table 3.29). When referring to mechanical properties it is useful to indicate the temper treatment as well (Table 3.30). The alloy AZ91A,

189

Improve elevated-temperature tensile and creep properties; solid-solution and precipitation hardening at ambient and elevated temperatures

for example, is a Mg-based alloy with nominally about 9% Al and 1% Zn, while the letter A indicates that only minor changes to the normal alloy were carried out.

190

Part B

Part B 3.7

Applications in Mechanical Engineering

Table 3.32 Typical tensile properties and characteristics of selected cast Mg alloys (after [3.1], see also [3.141–143]) ASTM designation

Condition

Tensile properties 0.2% proof Tensile stress strength (MPa) (MPa)

Elogation to fracture (%)

AZ63

AM50 AM20 AS41 AS21 ZK51

As-sand cast T6 As-sand cast T4 As-sand cast T4 T6 As-chill cast T4 T6 As-die cast As-die cast As-die cast As-die cast T5

75 110 80 80 95 80 120 100 80 120 125 105 135 110 140

180 230 140 220 135 230 200 170 215 215 200 135 225 170 253

4 3 3 5 2 4 3 2 5 2 7 10 4.5 4 5

ZK61 ZE41

T5 T5

175 135

275 180

5 2

ZC63

T6

145

240

5

EZ33

Sand cast T5 Chill cast T5 Sand cast T6

95 100 90

140 155 185

3 3 4

90

185

4

185

240

2

185

240

2

WE54

Sand or chill cast T5 Sand or chill cast T6 As-sand cast T6 T6

200

285

4

WE43

T6

190

250

7

AZ81 AZ91

HK31 HZ32 QE22 QH21

An overview of the general effect of certain alloying additions is given in Table 3.31 [3.1, 141–143]. The addition of up to 10% aluminum (Mg−Al alloys) increases the strength (age hardenable), castability, and corrosion resistance. During precipitation heat treatment the intermetallic phase Mg17 Al12 is formed, and is usually not finely distributed enough to lead to a strong strengthening effect. The supplementary addition of zinc (Mg−Al−Zn alloys) improves the strength

Characteristics

Good room-temperature strength and ductility Tough, leaktight casting with 0.0015 Be, used for pressure die casting General-purpose alloy used for sand and die casting

High-pressure die casting Good ductility and impact strength Good creep properties up to 150 ◦ C Good creep properties up to 150 ◦ C Sand casting, good room-temperature strength and ductility As for ZK51 Sand casting, good room-temperature strength, improved castability Pressure-tight casting, good elevatedtemperature strength, weldable Good castability, pressuretight, weldable, creep resistant up to 250 ◦ C Sand casting, good castability, weldable, creep resistant up to 350 ◦ C As for HK31 Pressuretight and weldable, high proof stress up to 250 ◦ C Pressuretight, weldable, good creep resistance and stressproof to 300 ◦ C High strength at room and elevated temperatures, good corrosion resistance Weldable

of Mg−Al alloys by refining the precipitates and by solid-solution strengthening. The frequently used alloy AZ91, for example, offers yield strength and ductility levels which are comparable to its aluminum counterpart A380. However, in terms of high-temperature creep resistance (application limited to about 125 ◦ C), fatigue strength, and corrosion resistance the alloy AZ91 is inferior to Al alloys. Its application is therefore restricted to nonstructural components such as

192

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Applications in Mechanical Engineering

Table 3.33 Typical tensile properties and characteristics of selected wrought Mg alloys (after [3.1], see also [3.141–143]) ASTM designation

Condition

M1

Sheet, plate F Extrusion F Forgings F Sheet, plate O H24 Extrusion F Forging F Extrusion F Forging F Forging T6 Sheet, plate O H24 Extrusions Forgings Extrusions T6 Sheet, plate T7 Extrusion F T5 Forging T5 Sheet, plate H24 Extrusion T5 Sheet, plate T8 T81 Forging T5 Extrusion F

AZ31

AZ61 AZ80 ZM21

ZMC711 LA141 ZK61

HK31 HM21

HZ11

Tensile properties 0.2% proof Tensile stress (MPa) strength (MPa)

Eloagation to fracture (%)

Characteristics

70 130 105 120 160 130 105 105 160 200 120 165 155 125 300 95 210 240 160 170 180 135 180 175 120

4 4 4 11 6 4 4 7 7 6 11 6 8 9 3 10 6 4 7 4 4 6 4 3 7

200 230 200 240 250 230 200 260 275 290 240 250 235 200 325 115 185 305 275 230 255 215 255 225 215

Low- to medium-strength alloy, weldable, corrosion resistant Medium-strength alloy, weldable, good formabilility

High-strength alloy, weldable High-strength alloy Medium-strength alloy, good formability, good damping capacity High-strength alloy Ultra-lightweight (S.G. 1.35) High-strength alloy

High-creep sesistance to 350 ◦ C, weldable High-creep sesistance to 350 ◦ C, weldable after short-time exposure to 425 ◦ C Creep resistance to 350 ◦ C, weldable

Table 3.34 Chemical composition and the mechanical properties of commercial pure and low-alloy grades of titanium

(from [3.1]) O (wt.%)

Tensile strength Rm (MPa)

Yield strength Rp0.2

Fracture strain A10 (%)

Standard grade a cp

Standard grade a low alloyed

0.12 0.18

290–410 390–540

> 180 > 250

> 30 > 22

Grade 1 Grade 2

Pd: grade 11 Pd: grade 7 Ru: grade 27 Ru: grade 26

0.25 460–590 > 320 > 18 0.35 540–740 > 390 > 16 0.25 > 480 > 345 > 18 a ASTM B265, ed 2001; N max : 0.03 wt. %; Cmax : 0.08 wt. %; Hmax : 0.015 wt. %

fore require titanium grades with extra-low interstitials (ELI). While having an hcp structure Ti exhibits surprisingly high room-temperature ductility and can be cold-rolled to > 90% without crack formation. This behavior is attributed to the relative ease of activating slip systems and the availability of twinning planes in the crystal lattice. The chemical composition and the me-

Grade 3 Grade 4

Ni + Mo: grade 12

chanical properties of commercial pure and low-alloy grades of titanium are given in Table 3.34. Titanium Alloys Alloying additions, which are usually added to improve the mechanical properties of Ti influence the phase stability in a different manner. The low-temperature

Materials Science and Engineering

3.7 Materials in Mechanical Engineering

Alloying element

Range (approx.) (wt.%)

Effect on structure

Carbon, oxygen, nitrogen Aluminum Tin Vanadium Molybdenum Chromium Copper Zirconium Silicon

– 2–7 2–6 2 – 20 2 – 20 2 – 12 2–6 2–8 0.05– 1

α stabilizer α stabilizer α stabilizer β stabilizer β stabilizer β stabilizer β stabilizer α and β strengtheners Improves creep resistance

Part B 3.7

Table 3.35 Alloying elements in Ti alloys [3.142, 144, 145]

Table 3.36 Chemical composition and mechanical properties of Ti-based alloys at room temperature (minimum values)

(after [3.1]) Alloy composition a

Alloy types

Ti5Al2.5Sn Ti6Al2Sn4Zr2MoSi

α near α

Ti6Al5Zr0.5MoSi

near α

950

Ti5.8Al4Sn3.5Zr0.7Nb 0.5Mo0.2Si0.05C Ti6Al4V Ti4Al4Mo2Sn Ti6Al6V2Sn Ti10V2Fe3Al Ti5V3Cr3Sn3Al

near α

Density  (g/cm3 ) 4.48 4.54

Young’s modulus E (GPa) 110 114

880

4.45

125

1030

910

4.55

120

α+β α+β α+β near β β

900 1100 1030 1250 1000

830 960 970 1100 965

4.43 4.60 4.54 4.65 4.76

114 114 116 103 103

Ti3Al8V6Cr4Zr4Mo

β

1170

1100

4.82

103

Ti15Mo3Nb3AlSi

β

1030

965

4.94

96

a b

Tensile strength Rm (MPa) 830 900

Yield strength Rp0.2 (MPa) 780 830

Main property High strength High-temperature strength High-temperature strength High-temperature strength High strength High strength High strength High strength High strength; cold formability High corrosion; resistance High corrosion; resistance

Standard grade b

3.7145 3.7155

3.7185 3.7185

Figure before chemical symbol denotes nominal wt.% According to DIN 17851, ASTM B 265 ed. 2001

hexagonal α-phase is stabilized by the impurities O, N, and C as well as by Al and Sn (Table 3.35), whereas elements such as V, Mo, and Cr expand the β-phase stability region (the Ti-rich part of the Ti−Al and the Ti−Mo phase diagram are shown in Fig. 3.149 [3.147]). By varying the alloying content pure α- or β-phase alloys can be stabilized at room temperature as well as a mixture of both phases. The α-phase Ti alloys have a high solid solubility at room temperature and are weldable. The most widely used α-Ti alloy is Ti-5Al2.5Sn (Table 3.36). While offering the highest strength

193

levels of the Ti alloys and the ability of cold working, the usage of β-phase alloys is rather limited compared with pure α- or α + β-alloys. Besides costs, the reasons for this include the higher density, caused by the addition of V or Mo, the low ductility in the highstrength condition, and the poor fatigue performance in thick sections, which is caused by segregations at grain boundaries. The most widely used group (about 60%) of Ti alloys are two-phase α + β-alloys, with Ti-6Al-4V being the most prominent representative. These alloys are heat treatable and allow large variations of the mi-

Materials Science and Engineering

1. Corrosion-resistant alloys 2. High-temperature alloys as will be described briefly in the following two subsections. A survey on commonly used alloying additions in nickel and their effects on properties and applications is shown in Fig. 3.151.

Corrosion-Resistant Alloys The main application of commercially pure nickel is to combine corrosion resistance with outstanding formability. The 200 alloy series typically contains minor amounts of less than 0.5 wt. % Cu, Fe, Mn, C, and Si. According to Fig. 3.148 the intrinsically good corrosion resistance of nickel 200 can be substantially improved by high alloying in solid solution with

• • •

Cu for increased resistance against seawater and reducing acids, leading to the Monel alloys (e.g., 400, K-500) Mo for increased resistance against reducing acids and halogens, leading to the Hastelloy alloys (B2, B3) Cr for increased high-temperature strength and resistance to oxidizing media, leading to alloy 600 (which also possesses about 8 wt. % Fe, mainly for economical reasons)

Alloy 600 can be considered as the base alloy for a series of further high-alloyed Ni-base alloys for various applications in aggressive environments, as displayed in Fig. 3.151. An extensive compilation of chemical compositions and mechanical properties may be found in [3.1] while some typical examples for Ni alloys are listed in Table 3.38 together with their corresponding field of application. Ni-Based Superalloys The term superalloy is generally used for metallic alloy systems which may operate under structural loading

Table 3.39 Compositions, microstructures, and properties of representative Co-bonded cemented carbides (after [3.1] p. 279) Nominal composition

Grain size

Hardness (HRA)

Density (g cm−3 )

(oz in−3 )

Transverse strength (MPa) (ksi)

Compressive strength (MPa) (ksi)

97WC-3Co 94WC-6Co

Medium Fine Medium Coarse Fine Coarse Fine Coarse Medium Medium

92.5–93.2 92.5–93.1 91.7–92.2 90.5–91.5 90.7–91.3 87.4–88.2 89 86.0–87.5 83–85 92.1–92.8

15.3 15.0 15.0 15.0 14.6 14.5 13.9 13.9 13.0 12.0

8.85 8.67 8.67 8.67 8.44 8.38 8.04 8.04 7.52 6.94

1590 1790 2000 2210 3100 2760 3380 2900 2550 1380

230 260 290 320 450 400 490 420 370 200

5860 5930 5450 5170 5170 4000 4070 3860 3100 5790

850 860 790 750 750 580 590 560 450 840

7.29

1720

250

5170

750

90WC-10Co 84WC-16Co

75WC-25Co 71WC-12.5TiC -12TaC-4.5Co 72WC-8TiC Medium 90.7–91.5 12.6 -11.5TaC-8.5Co a Based on a value of 100 for the most abrasion-resistant material

197

Part B 3.7

sumption is devoted to alloying of stainless steels and a further 10% is used in (ferritic) alloy steels. Nickel forms extensive solid solutions with many other elements: complete solid solutions with Fe and Cu (such as those exemplified with the phase diagrams in Figs 3.30,3.31) and limited solid solutions with < 35 wt. % Cr, < 20 wt. % Mo, < 10 wt. % Al, Ti, to mention the most important ones. Based on the fcc crystal structure Ni and its solid solutions show high ductility, fracture toughness, and formability. Alloys of Ni−Fe show ferromagnetism over a wide range of compositions which, in combination with other intrinsic properties, gives rise to alloys with soft magnetic [3.59] and controlled thermal expansion properties (Invar alloy, Sect. 3.4.1). Ti–Ni shape-memory alloys are briefly discussed in Sect. 3.7.4. Finally, nickel plating is widely used for decorative applications. Most frequently, electroless deposition of either nickel– phosphorous or nickel–boron binary solutions is carried out by autocatalytic reduction of Ni ions from aqueous solutions. For more details see [3.151]. Besides these functional applications, structural applications of nickel and its alloys can be essentially grouped into two categories, namely:

3.7 Materials in Mechanical Engineering

Materials Science and Engineering

some brasses Brass designation

Zn content (%)

Color

Gilding metal Commercial bronze Red brass Yellow brass Muntz metal (α + β)

5 10 15 35 40

Copper red Golden Red gold Yellow Yellow gold

(International Annealed Copper Standards) corresponds to a resistivity of 1.72438 μΩ cm. However, the properties of Cu are subject to dramatic changes with varying alloy content, i. e., the conductivity decreases substantially with increasing impurity content. Small oxygen additions of up to about 0.04% (electrolytic tough pitch copper) can bind metallic impurities to form oxides and therefore lead to an increase of the conductivity (Table 3.41), on the one hand. On the other hand, the presence of oxygen in Cu diminishes weldability, since hydrogen diffuses into the metal and interacts with oxide to form steam, which leads to cracking. For torch welding and brazing copper must be deoxidized, for example, by the addition of a small amount of phosphorus, which, however, lowers the electrical conductivity substantially but allows the material to be used in plumbing devices. Copper Alloys Elements which are solid-solution strengtheners in copper include Zn, Sn, Al, and Si, whereas Be, Cd, Zr, and

Cr are suitable for age hardening. Age-hardenable alloys with small amounts of alloying additions (up to about 3%) can reach very high strength levels (yield stress RpO.2 > 1300 MPa at RT in the case of copper beryllium), offer high stiffness, and are nonsparking. The term brass has been established for binary Cu−Zn alloys (Fig. 3.157) but is nowadays used for alloys containing additional components such as Pb, Fe, Ni, Al, and Si as well. Brasses are less expensive than pure Cu and can have different microstructures which depend on Zn content. Pure α-(Cu) solid solutions (up to about 38% Zn) are cold-working alloys. On increasing Zn content the natural color of brass changes form copper-like red (5% Zn) to yellow–gold (40% Zn) (Table 3.42). The Muntz metal brass is a binary α + β alloy with high strength and still reasonable ductility. The most important properties of selected commonly used brasses are summarized in Table 3.43. Wrought products of brasses and bronzes are used in automobile radiators, heat exchangers, and home heating systems, as pipes, valves, and fittings in carrying potable water and as springs, fasteners, hardware, small gears, and cams, to give a few examples. Cast leaded red and semi-red brasses find their application as lowerpressure-rating valves, fitting, and pump components as well as commercial plumbing fixtures, cocks, faucets, and certain lower-pressure valves. General hardware, ornamental parts, parts in contact with hydrocarbon fuels, and plumbing fixtures are made from yellow leaded brass, and high-strength (manganese-containing) yellow brass is suitable for structural, heavy-duty bearings,

Table 3.43 Composition and properties of characteristic brasses, bronzes, Cu−Ni and Cu−Ni−Zn alloys (after [3.1]) Material

UNS no.

Composition

Yield strength (MPa)

Tensile strength (MPa)

Gilding metal (cap copper) Red brass Yellow brass Muntz metal Free-cutting brass High-tensile brass (architecture bronze) Aluminum bronze Aluminum bronze Phosphor bronze D Silicon bronze A Copper nickel Nickel silver 10%

C21000

95Cu–5Zn

C23000 C26800 C28000 C36000 C38500 C60800 C63000 C52400 C65500 C71500 C74500

Elongation (%)

69 –400

234–441

8 – 45

85Cu–15Zn 65Cu–35Zn 60Cu–40Zn 61.5Cu–35.5Zn–3Pb 57Cu–40Zn–3Pb

69 –434 97 –427 145 –379 124 –310 138

269–724 317–883 372–510 338–469 414

3 – 55 3 – 65 10– 52 18– 53 30

95Cu–5Al Cu–9.5Al–4Fe–5Ni–1Mn 90Cu–10Sn 97Cu–3Si 67Cu–31Ni–0.7Fe–0.5Be 65Cu–25Zn–10Ni

186 345 –517 193 145 –483 138 –483 124 –524

414 621–814 455–1014 386–1000 372–517 338–896

55 15– 20 3 – 70 3 – 63 15– 45 1 – 50

Thermal conductivity κ (W m−1 K−1 )

Electrical resistivity ρ (μ  cm)

234

3.079

159 121 126 109 88–109

3.918 6.631 6.157 6.631 8.620

85 62 63 50 21 37

9.741 13.26 12.32 21.29 38.31 20.75

203

Part B 3.7

Table 3.42 Designation, composition, and natural color of

3.7 Materials in Mechanical Engineering

Materials Science and Engineering

3.7 Materials in Mechanical Engineering

groups within the backbone, and trademarks Polymer

Backbone unit

Backbone

Trademarks

Organic polymers Polyethylene (PE)

−CH2 −CH2 −

−C−C−C−C−

Polypropylene (PP)

−CH2 −(CH3 )−CH2 −

−C−C−C−C−

Polyvinylchloride (PVC)

−CH2 −CHCl−

−C−C−C−C−

Polystyrene (PS)

−CH2 −CH(C6 H5 )−

−C−C−C−C−

Polytetrafluorethylene (PTFE) Polyamide (PA) Polyethylene terephthalate (PET) Polyurethan (PUR) Polycarbonate (PC) Polyphenylene sulfide (PPS)

−CF2 −CF2 − −(CH2 )6 −NH−CO−(CH2 )6 − −O−CO−C6 H4 −CO−O−CH2 −CH2 −

−C−C−C−C− −C−N−C−C− −C−O−C−C−C−

Polythen, Lupolen, Hostalen Hostalen, PPH, Luparen Hostalit, Vinidur, Vinylite Styroflex, Vestyron, Styropor (foam) Teflon, Hostaflon Nylon, Perlon Trevira (fiber), Diolen, Mylar (folie)

−NH−CO−O− −O−CO−O−R −C6 H4 −S−

−C−C−N−C−O−C−C −C−O−C−C− −C−S−C−

−N=PCl2 − O−Si(CH3 )2 −O−

−N=P− −Si−O−Si−O−

Inorganic polymers Polyphosphazene Polysiloxane (polydimethylsiloxane) Polysilane

cases where a low-molar-mass byproduct is formed during polymerization. In polycondensation already generated polymer chains react with each other or with a monomer unit whereby a low-molar-mass byproduct is generated, for example, water as a byproduct in the reaction of an −OH group (alcohol group) with a −COOH group (organic acid group) resulting in an ester group. During polyaddition, growth of the polymer chains proceeds by an addition reaction between molecules of all degrees of polymerization or monomer units. The annual world production of polymer materials is about 150–200 Mt. Some polymer materials are produced in amounts of more than 1 Mt/year (polypropylene about 14 Mt/year, which is about the same amount as for cotton), whereas others are polymer materials for special purposes with only small production volumes. Beside the use of bulk polymers as engineering materials a great amount of polymers is fabricated in the shape of fibers for manufacturing fabric, packaging films, paintings, thermal isolation materials (foam), and, for example, artificial leather.

Noxon, Ryton, Sulfar (fiber)

−Si−Si−Si−Si−

Chemical Composition and Molecular Structure For the presentation of polymer molecules the monomer unit is enclosed in brackets [ ] and an index (n) shows that a certain number of monomer units react to form the backbone of the polymer molecules. The polymerization of ethylene to polyethylene, for example, is written as nCH2 =CH2 → [−CH2 − CH2 −]n , where the last part represents the whole molecule CH3 −CH2 −CH2 . . .CH2 −CH2 −CH3 , with n being between some hundreds and some millions. Most of the polymers which are used as engineering materials are organic polymers with backbones (main chains) consisting of C−C bonds, or they contain bondings between C and other chemical elements (Table 3.44). Polymers with a backbone containing no carbon atoms are regarded as inorganic polymers. For most polymers common abbreviations are used and trademarks exist (Table 3.44). Polymer materials can be classified, e.g., by their specific molecular structure and the resulting mechanical properties at different temperatures into thermoplastics, elastomers, and duromers [3.159].

Part B 3.7

Table 3.44 Examples of widely used polymer materials and their abbreviations, characteristic backbone units, element

205

206

Part B

Applications in Mechanical Engineering

Part B 3.7

chains, ≈ 10 side chains/1000 C atoms, example: highdensity PE; (c) backbone with longer side chains/branches, example: low-density PE; (d) a great number of side chains attached to the backbone, example very low-density PE

cally. The molecular structure of thermoplastics can be distinguished by the kind of atoms building the backbone and by the kind of atoms or chemical groups attached to the backbone (Table 3.45). The side groups determine the polymer properties to a large extent, because they influence the strength of the intermolecular bonding. Another significant parameter that determines the properties of polymer solids results from the mean size of the macromolecules (degree of polymerization, mean chain length, mean molar mass), and, because the polymer molecules show no unit length, the deviation of the molecule size, which depends on the production parameters.

Thermoplastics. Thermoplastics show good strength

Elastomers. Elastomers (rubber-like polymers) con-

and high Young’s modulus at RT and they are plastically deformable at elevated temperatures, in most cases above 100 ◦ C. They consist in their simplest molecule structure of linear molecules with no branches (Fig. 3.159). In technical products small (e.g., −CH3 groups) or larger side chains (short −C−C− chains) are attached to the main chain, forming a branched polymer. The degree of branching determines the density of solid polymers, because with increasing branching the possibility of a dense arrangement of the macromolecules decreases. A typical example is polyethylene, with a density of 0.91–0.94 g/cm3 for the strong branched low-density PE (LDPE) and a density of 0.94–0.97 g/cm3 for the weakly branched high-density PE (HDPE). Regarding thermoplastics, within chain molecules there exist very strong intramolecular covalent bondings (bonding energy of the −C−C-bonding: 348 kJ/mol), whereas between neighboring molecule chains only weak intermolecular bonds with small bonding energies are present (Van der Waals bond: 0.5–5 kJ/mol, hydrogen bond: ≈ 7 kJ/mol). Therefore the chain molecules can, already around room temperature (rubber-like polymers, elastomers) or at elevated temperatures (thermoplastics), shifted with respect to each other, and such polymer solids can be deformed elastically or plasti-

sist, similarly to thermoplastics, of linear molecules, but the molecule chains are bridged by small-molecule segments via covalent bondings. The molecules can therefore undergo a strong elastic deformation at room temperature. This effect is due to the stretching of the molecules out of the disordered state if a load is applied, and a re-deformation into the random tangle of molecules due to the increased entropy, after the load is released.

a) H H H H H H H H

c)

C C C C C C C C H H H H H H H H

b)

d)

Fig. 3.159a–d Examples of linear polymer molecules: (a) theoretical backbone with carbon–carbon bonds; no side chains, (b) backbone with only a few small side

Duromers. Duromers consist of a three-dimensional molecule network, bridged by covalent bondings. Even at elevated temperatures they undergo no plastic deformation and can, in most cases, be heated up to their decomposition temperature without any elastic or plastic deformation. Most duromers are thermosets (phenolics, unsaturated polyesters, epoxy resins, and polyurethanes) which solidify by an exothermal chemical reaction (curing). Thermosets are obtained by moulding a thermoplastic material into the desired shape, which is then cross-linked. The curing reaction can be initiated at room temperature (RT) by mixing the components, or it starts at an elevated temperature, or irradiation by energetic radiation (ultraviolet light, laser beam, or electron beam) is applied.

Table 3.45 Examples of chemical groups/atoms on the backbone of linear polymers Y Y Y | | | −CH2 − CH2 − CH2 − CH2 − CH2 − | | | X X X

X

Y

Polymer

H CH3 Cl C6 H5 CH3

H H H H COOCH3

Polyethylene Polypropylene Polyvinylchloride Polystyrene Polymethylmethacrylate

212

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Applications in Mechanical Engineering

Part B 3.7

Table 3.50 Comparison of the specific ultimate tensile

strength (tensile strength/density) with steel: value for Aramid set to 100 Material

Relative specific UTS

Aramid/KEVLAR Glasfiber E PA/nylon fiber Low-carbon steel

100 46 45 19

has a significant influence on the mechanical properties (Fig. 3.168). For the determination of dynamic mechanical properties of polymers a torsion pendulum is used [3.171]. As a result the elastic shear modulus G and tan δ are obtained. The shear modulus is strongly dependent on temperature (Fig. 3.169). The mechanical properties of polymer materials can be further improved by fiber reinforcement [3.173, 174] (Sect. 3.7.10). Polymer Interaction with Solvents The dissolution of solid polymers in organic solvents or water starts with swelling, whereby the macromolecules are not degraded, which means that the chain length is not changed [3.175]. Only in some polymers are the chain molecules shortened by a chemical reaction with a chemical substance contained in a solvent. For example, the amid bondings in polyamides undergo hydrolysis under basic conditions (saponification), resulting in the generation of chain molecule fragments of different length. Swelling and subsequent dissolution are due to a competition of the intermolecular bonding forces between chains of the polymer, and the bonding forces between the macromolecules and the small solvent molecules, respectively. As a result, increasing numbers of solvent molecules penetrate the tangled polymer chain arrangement and lead to an increase of the volume of the polymer solid. This is accompanied by a lowering of the interaction forces between adjacent macromolecule segments and an increase of the

Table 3.51 Solubility parameter for solvents and polymers [3.172] Solvent

δ (MPa)1/2

Polymer

δ (MPa)1/2

n-hexane Benzene

14.9 18.8

Polyethylene Polystyrene

12.7 18.4

mobility of the molecules with respect to each other and a loss of strength. The swelling and dissolution process may take up to several days or weeks at ambient temperature. Swelling often results in a sticky substance before the real dissolution happens. In some cases polymer solutions can be used as a glue which will have the strength of the starting polymer after the solvent has evaporated. Some polymers can only incorporate a limited fraction of solvent into the solid. The interaction between a polymer and a selected solvent and therefore the solubility of the polymer can be predicted using the solubility parameter δ (Table 3.51), which is based on the cohesion forces, beside other factors [3.172]. As a rule, a substance can be regarded as a solvent if the difference of δ values is less than 2. Aging and Corrosion Aging of polymers is mainly due to chemical changes of the structure of the macromolecules accompanied by a shortening of the chain molecules, branching, crosslinking, and the generation of new chemical groups. A prerequisite for aging is the influence of light, especially UV light, and eventually oxygen from the air. As a result the polymer becomes brittle, cracks are generated, the quality of the surface is changed, and a loss of electrical insulation behavior will appear. Loss of plasticizer by diffusion also lowers the elasticity and the ductility, especially at lower temperatures. An especially dangerous situation is the interaction of a solvent or a solution and mechanical stress on a polymer part, leading to stress-corrosion failure.

3.7.9 Glass and Ceramics Ceramic materials Glasses

Traditional Silicate Refractory Oxide ceramics ceramics ceramics ceramics and cements

Nonoxide ceramics

Glasses Glass ceramic

Fig. 3.170 Classification of ceramic materials on the basis of chem-

ical composition (after [3.1])

Ceramic and glass materials are complex compounds and solid solutions containing metallic and nonmetallic elements, which are composed either by ionic or covalent bonds. Typical properties of glasses and ceramics include high hardness, high compressive strength, high brittleness, high melting point, and low electrical and thermal conductivity. There are several ways in which ceramics may be classified, such as by chemical composition, properties or applications. In Fig. 3.170 this

Materials Science and Engineering

3.7 Materials in Mechanical Engineering

Glas type

Composition (wt%) SiO2 Na2 O

Fused silica

> 99.5

96% Silica (Vycor) Borosilicate (Pyrex) Container (soda lime) Fiberglass

96

Optical flint

54

1

Glass-ceramic (Pyroceram)

43.5

14

CaO

Al2 O3

B2 O3

Other

4

81

3.5

74

16

55

2.5 5

1

16

15

13 4MgO 10

4MgO 37PbO, 8K2 O

30

classification is made on the basis of chemical composition [3.1]. In the following, a closer look at some of the ceramic materials listed in Fig. 3.170 will be made. Detailed treatments of ceramics are given in [3.177, 178]. Glasses Glasses are solid materials which have become rigid without crystallization (amorphous structure, Sect. 3.1). The microstructure is based on SiO4 tetrahedral units which possess short-range order and are connected to each other by bridging oxygen, resulting in a threedimensional framework of strong Si−O−Si bonds. The main assets of glasses are their optical transparency, pronounced chemical resistance, high mechanical strength, and relatively low fabrication costs. Glasses usually contain other oxides, notably CaO, Na2 O, K2 O, and Al2 O3 , which influence the glass properties. Beside about 70% SiO2 soda-lime glasses, which are used for windows and containers, additionally consist of Na2 O (soda) and CaO (lime). Further applications of glasses are as lenses (optical glasses), fiberglass, industrial and laboratory ware, and as metalto-glass sealing and soldering. The compositions of some commercial glass materials are described in Table 3.52 [3.176]. Glass Ceramics Glass ceramics contain small amounts of nucleating agents (such as TiO2 and ZrO2 ) which induce crystallization of glasses when exposed to high tem-

5.5

6.5TiO2 , 0.5As2 O3

Characteristics and applications High melting temperature, very low coefficient of expansion (shock resistant) Thermal shock and chemically resistant (laboratory ware) Thermal shock and chemically resistant (ovenware) Low melting temperature, easily worked, also durable Easily drawn into fibers (glassresin composites) High density and high index of refraction (optical lenses) Easily fabricated; strong; resists thermal shock (ovenware)

peratures. After melting and shaping of the glassy material, it is partly crystallized using a specific heat treatment at temperatures between 800 and 1200 ◦ C. The residual glass phase occupies 5–50% of the volume and the crystalline phase has a grain size of 0.05–5 μm. In contrast to conventional ceramics, e.g., prepared by powder processing routes, glass ceramics are fully dense and pore-free, resulting in relatively high mechanical strength. Glass ceramics of the system Li2 O−Al2 O3 −SiO2 show near-zero linear thermal expansion, such that the glass ceramic ware will not experience thermal shock. These materials also have a relatively high thermal conductivity and show exceptionally high dimensional and shape stability, even when subjected to considerable temperature variations. Glass ceramics are used in astronomical telescopes, as mirror spacers in lasers, as ovenware and tableware, as electrical insulators, and are utilized for architectural cladding, and for heat exchangers and regenerators. Silicate Ceramics Silicates are the most important constituents of the Earth’s crust. Their structure, which is based on SiO4 tetrahedrons (glasses are a derivative of silicates) depends on the actual composition. A three-dimensional network (quartz) is only stable when the ratio of O/Si is exactly 2. The addition of alkali or alkalimetal oxides to silica increases the overall O/Si ratio of the silicate and results in the progressive breakdown of the silicate structure into smaller units. In Table 3.53 the relationship of the O/Si ratio and the

Part B 3.7

Table 3.52 Compositions and characteristics of some common commercial glasses (after [3.176])

213

Materials Science and Engineering

3.7 Materials in Mechanical Engineering

Melting temperature (◦ C)

Brick (major chemical components)

Density  (kg/m3 )

Thermal conductivity κ (W/(m K))

Building brick Chrome-magnesite brick (52 wt. % MgO, 23 wt% Cr2 O3 ) Fireclay brick (54 wt. % SiO2 , 40 wt% Al2 O3 ) High-alumina brick (90–99 wt. % Al2 O3 ) Silica brick (95–99 wt. % SiO2 Silicon carbide brick (80–90 wt. % SiC) Zirconia (stabilized) brick

1842 3100

1600 3045

0.72 3.5

2146–2243

1740

0.3 – 1.0

2810–2970

1760– 2030

3.12

1842 2595

1765 2305

1.5 20.5

3925

2650

2.0

Table 3.55 Properties of commercial oxides according to DIN EN 60672 [3.1] Oxide

MgO (C 820; 30% porosity)

Al2 O3 (> 99.9)

TiO2 (C 310)

Beryllium oxide C 810

Partially stabilized ZrO2

Density ρ (g/cm3 ) Young’s modulus (GPa) Bending strength (MPa) Coefficient of thermal expansion (RT) (10−6 K−1 ) Thermal conductivity (RT) (W m−1 K−1 ) Application examples

2.5

3.97 –3.99

3.5

2.8

5–6

90

366– 410

–

300

200–210

50

550– 600

70

150

500–1000

11– 13

6.5 – 8.9

6–8

7 –8.5

10–12.5

6 – 10

38.9

3–4

150–220

1.5 – 3

For insulation in sheathed thermocouples; in resistive heating elements

In insulators; in electrotechnical equipment; as wearresistant machine parts; in medical implants

In powder form as a pigment and filler material; in optical and catalytic applications

In heat sinks for electronic components

As thermal barrier coating of turbine blades

peratures without melting or decomposing and must remain nonreactive and inert when exposed to severe environments. Refractory ceramics are composed of coarse oxide particles bonded by a finer refractory material. The finer material usually melts during firing and bonds the remaining material. Refractory ceramics generally contain 20–25% porosity as an important microstructural variable that must be well controlled during manufacturing. They are used for various applications ranging from low- to intermediate-temperature building bricks to high-temperature applications, where magnesite, silicon carbide, and stabilized zirconia (also used as thermal barrier coatings of nickel-based turbine components) are suitable. Typical applications include

furnace linings for metal refining, glass manufacturing, metallurgical heat treatment, and power generation. Depending on their chemical composition and reaction oxide refractories can be classified into acidic, basic, and neutral refractories. Fireclays are acidic refractories and are formable with the addition of water (castable and cements). Very high melting points are provided by chromite and chromite–magnesite ceramics, which are neutral refractories. Examples of commercial refractories are given in Table 3.54. Oxide Ceramics Oxide ceramics are treated as a separate group of ceramics in [3.1] since they are the most common constituents

Part B 3.7

Table 3.54 Properties of fired refractory brick materials (after [3.1])

215

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Applications in Mechanical Engineering

Table 3.56 Properties and applications of advanced ceramics Property Thermal Insulation Refractoriness Thermal conductivity Electrical and dielectric Conductivity Ferroelectricity Low-voltage insulators Insulators in electronic applications Insulators in hostile environments Ion-conducting Semiconducting Nonlineal I –V characteristics Gas-sensitive conductivity Magnetic and superconductive Hard magnets Soft magnets Superconductivity Optical Transparency Translucency and chemical inertness Nonlinearity Infrared transparency Nuclear applications Fission Fusion Chemical Catalysis Anticorrosion properties Biocompatibility Mechanical Hardness High-temperature strength retention Wear resistance

Application (examples) High-temperature furnace linings for insulation (oxide fibers such as silica, alumina, and zirconia) High-temperature furnace linings for insulation and containment of molten metals and slags Heat sinks for electronic packages (AlN) Heat elements for furnaces (SiC, ZrO2 , MoSi2 ) Capacitors (Ba-titanate-based materials) Ceramic insulation (porcelain, steatite, forsterite) Substrate for electronic packaging and electical insulators in general (Al2 O3 , AlN) Spark plugs (Al2 O3 ) Sensors, fuel cells, and solid electrolytes (ZrO2 , β-alumina, etc.) Thermistors and heating elements (oxides of Fe, Co, Mn) Current surge protectors (Bi-doped ZnO, SiC) Gas sensors (SnO2 , ZnO) Ferrite magnets [(Ba, Sr)O × 6Fe2 O3 ] Transformer cores [(Zn, M)Fe2 O3 , with M = Mn, Co, Mg]; magnetic tapes (rare-earth garnets) Wires and SQUID magnetometers (YBa2 Cu3 O7 ) Windows (soda-lime glasses), cables for opticalcommunication (ultrapure silica) Heat- and corrosion-resistant materials, usually for Na lamps (Al2 O3 , MgO) Switching devices for optical computing (LiNbO3 ) Infrared laser windows (CaF2 , SrF2 , NaCl) Nuclear fuel (UO3 , UC), fuel cladding (C, SiC), neutron moderators (C, BeO) Tritium breeder materials (zirconates and silicates of Li, Li2 O; fusion reactor lining (C, SiC, Si3 N4 , B4 C) Filters (zeolites); purification of exhaust gases Heat exchangers (SiC), chemical equipment in corrosive environment Artificial joint prostheses (Al2 O3 ) Cutting tools (SiC whisker-reinforced Al2 O3 , Si3 N4 ) Stators and turbine blades, ceramic engines (Si3 N4 ) Bearings (Si3 N4 )

of ceramics. The properties and applications of some important members are summarized in Table 3.55. For further reading the extensive treatment in [3.179] is recommended. Nonoxide Ceramics The nonoxide ceramics include essentially borides, carbides, nitrides, and silicides. A comprehensive overview

of these materials is given in [3.1,177,178]. A few application examples will be given in the following. In recent years some effort has been made in the construction of ceramic automobile engine parts such as engine blocks, valves, cylinder liner, rotors for turbochargers, and so on. Ceramics under consideration for use in ceramic turbine engines include silicon nitride Si3 N4 , and silicon carbide SiC, which possess high thermal conductivity

218

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Part B 3

the fibers play a decisive role in the final performance of the reinforced composites. In the longitudinal direction (along the fiber axis) the strength is much higher than in the transverse direction (Table 3.57). The matrix of fiber-reinforced materials should be tough enough to support the fibers and prevent cracks in broken fibers from propagating, and one has to be aware of chemical reactions when the matrix is a metallic material. If the fibers are exposed to high temperatures the coefficient of thermal expansion should not differ substantially from that of the matrix. Fiber composites may be used as fan blades in gas turbine engines and other aircraft and aerospace components, in lightweight automotive applications such as fiber-reinforced Al-matrix

pistons, sporting goods (such as tennis rackets, golf club shafts, and fishing rods), and as corrosion-resistant components, to name some of the possible applications. Laminar compositions could be very thin coatings such as thermal barrier coatings to protect Ni-based superalloys in high-temperature turbine applications (Sect. 3.7.5), thicker protective layers, or two-dimensional sheets or panels that have a preferred high-strength direction. The layers are stacked and joined by organic adhesives. Examples of laminar structures are adjacent wood sheets in plywood, capacitors composed of alternating layers of aluminum and mica, printed circuit boards, and insulation for motors, to mention a few.

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J. Pohl, S. Herold, G. Mook, F. Michel: Damage detection in smart CFRP composites using impedance spectroscopy, Smart Mater. Struct. B 10, 834–842 (2001) H. Speckmann, R. Henrich: Structural Health Monitoring (SHM) – Overview on Airbus Activities (16th World Conf. NDT, Montreal 2004), paper 536 A.K. Mukherjee, J.E. Bird, J.E. Dorn: Experimental correlations for high-temperature creep, Trans. ASM 62, 155 (1969) W.J. Staszewski, C. Boller, G.R. Tomlinson: Health Monitoring of Aerospace Structures: Smart Sensor Technologies and Signal Processing (Wiley, New York 2003) F.-K. Chang (Ed.): Structural Health Monitoring. The Demands and Challenges (CRC Press, Boca Raton 2002) P.R. Roberge: Corrosion Basics – An Introduction (NACE International, Houston 2006) K.A. van Oeteren: Korrosionsschutz durch Beschichtungsstoffe (Hanser, München 1980), in German P. Maaß, P. Peißker: Handbuch Feuerverzinken (Deutscher Verlag Grundstoffindustrie, Stuttgart 1970), in German U.R. Evans: Some recent work on the corrosion of metals, Metal Ind. 29, 481 (1926) H. Baum: Untersuchungen zum Mechanismus der Deckschichtbildung beim atmosphärischen Rosten korrosionsträger Stähle Dissertation, Bergakademie Freiberg (1973) Institut für Korrosionsschutz Dresden: Vorlesungen über Korrosion und Korrosionsschutz (TAW, Wuppertal 1996) J. Göllner: Elektrochemisches Rauschen unter Korrosionsbedingungen, Habilitation, Otto-vonGuericke-Universität Magdeburg (2002) T. Shibata: Stochastic approach to the effect of alloying elements on the pitting resistance of ferritic stainless steels, Trans. ISIJ, 23, 785–788 (1983) H.H. Uhlig: Corrosion and Corrosion Control (Wiley, New York 1971) K. Mörbe, W. Morenz, H.-W. Pohlmann, H. Werner: Korrosionsschutz wasserführender Anlagen (Springer, Wien 1998) K.H. Tostmann: Korrosion (Verlag Chemie, Weinheim 2001) E. Wendler-Kalsch, H. Gräfen: Korrosionsschadenskunde (Springer, Berlin 1998), in German K. Schilling: Selektive Korrosion hochlegierter Stähle, Dissertation, Otto-von-Guericke-Universität Magdeburg (2005) H. Kaesche: Corrosion of Metals (Springer, Berlin 2003) C. Wagner, W. Traud: Über die Deutung von Korrosionsvorgängen durch Überlagerung von elektrochemischen Teilvorgängen und über die Poten-

Materials Science and Engineering

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3.112 3.113 3.114 3.115

3.116

3.117

3.118

3.119 3.120 3.121 3.122 3.123 3.124

3.125 3.126 3.127 3.128 3.129 3.130 3.131

3.132 J.R. Davis: Cast Irons, ASM Specialty Handbook (ASM, Metals Park 1996) 3.133 W.G. Moffatt, G.W. Pearsall, J. Wulff: The Structure and Properties of Materials, Structure, Vol. 1 (Wiley, New York 1964), p. 195 3.134 Specialty Castings Inc. http://www.specialtycastings. com/ductile_iron.html 3.135 G.E. Totten, D.S. MacKenzie: Physical Metallurgy and Processes, Handbook of Aluminum, Vol. 1 (Dekker, New York 2003) 3.136 C. Kammer: Fundamentals and Metarials, Aluminium Handbook 1 (Aluminium Verlag, Düsseldorf 2002), in German 3.137 J.R. Davis (Ed.): Aluminum and Aluminum Alloys, ASM Specialty Handbook (ASM, Metals Park 1993) 3.138 The University of British Columbia, Department of Materials Engineering, Mmat 380: online course material, Heat treatable aluminium alloys, http://www.mmat.ubc.ca/ courses/mmat380/default.htm 3.139 A. Dehler, S. Knirsch, V. Srivastava, H. Saage, M. Heilmaier: Assessment of creep behaviour of the die-cast cylinder-head alloy AlSi6Cu4-T6, Int. J. Met. Res. 97, 12 (2006) 3.140 H. Baker, B. David, K.W. Craig: Metals Hanbook, Vol. 2 (ASM, Metal Parks 1979) 3.141 M.M. Avdesian, H. Baker: Magnesium and Magnesium Alloys, ASM Specialty Handbook (ASM, Metals Park 1999) 3.142 I.J. Polmear: Light Alloys, Metallurgy of the Light Metals (Wiley, New York 1995) 3.143 G. Neite: Structure and properties of nonferrous alloys. In: Materials Science and Technologie, Vol. 8, ed. by K.H. Matucha (Verlag Chemie, Weinheim 1996) 3.144 The University of British Columbia, Department of Materials Engineering – mmat 380: online course material, Titanium alloys, http://www.mmat.ubc.ca/ courses/mmat380/default.htm 3.145 R. Boyer, G. Welsch, E.W. Collings: Materials Properties Hanbook: Titanium Alloys (ASM, Materials Park 1994) 3.146 K.H. Matchuta: Structure and properties of nonferrous alloys. In: Matreials Science and Technology, Vol. 8, ed. by R.W. Cahn, P. Haasen, E.J. Kramer (VCH, Weinheim 1996) 3.147 W.F. Hosford: Physical Metallurgy (Taylor Francis, New York 2005) 3.148 S.C. Huang, J.C. Chessnut: Intermetallic CompoundsPrinciples and Practice, Vol. 2, Vol. 2, ed. by J.H. Westbrook, R.L. Fleischer (Wiley, Chinchester 1994) p. 73 3.149 Forschungszentrum Jülich GmbH: Titan-AluminidLegierungen – eine Werkstoffgruppe mit Zukunft (Grafische Betriebe, Forschungszentrum Jülich GmbH, Jülich 2003), in German 3.150 K. Otsuka, C.M. Wayman: Shape Memory Materials (Cambridge Univ. Press, Cambridge 1998)

221

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tialbildung an Mischelektroden, Z. Elektroch. 44, 391–454 (1938), in German E. Hornbogen, H. Warlimont: Metallkunde (Springer, Berlin 2001), in German R.W. Cahnn, P. Haasen, E.J. Kramer, M. Schütze: Corrosion and Environmental Degradation, Materials Science and Technology (Wiley-VCH, Weinheim 2000) W. Schatt, H. Worch: Werkstoffwissenschaft (Deutscher Verlag Grundstoffindustrie, Stuttgart 1996) R.B. Ross: Metallic Materials Specification Handbook, 4th edn. (Chapman Hall, London 1992) A. Nayar: The Metals Databook (McGraw-Hill, New York 1997) M.F. Ashby, D.R.H. Jones: Engineering Materials 2: An Introduction to Microstructures, Processing and Design (Butterworth-Heinemann, Burlington 1998) A.M. Howatson, P.G. Lund, J.D. Todd: Engineering Tables and Data, 2nd edn. (Chapman Hall, London 1991) D.K. Roylance: Mechanics of Materials, Massachusetts Institute of Technology Department of Materials Science and Engineering, Cambridge (MITDMSE), Material Properties (http://web.mit.edu/ course/3/3.11/www/modules/props.pdf) R.W.K. Honeycombe, H.K.D.H. Bhadeshia: Steels – Microstructure and Properties, 2nd edn. (Edward Arnold, London, New York, Sydney, Auckland 1995) G. Krauss: Steel – Heat Treatment and Processing Principles (ASM Int., Materials Park 1989) W.C. Leslie: The Physical Metallurgy of Steels (McGraw-Hill, New York 1981) A.K. Sinha: Ferrous Physical Metallurgy (Butterworths, London 1989) D.T. Llewellyn, R.C. Hudd: Steels, Metallurgy and Applications (Butterworth Heinemann, Oxford 1998) Online Source: Key to Steel: Steel Database on http://www.key-to-steel.com/ H.K.D.H. Bhadeshia: Bainite in Steels, Transformation, Microstructure and Properties (IOM, London 2001) J.R. Davis: Carbon and Alloy Steels, ASM Speciality Handbook (ASM, Metals Park 1996) E.C. Bain, H.W. Paxton: Alloying Elements in Steel (ASM, Metals Park 1966) P.M. Unterweiser: Worldwide Guide to Equivalent Irons and Steels (ASM, Materials Park 1996) J.E. Bringes: Handbook of Comparative World Steel Standards (ASTM, West Conshohocken 2001) J.R. Davis: Stainless Steels, ASM Speciality Handbook (ASM, Metals Park 1994) J.R. Davis: Tool Materials, ASM Specialty Handbook (ASM, Metals Park 1995) H.E. McGannon: The Making, Shaping and Treatment of Steel (United States Steel Corporation, Pittsburgh 1971)

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3.151 J.R. Davies: Heat-Resistant Materials, ASM Specialty Handbook (ASM Int., Metals Park 1997) 3.152 G. Joseph, K.J.A. Kundig: Copper, Its Trade, Manufacture, Use, and Environment Status (ASM Int., Materials Park 1998) 3.153 J.R. Davis: Copper and Copper Alloys, ASM Specialty Handbook (ASM, Metals Park 2001) 3.154 H. Lipowsky, E. Arpaci: Copper in the Automotive Industry (Wiley-VCH, Weinheim 2006) 3.155 J. Brandrup, E.H. Immergut, E.A. Grulke: Polymer Handbook (Wiley, New York 2004) 3.156 H.-G. Elias: An Introduction to Polymer Science (Wiley-VCH, Weinheim 1999) 3.157 I. Mita, R.F.T. Stepto, U.W. Suter: Basic classification and definitions of polymerization reactions, Pure Appl. Chem. 66, 2483–2486 (1994) 3.158 K. Matyjaszewski, T.P. Davis: Handbook of Radical Polymerization (Wiley, New York 2002) 3.159 G.W. Ehrenstein, R.P. Theriault: Polymeric Materials: Structure, Properties, Applications (Hanser Gardner, Munich 2000) 3.160 G.H. Michler, F.J. Baltá-Calleja: Mechanical Properties of Polymers Based on Nano-Structure and Morphology (CRC, Boca Raton 2005) 3.161 A.E. Woodward: Atlas of Polymer Morphology (Hanser Gardner, Munich 1988) 3.162 E.A. Campo: The Complete Part Design Handbook for Injection Moulding of Thermoplastics (Hanser, Munich 2006) 3.163 D.V. Rosato, A.V. Rosato, D.P. DiMattia: Blow Moulding Handbook (Hanser Gardner, Munich 2003) 3.164 L.C.E. Struik: Internal Stresses, Dimensional Instabilities and Molecular Orientations in Plastics (Wiley, New York 1990) 3.165 ISO: ISO 1135 parts 1-7:1997: Plastics – Differential Scanning Calorimetry (DSC) – Part 1: General Principles (ISO, Geneva 1997) 3.166 T.A. Osswald, G. Menges: Materials Science of Polymers for Engineers (Hanser, Munich 1995) 3.167 P.C. Powell: Engineering with Polymers (CRC, Boca Raton 1998)

3.168 I.M. Ward, D.W. Hadley: An Introduction to the Mechanical Properties of Solid Polymers (Wiley, Chichester 1993) 3.169 H. Czidios, T. Saito, L. Smith (Eds.): Springer Handbook of Materials Measurement Methods (Springer, Berlin, Heidelberg 2006), Chap. 7 3.170 I.M. Ward: Structure and Properties of Oriented Polymers (Chapman Hall, London 1997) 3.171 ISO: ISO 6721-1:2001 Plastics – Determination of Dynamic Mechanical Properties – Part 1: General Principles; ISO 6721-2: 1994 Plastics – Determination of Dynamic Mechanical Properties – Part 2: Torsion-Pendulum Method (ISO, Geneva 2001) 3.172 E.A. Grulke: Solubility parameter values. In: Polymer Handbook 3rd. edn, ed. by J. Brandrup, E.H. Immergut (Wiley, New York 1989), VII/519–557 3.173 G.W. Ehrenstein: Faserverbund-Kunststoffe, Werkstoffe – Verarbeitung – Eigenschaften (Hanser, Munich 2006) 3.174 L.H. Sperling: Polymeric Multicomponent Materials (Wiley, New York 1997) 3.175 C.M. Hansen: Solubility Parameters: A User’s Handbook (CRC, Boca Raton 1999) 3.176 W.D. Callister Jr.: Fundamentals of Materials Science and Engineering (Wiley, New York 2001) 3.177 R. Freer: The Physics and Chemistry of Carbides, Nitrides and Borides (Kluwer, Boston 1989) 3.178 M.V. Swain: Structure and Properties of Ceramics, Materials Science and Technology, Vol. 11 (Verlag Chemie, Weinheim 1994) 3.179 G.V. Samson: The Oxides Handbook (Plenum, New York 1974) 3.180 D. Hull, T.W. Clyne: An Introduction to Composite Materials, 2nd edn. (Cambridge Univ. Press, Cambridge 1996) 3.181 J.S. Benjamin: Dispersion strengthened superalloys by mechanical alloying, Metall. Trans. 1, 2943 (1970) 3.182 Y. Estrin, S. Arndt, M. Heilmaier, Y. Brechet: Deformation beahviour of particle strengthened alloys: A Voronoi mesh approach, Acta Mater. 47, 595 (1999)

223

Thermodynam 4. Thermodynamics

This chapter presents the basic definitions, laws and relationships concerning the thermodynamic states of substances and the thermodynamic processes. It closes with a section describing the heat transfer mechanisms.

4.1

4.2

Scope of Thermodynamics. Definitions ... 223 4.1.1 Systems, System Boundaries, Surroundings ............................... 224 4.1.2 Description of States, Properties, and Thermodynamic Processes....... 224 Temperatures. Equilibria ....................... 4.2.1 Thermal Equilibrium ..................... 4.2.2 Zeroth Law and Empirical Temperature ........... 4.2.3 Temperature Scales ......................

225 225

First Law of Thermodynamics................. 4.3.1 General Formulation .................... 4.3.2 The Different Forms of Energy and Energy Transfer........ 4.3.3 Application to Closed Systems ........ 4.3.4 Application to Open Systems..........

228 228

4.4 Second Law of Thermodynamics............. 4.4.1 The Principle of Irreversibility ........ 4.4.2 General Formulation .................... 4.4.3 Special Formulations ....................

231 231 232 233

4.5 Exergy and Anergy ................................ 4.5.1 Exergy of a Closed System.............. 4.5.2 Exergy of an Open System ............. 4.5.3 Exergy and Heat Transfer............... 4.5.4 Anergy ........................................ 4.5.5 Exergy Losses ...............................

233 234 234 234 235 235

4.3

225 225

228 229 229

4.6 Thermodynamics of Substances.............. 4.6.1 Thermal Properties of Gases and Vapors ..................... 4.6.2 Caloric Properties of Gases and Vapors ..................... 4.6.3 Incompressible Fluids ................... 4.6.4 Solid Materials ............................. 4.6.5 Mixing Temperature. Measurement of Specific Heats ...... 4.7

235 235 239 250 252 254

Changes of State of Gases and Vapors..... 256 4.7.1 Change of State of Gases and Vapors in Closed Systems ........ 256 4.7.2 Changes of State of Flowing Gases and Vapors .................................. 259

4.8 Thermodynamic Processes ..................... 4.8.1 Combustion Processes ................... 4.8.2 Internal Combustion Cycles............ 4.8.3 Cyclic Processes, Principles ............ 4.8.4 Thermal Power Cycles.................... 4.8.5 Refrigeration Cycles and Heat Pumps .......................... 4.8.6 Combined Power and Heat Generation (Co-Generation) ..........

262 262 265 267 268 272 273

4.9 Ideal Gas Mixtures ................................ 274 4.9.1 Mixtures of Gas and Vapor. Humid Air ................................... 274 4.10 Heat Transfer ....................................... 4.10.1 Steady-State Heat Conduction ....... 4.10.2 Heat Transfer and Heat Transmission ................. 4.10.3 Transient Heat Conduction ............ 4.10.4 Heat Transfer by Convection .......... 4.10.5 Radiative Heat Transfer .................

280 280 281 284 286 291

References .................................................. 293

4.1 Scope of Thermodynamics. Definitions Thermodynamics is a subsection of physics that deals with energy and its relationship with properties of matter. It is concerned with the different forms of energy

and their transformation between one another. It provides the general laws that are the basis for energy conversion, transfer, and storage.

Part B 4

Frank Dammel, Jay M. Ochterbeck, Peter Stephan

224

Part B

Applications in Mechanical Engineering

4.1.1 Systems, System Boundaries, Surroundings

Part B 4.1

A thermodynamic system, or briefly a system, is a quantity of matter or a region in space chosen for a thermodynamic investigation. Some examples of systems are an amount of gas, a liquid and its vapor, a mixture of several liquids, a crystal or a power plant. The system is separated from the surroundings, the so-called environment, by a boundary (real or imaginary). The boundary is allowed to move during the process under investigation, e.g., during the expansion of a gas, and matter and energy may cross the boundary. Energy can cross a boundary with matter and in the form of heat transfer or work (Sect. 4.3.2). The system with its boundary serves as a region with a barrier in which computations of energy conversion processes take place. Using an energy balance relationship (the first law of thermodynamics) applied to a system, energies that cross the system boundary (in or out), the changes in stored energy, and the properties of the system are linked. A system is called closed when mass is not allowed to cross the boundary, and open when mass crosses the system boundary. While the mass of a closed system always remains constant, the mass inside an open system may also remain constant when the total mass flow in and the total mass flow out are equal. Changes of the mass stored in an open system will occur when the mass flow into the system over a certain time span is different from the mass flow out. Examples of closed systems are solid bodies, mass elements in mechanics, and a sealed container. Examples of open systems are turbines, turbojet engines, or a fluid (gases or liquids) flowing in channel. A system is called adiabatic when it is completely thermally isolated from its surrounding and no heat transfer can cross the boundary. A system that is secluded from all influences of its environment is called isolated. For an isolated system neither energy in the form of heat transfer or work nor matter are exchanged with the environment. The distinction between a closed and an open system corresponds to the distinction between a Lagrangian and an Eulerian reference system in fluid mechanics. In the Lagrangian reference system, which corresponds to the closed system, the fluid motion is examined by dividing the flow into small elements of constant mass and deriving the corresponding equations of motion. In the Eulerian reference system, which corresponds to the open system, a fixed volume element in space is selected and the fluid flow through

the volumetric element is examined. Both descriptions are equivalent, and it is often only a question of convenience whether one chooses a closed or an open system.

4.1.2 Description of States, Properties, and Thermodynamic Processes A system is characterized by physical properties, which can be given at any instant, for example, pressure, temperature, density, electrical conductivity, and refraction index. The state of a system is determined by the values of these properties. The transition of a system from one equilibrium state to another is called a change of state. Example 4.1: A balloon is filled with gas. The gas may then be the thermodynamic system. Measurements show that the mass of the gas is determined by volume, pressure, and temperature. The properties of the system are thus volume, pressure, and temperature, and the state of the system (the gas) is characterized through a fixed set of volume, pressure, and temperature. The transition to another fixed set, e.g., when a certain amount of gas effuses, is called a change of state.

The mathematical relationship between properties is called an equation of state. Example 4.2: The volume of the gas in the balloon

proves to be a function of pressure and temperature. The mathematical relationship between these properties is such an equation of state. Properties are subdivided into three classes: intensive properties are independent of the size of a system and thus keep their values after a division of the system into subsystems. Example 4.3: If a space filled with a gas of uniform temperature is subdivided into smaller spaces, the temperature remains the same in each subdivided space. Thus, temperature is an intensive property. Pressure would be another example of an intensive property.

Properties that are proportional to the mass of the system (i. e., the total is equal to the sum of the parts) are called extensive properties. Example 4.4: The volume, the energy or the mass.

An extensive property X divided by the mass m of the system yields the specific property x = X/m.

Thermodynamics

Example 4.5: Take the extensive property volume of a given gas. The associate specific property is the specific volume v = V/m, where m is the mass of the gas. The SI unit for specific volume is m3/kg. Specific properties all fall into the category of intensive properties.

boundary. In order to describe a change of state it is sufficient to specify the time history of the properties. The description of a process requires additional specifications of the extent and type of the interactions with the environment. Consequently, a process is a change of state caused by certain external influences. The term process is more comprehensive than the term change of state; for example, the same change between two states can be induced by different processes.

4.2 Temperatures. Equilibria 4.2.1 Thermal Equilibrium We often talk about hot or cold bodies without quantifying such states exactly by a property. When a closed hot system A is exposed to a closed cold system B, energy is transported as heat transfer through the contact area. Thereby, the properties of both systems change until after a sufficient period of time new fixed values are reached and the energy transport stops. The two systems are in thermal equilibrium in this final state. The speed with which this equilibrium state is approached depends on the type of contact between the two systems and on the thermal properties. If, for example, the two systems are separated only by a thin metal wall, the equilibrium is reached faster than in the case of a thick polystyrene wall. A separating wall, which inhibits mass transfer and also mechanical, magnetic or electric interactions, but permits the transport of heat, is called diatherm. A diatherm wall is thermally conductive. A completely thermally insulated wall such that no thermal interactions occur with the surroundings is called adiabatic.

4.2.2 Zeroth Law and Empirical Temperature In the case of thermal equilibrium between systems A and C and thermal equilibrium between systems B and C experience shows that the systems A and B must also be in thermal equilibrium. This empirical statement is called the zeroth law of thermodynamics. It reads: if two systems are both in thermal equilibrium with a third system, they are also in thermal equilibrium with each other. In order to find out if two systems A and B are in thermal equilibrium, they are exposed successively to a system C. The mass of system C may be small compared to those of systems A and B. If so, changes in state

of systems A and B are negligible during equilibrium adjustment. When C is exposed to A, certain properties of C will change, for example, its electrical resistance. These properties then remain unchanged during the following exposure of C to B, if A and B were originally in thermal equilibrium. Using C in this way it is possible to verify if A and B are in thermal equilibrium. It is possible to assign any fixed values to the properties of C after equilibrium adjustment. These values are called empirical temperatures, where the measurement instrument is a thermometer.

4.2.3 Temperature Scales A gas thermometer (Fig. 4.1), which measures the pressure p of a constant gas volume V , is used for the construction and definition of empirical temperature scales. The gas thermometer is brought into contact with systems of a constant state, e.g., a mixture of ice and water at a fixed pressure. After a sufficient period of time, the gas thermometer will be in thermal equilibrium with the system with which it is in contact. The gas volume is kept constant by changing the height Δz of the mercury column. The pressure exerted by the mercury column and environment is measured and the product pV is computed. The extrapolation of measurements at different, sufficiently low pressures leads to a threshold value A of the product pV for the pressure approaching zero. This value A, which is determined from the measurements, is assigned to an empirical temperature via the linear relationship T = const. A .

(4.1)

After fixing the value const it is only necessary to determine the value of A from the measurements in order to compute the empirical temperature with (4.1). The specification of the empirical temperature scale requires

225

Part B 4.2

Changes of state are caused by interactions of the system with the environment, for example, when energy is transferred to or from the system across the system

4.2 Temperatures. Equilibria

Thermodynamics

4.2 Temperatures. Equilibria

227

Table 4.1 Fixed points of the international temperature scale of 1990 (IPTS-90) Equilibrium state

Assigned values of the international practical temperature scale T90 (K) t90 (◦ C)

3 to 5 −270.15 to −268.15 13.8033 −259.3467 ≈ 17 ≈ −256.15 ≈ 20.3 ≈ −252.85 Triple point of neon 24.5561 −248.5939 Triple point of oxygen 54.3584 −218.7916 Triple point of argon 83.8058 −189.3442 Triple point of mercury 234.3156 −38.8344 Triple point of water 273.16 0.01 Melting point of gallium 302.9146 29.7646 Solidification point of indium 429.7485 156.5985 Solidification point of tin 505.078 231.928 Solidification point of zinc 692.677 419.527 Solidification point of aluminium 933.473 660.323 Solidification point of silver 1234.93 961.78 Solidification point of gold 1337.33 1064.18 Solidification point of copper 1357.77 1084.62 All substances beside helium may have their natural isotope composition. Hydrogen consists of ortho- and parahydrogen at equilibrium composition. Vapor pressure of helium Triple point of equilibrium hydrogen Vapor pressure of equilibrium hydrogen

◦C

Normal hydrogen

Tr

−259.198

Normal hydrogen

Sd

−252.762

Nitrogen

Sd

−195.798

Carbon dioxide

Tr

−56.559

Bromine benzene

Tr

−30.726

Water (saturated with air)

E

0

Benzoic acid

Tr

122.34

Indium

Tr

156.593

Bismuth

E

271.346

Cadmium

E

320.995

Lead

E

327.387

Mercury

Sd

356.619

Sulfur

Sd

444.613

Antimony

E

Palladium

E

1555

Platinium

E

1768

Rhodium

E

1962

Iridium

E

2446

Tungsten

E

3418

630.63

4. Formulas, which also are established by international agreements, are used for interpolation between fixed points. Thus, the indications of the standard instruments with which the temperatures have to be measured, are assigned to the numerical values of the international practical temperature. In order to simplify temperature measurements other additional thermometric fixed points for substances, which can be easily produced in sufficiently pure form, were associated as accurately as possible to the lawful temperature scale. The most important ones are summarized in Table 4.2. The platinum resistance thermometer is used as the normal instrument between the triple point of equilibrium hydrogen at 13.8033 K ( − 259.3467 ◦ C) and the melting point of silver at 1234.93 K (961.78 ◦ C). Between the melting point of silver and the melting point of gold at 1337.33 K (1064.18 ◦ C) a platinum–rhodium (10% rhodium)/platinum thermocouple is used as normal instrument. Above the melting point of gold, Planck’s radiation law defines the international practical temperature   exp λ(tAuc2+T0 ) − 1 Jt  c2  , = (4.6) JAu −1 exp λ(t+T 0)

Part B 4.2

Table 4.2 Some thermometric fixed points: E solidification point, Sd boiling point at pressure 101.325 kPa, Tr triple point (after [4.1])

228

Part B

Applications in Mechanical Engineering

where Jt and JAu are the radiation energies emitted by a black body at temperature t and at the gold point tAu , respectively, at a wavelength of λ per unit area, time, and wavelength interval. The value of the constant c2 is specified as 0.014388 Km

(Kelvin meter), T0 = 273.15 K is the numerical value of the melting temperature of ice, and λ is the numerical value in m of a wavelength in the visible spectrum. For practical temperature measurement [4.2, 3]

Part B 4.3

4.3 First Law of Thermodynamics 4.3.1 General Formulation The first law is an empirical statement, which is valid because all conclusions drawn from it are consistent with experience. Generally, it states that energy can be neither destroyed nor created, thus energy is a conserved property. This means that the energy E of a system can be changed only by energy exchange into or out of the system. It is generally agreed that energy transferred to a system is positive and energy transferred from a system is negative. A fundamental formulation of the first law reads: every system possesses an extensive property energy, which is constant in an isolated system.

4.3.2 The Different Forms of Energy and Energy Transfer

Work In thermodynamics the basic definition of the term work is adopted from mechanics: the work done on a system is equal to the product of the force acting on the system and the displacement from the point of application. The work done by a force F along the distance z between points 1 and 2 is given by

2 F dz .

(4.7)

1

The mechanical work Wm12 is the result of forces which accelerate a closed system of mass m from velocity w1 to w2 and raise it from level z 1 to level z 2 against gravity g. This associates a change in kinetic energy mw2 /2 and in potential energy mgz of the system Wm12 = m

 w2 2

2

−

w21  + mg(z 2 − z 1 ) . 2

A

and thus 2 Wv12 = −

p dV .

(4.10)

1

In order to set up the first law mathematically it is necessary to distinguish and define the different forms of energy transfer.

W12 =

Equation (4.8) is known as the energy theorem of mechanics. Moving boundary work, or simply boundary work, is the work that has to be done to change the volume of a system. In a system of volume V , which possesses the variable pressure p, a differential element dA of the boundary surface thereby moves the distance dz. The work done is  (4.9) dWv = − p dAdz = − p dV ,

(4.8)

The minus sign is due to the formal sign convention which states that work transferred to the system, which is connected to a volume reduction, is positive. Equation (4.10) is only valid if the pressure p of the system is in each instance of the change of state a continuous function of volume and equal to the pressure exerted by the environment. Then a small excess or negative pressure of the environment causes either a decrease or an increase of the system volume. Such changes between states, where even the slightest imbalance is sufficient to drive them in either direction, are called reversible. Accordingly, (4.10) is the moving boundary work for reversible changes of state. In real processes a finite excess pressure of the environment is necessary to overcome the internal friction of the system. Such changes in state are irreversible, where the added work is increased by the dissipated part Wdiss12 . The moving boundary work for an irreversible change of state is 2 Wv12 = −

p dV + Wdiss12 .

(4.11)

1

The dissipation work is always positive and increases the system energy and causes a different path p(V )

Thermodynamics

This equation shows that in irreversible processes (Wdiss > 0) more work has to be done or less work is received than in reversible processes (Wdiss = 0). Table 4.3 includes different forms of work. Shaft work is work derived from a mass flow through a machine such as compressors, turbines, and jet engines. When a machine increases the pressure of a mass m along the path dz by d p, the shaft work is dWt = mv d p + dWdiss .

(4.13)

When kinetic energy and potential energy of the mass flow are also changed, mechanical work is done additionally. The shaft work done along path 1–2 is 2 Wt12 =

V d p + Wdiss12 + Wm12 ,

(4.14)

1

with Wm12 is given according to (4.8). Internal Energy In addition to any kinetic and potential energy, every system possesses energy stored internally as translational, rotational, and vibrational kinetic energy of the elementary particles. This is called the internal energy U of the system and is an extensive property. The total energy E a system of mass m possesses consists of internal energy, kinetic energy E kin , and potential energy E pot

E = U + E kin + E pot .

(4.15)

Heat Transfer The internal energy of a system can be changed by doing work on it or by adding or removing matter. However, it can also be changed by exposing the system to its environment which has a different temperature. As a consequence, energy is transferred across the system boundary as the system will try to reach thermal equilibrium with the environment. This energy transfer

229

is called heat transfer. Thus heat transfer can generally be defined as that energy a system exchanges with its environment which does not cross the system boundary as work or by accompanying mass transfer. The heat transfer from state 1 to 2 is denoted Q 12 .

4.3.3 Application to Closed Systems The heat transfer Q 12 and work W12 to a closed system during the change of state from 1 to 2 cause a change of the system energy E E 2 − E 1 = Q 12 + W12 ,

(4.16)

where W12 includes all forms of work done on the system. If no mechanical work is done, only the internal energy changes, and according to (4.15), E = U holds. If it is additionally assumed that only moving boundary work is done on the system, (4.16) reads 2 U2 − U1 = Q 12 −

p dV + Wdiss12 .

(4.17)

1

4.3.4 Application to Open Systems Steady-State Processes Very often work is done by a fluid flowing steadily through a device. If the work per unit time remains constant, such a process is called a steady flow process. Figure 4.2 shows a typical example: a flowing fluid (gas or liquid) of pressure p1 and temperature T1 may flow with velocity w1 into system σ . If machine work is done as shaft work, Wt12 is supplied at the shaft. Then the fluid flows through a heat exchanger, in which the heat transfer Q 12 occurs with the environment, and the fluid eventually leaves the system σ with pressure p2 , temperature T2 , and velocity w2 . Tracking the path of a constant mass element Δm through the system σ means that a moving observer would consider the mass element Δm as a closed system, thus this corresponds to the Lagrangian description in fluid mechanics. Therefore, the first law for closed systems (4.16) is valid in this case. The work done on Δm consists of Δm p1 v1 to push Δm out of the environment across the system boundary, of the technical work Wt12 , and of −Δm p2 v2 to bring Δm back into the environment. Thus, the work done on the closed system is

W12 = Wt12 + Δm( p1 v1 − p2 v2 ) .

(4.18)

The term Δm ( p1 v1 − p2 v2 ) is referred to as the flow work. This flow work is the difference between

Part B 4.3

between the states than in the reversible case. The determination of the integral in (4.11) requires that p is a unique function of V . Equation (4.11) is, for example, not valid for a system area through which a sound wave travels. Work can be derived as the product of a generalized force Fk and a generalized displacement dX k . In real processes the dissipated work has to be added  (4.12) dW = Fk dX k + dWdiss .

4.3 First Law of Thermodynamics

232

Part B

Applications in Mechanical Engineering

Part B 4.4

ous series of equilibrium states is reversible. This may be exemplified by the frictionless, adiabatic compression of a gas. It is possible to transfer moving boundary work to the system gas by exerting a force, for example, an excess pressure of the environment, on the system boundary. If this force is increased very slowly, the volume of the gas decreases and the temperature increases, whereas the gas is at any time in an equilibrium state. If the force is slowly reduced to zero, the gas returns to its initial state; thus, this process is reversible. Reversible processes are idealized borderline cases of real processes and do not occur in nature. All natural processes are irreversible, because a finite force is necessary to initiate a process, e.g., a finite force to move a body against friction or a finite temperature difference for heat transfer. These facts known from experience lead to the following formulations of the second law:

• • •

All natural processes are irreversible. All processes including friction are irreversible. Heat transfer does not independently occur from a body of lower to a body of higher temperature.

Independently in this connection means that it is not possible to carry out the mentioned process without causing effects on nature. Beside these examples, further formulations valid for other special processes exist.

4.4.2 General Formulation The mathematical formulation of the second law is realized by introducing the term entropy as another property of a system. The practicality of this property can be shown by using the example of heat transfer between a system and its environment. According to the first law, a system can exchange energy by work and by heat transfer with its environment. The supply of work causes a change of the internal energy such that, for example, the system’s volume is changed at the expense of the environment’s volume. Consequently, U = U(V, . . .). The volume is an exchange variable. It is an extensive property, which is exchanged between the system and environment. It is also possible to look upon the heat transfer between a system and its environment as an exchange of an extensive property. In this way, only the existence of such a property is postulated. Its introduction is solely justified by the fact that all statements derived from it correspond with experience. This new extensive property is called entropy and denoted with S. Consequently, U = U(V, S, . . .). If only moving boundary work occurs and heat transfer

occurs, U = U(V, S). Differentiation leads to the Gibbs equation dU = T dS − p dV

(4.29)

with the thermodynamic temperature T = (∂U/∂S)V

(4.30)

and the pressure p = −(∂U/∂V )S .

(4.31)

A relationship equivalent to (4.29) is derived by eliminating U and replacing it by enthalpy H = U + pV such that dH = T dS + V d p .

(4.32)

It can be shown that the thermodynamic temperature is identical to the temperature measured by a gas thermometer (Sect. 4.2.3). From examination of the characteristics of entropy it follows that in an isolated system, which is initially in nonequilibrium (for example, because of a nonuniform temperature distribution) and then approaches equilibrium, the entropy always increases. In the borderline case of equilibrium a maximum of entropy is reached. The internal entropy increase is denoted by dSgen . For the considered case of an isolated system it holds that dS = dSgen with dSgen > 0. If a system is not isolated, entropy is also changed by dSQ due to heat transfer (with the environment) and by dSm because of mass transfer with the environment. However, energy transfer by work with the environment does not change the system entropy. Thus, it holds generally that dS = dSQ + dSm + dSgen .

(4.33)

The formulation for the time-variable system entropy S˙ = dS/ dτ reads S˙ = S˙Q + S˙m + S˙gen

(4.34)

with S˙gen being the entropy generation rate caused by internal irreversibilities, and S˙Q + S˙m is called the entropy flow. These values, which are exchanged across the system boundary, are combined to S˙fl = S˙Q + S˙m .

(4.35)

The rate of change of the system entropy S consists, thus, of the entropy flow S˙fl and entropy generation S˙gen S˙ = S˙fl + S˙gen .

(4.36)

Thermodynamics

For the entropy generation it holds that S˙gen = 0 for reversible processes, S˙gen > 0 for irreversible processes, S˙gen < 0 for impossible processes.

(4.37)

4.5 Exergy and Anergy

4.4.3 Special Formulations Adiabatic, Closed Systems Since S˙Q = 0 for adiabatic systems and S˙m = 0 for closed systems, it follows that S˙ = S˙gen . Thus, the entropy of an adiabatic, closed system can never decrease. It can only increase during an irreversible process or remain constant during a reversible process. If an adiabatic, closed system consists of α subsystems, then it holds for the sum of entropy changes ΔSα of the subsystems that  ΔSα ≥ 0 . (4.38) α

With dS = dSgen , (4.29) reads for an adiabatic, closed system dU = T dSgen − p dV .

Systems with Heat Transfer For closed systems with heat transfer (4.29) becomes

dU = T dSQ + T dSgen − p dV = T dSQ + dWdiss − p dV . A comparison with the first law, (4.17), results in dQ = T dSQ .

(4.42)

Thus, heat transfer is energy transfer, which together with entropy crosses the system boundary, whereas work is exchanged without entropy exchange. Adding the always positive term T dSgen to the right-hand side of (4.42) leads to the Clausius inequality 2 dQ ≤ T dS

On the other hand it follows from the first law according to (4.17)

(4.41)

or ΔS ≥

dQ . T

(4.43)

1

dWdiss = T dSgen = dΨ

(4.39)

Wdiss12 = TSgen12 = Ψ12 ,

(4.40)

In irreversible processes the entropy change is larger than the integral over all dQ/T ; the equals sign is only valid for the reversible case. For open systems with heat addition, dSQ in (4.41) has to be replaced by dSfl = dSQ + dSm .

According to the first law, the energy of an isolated system is constant. As it is possible to transform every nonisolated system into an isolated one by adding the environment, it is always possible to define a system in which the energy remains constant during a thermodynamic process. Thus, a loss of energy is not possible, and energy is only converted in a thermodynamic process. How much of the energy stored in a system is converted depends on the state of the environment. If it is in equilibrium with the system, no energy is converted. The larger the difference from equilibrium, the more energy of the system can be converted and thus the greater the potential to perform work. Many thermodynamic processes take place in the Earth’s atmosphere, which is the environment of

most thermodynamic systems. In comparison to the much smaller thermodynamic systems, the Earth’s atmosphere can be considered as an infinitely large system, in which the intensive properties pressure, temperature, and composition do not change during a process (as long as daily and seasonal variations of the intensive properties are neglected). In many engineering processes work is obtained by bringing a system with a given initial state into equilibrium with the environment. The maximum work is obtained when all changes of state are reversible. The maximum work that could be obtained by establishing equilibrium with the environment is called the exergy Wex .

or

4.5 Exergy and Anergy

Part B 4.5

where Ψ12 is called the dissipated energy during the change in state 1–2. The dissipated energy is always positive. This statement is not only true for adiabatic systems but also for all general cases, because, according to definition, the entropy generation is the fraction of entropy change, which arises when the system is adiabatic and closed and therefore S˙fl = 0 holds.

233

Thermodynamics

− Wex =

2 

1−

Tenv  dQ T

4.5.4 Anergy Energy that cannot be converted into exergy Wex is called anergy B. Each amount of energy consists of exergy Wex and anergy B, i. e.,

For a closed system according to (4.48) with E = U1 B = Uenv + Tenv (S1 − Senv ) − penv (V1 − Venv ) (4.53)

For an open system according to (4.49) with E = H1 B = Henv + Tenv (S1 − Senv )

•

(4.54)

For heat transfer according to (4.51) with dE = dQ 2 B=

Tenv dQ T

2 Wloss12 =

(4.52)

Thus it holds that:

•

The energy dissipated in a process is not lost completely. It increases the entropy, and because of U(S, V ), also the internal energy of a system. It is possible to think of the dissipated energy as heat transfer in a substitutional process, which is transferred from the outside ( dΨ = dQ) and causes the same entropy increase as in the irreversible process. Since the heat transfer dQ, (4.51), is partly transformable into work, the fraction  Tenv  (4.56) dΨ − dWex = 1 − T of the dissipated energy dΨ can also be obtained as work (exergy). The remaining fraction Tenv dΨ /T of the dissipated energy has to be transferred to the environment as heat transfer and is not transformable into work. This exergy loss is equal to the anergy of the dissipated energy and is, according to (4.55), given by

(4.55)

1

Tenv dΨ = T

1

2 Tenv dSi .

(4.57)

1

For a process in a closed, adiabatic system it holds that dSi = dS and thus 2 Wloss12 =

Tenv dS = Tenv (S2 − S1 ) .

(4.58)

1

In contrast to energy, exergy does not follow a conservation equation. The exergy transferred to a system at steady state is equal to the sum of the exergy transferred from the system plus exergy losses. The thermodynamic effect of losses caused by irreversibilities is more unfavorable for lower temperatures T at which the process takes place; see (4.57).

4.6 Thermodynamics of Substances In order to utilize the primary laws of thermodynamics, which are generally set up for any arbitrary substance, and to calculate exergies and anergies, it is necessary to determine actual numerical values for the properties U, H, S, p, V , and T . From these U, H, and S typically are called caloric, where p, V , and T are thermal properties. The relationships between properties depend on the corresponding substance. Equations that specify the relationships between the properties p, V , and T are called equations of state.

4.6.1 Thermal Properties of Gases and Vapors An equation of state for pure substances is of the form F( p, v, T ) = 0

(4.59)

or p = p(v, T ), v = v( p, T ), and T = T ( p, v). For calculations equations of state of the form v = v( p, T ) are preferred, as the pressure and temperature are usually the independent variables used to describe a system.

Part B 4.6

or in differential notation  Tenv  − dWex = 1 − (4.51) dQ . T In a reversible process only the fraction of the supplied heat transfer multiplied with the so-called Carnot factor 1 − (Tenv /T ) can be transformed into work. The fraction dQ env = −Tenv ( dQ/T ) has to be transferred to the environment and it is impossible to obtain it as work. This shows additionally that the heat transfer, which is available at ambient temperature, can not be transformed into exergy.

•

235

4.5.5 Exergy Losses (4.50)

1

E = Wex + B .

4.6 Thermodynamics of Substances

236

Part B

Applications in Mechanical Engineering

Table 4.4 Critical data of some substances, ordered according to the critical temperature (after [4.4–6])

Part B 4.6

Mercury Aniline Water Benzene Ethyl alcohol Diethyl ether Ethyl chloride Sulfur dioxide Methyl chloride Ammonia Hydrogen chloride Nitrous oxide Acetylene Ethane Carbon dioxide Ethylene Methane Nitrous monoxide Oxygen Argon Carbon monoxide Air Nitrogen Hydrogen Helium-4

Symbol

M (kg/kmol)

Pcr (bar)

Tcr (K)

vcr (dm3/kg)

Hg C6 H7 N H2 O C6 H6 C2 H5 OH C4 H10 O C2 H5 Cl SO2 CH3 Cl NH3 HCl N2 O C2 H2 C2 H6 CO2 C2 H4 CH4 NO O2 Ar CO – N2 H2 He

200.59 93.1283 18.0153 78.1136 46.0690 74.1228 64.5147 64.0588 50.4878 17.0305 36.4609 44.0128 26.0379 30.0696 44.0098 28.0528 16.0428 30.0061 31.999 39.948 28.0104 28.953 28.0134 2.0159 4.0026

1490 53.1 220.55 48.98 61.37 36.42 52.7 78.84 66.79 113.5 83.1 72.4 61.39 48.72 73.77 50.39 45.95 65 50.43 48.65 34.98 37.66 33.9 12.97 2.27

1765 698.7 647.13 562.1 513.9 466.7 460.4 430.7 416.3 405.5 324.7 309.6 308.3 305.3 304.1 282.3 190.6 180 154.6 150.7 132.9 132.5 126.2 33.2 5.19

0.213 2.941 3.11 3.311 3.623 3.774 2.994 1.901 2.755 4.255 2.222 2.212 4.329 4.926 2.139 4.651 6.173 1.901 2.294 1.873 3.322 3.195 3.195 32.26 14.29

Ideal Gases A particularly simple equation of state is that for ideal gases

pV = mRT

or

pv = RT,

(4.60)

which relates the absolute pressure p, the volume V , the specific volume v, the individual gas constant R, and the thermodynamic temperature T . A gas is assumed to behave as an ideal gas only when the pressure is sufficiently low compared to the critical pressure pcr of the substance, i. e., p/ pcr → 0. Gas Constant and Avogadro’s Law As a measure of the amount of a given system, the mole is defined with the unit symbol mol. The amount of a substance is 1 mol when it contains as many identical elementary entities (i. e., molecules, atoms, elementary particles) as there are atoms in exactly 12 g of pure carbon-12.

The number of particles of the same type contained in a mole is called Avogadro’s number (in German literature the number is sometimes referred to as Loschmidt’s number). It has the numerical value NA = (6.02214199 ± 4.7 × 10−7 ) × 1026 /kmol . (4.61)

The mass of a mole (NA particles of the same type) is a specific quantity for each substance and is referred to as the molar mass (see tab003-9 for values), which is given by M = m/n

(4.62)

(SI unit kg/kmol, m mass in kg, n molar amount in kmol). According to Avogadro (1811), ideal gases contain an equal number of molecules at the same pressure and at the same temperature occupying equal spaces.

240

Part B

Applications in Mechanical Engineering

Table 4.6 Saturated water temperature table (after [4.10])

Part B 4.6

t (◦ C)

p (bar)

v (m3 /kg)

v (m3 /kg)

h (kJ/kg)

h (kJ/kg)

Δhv (kJ/kg)

s (kJ/(kgK))

s (kJ/(kgK))

0.01 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86

0.006117 0.007060 0.008135 0.009354 0.010730 0.012282 0.014028 0.015989 0.018188 0.020647 0.023392 0.026452 0.029856 0.033637 0.037828 0.042467 0.047593 0.053247 0.059475 0.066324 0.073844 0.082090 0.091118 0.10099 0.11176 0.12351 0.13631 0.15022 0.16532 0.18171 0.19946 0.21866 0.23942 0.26183 0.28599 0.31201 0.34000 0.37009 0.40239 0.43703 0.47415 0.51387 0.55636 0.60174

0.001000 0.001000 0.001000 0.001000 0.001000 0.001000 0.001001 0.001001 0.001001 0.001001 0.001002 0.001002 0.001003 0.001003 0.001004 0.001004 0.001005 0.001006 0.001006 0.001007 0.001008 0.001009 0.001009 0.001010 0.001011 0.001012 0.001013 0.001014 0.001015 0.001016 0.001017 0.001018 0.001019 0.001020 0.001022 0.001023 0.001024 0.001025 0.001026 0.001028 0.001029 0.001030 0.001032 0.001033

205.998 179.764 157.121 137.638 120.834 106.309 93.724 82.798 73.292 65.003 57.762 51.422 45.863 40.977 36.675 32.882 29.529 26.562 23.932 21.595 19.517 17.665 16.013 14.535 13.213 12.028 10.964 10.007 9.145 8.369 7.668 7.034 6.460 5.940 5.468 5.040 4.650 4.295 3.971 3.675 3.405 3.158 2.932 2.724

0.00 8.39 16.81 25.22 33.63 42.02 50.41 58.79 67.17 75.55 83.92 92.29 100.66 109.02 117.38 125.75 134.11 142.47 150.82 159.18 167.54 175.90 184.26 192.62 200.98 209.34 217.70 226.06 234.42 242.79 251.15 259.52 267.89 276.27 284.64 293.02 301.40 309.78 318.17 326.56 334.95 343.34 351.74 360.15

2500.91 2504.57 2508.24 2511.91 2515.57 2519.23 2522.89 2526.54 2530.19 2533.83 2537.47 2541.10 2544.73 2548.35 2551.97 2555.58 2559.19 2562.79 2566.38 2569.96 2573.54 2577.11 2580.67 2584.23 2587.77 2591.31 2594.84 2598.35 2601.86 2605.36 2608.85 2612.32 2615.78 2619.23 2622.67 2626.10 2629.51 2632.91 2636.29 2639.66 2643.01 2646.35 2649.67 2652.98

2500.91 2496.17 2491.42 2486.68 2481.94 2477.21 2472.48 2467.75 2463.01 2458.28 2453.55 2448.81 2444.08 2439.33 2434.59 2429.84 2425.08 2420.32 2415.56 2410.78 2406.00 2401.21 2396.42 2391.61 2386.80 2381.97 2377.14 2372.30 2367.44 2362.57 2357.69 2352.80 2347.89 2342.97 2338.03 2333.08 2328.11 2323.13 2318.13 2313.11 2308.07 2303.01 2297.93 2292.83

0.0000 0.0306 0.0611 0.0913 0.1213 0.1511 0.1806 0.2099 0.2390 0.2678 0.2965 0.3250 0.3532 0.3813 0.4091 0.4368 0.4643 0.4916 0.5187 0.5457 0.5724 0.5990 0.6255 0.6517 0.6778 0.7038 0.7296 0.7552 0.7807 0.8060 0.8312 0.8563 0.8811 0.9059 0.9305 0.9550 0.9793 1.0035 1.0276 1.0516 1.0754 1.0991 1.1227 1.1461

9.1555 9.1027 9.0506 8.9994 8.9492 8.8998 8.8514 8.8038 8.7571 8.7112 8.6661 8.6218 8.5783 8.5355 8.4934 8.4521 8.4115 8.3715 8.3323 8.2936 8.2557 8.2183 8.1816 8.1454 8.1099 8.0749 8.0405 8.0066 7.9733 7.9405 7.9082 7.8764 7.8451 7.8142 7.7839 7.7540 7.7245 7.6955 7.6669 7.6388 7.6110 7.5837 7.5567 7.5301

Thermodynamics

4.6 Thermodynamics of Substances

241

Table 4.6 (cont.) p (bar)

v (m3 /kg)

v (m3 /kg)

h (kJ/kg)

h (kJ/kg)

Δhv (kJ/kg)

s (kJ/(kgK))

s (kJ/(kgK))

88 90 92 94 96 98 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240 245 250 255 260 265 270 275 280 285

0.65017 0.70182 0.75685 0.81542 0.87771 0.94390 1.0142 1.2090 1.4338 1.6918 1.9867 2.3222 2.7026 3.1320 3.6150 4.1564 4.7610 5.4342 6.1814 7.0082 7.9205 8.9245 10.026 11.233 12.550 13.986 15.547 17.240 19.074 21.056 23.193 25.494 27.968 30.622 33.467 36.509 39.759 43.227 46.921 50.851 55.028 59.463 64.165 69.145

0.001035 0.001036 0.001037 0.001039 0.001040 0.001042 0.001043 0.001047 0.001052 0.001056 0.001060 0.001065 0.001070 0.001075 0.001080 0.001085 0.001091 0.001096 0.001102 0.001108 0.001114 0.001121 0.001127 0.001134 0.001141 0.001149 0.001157 0.001164 0.001173 0.001181 0.001190 0.001199 0.001209 0.001219 0.001229 0.001240 0.001252 0.001264 0.001276 0.001289 0.001303 0.001318 0.001333 0.001349

2.534 2.359 2.198 2.050 1.914 1.788 1.672 1.418 1.209 1.036 0.8913 0.7701 0.6681 0.5818 0.5085 0.4460 0.3925 0.3465 0.3068 0.2725 0.2426 0.2166 0.1939 0.1739 0.1564 0.1409 0.1272 0.1151 0.1043 0.09469 0.08610 0.07841 0.07151 0.06530 0.05971 0.05466 0.05009 0.04594 0.04218 0.03875 0.03562 0.03277 0.03015 0.02776

368.56 376.97 385.38 393.81 402.23 410.66 419.10 440.21 461.36 482.55 503.78 525.06 546.39 567.77 589.20 610.69 632.25 653.88 675.57 697.35 719.21 741.15 763.19 785.32 807.57 829.92 852.39 874.99 897.73 920.61 943.64 966.84 990.21 1013.77 1037.52 1061.49 1085.69 1110.13 1134.83 1159.81 1185.09 1210.70 1236.67 1263.02

2656.26 2659.53 2662.78 2666.01 2669.22 2672.40 2675.57 2683.39 2691.07 2698.58 2705.93 2713.11 2720.09 2726.87 2733.44 2739.80 2745.92 2751.80 2757.43 2762.80 2767.89 2772.70 2777.22 2781.43 2785.31 2788.86 2792.06 2794.90 2797.35 2799.41 2801.05 2802.26 2803.01 2803.28 2803.06 2802.31 2801.01 2799.13 2796.64 2793.51 2789.69 2785.14 2779.82 2773.67

2287.70 2282.56 2277.39 2272.20 2266.98 2261.74 2256.47 2243.18 2229.70 2216.03 2202.15 2188.04 2173.70 2159.10 2144.24 2129.10 2113.67 2097.92 2081.86 2065.45 2048.69 2031.55 2014.03 1996.10 1977.75 1958.94 1939.67 1919.90 1899.62 1878.80 1857.41 1835.42 1812.80 1789.52 1765.54 1740.82 1715.33 1689.01 1661.82 1633.70 1604.60 1574.44 1543.15 1510.65

1.1694 1.1927 1.2158 1.2387 1.2616 1.2844 1.3070 1.3632 1.4187 1.4735 1.5278 1.5815 1.6346 1.6872 1.7393 1.7909 1.8420 1.8926 1.9428 1.9926 2.0419 2.0909 2.1395 2.1878 2.2358 2.2834 2.3308 2.3779 2.4248 2.4714 2.5178 2.5641 2.6102 2.6561 2.7019 2.7477 2.7934 2.8391 2.8847 2.9304 2.9762 3.0221 3.0681 3.1143

7.5039 7.4781 7.4526 7.4275 7.4027 7.3782 7.3541 7.2951 7.2380 7.1827 7.1291 7.0770 7.0264 6.9772 6.9293 6.8826 6.8370 6.7926 6.7491 6.7066 6.6649 6.6241 6.5841 6.5447 6.5060 6.4679 6.4303 6.3932 6.3565 6.3202 6.2842 6.2485 6.2131 6.1777 6.1425 6.1074 6.0722 6.0370 6.0017 5.9662 5.9304 5.8943 5.8578 5.8208

Part B 4.6

t (◦ C)

242

Part B

Applications in Mechanical Engineering

Table 4.6 (cont.)

Part B 4.6

t (◦ C)

p (bar)

v (m3/kg)

v (m3/kg)

h (kJ/kg)

h (kJ/kg)

Δhv (kJ/kg)

s (kJ/(kgK))

s (kJ/(kgK))

290 295 300 305 310 315 320 325 330 335 340 345 350 355 360 365 370 373.946

74.416 79.990 85.877 92.092 98.647 105.56 112.84 120.51 128.58 137.07 146.00 155.40 165.29 175.70 186.66 198.22 210.43 220.64

0.001366 0.001385 0.001404 0.001425 0.001448 0.001472 0.001499 0.001528 0.001561 0.001597 0.001638 0.001685 0.001740 0.001808 0.001895 0.002016 0.002222 0.003106

0.02556 0.02353 0.02166 0.01994 0.01834 0.01686 0.01548 0.01419 0.01298 0.01185 0.01078 0.009770 0.008801 0.007866 0.006945 0.006004 0.004946 0.003106

1289.80 1317.03 1344.77 1373.07 1402.00 1431.63 1462.05 1493.37 1525.74 1559.34 1594.45 1631.44 1670.86 1713.71 1761.49 1817.59 1892.64 2087.55

2766.63 2758.63 2749.57 2739.38 2727.92 2715.08 2700.67 2684.48 2666.25 2645.60 2622.07 2595.01 2563.59 2526.45 2480.99 2422.00 2333.50 2087.55

1476.84 1441.60 1404.80 1366.30 1325.92 1283.45 1238.62 1191.11 1140.51 1086.26 1027.62 963.57 892.73 812.74 719.50 604.41 440.86 0.00

3.1608 3.2076 3.2547 3.3024 3.3506 3.3994 3.4491 3.4997 3.5516 3.6048 3.6599 3.7175 3.7783 3.8438 3.9164 4.0010 4.1142 4.4120

5.7832 5.7449 5.7058 5.6656 5.6243 5.5816 5.5373 5.4911 5.4425 5.3910 5.3359 5.2763 5.2109 5.1377 5.0527 4.9482 4.7996 4.4120

for triatomic gases = 1.30. The average specific heat is the integral mean value defined by  t2 cp t = 1

 t2 cv t = 1

1 t2 − t1 1 t2 − t1

t2

Taking into account (4.71) and (4.60), the specific entropy arises from (4.29) as dT dv du + p dv = cv +R , T T v or after integration with cv = const. as ds =

cp dt , t1 t2

cv dt .

s2 − s1 = cv ln

(4.74)

t1

From (4.71) and (4.72) it follows for the change of internal energy and enthalpy that  t  t  t u 2 − u 1 = cv t2 (t2 − t1 ) = cv 02 t2 − cv 01 t1 (4.75)  t  t  t h 2 − h 1 = cp t2 (t2 − t1 ) = cp 02 t2 − cp 01 t1 . 1

(4.76)

 t  t Numerical values for cp 0 and cv 0 can be determined from the average molar specific heats given in Table 4.8.

(4.78)

The integration of (4.32) with constant cp leads to the equivalent equation s2 − s1 = cp ln

1

and

T2 v2 + R ln . T1 v1

(4.77)

T2 p2 + R ln . T1 p1

(4.79)

Real Gases and Vapors The caloric properties of real gases and vapors are usually determined by measurements, but it is also possible to derive them, apart from an initial value, from equation of states. They are displayed in tables and diagrams as u = u(v, T ), h = h( p, T ), s = s( p, T ), cv = cv (v, T ),

Table 4.7 Specific heats of air at different pressures calculated with the equation of state (after [4.11]) p (bar) t = 0 ◦C t = 50 ◦ C t = 100 ◦ C

cp = cp = cp =

1

25

50

100

150

200

300

1.0065 1.0080 1.0117

1.0579 1.0395 1.0330

1.1116 1.0720 1.0549

1.2156 1.1335 1.0959

1.3022 1.1866 1.1316

1.3612 1.2288 1.1614

1.4087 1.2816 1.2045

kJ/(kgK) kJ/(kgK) kJ/(kgK)

Thermodynamics

4.6 Thermodynamics of Substances

243

Table 4.8 Mean molar specific heats [C¯ p ]t0 of ideal gases in kJ/(kmolK) between 0 ◦ C and t ◦ C. The mean molar specific heat [C¯ v ]t0 is determined by subtracting the value of the universal gas constant 8.3143 kJ/(kmolK) from the numerical values given in the table. For the conversion to 1 kg the numerical values have to be divided by the molar weights given in the last line t (◦ C)

[C¯ p ]t0 (kJ/(kmolK)) H2

N2

O2

CO

H2 O

CO2

Air

NH3

28.6202 28.9427 29.0717 29.1362 29.1886 29.2470 29.3176 29.4083 29.5171 29.6461 29.7892 29.9485 30.1158 30.2891 30.4705 30.6540 30.8394 31.0248 31.2103 31.3937 31.5751 2.01588

29.0899 29.1151 29.1992 29.3504 29.5632 29.8209 30.1066 30.4006 30.6947 30.9804 31.2548 31.5181 31.7673 31.9998 32.2182 32.4255 32.6187 32.7979 32.9688 33.1284 33.2797 28.01340

29.2642 29.5266 29.9232 30.3871 30.8669 31.3244 31.7499 32.1401 32.4920 32.8151 33.1094 33.3781 33.6245 33.8548 34.0723 34.2771 34.4690 34.6513 34.8305 35.0000 35.1664 31.999

29.1063 29.1595 29.2882 29.4982 29.7697 30.0805 30.4080 30.7356 31.0519 31.3571 31.6454 31.9198 32.1717 32.4097 32.6308 32.8380 33.0312 33.2103 33.3811 33.5379 33.6890 28.01040

33.4708 33.7121 34.0831 34.5388 35.0485 35.5888 36.1544 36.7415 37.3413 37.9482 38.5570 39.1621 39.7583 40.3418 40.9127 41.4675 42.0042 42.5229 43.0254 43.5081 43.9745 18.01528

35.9176 38.1699 40.1275 41.8299 43.3299 44.6584 45.8462 46.9063 47.8609 48.7231 49.5017 50.2055 50.8522 51.4373 51.9783 52.4710 52.9285 53.3508 53.7423 54.1030 54.4418 44.00980

29.0825 29.1547 29.3033 29.5207 29.7914 30.0927 30.4065 30.7203 31.0265 31.3205 31.5999 31.8638 32.1123 32.3458 32.5651 32.7713 32.9653 33.1482 33.3209 33.4843 33.6392 28.953

34.99 36.37 38.13 40.02 41.98 44.04 46.09 48.01 49.85 51.53 53.08 54.50 55.84 57.06 58.14 59.19 60.20 61.12 61.95 62.75 63.46 17.03052

and cp = cp ( p, T ). Often computer software is necessary to analyze equations of state. For vapors it holds that the enthalpy h  of the saturated vapor differs from the enthalpy h  of the saturated boiling liquid at p, T = const. by the enthalpy of vaporization Δh v = h  − h  ,

(4.80)

which decreases with increasing temperature and reaches zero at the critical point, where h  = h  . The enthalpy of wet vapor is h = (1 − x)h  + xh  = h  + xΔh v .

(4.81)

Accordingly, the internal energy is 









(4.82)

s = (1 − x)s + xs = s + xΔh v /T ,

(4.83)

u = (1 − x)u + xu = u + x(u − u ) and the entropy

because enthalpy of vaporization and entropy of vaporization s − s are related through Δh v = T (s − s ) .

(4.84)

According to the Clausius–Clapeyron relation, the enthalpy of vaporization with gradient d p/ dT is connected to the liquid–vapor saturation curve p(T ) via Δh v = T (v − v )

dp , dT

(4.85)

with T being the saturation temperature at pressure p. This relationship can be used to calculate the remaining quantity when two out of the three quantities Δh v , v − v , and d p/ dT are known. If properties do not have to be calculated continuously or if powerful computers are not available,

Part B 4.6

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 M (kg/kmol)

0.06 42.12 84.01 167.62 251.22 334.99 2675.77 2716.61 2756.70 2796.42 2835.97 2875.48 2915.02 2954.66 2994.45 3034.40 3074.54 3114.89 3155.45 3196.24 3237.27 3278.54 3320.06 3361.83 3403.86 3446.15 3488.71 3531.53 3574.63 3618.00 3661.65

0.001000 0.001000 0.001002 0.001008 0.001017 0.001029 1.695959 1.793238 1.889133 1.984139 2.078533 2.172495 2.266142 2.359555 2.452789 2.545883 2.638868 2.731763 2.824585 2.917346 3.010056 3.102722 3.195351 3.287948 3.380516 3.473061 3.565583 3.658087 3.750573 3.843045 3.935503

0 10 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560 580

t (◦ C) 0.001000 0.001000 0.001002 0.001008 0.001017 0.001029 0.001043 0.001060 0.001080 0.383660 0.404655 0.425034 0.445001 0.464676 0.484135 0.503432 0.522603 0.541675 0.560667 0.579594 0.598467 0.617294 0.636083 0.654838 0.673565 0.692267 0.710947 0.729607 0.748250 0.766878 0.785493

7.3588 s (kJ/(kgK)) −0.0001 0.1511 0.2965 0.5724 0.8312 1.0754 7.3610 7.4676 7.5671 7.6610 7.7503 7.8356 7.9174 7.9962 8.0723 8.1458 8.2171 8.2863 8.3536 8.4190 8.4828 8.5451 8.6059 8.6653 8.7234 8.7803 8.8361 8.8907 8.9444 8.9971 9.0489 0.47 42.51 84.39 167.98 251.56 335.31 419.40 504.00 589.29 2767.38 2812.45 2855.90 2898.40 2940.31 2981.88 3023.28 3064.60 3105.93 3147.32 3188.83 3230.48 3272.29 3314.29 3356.49 3398.90 3441.54 3484.41 3527.52 3570.87 3614.48 3658.34

5 bar ts = 151.884 ◦ C v h 0.37480 2748.1 v h (m3 /kg) (kJ/kg)

s

−0.0001 0.1510 0.2964 0.5722 0.8310 1.0751 1.3067 1.5275 1.7391 6.8655 6.9672 7.0611 7.1491 7.2324 7.3119 7.3881 7.4614 7.5323 7.6010 7.6676 7.7323 7.7954 7.8569 7.9169 7.9756 8.0329 8.0891 8.1442 8.1981 8.2511 8.3031

6.8206 s (kJ/(kgK))

s

0.001000 0.001000 0.001001 0.001007 0.001017 0.001029 0.001043 0.001060 0.001079 0.001102 0.194418 0.206004 0.216966 0.227551 0.237871 0.247998 0.257979 0.267848 0.277629 0.287339 0.296991 0.306595 0.316158 0.325687 0.335186 0.344659 0.354110 0.363541 0.372955 0.382354 0.391738

0.98 42.99 84.86 168.42 251.98 335.71 419.77 504.35 589.61 675.80 2777.43 2828.27 2875.55 2920.98 2965.23 3008.71 3051.70 3094.40 3136.93 3179.39 3221.86 3264.39 3307.01 3349.76 3392.66 3435.74 3479.00 3522.47 3566.15 3610.05 3654.19

10 bar ts = 179.89 ◦ C v h 0.19435 2777.1 v h (m3 /kg) (kJ/kg) −0.0001 0.1510 0.2963 0.5720 0.8307 1.0748 1.3063 1.5271 1.7386 1.9423 6.5857 6.6955 6.7934 6.8837 6.9683 7.0484 7.1247 7.1979 7.2685 7.3366 7.4026 7.4668 7.5292 7.5900 7.6493 7.7073 7.7640 7.8195 7.8739 7.9272 7.9795

6.5850 s (kJ/(kgK))

s

0.000999 0.001000 0.001001 0.001007 0.001016 0.001028 0.001043 0.001060 0.001079 0.001101 0.001127 0.132441 0.140630 0.148295 0.155637 0.162752 0.169699 0.176521 0.183245 0.189893 0.196478 0.203012 0.209504 0.215960 0.222385 0.228784 0.235160 0.241515 0.247854 0.254176 0.260485

1.48 43.48 85.33 168.86 252.40 336.10 420.15 504.70 589.94 676.09 763.44 2796.02 2850.19 2900.00 2947.45 2993.37 3038.27 3082.48 3126.25 3169.75 3213.09 3256.37 3299.64 3342.96 3386.37 3429.90 3473.57 3517.40 3561.41 3605.61 3650.02

15 bar ts = 198.330 ◦ C v h 0.13170 2791.0 v h (m3 /kg) (kJ/kg)

Part B 4.6

1 bar ts = 99.61 ◦ C v h 1.69402 2674.9 v h (m3 /kg) (kJ/kg) −0.0001 0.1510 0.2962 0.5719 0.8304 1.0744 1.3059 1.5266 1.7381 1.9417 2.1389 6.4537 6.5658 6.6649 6.7556 6.8402 6.9199 6.9957 7.0683 7.1381 7.2055 7.2708 7.3341 7.3957 7.4558 7.5143 7.5716 7.6275 7.6823 7.7360 7.7887

s 6.4431 s (kJ/(kgK))

Part B

p→

244 Applications in Mechanical Engineering

Table 4.9 Properties of water and superheated water vapor (after [4.10])

20 bar ts = 212.38 ◦ C v h 0.09958 2798.4 v h (m3 /kg) (kJ/kg)

0.000999 0.000999 0.001001 0.001007 0.001016 0.001028 0.001042 0.001059 0.001079 0.001101 0.001127 0.001156

p→

0 10 20 40 60 80 100 120 140 160 180 200

t (◦ C) 1.99 43.97 85.80 169.31 252.82 336.50 420.53 505.05 590.26 676.38 763.69 852.57

3705.57 3749.77 3794.26 3839.02 3884.06 3929.38 3974.99 4020.87 4067.04 4113.48 4160.21

4.027949 4.120384 4.212810 4.305227 4.397636 4.490037 4.582433 4.674822 4.767206 4.859585 4.951960

600 620 640 660 680 700 720 740 760 780 800

t (◦ C)

1 bar ts = 99.61 ◦ C v h 1.69402 2674.9 v h (m3 /kg) (kJ/kg)

0.0000 0.1509 0.2961 0.5717 0.8302 1.0741 1.3055 1.5262 1.7376 1.9411 2.1382 2.3301

6.3392 s (kJ/(kgK))

s

9.0998 9.1498 9.1991 9.2476 9.2953 9.3424 9.3888 9.4345 9.4796 9.5241 9.5681

s 7.3588 s (kJ/(kgK)) 3702.46 3746.84 3791.49 3836.41 3881.59 3927.05 3972.77 4018.77 4065.04 4111.58 4158.40

0.000999 0.000999 0.001001 0.001007 0.001016 0.001028 0.001042 0.001059 0.001078 0.001101 0.001126 0.001156

2.50 44.45 86.27 169.75 253.24 336.90 420.90 505.40 590.59 676.67 763.94 852.77

25 bar ts = 223.96 ◦ C v h 0.07995 2802.0 v h (m3 /kg) (kJ/kg)

0.804095 0.822687 0.841269 0.859842 0.878406 0.896964 0.915516 0.934061 0.952601 0.971136 0.989667

5 bar ts = 151.884 ◦ C v h 0.37480 2748.1 v h (m3 /kg) (kJ/kg)

0.0000 0.1509 0.2960 0.5715 0.8299 1.0738 1.3051 1.5257 1.7371 1.9405 2.1375 2.3293

6.2560 s (kJ/(kgK))

s

8.3543 8.4045 8.4539 8.5026 8.5505 8.5977 8.6442 8.6901 8.7353 8.7799 8.8240

s 6.8206 s (kJ/(kgK)) 3698.56 3743.17 3788.03 3833.14 3878.50 3924.12 3970.00 4016.14 4062.54 4109.21 4156.14

0.000998 0.000998 0.001000 0.001006 0.001015 0.001027 0.001041 0.001058 0.001077 0.001099 0.001124 0.001153

5.03 46.88 88.61 171.96 255.33 338.89 422.78 507.17 592.22 678.14 765.22 853.80

50 bar ts = 263.94 ◦ C v h 0.03945 2794.2 v h (m3 /kg) (kJ/kg)

0.401111 0.410472 0.419824 0.429167 0.438502 0.447829 0.457150 0.466465 0.475775 0.485080 0.494380

10 bar ts = 179.89 ◦ C v h 0.19435 2777.1 v h (m3 /kg) (kJ/kg)

0.0001 0.1506 0.2955 0.5705 0.8286 1.0721 1.3032 1.5235 1.7345 1.9376 2.1341 2.3254

5.9737 s (kJ/(kgK))

s

8.0309 8.0815 8.1311 8.1800 8.2281 8.2755 8.3221 8.3681 8.4135 8.4582 8.5024

s 6.5850 s (kJ/(kgK)) 3694.64 3739.48 3784.55 3829.86 3875.40 3921.18 3967.22 4013.50 4060.03 4106.82 4153.87

0.000995 0.000996 0.000997 0.001004 0.001013 0.001024 0.001039 0.001055 0.001074 0.001095 0.001120 0.001148

10.07 51.72 93.29 176.37 259.53 342.87 426.55 510.70 595.49 681.11 767.81 855.92

100 bar ts = 311.0 ◦ C v h 0.01803 2725.5 v h (m3 /kg) (kJ/kg)

0.266781 0.273066 0.279341 0.285608 0.291866 0.298117 0.304361 0.310600 0.316833 0.323061 0.329284

15 bar ts = 198.330 ◦ C v h 0.13170 2791.0 v h (m3 /kg) (kJ/kg)

0.0003 0.1501 0.2944 0.5685 0.8259 1.0689 1.2994 1.5190 1.7294 1.9318 2.1274 2.3177

s 5.6159 s (kJ/(kgK))

7.8404 7.8912 7.9411 7.9902 8.0384 8.0860 8.1328 8.1789 8.2244 8.2693 8.3135

s 6.4431 s (kJ/(kgK))

Table 4.9 (cont.) 4.6 Thermodynamics of Substances

Part B 4.6

p→

Thermodynamics 245

Table 4.9 (cont.)

2821.67 2877.21 2928.47 2977.21 3024.25 3070.16 3115.28 3159.89 3204.16 3248.23 3292.18 3336.09 3380.02 3424.01 3468.09 3512.30 3556.64 3601.15 3645.84 3690.71 3735.78 3781.07 3826.57 3872.29 3918.24 3964.43 4010.86 4057.52 4104.43 4151.59

0.102167 0.108488 0.114400 0.120046 0.125501 0.130816 0.136023 0.141147 0.146205 0.151208 0.156167 0.161088 0.165978 0.170841 0.175680 0.180499 0.185300 0.190085 0.194856 0.199614 0.204362 0.209099 0.213827 0.218547 0.223260 0.227966 0.232667 0.237361 0.242051 0.246737

220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560 580 600 620 640 660 680 700 720 740 760 780 800

t (◦ C) 6.3868 6.4972 6.5952 6.6850 6.7685 6.8472 6.9221 6.9937 7.0625 7.1290 7.1933 7.2558 7.3165 7.3757 7.4335 7.4899 7.5451 7.5992 7.6522 7.7042 7.7552 7.8054 7.8547 7.9032 7.9509 7.9978 8.0441 8.0897 8.1347 8.1791

6.3392 s (kJ/(kgK))

s

0.001190 0.084437 0.089553 0.094351 0.098932 0.103357 0.107664 0.111881 0.116026 0.120115 0.124156 0.128159 0.132129 0.136072 0.139990 0.143887 0.147766 0.151629 0.155477 0.159313 0.163138 0.166953 0.170758 0.174556 0.178346 0.182129 0.185907 0.189679 0.193446 0.197208

943.69 2852.28 2908.19 2960.16 3009.63 3057.40 3104.01 3149.81 3195.07 3239.96 3284.63 3329.15 3373.62 3418.08 3462.59 3507.17 3551.85 3596.67 3641.64 3686.76 3732.07 3777.57 3823.27 3869.17 3915.30 3961.64 4008.21 4055.01 4102.04 4149.32

25 bar ts = 223.96 ◦ C v h 0.07995 2802.0 v h (m3 /kg) (kJ/kg) 2.5175 6.3555 6.4624 6.5581 6.6460 6.7279 6.8052 6.8787 6.9491 7.0168 7.0822 7.1455 7.2070 7.2668 7.3251 7.3821 7.4377 7.4922 7.5455 7.5978 7.6491 7.6995 7.7490 7.7976 7.8455 7.8927 7.9391 7.9848 8.0299 8.0744

6.2560 s (kJ/(kgK))

s

0.001187 0.001227 0.001275 0.042275 0.045347 0.048130 0.050726 0.053188 0.055552 0.057840 0.060068 0.062249 0.064391 0.066501 0.068583 0.070642 0.072681 0.074703 0.076710 0.078703 0.080684 0.082655 0.084616 0.086569 0.088515 0.090453 0.092385 0.094312 0.096234 0.098151

944.38 1037.68 1134.77 2858.08 2925.64 2986.18 3042.36 3095.62 3146.83 3196.59 3245.31 3293.27 3340.68 3387.71 3434.48 3481.06 3527.54 3573.96 3620.38 3666.83 3713.34 3759.94 3806.65 3853.48 3900.45 3947.58 3994.88 4042.35 4090.02 4137.87

50 bar ts = 263.94 ◦ C v h 0.03945 2794.2 v h (m3 /kg) (kJ/kg) 2.5129 2.6983 2.8839 6.0909 6.2109 6.3148 6.4080 6.4934 6.5731 6.6481 6.7194 6.7877 6.8532 6.9165 6.9778 7.0373 7.0952 7.1516 7.2066 7.2604 7.3131 7.3647 7.4153 7.4650 7.5137 7.5617 7.6088 7.6552 7.7009 7.7459

5.9737 s (kJ/(kgK))

s

0.001181 0.001219 0.001265 0.001323 0.001398 0.019272 0.021490 0.023327 0.024952 0.026439 0.027829 0.029148 0.030410 0.031629 0.032813 0.033968 0.035098 0.036208 0.037300 0.038377 0.039442 0.040494 0.041536 0.042569 0.043594 0.044612 0.045623 0.046629 0.047629 0.048624

945.87 1038.30 1134.13 1234.82 1343.10 2782.66 2882.06 2962.61 3033.11 3097.38 3157.45 3214.57 3269.53 3322.89 3375.06 3426.31 3476.87 3526.90 3576.52 3625.84 3674.95 3723.89 3772.73 3821.51 3870.27 3919.04 3967.85 4016.72 4065.68 4114.73

100 bar ts = 311.0 ◦ C v h 0.01803 2725.5 v h (m3 /kg) (kJ/kg)

Part B 4.6

20 bar ts = 212.38 ◦ C v h 0.09958 2798.4 v h (m3 /kg) (kJ/kg) 2.5039 2.6876 2.8708 3.0561 3.2484 5.7131 5.8780 6.0073 6.1170 6.2139 6.3019 6.3831 6.4591 6.5310 6.5993 6.6648 6.7277 6.7885 6.8474 6.9045 6.9601 7.0143 7.0672 7.1189 7.1696 7.2192 7.2678 7.3156 7.3625 7.4087

s 5.6159 s (kJ/(kgK))

Part B

p→

246 Applications in Mechanical Engineering

Table 4.9 (cont.)

(kJ/kg) 15.07

h

v

(m3 /kg)

0.000993

0.000993

0.000995

0.001001

0.001011

0.001022

0.001036

0.001052

0.001071

0.001092

0.001116

0.001144

0.001175

0.001212

0.001256

0.001310

0.001378

0.001473

0.001631

0.012582

0.014289

0.015671

0.016875

0.017965

0.018974

0.019924

0.020828

0.021696

(◦ C)

0

10

20

40

60

80

100

120

140

160

180

200

220

240

260

280

300

320

340

360

380

400

420

440

460

480

500

520

3367.79

3310.79

3251.76

3190.02

3124.58

3053.94

2975.55

2884.61

2769.56

1592.27

1453.85

1338.06

1232.79

1133.83

1039.13

947.49

858.12

770.46

684.12

598.79

514.25

430.32

346.85

263.71

180.78

97.94

56.52

2610.9

0.01034

t

6.4207

6.3479

6.2706

6.1875

6.0970

5.9965

5.8817

5.7445

5.5654

3.6553

3.4260

3.2275

3.0406

2.8584

2.6774

2.4952

2.3102

2.1209

1.9261

1.7244

1.5147

1.2956

1.0657

0.8233

0.5666

0.2932

0.1495

0.0004

(kJ/(kgK))

s

5.3108

0.015530

0.014793

0.014011

0.013170

0.012246

0.011199

0.009950

0.008258

0.001825

0.001569

0.001445

0.001361

0.001298

0.001247

0.001205

0.001170

0.001139

0.001112

0.001089

0.001068

0.001050

0.001034

0.001020

0.001008

0.000999

0.000993

0.000991

0.000990

(m3 /kg)

v

0.00586

v

3305.21

3241.19

3173.45

3100.57

3020.26

2928.51

2816.84

2659.19

1740.13

1571.52

1445.30

1334.14

1231.29

1133.83

1040.14

949.22

860.39

773.16

687.15

602.11

517.81

434.10

350.83

267.89

185.17

102.57

61.30

20.03

(kJ/kg)

h

2411.4

h

200 bar ts = 365.765 ◦ C

h

v

s

150 bar ts = 342.16 ◦ C

6.2263

6.1445

6.0558

5.9577

5.8466

5.7160

5.5525

5.3144

3.8787

3.6085

3.3993

3.2087

3.0261

2.8466

2.6675

2.4868

2.3030

2.1146

1.9205

1.7195

1.5104

1.2918

1.0625

0.8207

0.5646

0.2921

0.1489

0.0005

(kJ/(kgK))

s

4.9299

s

0.011810

0.011142

0.010418

0.009617

0.008697

0.007579

0.006005

0.002218

0.001697

0.001526

0.001421

0.001346

0.001287

0.001239

0.001199

0.001164

0.001135

0.001108

0.001085

0.001065

0.001047

0.001031

0.001018

0.001006

0.000997

0.000991

0.000989

0.000988

(m3 /kg)

v

250 bar

h

3238.48

3165.92

3087.11

2999.20

2897.06

2769.45

2578.59

1935.67

1698.63

1557.48

1438.72

1331.06

1230.24

1134.08

1041.31

951.06

862.73

775.90

690.22

605.45

521.38

437.88

354.82

272.07

189.54

107.18

66.06

24.96

(kJ/kg)

6.0569

5.9642

5.8609

5.7426

5.6013

5.4196

5.1399

4.1670

3.7993

3.5729

3.3761

3.1915

3.0125

2.8355

2.6581

2.4787

2.2959

2.1084

1.9150

1.7147

1.5061

1.2881

1.0593

0.8181

0.5627

0.2909

0.1482

0.0004

(kJ/(kgK))

s

0.009320

0.008690

0.007992

0.007193

0.006228

0.004921

0.002796

0.001873

0.001628

0.001493

0.001401

0.001332

0.001277

0.001231

0.001193

0.001159

0.001130

0.001105

0.001082

0.001062

0.001045

0.001029

0.001016

0.001004

0.000995

0.000989

0.000987

0.000986

(m3 /kg)

v

300 bar

0.0003 0.1474 0.2897 0.5607 0.8156 1.0562 1.2845 1.5019 1.7099 1.9097 2.1023 2.2890 2.4709 2.6490 2.8248 2.9997 3.1756 3.3554 3.5437 3.7498 4.0026 4.4750 5.0625 5.3416 5.5284 5.6740 5.7956 5.9015

70.79 111.78 193.91 276.24 358.80 441.67 524.97 608.80 693.31 778.68 865.14 952.99 1042.62 1134.57 1229.56 1328.66 1433.51 1547.07 1675.57 1838.26 2152.37 2552.87 2748.86 2883.84 2991.99 3084.79 3167.67

(kJ/(kgK))

29.86

s

h (kJ/kg)

4.6 Thermodynamics of Substances

Part B 4.6

p→

Thermodynamics 247

Table 4.9 (cont.)

h

(m3 /kg)

0.022535

0.023350

0.024144

0.024921

0.025683

0.026432

0.027171

0.027899

0.028619

0.029332

0.030037

0.030736

0.031430

0.032118

540

560

580

600

620

640

660

680

700

720

740

760

780

800

4091.33

4041.03

3990.72

3940.39

3889.99

3839.48

3788.82

3737.95

3686.79

3635.28

3583.31

3530.75

3477.46

3423.22

(kJ/kg)

v

(◦ C)

7.2039

7.1566

7.1084

7.0592

7.0090

6.9576

6.9050

6.8510

6.7956

6.7386

6.6797

6.6188

6.5556

6.4897

(kJ/(kgK))

s

0.023869

0.023333

0.022792

0.022246

0.021693

0.021133

0.020564

0.019987

0.019399

0.018799

0.018184

0.017554

0.016904

0.016231

(m3 /kg)

v

0.00586

t

5.3108

2610.9

0.01034

4067.73

4016.13

3964.43

3912.57

3860.50

3808.15

3755.46

3702.35

3648.69

3594.37

3539.23

3483.05

3425.57

3366.45

(kJ/kg)

h

2411.4

h

v

h

v

s

200 bar ts = 365.765 ◦ C

7.0534

7.0048

6.9553

6.9046

6.8527

6.7994

6.7447

6.6884

6.6303

6.5701

6.5077

6.4426

6.3744

6.3026

(kJ/(kgK))

s

4.9299

s

0.018922

0.018479

0.018030

0.017575

0.017113

0.016643

0.016165

0.015678

0.015179

0.014667

0.014140

0.013595

0.013028

0.012435

(m3 /kg)

v

250 bar

h

4044.00

3991.08

3937.92

3884.47

3830.64

3776.37

3721.54

3666.03

3609.69

3552.32

3493.69

3433.49

3371.29

3306.55

(kJ/kg)

6.9324

6.8826

6.8317

6.7794

6.7258

6.6706

6.6136

6.5548

6.4937

6.4302

6.3638

6.2941

6.2203

6.1416

(kJ/(kgK))

s

0.015629

0.015246

0.014858

0.014464

0.014063

0.013654

0.013236

0.012808

0.012368

0.011914

0.011444

0.010955

0.010442

0.009899

(m3 /kg)

v

300 bar

4020.23

3965.93

3911.27

3856.17

3800.53

3744.24

3687.16

3629.12

3569.91

3509.28

3446.87

3382.25

3314.82

3243.71

(kJ/kg)

h

Part B 4.6

150 bar ts = 342.16 ◦ C

6.8303

6.7792

6.7268

6.6729

6.6175

6.5602

6.5009

6.4394

6.3752

6.3081

6.2374

6.1626

6.0826

5.9962

(kJ/(kgK))

s

Part B

p→

248 Applications in Mechanical Engineering

Table 4.9 (cont.)

Thermodynamics

4.6 Thermodynamics of Substances

249

Table 4.9 (cont.) 350 bar v (m3 /kg)

h (kJ/kg)

s (kJ/(kgK))

400 bar v (m3 /kg)

h (kJ/kg)

s (kJ/(kgK))

500 bar v (m3 /kg)

h (kJ/kg)

s (kJ/(kgK))

0 10 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 420 540 560 580 600 620 640 660 680 700 720 740 760 780 800

0.000983 0.000984 0.000987 0.000993 0.001002 0.001013 0.001027 0.001042 0.001060 0.001079 0.001101 0.001126 0.001155 0.001187 0.001224 0.001268 0.001320 0.001384 0.001466 0.001579 0.001755 0.002106 0.003082 0.004413 0.005436 0.006246 0.006933 0.007540 0.008089 0.008597 0.009073 0.009523 0.009953 0.010365 0.010763 0.011149 0.011524 0.011889 0.012247 0.012598 0.012942 0.013280

34.72 75.49 116.35 198.27 280.40 362.78 445.47 528.56 612.18 696.44 781.51 867.60 955.00 1044.06 1135.25 1229.20 1326.81 1429.36 1538.97 1659.61 1800.51 1988.43 2291.32 2571.64 2753.55 2888.06 2998.02 3093.08 3178.24 3256.46 3329.64 3399.02 3465.45 3529.55 3591.77 3652.46 3711.88 3770.27 3827.78 3884.58 3940.78 3996.48

0.0001 0.1466 0.2884 0.5588 0.8130 1.0531 1.2809 1.4978 1.7052 1.9044 2.0964 2.2823 2.4632 2.6402 2.8145 2.9875 3.1608 3.3367 3.5184 3.7119 3.9309 4.2140 4.6570 5.0561 5.3079 5.4890 5.6331 5.7546 5.8606 5.9557 6.0425 6.1229 6.1981 6.2691 6.3365 6.4008 6.4625 6.5219 6.5793 6.6348 6.6887 6.7411

0.000981 0.000982 0.000985 0.000991 0.001000 0.001011 0.001024 0.001040 0.001057 0.001076 0.001098 0.001122 0.001150 0.001181 0.001217 0.001259 0.001308 0.001368 0.001443 0.001542 0.001682 0.001911 0.002361 0.003210 0.004149 0.004950 0.005625 0.006213 0.006740 0.007221 0.007669 0.008089 0.008488 0.008869 0.009235 0.009589 0.009931 0.010264 0.010589 0.010906 0.011217 0.011523

39.56 80.17 120.90 202.61 284.56 366.76 449.26 532.17 615.57 699.59 784.37 870.12 957.10 1045.62 1136.11 1229.13 1325.41 1426.02 1532.52 1647.62 1776.72 1931.13 2136.30 2394.03 2613.32 2777.18 2906.69 3015.42 3110.69 3196.67 3276.01 3350.43 3421.10 3488.82 3554.17 3617.59 3679.42 3739.95 3799.38 3857.91 3915.68 3972.81

−0.0002 0.1458 0.2872 0.5568 0.8105 1.0501 1.2773 1.4937 1.7006 1.8992 2.0906 2.2758 2.4558 2.6317 2.8047 2.9760 3.1469 3.3195 3.4960 3.6807 3.8814 4.1141 4.4142 4.7807 5.0842 5.3048 5.4746 5.6135 5.7322 5.8366 5.9308 6.0170 6.0970 6.1720 6.2428 6.3100 6.3743 6.4358 6.4951 6.5523 6.6077 6.6614

0.000977 0.000978 0.000980 0.000987 0.000996 0.001007 0.001020 0.001035 0.001052 0.001070 0.001091 0.001115 0.001141 0.001171 0.001204 0.001243 0.001288 0.001341 0.001405 0.001485 0.001588 0.001731 0.001940 0.002266 0.002745 0.003319 0.003889 0.004417 0.004896 0.005332 0.005734 0.006109 0.006461 0.006796 0.007115 0.007422 0.007718 0.008004 0.008281 0.008552 0.008816 0.009074

49.13 89.46 129.96 211.27 292.86 374.71 456.87 539.41 622.40 705.95 790.20 875.31 961.50 1049.05 1138.29 1229.67 1323.74 1421.22 1523.05 1630.63 1746.51 1874.31 2020.07 2190.53 2380.52 2563.86 2722.52 2857.36 2973.16 3075.37 3167.66 3252.61 3332.05 3407.21 3478.99 3548.00 3614.76 3679.64 3742.97 3804.99 3865.93 3925.96

−0.0010 0.1440 0.2845 0.5528 0.8054 1.0440 1.2703 1.4858 1.6917 1.8891 2.0793 2.2631 2.4415 2.6155 2.7861 2.9543 3.1214 3.2885 3.4574 3.6300 3.8101 4.0028 4.2161 4.4585 4.7212 4.9680 5.1759 5.3482 5.4924 5.6166 5.7261 5.8245 5.9145 5.9977 6.0755 6.1487 6.2180 6.2840 6.3471 6.4078 6.4662 6.5226

Part B 4.6

p→ t (◦ C)

250

Part B

Applications in Mechanical Engineering

Table 4.10 Properties of ammonia (NH3 ) at saturation (after [4.14]) Temperature

Pressure

t

p (bar)

(◦ C)

Specific volume

Enthalpy

Part B 4.6

Enthalpy

Entropy

liquid

vapor

liquid

v

v

h

vapor

vaporization

liquid

vapor

h

Δhv = h − h

s

(dm3 /kg)

(dm3 /kg)

s

(kJ/kg)

(kJ/kg)

(kJ/kg)

(kJ/(kgK))

(kJ/(kgK))

−110.81

−70

0.10941

1.3798

9007.9

1355.6

1466.4

−0.30939

6.9088

−60

0.21893

1.4013

4705.7

−68.062

1373.7

1441.8

−0.10405

6.6602

−50

0.40836

1.4243

2627.8

−24.727

1391.2

1415.9

0.09450

6.4396

−40

0.71692

1.4490

1553.3

19.170

1407.8

1388.6

0.28673

6.2425

−30

1.1943

1.4753

963.96

63.603

1423.3

1359.7

0.47303

6.0651

−20

1.9008

1.5035

623.73

108.55

1437.7

1329.1

0.65376

5.9041

−10

2.9071

1.5336

418.30

154.01

1450.7

1296.7

0.82928

5.7569

0

4.2938

1.5660

289.30

200.00

1462.2

1262.2

1.0000

5.6210

10

6.1505

1.6009

205.43

246.57

1472.1

1225.5

1.1664

5.4946

8.5748

20

1.6388

149.20

293.78

1480.2

1186.4

1.3289

5.3759

30

11.672

1.6802

110.46

341.76

1486.2

1144.4

1.4881

5.2631

40

15.554

1.7258

83.101

390.64

1489.9

1099.3

1.6446

5.1549

50

20.340

1.7766

63.350

440.62

1491.1

1050.5

1.7990

5.0497

60

26.156

1.8340

48.797

491.97

1489.3

997.30

1.9523

4.9458

70

33.135

1.9000

37.868

545.04

1483.9

938.90

2.1054

4.8415

80

41.420

1.9776

29.509

600.34

1474.3

873.97

2.2596

4.7344

90

51.167

2.0714

22.997

658.61

1459.2

800.58

2.4168

4.6213

100

62.553

2.1899

17.820

721.00

1436.6

715.63

2.5797

4.4975

110

75.783

2.3496

13.596

789.68

1403.1

613.39

2.7533

4.3543

120

91.125

2.5941

9.9932

869.92

1350.2

480.31

2.9502

4.1719

3.2021

6.3790

992.02

1239.3

247.30

3.2437

3.8571

130

108.98

At the reference state t

= 0 ◦C

saturated liquid possesses the enthalpy

h

= 200.0 kJ/kg and the specific entropy

saturated water tables, in which the results of theoretical and experimental investigations are collected, are used for practical calculations. Such tables are collected in Tables 4.6–4.13, for working fluids important in engineering. Diagrams are advantageous to determine reference values and to display changes of state, e.g., a t–s diagram as shown in Fig. 4.9. Most commonly used in practice are Mollier diagrams, which include the enthalpy as one of the coordinates, see Fig. 4.10. The specific heat cp = (∂h/∂T )p of vapor depends, as well as on temperature, also considerably on pressure. In the same way, cv = (∂u/∂T )v depends, besides on temperature, also on the specific volume. Approaching the saturated vapor line, cp of the superheated vapor increases considerably with decreasing temperature and tends toward infinity at the critical point. While cp − cv is a constant for ideal gases, this is not true for vapors.

s

= 1.0 kJ/(kgK)

4.6.3 Incompressible Fluids An incompressible fluid is a fluid whose specific volume depends neither on temperature nor on pressure, such that the equation of state is given by v = const. As a good approximation, liquids and solids can generally be considered as incompressible. The specific heats cp and cv do not differ for incompressible fluids, cp = cv = c. Thus the caloric equations of state are du = c dT

(4.86)

dh = c dT + v d p ,

(4.87)

and

as well as ds = c

dT . T

(4.88)

252

Part B

Applications in Mechanical Engineering

Table 4.11 Properties of carbon dioxide (CO2 ) at saturation (after [4.15]) Temperature

Pressure

t

p (bar)

(◦ C)

Specific volume

Enthalpy

liquid

vapor

liquid

v

v

h

(dm3 /kg)

(dm3 /kg)

(kJ/kg)

Enthalpy

Entropy

vapor

vaporization

liquid

vapor

h

Δhv = h − h

s

s

(kJ/kg)

(kJ/kg)

(kJ/(kgK))

(kJ/(kgK))

Part B 4.6

−55

5.540

0.8526

68.15

83.02

431.0

348.0

0.5349

2.130

−50

6.824

0.8661

55.78

92.93

432.7

339.8

0.5793

2.102

8.319

−45

0.8804

46.04

102.9

434.1

331.2

0.6629

2.075

−40

10.05

0.8957

38.28

112.9

435.3

322.4

0.6658

2.048

−35

12.02

0.9120

32.03

123.1

436.2

313.1

0.7081

2.023

−30

14.28

0.9296

26.95

133.4

436.8

303.4

0.7500

1.998

−25

16.83

0.9486

22.79

143.8

437.0

293.2

0.7915

1.973

−20

19.70

0.9693

19.34

154.5

436.9

282.4

0.8329

1.949

−15

22.91

0.9921

16.47

165.4

436.3

270.9

0.8743

1.924

−10

26.49

1.017

14.05

176.5

435.1

258.6

0.9157

1.898

−5

30.46

1.046

12.00

188.0

433.4

245.3

0.9576

1.872

0

34.85

1.078

10.24

200.0

430.9

230.9

1.000

1.845

5

39.69

1.116

8.724

212.5

427.5

215.0

1.043

1.816

10

45.02

1.161

7.399

225.7

422.9

197.1

1.088

1.785

15

50.87

1.218

6.222

240.0

416.6

176.7

1.136

1.749

20

57.29

1.293

5.150

255.8

407.9

152.0

1.188

1.706

25

64.34

1.408

4.121

274.8

394.5

119.7

1.249

1.650

30

72.14

1.686

2.896

304.6

365.0

1.343

1.543

60.50

Reference points: see footnote of Table 4.10

4.6.4 Solid Materials Thermal Expansion Similar to liquids, the influence of pressure on volume in equations of state V = V ( p, T ) for solids is mostly negligibly small. Nearly all solids expand like liquids with increasing temperature and shrink with decreasing temperature. An exception is water, which has its highest density at 4 ◦ C and expands both at higher and lower temperatures than 4 ◦ C. A Taylor-series expansion with respect to temperature of the equation of state, truncated after the linear term, leads to the volumetric expansion with the cubic volumetric expansion coefficient γV (SI unit 1/K)

 V = V0 1 + γV (t − t0 ) . Accordingly, the area expansion is  A = A0 1 + γA (t − t0 )

and the length expansion  l = l0 1 + γL (t − t0 ) , where γA = (2/3)γV and γL = (1/3)γV . Average values for γL in the temperature interval between 0 ◦ C and t ◦ C can be derived for some solids from the values in Table 4.14 by dividing the given length change (l − l0 )/l0 by the temperature interval t − 0 ◦ C. Melting and Sublimation Curve Within certain limits, each pressure of a liquid corresponds to a temperature at which the liquid is in equilibrium with its solid. This relationship p(T ) is determined by the melting curve (Fig. 4.11), whereas the sublimation curve displays the equilibrium between gas and solid. Figure 4.11 includes additionally the liquid–vapor saturation curve. All three curves meet at the triple point at which the solid, the liquid, and the gaseous phase of a substance are in equilibrium with

Thermodynamics

4.6 Thermodynamics of Substances

253

Table 4.12 Properties of tetrafluoroethane (C2 H2 F4 (R134a)) at saturation (after [4.16, 17]) Temperature

Pressure p (bar)

−100 −95 −90 −85 −80 −75 −70 −65 −60 −55 −50 −45 −40 −35 −30 −25 −20 −15 −10 −5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

0.0055940 0.0093899 0.015241 0.023990 0.036719 0.054777 0.079814 0.11380 0.15906 0.21828 0.29451 0.39117 0.51209 0.66144 0.84378 1.0640 1.3273 1.6394 2.0060 2.4334 2.9280 3.4966 4.1461 4.8837 5.7171 6.6538 7.7020 8.8698 10.166 11.599 13.179 14.915 16.818 18.898 21.168 23.641 26.332 29.258 32.442 35.912 39.724

0.63195 0.63729 0.64274 0.64831 0.65401 0.65985 0.66583 0.67197 0.67827 0.68475 0.69142 0.69828 0.70537 0.71268 0.72025 0.72809 0.73623 0.74469 0.75351 0.76271 0.77233 0.78243 0.79305 0.80425 0.81610 0.82870 0.84213 0.85653 0.87204 0.88885 0.90719 0.92737 0.94979 0.97500 1.0038 1.0372 1.0773 1.1272 1.1936 1.2942 1.5357

Reference points: see footnote of Table 4.10

25 193 15 435 9769.8 6370.7 4268.2 2931.2 2059.0 1476.5 1079.0 802.36 606.20 464.73 361.08 284.02 225.94 181.62 147.39 120.67 99.590 82.801 69.309 58.374 49.442 42.090 35.997 30.912 26.642 23.033 19.966 17.344 15.089 13.140 11.444 9.9604 8.6527 7.4910 6.4483 5.4990 4.6134 3.7434 2.6809

Enthalpy liquid h (kJ/kg)

vapor h (kJ/kg)

Enthalpy vaporization Δhv = h − h (kJ/kg)

Entropy liquid s (kJ/(kgK))

vapor s (kJ/(kgK))

75.362 81.288 87.226 93.182 99.161 105.17 111.20 117.26 123.36 129.50 135.67 141.89 148.14 154.44 160.79 167.19 173.64 180.14 186.70 193.32 200.00 206.75 213.58 220.48 227.47 234.55 241.72 249.01 256.41 263.94 271.62 279.47 287.50 295.76 304.28 313.13 322.39 332.22 342.93 355.25 373.30

336.85 339.78 342.76 345.77 348.83 351.91 355.02 358.16 361.31 364.48 367.65 370.83 374.00 377.17 380.32 383.45 386.55 389.63 392.66 395.66 398.60 401.49 404.32 407.07 409.75 412.33 414.82 417.19 419.43 421.52 423.44 425.15 426.63 427.82 428.65 429.03 428.81 427.76 425.42 420.67 407.68

261.49 258.50 255.53 252.59 249.67 246.74 243.82 240.89 237.95 234.98 231.98 228.94 225.86 222.72 219.53 216.26 212.92 209.49 205.97 202.34 198.60 194.74 190.74 186.59 182.28 177.79 173.10 168.18 163.02 157.58 151.81 145.68 139.12 132.06 124.37 115.90 106.42 95.536 82.487 65.423 34.385

0.43540 0.46913 0.50201 0.53409 0.56544 0.59613 0.62619 0.65568 0.68462 0.71305 0.74101 0.76852 0.79561 0.82230 0.84863 0.87460 0.90025 0.92559 0.95065 0.97544 1.0000 1.0243 1.0485 1.0724 1.0962 1.1199 1.1435 1.1670 1.1905 1.2139 1.2375 1.2611 1.2848 1.3088 1.3332 1.3580 1.3836 1.4104 1.4390 1.4715 1.5188

1.9456 1.9201 1.8972 1.8766 1.8580 1.8414 1.8264 1.8130 1.8010 1.7902 1.7806 1.7720 1.7643 1.7575 1.7515 1.7461 1.7413 1.7371 1.7334 1.7300 1.7271 1.7245 1.7221 1.7200 1.7180 1.7162 1.7145 1.7128 1.7111 1.7092 1.7072 1.7050 1.7024 1.6993 1.6956 1.6909 1.6850 1.6771 1.6662 1.6492 1.6109

Part B 4.6

t (◦ C)

Specific volume liquid vapor v v 3 (dm /kg) (dm3 /kg)

254

Part B

Applications in Mechanical Engineering

Table 4.13 Properties of chlorodifluoromethane (CHF3 Cl (R22)) at saturation (after [4.18]) Temperature

Pressure

t

p (bar)

(◦ C)

Specific volume

Enthalpy

Enthalpy

Entropy

liquid

vapor

liquid

v

v

h

vapor

vaporization

liquid

vapor

h

Δhv = h − h

s

(dm3 /kg)

(dm3 /kg)

s

(kJ/kg)

(kJ/kg)

(kJ/kg)

(kJ/(kgK))

(kJ/(kgK))

Part B 4.6

−110

0.00730

0.62591

21 441.0

79.474

354.05

274.57

0.43930

2.1222

−100

0.01991

0.63636

8338.8

90.056

358.80

268.75

0.50224

2.0544

−90

0.04778

0.64725

3667.5

100.65

363.64

262.98

0.56174

1.9976

−80

0.10319

0.65866

1785.5

111.29

368.53

257.24

0.61824

1.9501

−70

0.20398

0.67064

945.76

121.97

373.44

251.47

0.67241

1.9100

−60

0.37425

0.68329

537.47

132.73

378.34

245.61

0.72377

1.8761

−50

0.64457

0.69669

323.97

143.58

383.18

239.60

0.77342

1.8472

−40

1.0519

0.71096

205.18

154.54

387.92

233.38

0.82134

1.8223

−30

1.6389

0.72626

135.46

165.63

392.52

226.88

0.86776

1.8009

−20

2.4538

0.74275

92.621

176.89

396.92

220.03

0.91288

1.7821

−10

3.5492

0.76065

65.224

188.33

401.09

212.76

0.95690

1.7654

0

4.9817

0.78027

47.078

200.00

404.98

204.98

1.0000

1.7505

10

6.8115

0.80196

34.684

211.93

408.52

196.60

1.0424

1.7367

20

9.1018

0.82623

25.983

224.16

411.65

187.50

1.0842

1.7238

30

11.919

0.85380

19.721

236.76

414.29

177.53

1.1256

1.7112

40

15.334

0.88571

15.109

249.80

416.30

166.50

1.1670

1.6987

50

19.421

0.92360

11.638

263.41

417.51

154.10

1.2086

1.6855

60

24.265

0.97028

8.9656

277.78

417.65

139.87

1.2510

1.6708

70

29.957

1.0312

6.8541

293.24

416.20

122.96

1.2950

1.6534

80

36.616

1.1195

5.1213

310.52

412.11

101.60

1.3426

1.6303

90

44.404

1.2827

3.5651

331.97

401.92

1.3999

1.5925

69.945

Reference points: see footnote of Table 4.10

each other. The triple point of water is 273.16 K by definition, which corresponds to a pressure at the triple point of 611.657 Pa. Caloric Properties During the freezing of a liquid the latent heat of fusion Δh f is released (Table 4.15). At the same time the liquid entropy is reduced by Δsf = Δh f /Tf with Tf being the melting or freezing temperature. According to the Dulong–Petit law the molar specific heat divided by the number of atoms in the molecule is, above ambient temperature, about 25.9 kJ/kmol K. If absolute zero is approached, this approximation rule is no longer valid. Therefore, the molar specific heat at constant volume is for all solids

C = a(T/Θ)3 ,

for

T/Θ < 0.1

with a = 4782.5 J/mol K and where Θ is the Debye temperature (Table 4.16).

4.6.5 Mixing Temperature. Measurement of Specific Heats If several substances with different masses m i , temperatures ti , and specific heats cpi (i = 1, 2, . . .) are mixed at constant pressure without external heat supply, a mixing temperature tm arises after a sufficient period of time. It is     m i cpi m i cpi ti tm = with cpi being the mean specific heats between 0 ◦ C and t ◦ C. It is possible to calculate an unknown specific heat from the measured temperature tm , if all other specific heats are known.

0 to 100 ◦ C 2.38 2.90 2.35 0.15 – 0.81 0.345 1.42 1.04 1.52 1.65 – 2.60 1.75

1.75 1.84 0.52 1.30 1.19 0.90 0.83 0.05 1.95 – 1.20 1.17 1.65 2.67 0.45

0 to −190 ◦ C −3.43 −5.08 – – – −1.13 – −2.48 −1.59 −2.26 −2.65 – −4.01 −2.84

– −3.11 −0.79 −1.89 −1.93 −1.51 −1.43 +0.03 −3.22 – −1.67 −1.64 −1.85 −4.24 −0.73

Aluminium Lead Al-Cu-Mg [0.95 Al; 0.04 Cu + Mg, Mn, St, Fe] Iron–nickel alloy [0.64 Fe; 0.36 Ni] Iron–nickel alloy [0.77 Fe; 0.23 Ni] Glass: Jena, 16 III Glass: Jena, 1565 III Gold Gray cast iron Constantane [0.60 Cu; 0.40 Ni] Copper Sintered magnesia Magnesium Manganese bronze [0.85 Cu; 0.09 Mn; 0.06 Sn] Manganin [0.84 Cu; 0.12 Mn; 0.04 Ni] Brass [0.62 Cu; 0.38 Zn] Molybdenum Nickel Palladium Platinum Platinum-iridium-alloy [0.80 Pt; 0.20 Ir] Quartz glass Silver Sintered corundum Steel, soft Steel, hard Zinc Tin Tungsten 1.70 0.12 4.00 1.30 2.51 2.45 – – 0.90

3.85 1.07 2.75 2.42 1.83

3.65

3.58

3.12 3.38 2.45 5.41

– 1.67 0.72 2.92 2.21

0.75

4.90

4.90 5.93

0 to 200 ◦ C

2.59 0.19 6.08 2.00 3.92 3.83 – – 1.40

6.03 1.64 4.30 3.70 2.78

5.60

5.50

4.81 5.15 3.60 8.36

2.80 2.60 1.12 4.44 3.49

1.60

7.80

7.65 9.33

0 to 300 ◦ C

– – 1.90

3.51 0.25 8.23 2.75 5.44 5.31

8.39 2.24 5.95 5.02 3.76

7.55

7.51

6.57 7.07 4.90 11.53

4.00 3.59 1.56 6.01 4.90

3.10

10.70

10.60 –

0 to 400 ◦ C

7.60 6.38 4.77 4.45 0.31 10.43 3.60 7.06 6.91 – – 2.25

– –

9.70

9.61

8.41 9.04 6.30 14.88

5.25 4.63 2.02 7.62 6.44

4.70

13.65

13.70 –

0 to 500 ◦ C

9.35 8.09

6.50

6.50

9.27 7.79 5.80 5.43 0.36 12.70 4.45 8.79 8.60 – – 2.70

– –

11.90

–

– 11.09 7.75 –

– –

–

17.00 –

0 to 600 ◦ C

8.5

9.30

6.43 0.40 15.15 5.30 10.63 10.40 – – 3.15

– – 11.05 9.24 6.86

14.3

–

–

– –

7.80 – – 11.15 9.87

–

– –

0 to 700 ◦ C

7.47 0.45 17.65 6.25 – – – – 3.60

– – 12.89 10.74 7.94

16.80

–

– – 10.80 –

9.25 – – 13.00 11.76

10.5

–

– –

0 to 800 ◦ C

– – – –

–

4.05

7.15

8.53 0.50

– – 14.80 12.27 9.05

–

–

– – 12.35 –

10.50 – – 14.90 –

12.55

–

– –

0 to 900 ◦ C

– – – –

–

4.60

8.15

9.62 0.54

– – 16.80 13.86 10.19

–

–

– – 13.90 –

11.85 – – – –

–

–

– –

0 to 1000 ◦ C

4.6 Thermodynamics of Substances

Part B 4.6

Substance

Thermodynamics 255

Table 4.14 Thermal extension (l − l0 )/l0 of some solids in mm/m in the temperature interval between 0 ◦ C and t ◦ C; l0 is the length at 0 ◦ C

Thermodynamics

4.7 Changes of State of Gases and Vapors

257

Table 4.15 Thermal engineering properties: density ρ, specific heat cp for 0–100 ◦ C, melting temperature tf , latent heat of fusion Δh f , boiling temperature ts and enthalpy of vaporization Δh v ρ

cp

tf

Δhf

ts

Δhv

(kg/dm3 )

(kJ/(kgK))

(◦ C)

(kJ/kg)

(◦ C)

(kJ/kg)

Solids (metals and sulfur) at 1.0132 bar 2.70

0.921

660

355.9

2270

11 723

Antimony

6.69

0.209

630.5

167.5

1635

1256

11.34

0.130

327.3

23.9

1730

921

Chrome

7.19

0.506

1890

293.1

2642

6155

Iron (pure)

7.87

0.465

1530

272.1

2500

6364

Gold

19.32

0.130

1063

67.0

2700

1758

Iridium

22.42

0.134

2454

117.2

2454

3894

Copper

8.96

0.385

1083

209.3

2330

4647

Magnesium

1.74

1.034

650

209.3

1100

5652

Manganese

7.3

0.507

1250

251.2

2100

4187

10.2

Lead

Molybdenum

0.271

2625

–

3560

7118

8.90

0.444

1455

293.1

3000

6197

Platinum

21.45

0.134

1773

113.0

3804

2512

Mercury

13.55

0.138

−38.9

11.7

357

301

Silver

10.45

0.234

960.8

104.7

1950

2177

Titanium

4.54

0.471

1800

–

3000

Bismuth

9.80

0.126

271

54.4

1560

837

0.134

3380

Nickel

Tungsten

19.3

–

251.2

6000

4815

Zinc

7.14

0.385

419.4

112.2

907

1800

Tin

7.28

0.226

231.9

58.6

2300

2596

Sulfur (rhombic)

2.07

0.720

112.8

39.4

444.6

Ethyl alcohol

0.79

2.470

−114.5

104.7

78.3

841.6

Ethyl ether

0.71

2.328

−116.3

100.5

34.5

360.1

Acetone

0.79

2.160

−94.3

96.3

56.1

523.4

Benzene

0.88

1.738

5.5

127.3

80.1

395.7

Glycerin a

1.26

2.428

18.0

200.5

290.0

Saline solution (saturated)

1.19

3.266

−18.0

–

108.0

–

Sea water (3.5% salt content)

1.03

–

−2.0

–

100.5

–

Methyl alcohol

0.79

2.470

−98.0

100.5

64.5

1101.1

n-Heptane

0.68

2.219

−90.6

141.5

98.4

318.2

n-Hexane

0.66

1.884

−95.3

146.5

68.7

330.8

Spirits of turpentine

0.87

1.800

−10.0

116.0

160.0

293.1

Water

1.00

4.183

0.0

333.5

100.0

2257.1

293

Liquids at 1.0132 bar

a

854.1

Solidification point at 0 ◦ C. Melting and solidification point do not always coincide

whereas in practice n is usually between 1 and . Isochore, isobar, isotherm, and reversible adiabate are

special cases of a polytrope with the following exponents (Fig. 4.12): isochore (n = ∞), isotherm (n = 1),

Part B 4.7

Aluminium

262

Part B

Applications in Mechanical Engineering

4.8 Thermodynamic Processes 4.8.1 Combustion Processes

Part B 4.8

Heat transfer for technical processes is still mostly obtained through combustion. Combustion is a chemical reaction during which a substance, e.g., carbon, hydrogen, or hydrocarbons, is oxidized and which is strongly exothermic, i. e., a large quantity of heat is released. Fuels can be solid, liquid, or gaseous. The required oxygen is mostly provided by atmospheric air. To start a combustion process the fuel must be brought above its ignition temperature, which, in turn, varies according to the type of fuel being used. The main components of all important technical fuels are carbon C, and hydrogen H. In addition, oxygen O, and, with the exception of natural gas, a certain amount of sulfur are also present. Sulfur reacts during a combustion process to produce the unwanted compound sulfur dioxide SO2 . Equations of Reactions The elements H, C, and S, which are contained in fuels as mentioned above, are burned to CO2 , H2 O, and SO2 , if complete combustion takes place. The equation of reaction leads to the required amount of oxygen and to the resulting amount of each product in the exhaust gas. For the combustion of carbon C it holds that

C + O2 = CO2 , 1 kmol C + 1 kmol O2 = 1 kmol CO2 , 12 kg C + 32 kg O2 = 44 kg CO2 . From this it follows that the minimum oxygen demand for complete combustion is omin = 1/12 kmol/kg C or Omin = 1 kmol/kmol C. The minimum air demand for complete combustion is called the theoretical air and results from the oxygen fraction of 21 mol% in air lmin = (omin /0.21) kmol air / kg C or

combustion of hydrogen H2 and sulfur S are H2 + 1/2 O2 = H2 O , 1 kmol H2 + 1/2 kmol O2 = 1 kmol H2 O , 2 kg H2 + 16 kg O2 = 18 kg H2 O , S + O2 = SO2 , 1 kmol S + 1 kmol O2 = 1 kmol SO2 , 32 kg S + 32 kg O2 = 64 kg SO2 . Denoting the carbon, hydrogen, sulfur, and oxygen fractions by c, h, s, and o in kg per kg fuel, according to the above calculations, the minimum oxygen demand becomes  c h s o (4.102) + + − kmol/kg , omin = 12 4 32 32 or for short 1 (4.103) omin cσ kmol/kg , 12 where σ is a characteristic of the fuel (O2 demand in kmol related to the kmol C in the fuel). The actual air demand (related to 1 kg fuel) is l = λlmin = (λomin /0.21) kmol air/kg ,

where λ is the excess air number. In addition to the combustion products CO2 , H2 O, and SO2 , exhaust gases also ordinarily contain water with a content of w/18 (SI units of kmol per kg fuel), and the supplied combustion air l less the spent oxygen omin . The supplied combustion air is therefore assumed to be dry or it is assumed that the water vapor content is negligibly small. The following exhaust amounts, related to 1 kg of fuel, are given by n CO = c/12 , 2

nH

2O

= h/2 + w/18 ,

n SO = s/32 , 2

n O = (λ − 1)omin , 2

n N = 0.79 l . 2

L min = (Omin /0.21) kmol air / kmol C . The amount of CO2 in the exhaust gas is (1/ 12) kmol/kg C. Similarly, the equations of reaction for the

(4.104)

The sum is the total exhaust amount  n exh = c/12 + h/2 + w/18 + s/32 +(λ − 1)omin + 0.79 l) kmol/kg.

Thermodynamics

4.8 Thermodynamic Processes

263

Table 4.18 Net calorific values of the simplest fuels at 25 ◦ C and 1.01325 bar

kJ/kmol kJ/kg

C

CO

H2 (gross calorific value)

H2 (net calorific value)

S

393 510 32 762

282 989 10 103

285 840 141 800

241 840 119 972

296 900 9260

(4.105)

Example 4.11: 500 kg coal with the composition

c = 0.78, h = 0.05, o = 0.08, s = 0.01, and w = 0.02 and an ash content a = 0.06 are completely burned per hour in a furnace with excess air number λ = 1.4. How much air is necessary, how much exhaust arises, and what is its composition? The minimum oxygen demand is determined according to (4.102)  0.78 0.05 0.01 0.08  + + − kmol/kg omin = 12 4 32 32 = 0.0753 kmol/kg . The minimum air demand is

Water is included in the exhaust gases as vapor. If the water vapor is condensed, the released heat is called the gross calorific value. Net and gross calorific values are specified, according to DIN 51900, for combustion at atmospheric pressure, if all involved substances possess a temperature of 25 ◦ C before and after combustion. Net and gross calorific values (Tables 4.18–4.20) are independent of the amount of excess air and are only a characteristic of the fuel. The gross calorific value Δh gcv exceeds the net calorific value Δh ncv by the enthalpy of vaporization Δh v of the water included in the exhaust gas Δh gcv = Δh ncv + (8.937h + w) Δh v . Because the water leaves technical furnaces mostly as vapor, often only the net calorific value can be utilized. The net calorific value of heating oil can be expressed quite well, as experience shows [4.19], by the equation Δh ncv = (54.04 − 13.29 − 29.31s) MJ/kg ,

lmin = omin /0.21 = 0.3586 kmol/kg . The amount of air that has to be supplied is l = λlmin = 1.4 × 0.3586 = 0.502 kmol/kg . Thus 0.502 kmol/kg × 500 kg/h = 251 kmol/h. With the molar mass of air M = 28.953 kg/kmol, the air demand becomes 0.502 × 28.953 kg/kg = 14.54 kg/kg. Thus, 14.54 kg/kg × 500 kg/h = 7270 kg/h. The exhaust amount is determined according to (4.105) n exh = (0.502 + 1/12(3 × 0.05 + 3/8 × 0.08 + 2/3 × 0.02)) kmol/kg = 0.518 kmol/kg . Thus 0.581 kmol/kg × 500 kg/h = 259 kmol/h with 0.065 kmol CO2 /kg, 0.0261 kmol H2 O/kg, 0.0003 kmol SO2 /kg, 0.3966 kmol N2 /kg and 0.0301 kmol O2 /kg. Net Calorific Value and Gross Calorific Value The net calorific value is the energy released during combustion, if the exhaust gases are cooled down to the temperature at which the fuel and air are supplied.

(4.106)

where the density of the heating oil in kg/dm3 is at 15 ◦ C and the sulfur content s is in kg/kg. Example 4.12: What is the net calorific value of a light heating oil with a density of = 0.86 kg/dm3 and a sulfur content of s = 0.8 mass%? According to (4.106)

Δh ncv = (54.04 − 13.29 × 0.86 − 29.31 × 0.8 × 10−2 ) MJ/kg = 42.38 MJ/kg . Combustion Temperature The theoretical combustion temperature is the temperature of the exhaust gas at complete isobar-adiabatic combustion if no dissociation takes place. The heat released during combustion increases the internal energy and thus the temperature of the gas, which provides the basis for doing flow work. The theoretical combustion temperature is calculated under the condition that the enthalpy of all substances transferred to the combustion

Part B 4.8

This can be simplified by using (4.102) and (4.104) to yield   1 3 2  3h + o + w kmol/kg . n exh = l + 12 8 3

264

Part B

Applications in Mechanical Engineering

Table 4.19 Combustion of liquid fuels Fuel

Part B 4.8

Ethyl alcohol C2 H5 OH Spirit 95% 90% 85% Benzene (pure) C6 H6 Toluene (pure) C7 H8 Xylene (pure) C8 H10 Benzene I on sale a Benzene II on sale b Naphtalene (pure) C10 H8 (melting temp. 80 ◦ C) Tetralin C10 H12 Pentane C5 H12 Hexane C6 H14 Heptane C7 H16 Octane C8 H18 Benzine (mean values) a b

Molar weight

Content (mass%)

Characteristic

Calorific value (kJ/kg)

(kg/kmol)

C

H

σ

Gross

Net

46.069 – – – 78.113 92.146 106.167 – –

52 – – – 92.2 91.2 90.5 92.1 91.6

13 – – – 7.8 8.8 9.5 7.9 8.4

1.50 1.50 1.50 1.50 1.25 1.285 1.313 1.26 1.30

29 730 28 220 26 750 25 250 41 870 42 750 43 000 41 870 42 290

26 960 25 290 23 860 22 360 40 150 40 820 40 780 40 190 40 400

128.19 132.21 72.150 86.177 100.103 114.230 –

93.7 90.8 83.2 83.6 83.9 84.1 85

6.3 9.2 16.8 16.4 16.1 15.9 15

1.20 1.30 1.60 1.584 1.571 1.562 1.53

40 360 42 870 49 190 48 360 47 980 48 150 46 050

38 940 40 820 45 430 44 670 44 380 44 590 42 700

0.84 benzene, 0.31 toluene, 0.03 xylene (mass fractions) 0.43 benzene, 0.46 toluene, 0.11 xylene (mass fractions)

Table 4.20 Combustion of some simple gases at 25 ◦ C and 1.01325 bar Gas

Hydrogen H2 Carbon monoxide CO Methane CH4 Ethane C2 H6 Propane C3 H8 Butane C4 H10 Ethylene C2 H4 Propylene C3 H6 Butylene C4 H8 Acetylene C2 H2 a

Molar mass a

Density

Characteristic

Calorific value (MJ/kg)

(kg/kmol)

(kg/m3 )

σ

Gross

Net

2.0158 28.0104 16.043 30.069 44.09 58.123 28.054 42.086 56.107 26.038

0.082 1.14 0.656 1.24 1.80 2.37 1.15 1.72 2.90 1.07

∞ 0.50 2.00 1.75 1.67 1.625 1.50 1.50 1.50 1.25

141.80 10.10 55.50 51.88 50.35 49.55 50.28 48.92 48.43 49.91

119.97 10.10 50.01 47.49 46.35 45.72 47.15 45.78 45.29 48.22

According to DIN 51850: gross and net calorific values of gaseous fuels, April 1980

chamber must be equal to the enthalpy of the discharged exhaust gas.  tfuel ◦ Δh ncv cfuel 25 ◦ C (tfuel − 25 C) tair  + l C p air 25 ◦ C (tair − 25◦ C)  t (4.107) = n exh C p exh 25 ◦ C (t − 25 ◦ C) .

This equation includes the temperatures tfuel of the fuel and tair of the air, the theoretical  tcombustion fuel of the temperature t, the mean specific heat c 25 tair◦ C  fuel, and the mean specific heats C p air 25 ◦ C of air t  and C p exh 25 ◦ C of the exhaust gas. The latter consists of the mean molar specific heats of the single

274

Part B

Applications in Mechanical Engineering

4.9 Ideal Gas Mixtures A mixture of ideal gases that do not react chemically with each other also behaves as an ideal gas. The following equation of state holds pV = n Ru T .

(4.144)

Part B 4.9

Each single gas, called a component, spreads over the entire space V as though the other gases were not present. Thus, the following equation holds for each component pi V = n i Ru T ,

(4.145)

where pi is the pressure exerted by each gas individually, which is referred to as the partial pressure. The  sum of all thepartial pressures leads to   pi = Ru T n i . Comparpi V = n i Ru T or V ison with (4.144) shows that  (4.146) p= pi holds. In other words, the total pressure p of the gas mixture is equal to the sum of the partial pressures of the single gases, if each gas occupies the volume V of the mixture at temperature T (Dalton’s law). The thermal equation of state of an ideal gas mixture can also be written as pV = m RT , with the gas constant R of the mixture  R= Ri m i /m .

(4.147)

(4.148)

Specific (related to the mass in kg) caloric properties of a mixture at pressure p and temperature T result from adding the caloric properties at the same values p, T of the single gases according to their mass fractions, or 1  1  cp = m i cvi , m i cpi , cv = m m   1 1 h= mi ui , m i h i . (4.149) u= m m An exception to this general rule is entropy. During the mixing of single gases of state p, T to a mixture of the same state, an entropy increase takes place. This process is described by the following relation  ni  1  m i Ri ln (4.150) m i si − , s= m n where n i is the number of moles of the single gases and n is the number of moles  of the mixture. Consequently, n i = m i /Mi and n = n i with the mass m i

and the molar mass Mi of the single gases. Mixtures of real gases and liquids deviate from the above relations, in particular at higher pressures.

4.9.1 Mixtures of Gas and Vapor. Humid Air Mixtures of gases and easily condensable vapors occur often in physics and in technology. Atmospheric air consists mostly of dry air and water vapor. Drying and climatization processes are governed by the laws of vapor–air mixtures. This holds true in the same way for the formation of fuel and vapor–air mixtures in a combustion engine. The following is limited to the examination of atmospheric air. Dry air consists of 78.04 mol% nitrogen, 21.00 mol% oxygen, 0.93 mol% argon, and 0.03 mol% carbon dioxide. Atmospheric air can be considered as a binary mixture of dry air and water, which can be present as vapor, liquid, or solid. This mixture is also called humid air. Dry air is considered a uniform substance. Since the total pressure during changes of state is almost always close to atmospheric pressure, it is possible to consider humid air, consisting of dry air and water vapor, as a mixture of ideal gases. The following relation then holds for dry air and water vapor pair V = m air Rair T

and

pv V = m v Rv T . (4.151)

These equations, together with p = pair + pv , allows for the determination of the mass of water vapor which is added to 1 kg dry air. xv =

mv Rair pv = . m air R v ( p − pv )

(4.152)

The quantity xv = m v /m air is called the absolute or specific humidity. This quantity must not be confused with the quality x for mixtures of vapors and liquid. If water in the air is not only present as vapor, but also as liquid or solid, the water content x must be distinguished from the specific humidity xv . The water content is defined as x=

mw m v + m  + m ice = = sv + x + xice , m air m air (4.153)

where m v denotes the vapor mass, m  , the liquid mass, and m ice , the ice mass in the dry air of mass m air . The value xv is the specific humidity (vapor content), x , the liquid content, and xice , the ice content. The water content can lie between 0 (dry air) and ∞ (pure water). If

Thermodynamics

4.9 Ideal Gas Mixtures

275

Table 4.21 Partial pressure pvs , specific humidity xs , and enthalpy h 1+x of saturated humid air of temperature t related to 1 kg dry air at a total pressure of 1000 mbar pvs (mbar)

xs (g/kg)

h1+x (kJ/kg)

t (◦ C)

pvs (mbar)

xs (g/kg)

h1+x (kJ/kg)

−20 −19 −18 −17 −16 −15 −14 −13 −12 −11 −10 −9 −8 −7 −6 −5 −4 −3 −2 −1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

1.032 1.136 1.249 1.372 1.506 1.652 1.811 1.984 2.172 2.377 2.598 2.838 3.099 3.381 3.686 4.017 4.374 4.760 5.177 5.626 6.117 6.572 7.061 7.581 8.136 8.726 9.354 10.021 10.730 11.483 12.281 13.129 14.027 14.979 15.988 17.056 18.185 19.380 20.644 21.979 23.388

0.64290 0.70776 0.77825 0.85499 0.93862 1.02977 1.12906 1.23713 1.35462 1.48277 1.62099 1.77117 1.93456 2.11120 2.30235 2.50993 2.73398 2.97640 3.23851 3.52097 3.8303 4.1167 4.4251 4.7540 5.1046 5.4781 5.8759 6.2993 6.7497 7.2288 7.7377 8.2791 8.8534 9.4635 10.111 10.798 11.526 12.299 13.118 13.985 14.903

−18.5164 −17.3503 −16.1700 −14.9741 −13.7609 −12.5288 −11.2762 −10.0015 −8.7030 −7.3777 −6.0269 −4.6459 −3.2314 −1.7834 −0.2987 1.2277 2.7960 4.4109 6.0758 7.7926 9.5778 11.3064 13.0915 14.9290 16.8222 18.7741 20.7884 22.8684 25.0181 27.2416 29.5421 31.9263 34.3956 36.9572 39.6166 42.3778 45.2449 48.2272 51.3306 54.5595 57.9202

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

24.877 26.447 28.104 29.850 31.691 33.629 35.670 37.818 40.078 42.455 44.953 47.578 50.335 53.229 56.267 59.454 62.795 66.298 69.969 73.814 77.840 82.054 86.464 91.076 95.898 100.94 106.21 111.71 117.45 123.44 129.70 136.23 143.03 150.12 157.52 165.22 173.24 181.59 190.28 199.32

15.876 16.906 17.995 19.148 20.367 21.656 23.019 24.460 25.983 27.592 29.292 31.088 32.985 34.988 37.104 39.338 41.697 44.188 46.819 49.597 52.530 55.628 58.901 62.358 66.009 69.868 73.947 78.259 82.817 87.637 92.743 98.149 103.87 109.92 116.36 123.17 130.40 138.08 146.24 154.92

61.4240 65.0741 68.8823 72.8537 77.0006 81.3286 85.8505 90.5757 95.5160 100.683 106.088 111.745 117.668 123.869 130.368 137.179 144.317 151.805 159.662 167.907 176.563 185.654 195.208 205.248 215.806 226.912 238.603 250.913 263.878 277.536 291.958 307.175 323.221 340.176 358.126 377.094 397.178 418.457 441.020 464.964

humid air of temperature T is saturated with water vapor, the partial pressure of the water vapor is equal to the saturation pressure p = pvs at temperature T , and

the specific humidity becomes Rair pvs . xs = Rv ( p − pvs )

(4.154)

Part B 4.9

t (◦ C)

276

Part B

Applications in Mechanical Engineering

Table 4.21 (cont.)

Part B 4.9

t (◦ C)

pvs (mbar)

xs (g/kg)

h1+x (kJ/kg)

t (◦ C)

pvs (mbar)

xs (g/kg)

h1+x (kJ/kg)

61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

208.73 218.51 228.68 239.25 250.22 261.63 273.47 285.76 298.52 311.76 325.49 339.72 358.00 369.78 385.63 402.05 419.05 436.65 454.87 473.73

164.16 174.00 184.50 195.71 207.68 220.51 234.24 248.98 264.83 281.90 300.30 320.19 347.02 365.14 390.62 418.43 448.89 482.36 519.28 560.19

490.418 517.474 546.288 577.001 609.745 644.782 682.254 722.413 765.546 811.941 861.924 915.870 988.219 1037.670 1106.609 1181.826 1264.123 1354.501 1454.151 1564.509

81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100

493.24 513.42 534.28 555.85 578.15 601.19 624.99 649.58 674.96 701.17 728.23 756.14 784.95 814.65 845.29 876.88 909.45 943.01 977.59 1013.20

605.71 656.65 713.93 778.83 852.89 938.12 1037.15 1153.60 1292.27 1460.20 1667.55 1929.63 2271.51 2735.21 3400.16 4432.25 6250.33 10 297.46 27 147.34 –

1687.252 1824.503 1978.817 2153.558 2352.928 2582.259 2848.667 3161.844 3534.691 3986.110 4543.419 5247.698 6166.305 7412.089 9198.391 11 970.735 16 854.112 27 724.303 72 980.326 –

Example 4.13: What is the specific humidity of satu-

rated humid air at a temperature of 20 ◦ C and a total pressure of 1000 mbar? The gas constants are Rair = 0.2872 kJ/kg K and Rv = 0.4615 kJ/kg K. The saturated water temperature (Table 4.6) includes the vapor pressure, which is pvs (20 ◦ C) = 23.39 mbar. It follows, then xs =

0.2872 × 23.39 g g × 103 = 14.905 . 0.4615 (1000 − 23.39) kg kg

Other values of xs are given in Table 4.21. Degree of Saturation and Relative Humidity. The degree of saturation is defined as Ψ = xv /xs , which is a relative measure of the vapor content. In meteorology, however, the relative humidity ϕ = pv (t)/ pvs (t) is often used. Close to saturation, the two values differ only slightly because

pv ( p − pvs ) xv = xs pvs ( p − pv )

or

Ψ =ϕ

( p − pvs ) . ( p − pv )

At saturation, Ψ = ϕ = 1. If the pressure of saturated humid air is increased or if the temperature is decreased, the excess water vapor condenses. The condensed vapor drops out as fog or precipitation (rain);

at temperatures below 0 ◦ C, ice crystals (snow) arise. In this case, the water content is larger than the vapor content: x > xv = xs . The relative humidity can be determined with directly displaying instruments (e.g., a hair hygrometer) or with the help of an aspiration psychrometer. Enthalpy of Humid Air Since the amount of dry air remains constant during changes of state of humid air, and only the added amount of water varies as a result of thawing or evaporation, all properties are related to 1 kg dry air. The dry air contains x = m w /m air kg water from which xv = m v /m air is vaporous. For the enthalpy h 1+x of the unsaturated (x = xv < xs ) mixture of 1 kg dry air and x kg vapor it holds that

h 1+x = c p air t + xv (c p v t + Δh v ) ,

(4.155)

with the constant-pressure specific heats c p air = 1.005 kJ/kgK of air and c p v = 1.86 kJ/kgK of water vapor, and the enthalpy of vaporization Δh v = 2500.5 kJ/kg of water at 0 ◦ C. In the temperature range of interest between −60 ◦ C and 100 ◦ C, constant values of cp can be assumed. At saturation, xv = xs and h 1+x = (h 1+x )s . If the water content x is larger than the saturation content xs at temperatures t > 0◦ C, the water

Thermodynamics

42.46 mbar, thus,

The 1000 kg of humid air consists of 1000/(1+x1 ) = 1000/1.01625 kg = 984.01 kg dry air and (1000 − 984.01) kg = 15.99 kg water vapor. The water content at point 3, x3 = xs , follows from Table 4.21 at t3 = 15 ◦ C to x3 = 10.79 g/kg, thus, m  = 984.01 × (16.25 − 10.80) × 10−3 kg = 5.36 kg. Mixture of Two Amounts of Air. If two amounts of hu-

mid air at states 1 and 2 are mixed adiabatically (i. e., without heat exchange with the environment), state m after the mixture (point 3 in Fig. 4.31c) is located on the straight line connecting states 1 and 2. Point m is determined by subdividing the straight connecting line 1–2 equivalent to the ratio of the dry air masses m air2 /m air1 . It is then m air1 x1 + m air2 x2 . (4.162) xm = m air1 + m air2 Mixing two saturated air amounts of different temperatures always leads to the formation of fog, as the water amount xm − xs drops out, where xs is the specific humidity at saturation on the isotherm passing through the mixture point in the fog region. Example 4.15: 1000 kg of humid air at t1 = 30 ◦ C and

ϕ1 = 0.6 are mixed at 1000 mbar with 1500 kg of saturated humid air at t2 = 10 ◦ C. What is the temperature after the mixture? As calculated in the previous example, x1 = 16.25 g/kg. The specific humidity at saturation for t2 = 10 ◦ C given in Table 4.21 is x2s = 7.7377 g/kg. The dry air masses are m air1 = 1000/(1 + x1 ) kg = 1000/(1 + 16.25 × 10−3 ) kg = 984.01 kg , and m air2 = 1500/(1 + x2s ) kg = 1500/(1 + 7.7377 × 10−3 ) kg = 1488.5 kg .

279

The water content after the mixture therefore becomes 984.01 × 16.25 + 1488.5 × 7.7377 g/kg xm = 984.01 + 1488.5 = 11.12 g/kg . The enthalpies, calculated according to (4.155), are  (h 1+x )1 = 1.005 × 30 + 16.25 × 10−3 × (1.86 × 30 + 2500.5) kJ/kg = 71.69 kJ/kg ,  (h 1+x )2 = 1.005 × 10 + 7.7377 × 10−3 × (1.86 × 10 + 2500.5) kJ/kg = 29.54 kJ/kg . The enthalpy of the mixture is m air1 (h 1+x )1 + m air2 (h 1+x )2 (h 1+x )m = m air1 + m air2 984.01 × 71.69 + 1488.5 × 29.54 kJ/kg = 984.01 + 1488.5 = 46.31 kJ/kg. On the other hand, according to (4.155), the following also holds  (h 1+x )m = 1.005 tm + 11.12 × 10−3  × (1.86 tm + 2500.5) kJ/kg. From this it follows that tm = 18 ◦ C. Addition of Water or Vapor. If humid air is mixed with

m w kg of water or water vapor, the water content after the mixture is xm = (m air1 x1 + m w )/m air1 . The enthalpy is  (h 1+x )m = m air 1 (h 1+x )1 + m w h w /m air1 . (4.163) The final state after the mixture is located in the Mollier diagram for humid air (Fig. 4.31d) on a straight line passing through the origin with the gradient h w , where h w = Δh 1+x /Δx is given by the pieces of straight lines on the boundary scale. Wet-Bulb Temperature. When unsaturated humid air

of state t1 , x1 passes over a water or ice surface, water evaporates or ice sublimates, causing the specific humidity of the humid air to increase. During this increase in specific humidity, the temperature of the water or of the ice decreases and adopts, after a sufficiently long time, a final value, which is called the wet-bulb temperature. The wet-bulb temperature twb can be determined in the Mollier diagram by looking for the isotherm twb in the fog region whose extension passes through state 1.

Part B 4.9

Rair (ϕ1 pvs ) Rv ( p − ϕ1 pvs ) 0.2872 × 0.6 × 42.46 = 0.4615 (1000 − 0.6 × 42.46) = 16.25 × 10−3 kg/kg = 16.25 g/kg .

x1 =

4.9 Ideal Gas Mixtures

280

Part B

Applications in Mechanical Engineering

4.10 Heat Transfer

Part B 4.10

If temperature differences exist between bodies that are not isolated from each other or within different areas of the same body, energy flows from the region of higher temperature to the region of lower temperature. This process is called heat transfer and will continue until the temperatures are balanced. Three modes of heat transfer are distinguished.

• • •

Heat transfer by conduction in solids, motionless liquids, or motionless gases. Kinetic energy is hereby transferred from a molecule or an elementary particle to its neighbor. Heat transfer by convection in liquids or gases with bulk fluid motion. Heat transfer by radiation takes place in the form of electromagnetic waves and without the presence of an intervening medium.

In engineering, all three modes of heat transfer are often present at the same time.

4.10.1 Steady-State Heat Conduction Steady-State Heat Conduction Through a Plane Wall If different temperatures are prescribed on two surfaces of a plane wall with thickness δ, according to Fourier’s law, the heat transfer

Q = λA

T1 − T2 τ δ

flows through the area A over time τ. Here, λ is a material property (SI unit W/(Km)) that is called the thermal conductivity (Table 4.22). The rate of heat transfer is given by Q/τ = Q˙ (SI unit W), and Q/(τ A) = q˙ is referred to as the heat flux (SI unit W/m2 ). It holds, then Q˙ = λ A

T1 − T2 δ

and q˙ = λ

T1 − T2 . δ

(4.164)

Similar to electric conduction, where a current I flows only when a voltage U exists to overcome the resistance R (I = U/R), heat transfer occurs only when a temperature difference ΔT = T2 − T1 exists Q˙ =

λA ΔT . s

Analogous to Ohm’s law, Rth = δ/(λA) is called the thermal resistance (SI unit K/W).

Fourier’s Law Considering a layer perpendicular to the heat transfer of thickness dx instead of the wall with the finite thickness δ leads to Fourier’s law in the differential form dT dT (4.165) and q˙ = −λ , Q˙ = −λ A dx dx where the minus sign results from the fact that heat transfer occurs in the direction of decreasing temperature. Here, Q˙ is the heat transfer in the direction of the x-axis, as is the same for q. ˙ The heat flux in the direction of the three coordinates x, y, and z is given in vector form by   ∂T ∂T ∂T + + (4.166) e e e q˙ = −λ x y z ∂x ∂y ∂z

with the unit vectors ex , e y , ez . At the same time, (4.166) is the general form of Fourier’s law. In this form, Fourier’s law holds for isotropic materials, i. e., materials with equal thermal conductivities in the direction of the three coordinate axes. Steady-State Heat Conduction Through a Tube Wall According to Fourier’s law, the heat transfer rate through a cylindrical area of radius r and length l is Q˙ = −λ 2πrl( dT/ dr). Under steady-state conditions, the heat transfer rate is the same for all radii and thus Q˙ = const. It is therefore possible to separate the variables T and r and to integrate from the inner surface of the cylinder, r = ri with T = Ti , to an arbitrary location r with temperature T . The temperature profile in a tube wall of thickness r − ri becomes

Ti − T =

Q˙ r ln . λ 2πl ri

With temperature To at the outer surface at radius ro , the heat transfer rate through a tube of thickness ro − ri and length l becomes Q˙ = λ 2πl

Ti − To . ln ro /ri

(4.167)

In order to obtain formal agreement with (4.164), it is also possible to write Q˙ = λ Am

Ti − To δ

(4.168)

i where δ = ro − ri and Am = ln(AAo −A , if Ao = 2πrol is o / Ai ) the outer and Ai = 2πril is the inner surface of the tube.

Thermodynamics

4.10 Heat Transfer

283

Table 4.24 Material properties of liquids, gases, and solids

Thermal oil

Air

Water vapor

Aluminium 99.99% V2A steel, hardened and tempered Lead Chrome Gold, pure UO2

Gravel concrete Plaster Fir, radial Cork plates Glass wool Soil Quartz Marble Chamotte Wool Hard coal Snow (compact) Ice Sugar Graphite

ρ (kg/m3 )

cp (J/kg)

λ (W/(mK))

20 100 400 0 5 20 99.3 20 80 150 −20 0 20 100 200 300 400 100 300 500 20

13 600 927 10 600 999.8 1000 998.3 958.4 887 835 822 1.3765 1.2754 1.1881 0.9329 0.7256 0.6072 0.5170 0.5895 0.379 0.6846 2700

139 1390 147 4217 4202 4183 4215 1000 2100 2160 1006 1006 1007 1012 1026 1046 1069 2032 2011 1158 945

8000 8600 15 100 0.562 0.572 0.5996 0.6773 0.133 0.128 0.126 0.02301 0.02454 0.02603 0.03181 0.03891 0.04591 0.05257 0.02478 0.04349 0.05336 238

20 20 20 20 600 1000 1400 20 20 20 30 0 20 20 20 20 20 20 0 0 0 20

8000 11 340 6900 19 290 11 000 10 960 10 900 2200 1690 410 190 200 2040 2300 2600 1850 100 1350 560 917 1600 2250

477 131 457 128 313 326 339 879 800 2700 1880 660 1840 780 810 840 1720 1260 2100 2040 1250 610

15 35.3 69.1 295 4.18 3.05 2.3 1.28 0.79 0.14 0.041 0.037 0.59 1.4 2.8 0.85 0.036 0.26 0.46 2.25 0.58 155

a × 106 (m2/s) 4.2 67 9.7 0.133 0.136 0.144 0.168 0.0833 0.073 0.071 16.6 17.1 21.8 33.7 51.6 72.3 95.1 20.7 57.1 67.29 93.4 3.93 23.8 21.9 119 1.21 0.854 0.622 0.662 0.58 0.13 0.11 0.28 0.16 0.78 1.35 0.52 0.21 0.16 0.39 1.2 0.29 1.14

η × 106 (Pas)

Pr

1550 710 2100 1791.8 519.6 1002.6 283.3 426 26.7 18.08 16.15 19.1 17.98 21.6 25.7 29.2 32.55 12.28 20.29 34.13 –

0.027 0.0114 0.02 13.44 11.16 6.99 1.76 576 43.9 31 0.71 0.7 0.7 0.69 0.68 0.67 0.66 1.01 0.938 0.741 –

– – – – – – – – – – – – – – – – – – – – – –

– – – – – – – – – – – – – – – – – – – – – –

Part B 4.10

Mercury Sodium Lead Water

t (◦ C)

Thermodynamics

4.10 Heat Transfer

287

Table 4.27 Constants C and δ in (4.182) Bi

∞

10

5

2

1

0.5

0.2

0.1

0.01

C δ

1.6020 2.4048

1.5678 2.1795

1.5029 1.9898

1.3386 1.5994

1.2068 1.2558

1.1141 0.9408

1.0482 0.6170

1.0245 0.4417

1.0025 0.1412

Table 4.28 Constants C and δ in (4.183) ∞

10

5

2

1

0.5

0.2

0.1

0.01

C δ

2.0000 3.1416

1.9249 2.8363

1.7870 2.5704

1.4793 2.0288

1.2732 1.5708

1.1441 1.1656

1.0592 0.7593

1.0298 0.5423

1.0030 0.1730

sionless characteristic numbers are of importance Nusselt number Reynolds number Prandtl number Péclet number

Nu = αl/λ , Re = wl/ν , Pr = ν/a , Pe = wl/a = RePr ,

Gr = l 3 gβΔT/ν2 ,   Stanton number St = α/ wcp = Nu/(RePr) , Geometric characteristic numbers ln /l; n = 1, 2, . . . . Grashof number

Heat Transfer Without Change of Phase Forced Convection. Laminar Flow Along a Flat Plate. According to

The variables signify the following: λ – thermal conductivity of the fluid, l – a characteristic length of the flow domain l1 , l2 , . . ., ν – the kinematic viscosity of the fluid, – density, a = λ/( cp ) – thermal diffusivity, cp – constant-pressure specific heat of the fluid, g – gravitational acceleration, ΔT = Tw − Tf – difference between the wall temperature Tw of a cooled or heated body and the mean temperature Tf of the fluid along the body, β – thermal volume expansivity at the wall temperature with β = 1/Tw for ideal gases. The Prandtl number is a fluid property (Table 4.24). Forced and natural convection are distinguished as follows. In forced convection, the fluid motion is caused by outer forces, e.g., by the pressure increase in a pump. In natural convection, the fluid motion is caused by density differences in the fluid and the corresponding buoyancy effects in a gravitational field. These density differences usually arise due to temperature differences, rarely due to pressure differences. In mixtures, density differences are also caused by concentration differences. The heat transfer in forced convection is described by equations of the form Nu = f 1 (Re, Pr, ln /l)

(4.184)

and in natural convection by Nu = f 2 (Gr, Pr, ln /l) .

The desired heat transfer coefficient is obtained from the Nusselt number by α = Nuλ/l. The functions f 1 and f 2 can be determined theoretically only for special cases. In general, they must be determined through experimentation and depend on the shape of the cooling or heating areas (even, vaulted, smooth, rough or finned), the flow structure and, usually to a minor extent, on the direction of the heat transfer (heating or cooling).

(4.185)

Pohlhausen [4.24], for the mean Nusselt number of a plate of length l, the following relation holds Nu = 0.664 Re1/2 Pr1/3 ,

(4.186)

where Nu = αl/λ, Re = wl/ν < 105 , and 0.6≤Pr≤2000. The material properties must be evaluated at the mean fluid temperature Tm = (Tw − T∞ )/2, where Tw is the wall temperature and T∞ the free-stream temperature far beyond the wall surface. Turbulent Flow Along a Flat Plate. From about

Re = 5 × 105 the boundary layer becomes turbulent. The mean Nusselt number of a plate of length l in this case is Nu =

0.037 Re0.8 Pr , 1 + 2.443 Re−0.1 (Pr2/3 − 1)

(4.187)

where Nu = αl/λ, Re = wl/ν, 5 × 105 < Re < 107 , and 0.6 ≤ Pr ≤ 2000. The material properties must be evaluated at the mean fluid temperature Tm = (Tw − T∞ )/2. Tw is the wall temperature and T∞ the free-stream temperature far beyond the wall surface. Flow Through Pipes in General. Below a Reynolds

number of Re = 2300 (Re = wd/ν, where w is the mean cross-sectional velocity and d is the pipe diameter), the flow is laminar, while above Re = 104 , the flow is turbulent. In the range 2300 < Re < 104 , whether the flow

Part B 4.10

Bi

288

Part B

Applications in Mechanical Engineering

is laminar or turbulent depends on the roughness of the pipe, the means of inflow, and the shape of the pipe in the inflow section. The mean heat transfer coefficient α over the pipe length l is defined by q˙ = αΔϑ, with the mean logarithmic temperature difference described by

Part B 4.10

Δϑ =

(Tw − Tin ) − (Tw − Tout ) ln

Tw −Tin Tw −Tout

,

(4.188)

where Tw is the wall temperature, Tin is the temperature at the inlet, and Tout is the temperature at the outlet cross-section. Laminar Flow Through Pipes. A flow is termed hydrodynamically developed if the velocity profile no longer changes in the flow direction. In a laminar flow of a highly viscous fluid, the velocity profile adopts the shape of a Poiseuillean parabola after only a short distance from the inlet. The mean Nusselt number at constant wall temperature can be calculated exactly via an infinite series (the Graetz solution), which, however, converges poorly. According to Stephan [4.25], as an approximate solution for the hydrodynamically developed laminar flow, the following equation holds

Nu0 =

3.657 0.0499 tanhX , + 1/3 2/3 X tanh(2.264X +1.7X ) (4.189)

where Nu0 = αd/λ, X = l/(dRe Pr), Re = wd/ν, and Pr = ν/a. This equation is valid for laminar flow (Re ≤ 2300) in the entire range 0 ≤ X ≤ ∞ and the maximum deviation from the exact values of the Nusselt number is 1%. The fluid properties must be evaluated at the mean fluid temperature Tm = (Tw + TB )/2, where TB = (Tin + Tout )/2. If a fluid enters a pipe at an approximately constant velocity, the velocity profile changes along the flow path until it reaches the Poiseuillean parabola after a distance described by the equation l/(dRe) = 5.75 × 10−2 . According to Stephan [4.25], for this case, that of a hydrodynamically developed laminar flow, the following equation holds for the range 0.1 ≤ Pr ≤ ∞ 1 Nu = , Nu0 tanh(2.43 Pr1/6 X 1/6 )

Heat Transfer for Turbulent Flow Through Pipes.

For a hydrodynamically developed flow (l/d ≥ 60) the McAdam equation holds in the range 104 ≤ Re ≤ 105 and 0.5 < Pr < 100 Nu = 0.024 Re0.8 Pr1/3 .

(4.191)

The fluid properties have to be evaluated at the mean temperature Tm = (Tw + TB )/2 with TB = (Tin + Tout )/2. For hydrodynamically undeveloped flow and for developed flow, Petukhov’s equation (modified by Gnielinski) holds in the range 104 ≤ Re ≤ 106 and 0.6 ≤ Pr ≤ 1000   2/3  d Re Prζ /8 , 1+ Nu = √ l 1 + 12.7 ζ /8(Pr2/3 − 1) (4.192)

where the friction factor ζ = (0.78 ln Re − 1.5)−2 , Nu = αd/λ, and Re = wd/ν. The fluid properties must be evaluated at the mean temperature Tm = (Tw + TB )/2. Under otherwise similar conditions, the heat transfer coefficients are larger in pipe bends than in straight pipes with the same cross section. For a pipe bend with a bend diameter D, the following equation holds, according to Hausen, for turbulent flow    (4.193) α = αstraight 1 + 21 Re0.14 (d/D) . A Single Pipe Placed Transversely in a Flow. The

heat transfer coefficient for a pipe placed transversely in a flow can be determined from Gnielinski’s equation 1/2  , (4.194) Nu = 0.3 + Nu2 + Nu2t where the Nusselt number Nu of the laminar plate flow is described according to (4.186), Nut of the turbulent plate flow is described according to (4.187), and Nu = αl/λ, 1 < Re = wl/ν < 107 , and 0.6 < Pr < 1000. For length l, the overflowed length l = dπ/2 must be inserted. The fluid properties must be evaluated at the mean temperature Tm = (Tin + Tout )/2. This equation holds for mean turbulence intensities of 6–10%, which can be expected in technical applications.

(4.190)

where Nu = αd/λ and the quantities are defined as above. The error is less than 5% for 1 ≤ Pr ≤ ∞ but is up to 10% for 0.1 ≤ Pr < 1. The fluid properties must be evaluated at the mean fluid temperature Tm = (Tw + TB )/2, where TB = (Tin + Tout )/2.

A Row of Pipes Placed Transversely in a Flow. Mean

heat transfer coefficients for a single row of pipes placed transversely in a flow (Fig. 4.38) can also be determined using (4.194). Now, however, the Reynolds number must be calculated with the mean velocity wm in the pipe row placed transversely in the flow.

Thermodynamics

Nu = αd/λ is formed with the detachment diameter  1/2 of the vapor bubbles d = 0.851β0 2σ/g(  −  ) , where the contact angle is β0 = 45◦ for water, 1◦ for low-boiling and 35◦ for other liquids. Quantities denoted with a single prime relate to the boiling liquid, those with a double prime relate to the saturated vapor. The equations above are not valid for boiling in forced flow.

4.10.5 Radiative Heat Transfer In addition to direct contact modes, heat can also be transferred by radiation. Thermal radiation (heat radiation) consists of a spectrum of electromagnetic waves in the wavelength range between 0.1 and 1000 μm. Visible light, as a reference, has a wavelength range between 0.4 and 0.76 μm. If a body is supplied with a heat transfer Q˙ by radiation, the fraction r Q˙ is reflected, the fraction a Q˙ is absorbed, and the fraction d Q˙ passes through (where r + d + a = 1). A body that reflects radiation completely (r = 1, d = a = 0) is called an ideal mirror, while a body that absorbs radiation completely (a = 1, r = d = 0) is called a black body. A body is called diathermal (d = 1, r = a = 0) if radiation passes completely through, where examples for this are gases such as O2 , N2 , etc. Stefan–Boltzmann Law Every body emits radiation corresponding to its surface temperature. The maximum radiation possible is emitted by a black body. It can be experimentally approximated by a blackened surface (e.g., with soot) or by a hollow space, whose walls have the same temperature everywhere, that has a small opening to let radiation out. The total radiation emitted by a black body per unit area is

e˙ s = σ T 4 ,

(4.208)

where e˙ s is called the emission of the black radiator, and σ = 5.67 × 10−8 W/m2 K4 is the radiation coefficient, also called the Stefan–Boltzmann constant. (W/m2 )

The emission e˙ s is an energy flux and thus equal to the ˙ dA a black radiator emits. With the heat flux q˙s = d Q/ emission e˙ n in a normal direction and e˙ ϕ in the direction of angle ϕ to the normal, Lambert’s cosine law e˙ ϕ = e˙ n cos ϕ for black radiators holds true. Often the radiation of real bodies differs from this general law, however. Kirchhoff’s Law Real bodies emit less than black radiators, where the energy emitted from real surfaces is

e˙ = ε˙es = εσ T 4

(4.209)

with the emissivity being in the range 0 < ε < 1 and in general depending on temperature (Table 4.29). In limited temperature ranges, many engineering surfaces (with the exception of shiny metal) can be interpreted as grey radiators. The energy radiated by them is distributed over wavelength in the same way as it is for black radiators, but reduced by a factor ε < 1. Strictly speaking, ε = ε(T ) holds true for grey radiators. For small temperature ranges, however, it is admissible to assume ε as constant. Assuming a body emitts the energy per unit area e˙ , and this energy flux strikes another body, this second body absorbs the energy or rather the heat transfer d Q˙ = a˙e dA .

(4.210)

The absorptivity defined by this equation depends on the temperature T of the origin of the incident radiation and on the temperature T  of the receiving surface. For black bodies, this value is a = 1, as all radiation striking the surface is absorbed. For surfaces which are not black, this value is a < 1. For grey radiators, the absorptivity is a = ε. According to Kirchhoff’s law, the emissivity is equal to the absorptivity, ε = a, for each surface which is in thermal equilibrium with its environment so that the temperature of the surface does not change in time. Heat Exchange by Radiation Between two parallel black surfaces of temperatures T1 and T2 and area A, which is very large in comparison to their separation, the heat transfer   (4.211) Q˙ 12 = σ A T14 − T24

is exchanged by radiation. Between grey radiators with emissivities ε1 and ε2 , the heat transfer is   Q˙ 12 = C12 A T14 − T24 (4.212)

291

Part B 4.10

with α in W/(m2 K), q˙ in W/m2 and p in bar. According to Stephan and Preußer, for arbitrary liquids the following relation is valid for nucleate boiling close to ambient pressure 0.674   0.156  2 0.371 

rd qd ˙ Nu = 0.0871 λ Ts

 a 2   2  0.350   −0.162 a × . (4.207) Pr σd

4.10 Heat Transfer

292

Part B

Applications in Mechanical Engineering

Table 4.29 Emissivity ε at temperature t Substance

Surface

ε

t ◦C

Roofing paper

Part B 4.10

21

0.91

Oak wood

Planed

21

0.89

Enamel varnish

Snow white

24

0.91

Glass

Smooth

22

0.94

Lime mortar

Rough, white

21–83

0.93

Marble

Light grey, polished

22

0.93

Porcelain

Glazed

22

0.92

Soot

Smooth

–

0.93

Chamotte slab

Glazed

1000

0.75

Spirit varnish

Black, shiny

25

0.82

Brick

Red, rough

22

0.93–0.95

Water

Vertical radiation

–

0.96

Oil

Thick layer

–

0.82

–

0.78

Oil coating Aluminum

Rough

26

Aluminum

Polished

230

0.038

Lead

Polished

130

0.057

Gray cast iron

Turned off

22

0.44

Gray cast iron

Liquid

1330

0.28

Gold

Polished

630

0.035

Copper

Polished

23

0.049

Copper

Rolled

–

0.16

Brass

Polished

19

0.05

Brass

Polished

300

0.031

Brass

Dead

Nickel

Polished

230

0.071

Nickel

Polished

380

0.087

Silver

Polished

230

0.021

Steel

Polished

–

0.29

Zinc

Zinc-coated iron sheet

28

0.23

Zinc

Polished

230

0.045

Zinc

Shiny, tinned sheet

24

0.057–0.087

Iron

Red, slightly rosted

20

0.61

Iron

Totally rusted

20

0.69

Iron

Smooth or rough cast skin

23

0.81

Copper

Black

25

0.78

Copper

Oxidized

600

0.56–0.7

Nickel

Oxidized

330

0.40

Nickel

Oxidized

1330

0.74

Steel

Dead oxidized

56–338

0.071–0.087

0.22

Oxidized metals

26–356

0.96

Thermodynamics

with the radiation exchange number 1  1 + −1 . C12 = σ/ ε1 ε2

(4.213)

 1 A1  1 + −1 . ε1 A 2 ε2

arbitrarily arranged in space, a heat flow   ε1 ε2 ϕ12 Q˙ 12 = σ A1 T14 − T24 1 − (1 − ε1 ) (1 − ε2 ) ϕ12 ϕ21

(4.214)

If A1  A2 , e.g., for a pipe in a large room, it holds that C12 = σε1 . Between two surfaces of areas A1 , A2 , temperatures T1 , T2 , and emissivities ε1 , ε2 , which are

exists, where ϕ12 and ϕ21 are the so-called view factors that depend on the geometric arrangement or the surfaces, values of which are given in [4.27]. Gas Radiation Most gases are transparent to thermal radiation and neither emit nor absorb radiation. Exceptions are carbon dioxide, carbon monoxide, hydrocarbons, water vapor, sulfur dioxide, ammonia, hydrochloric acid, and alcohols. They emit and absorb radiation only in certain wavelength regions. The emissivity and absorptivity of these gases depend not only on temperature, but also on the geometric shape of the gas body.

References 4.1

4.2

4.3

4.4

4.5 4.6 4.7

4.8 4.9

4.10

4.11

F. Pavese, G.F. Molinar: Modern Gas-Based Temperature and Pressure Measurements (Plenum, New York 1992) O. Knoblauch, K. Hencky: Anleitung zu genauen technischen Temperaturmessungen, 2nd edn. (Oldenbourg, München 1926) VDI/VDE (Ed.): Temperature Measurement in Industry - Principles and Special Methods of Temperature Measurement, VDI/VDE 3511 (VDI/VDE-Gesellschaft Mess- und Automatisierungstechnik, Berlin 1996) D. Rathmann, J. Bauer, P.A. Thompson: A Table of Miscellaneous Thermodynamic Properties for Various Sustances, with Emphasis on the Critical Properties (Max-Planck-Inst. Strömungsforsch., Göttingen 1978), Ber. 6 N.E. Holden, R.L. Martin: Atomic weights of elements 1981, Pure Appl. Chem. 55, 1102–1118 (1983) D. Ambrose: Vapour-Liquid Critical Properties (Nat. Phys. Lab., Teddington 1980) K. Schäfer, G. Beggerow (Eds.): Mechanical-Thermal Properties of State, Landolt-Börnstein, Vol. II/1, 6th edn. (Springer, Heidelberg 1971) pp. 245–297 J.R. Dymond, E.B. Smith: The Virial Coefficients of Pure Gases and Mixtures (Clarendon, Oxford 1980) R.C. Reid, J.M. Prausnitz, B.E. Poling: The Properties of Gases and Liquids, 4th edn. (McGraw-Hill, New York 1986) W. Wagner, A. Kruse: Properties of Water and Steam. Zustandsgrößen von Wasser und Wasserdampf (Springer, Heidelberg 1998) H.D. Baehr, K. Schwier: Die thermodynamischen Eigenschaften der Luft (Springer, Berlin 1961), in German

4.12

4.13

4.14

4.15

4.16

4.17

4.18

4.19 4.20

R. Span, W. Wagner: Equations of state for technical applications, III. Results for polar fluids, Int. J. Thermophys. 24, 111–162 (2003) R.C. Wilhoit, B.J. Zwolinski: Handbook of Vapor Pressures and Heats of Vaporization of Hydrocarbons and Related Compounds, Thermodyn. Res. Center Dept. Chem. Texas A&M Univ. (American Petroleum Institute Research, Texas 1971), Publ. 101, Proj. 44 R. Tillner-Roth, F. Harms-Watzenberg, H.D. Baehr: Eine neue Fundamentalgleichung für Ammoniak, DKV-Tagungsbericht 20(II/1), 167–181 (1993) R. Span, W. Wagner: A new equation of state for carbon dioxide covering the fluid region from the triple-point temperature to 1100 K at pressures up to 800 MPa, J. Phys. Chem. Ref. Data 25, 1509–1596 (1996) R. Tillner-Roth: Die thermodynamischen Eigenschaften von R134a, R152a und ihren Gemischen – Messungen und Fundamentalgleichungen, Forsch.Ber. DKV (1993) R. Tillner-Roth, H.D. Baehr: An international standard formulation for the thermodynamic properties of 1,1,1,2-tetrafluoroethane (HFC-134a) for temperatures from 170 K to 455 K and pressures up to 70 MPa, J. Phys. Chem. Ref. Data 23, 657–729 (1994) W. Wanger, V. Marx, A. Pruß: A new equation of state for chlorodifluoromethane (R22) covering the entire fluid region from 116 K to 550 K at pressures up to 200 MPa, Int. J. Refrig. 16, 373–389 (1993) F. Brandt: Brennstoffe und Verbrennungsrechnung, 3rd edn. (Vulkan, Essen 1999), in German H.D. Baehr: Zur Thermodynamik des Heizens, Part I, Brennst. Wärme Kraft 32, 9–15 (1980), in German

Part B 4



293

(4.215)

Between an internal pipe with outer surface A1 and an external pipe with inner surface A2 , which are both grey radiators with emissivities ε1 and ε2 , respectively, the heat transfer rate is given according to (4.212), however, with C12 = σ/

References

294

Part B

Applications in Mechanical Engineering

4.21 4.22 4.23

Part B 4

4.24

E. Schmidt: Properties of Water and Steam in SI Units, 3rd edn. (Springer, Berlin 1982) I.N. Bronstein: Taschenbuch der Mathematik, 5th edn. (Deutsch, Frankfurt/Main 2000), in German I.N. Bronshtein, K.A. Semendyayev, G. Musiol, H. Mühlig: Handbook of Mathematics, 5th edn. (Springer, Berlin 2007) E. Pohlhausen: Der Wärmeaustausch zwischen festen Körpern und Flüssigkeiten mit kleiner Reibung

4.25 4.26 4.27

und kleiner Wärmeleitung, Z. Angew. Math. Mech. 1, 115–121 (1921) H.D. Baehr, K. Stephan: Heat and Mass Transfer (Springer, Berlin 2006) W. Fritz: In VDI-Wärmeatlas (VDI, Düsseldorf 1963), Hb2 VDI/GVC (Ed.): VDI-Wärmeatlas, 10th edn. (Springer, Berlin 2006), in German

295

Tribology

5. Tribology

Ludger Deters

5.1

Tribology ............................................. 5.1.1 Tribotechnical System ................. 5.1.2 Friction ..................................... 5.1.3 Wear ........................................ 5.1.4 Fundamentals of Lubrication ....... 5.1.5 Lubricants .................................

295 296 301 303 310 315

References .................................................. 326

mineral, synthetic and biodegradable oils and additives, lubricating greases and solid lubricants, and on the properties of lubricants, like the behaviour of the oil viscosity depending on temperature, pressure and shear rate and the consistency of lubricating greases.

5.1 Tribology Tribology is the science and technology of interacting surfaces in relative motion. Tribology includes boundary-layer interactions both between solids and between solids and liquids and/or gases. Tribology encompasses the entire field of friction and wear, including lubrication [5.1]. Tribology aims to optimize friction and wear for a particular application case. Apart from fulfilling the required function, this means assuring high efficiency and sufficient reliability at the lowest possible manufacturing, assembly, and maintenance costs. Friction and wear are frequently undesirable. While friction impairs the efficiency of machine elements, machines, and plants and thus increases the energy demand, wear diminishes the value of components and assemblies and can lead to the failure of machines and plants. On the other hand, many technical applications strive for high friction, e.g., brakes, clutches, wheels/rails, car tires/road, friction gears, belt drives,

bolted joints, and press fits. To a limited extent, wear can also be advantageous in special cases, e.g., in breaking-in processes. Friction and wear are not properties specific to the geometry or substance of only one of the elements involved in friction and wear, e.g., external dimensions, surface roughnesses, thermal conductivity, hardness, yield point, density or structure, but rather are properties of a system. The system’s friction and/or wear behavior can already change seriously when one influencing variable of the tribotechnical system is marginally modified. Lubrication is employed to lessen friction and minimize wear or to prevent them entirely. In the case of circulatory lubrication, the lubricant can additionally remove wear particles and heat from the friction contact. Other important tasks of lubrication are preventing corrosion (rusting) and, in the case of grease lubrication, sealing the friction points.

Part B 5

The main subjects of this chapter are the tribotechnical system, friction, wear and lubrication. Regarding the tribotechnical system essential information on structure, real contact geometry, tribological loads, operating and loss variables are provided. Concerning friction the different friction types, states and mechanisms are discussed. In the sections on wear a lot of details on types and mechanisms of wear, wear profiles and the determination of wear and the average useful life are introduced. The sections on lubrication contain relevant expositions on the lubrication states, like hydrodynamic, elastohydrodynamic, hydrostatic, mixed and boundary lubrication and lubrication with solid lubricants, on the lubricants, like

Tribology

5.1 Tribology

299

Table 5.2 Tribologically relevant properties of elements of the tribotechnical system (TTS) (Fig. 5.1)

1. Base body and counterpart 1.1 Geometric poperties • External dimensions • Shape and position tolerances

1.2.2 Near-surface zone • Hardness (macro, micro, and Martens hardness) • Surface energy • Metallurgical structures, texture, microstructure phases (distribution, size, number type) • Chemical composition

• Modulus of el. Poisson’s ratio • Residual stress • Chemical composition

• Modulus of el. Poisson’s ratio • Residual stress • Boundary-layer thickness and structure

1.3 Physical variables • Density • Heat conductivity • Coefficient of thermal expansion

• Melting point • Spec. thermal capacity • Hygroscopic properties

2. Interfacial medium (lubricant) • Aggregate state (solid, liquid, gaseous) • For solid interfacial medium – Hardness – Grain size distribution – Grain shape – Grain quantity, grain number – Number of components, mixing ratio – Chemical composition

• For liquid interfacial medium – Viscosity depending on temperature, pressure, shear rate – Consistency – Wettability – Lubricant quantity and pressure – Chemical composition – Mixing ratio of components

3. Ambient medium • Aggregate state (solid, liquid, gaseous) • Heat conductivity • Chemical composition

• Moisture • Ambient pressure

Tribological Loads and Interactions Tribological loads in a TTS are generated by the input and disturbance variables’ action on the system

structure. They chiefly include contact, kinematic, and thermal processes [5.2]. According to [5.1], the tribological load represents “the loading of the surface of

Part B 5.1

1.2 Material properties 1.2.1 Bulk material • Strength • Hardness (macro, micro, and Martens hardness) • Structure, texture, microstructure phases (distribution, size, number type)

• Waviness • Surface roughnesses

300

Part B

Applications in Mechanical Engineering

Part B 5.1

a solid caused by contact and relative motion of a solid, liquid or gaseous counterbody.” It is introduced via the real contact areas. Plastic deformation and wear can cause the real contact areas to change during TTS operation. When mechanical energy is converted by friction, energy dissipates, which makes itself noticeable by changing the thermal situation. Since the thermal behavior also continuously adapts to the new conditions as a result of wear, changes to the contact geometry, and resulting changes in the friction, dynamic rather than static influencing variables determine the tribological loading in a real contact. The contact geometry, the processes occurring in the contact, and the thermal behavior of a TTS are influenced by, among other things, the load, the motion conditions, the element properties, and the friction state. While the apparent contact area alone is decisive in fluid lubrication, according to [5.6], in mixed lubrication, i. e., when the dimensionless film parameter Λ= 

h min 2 + R2 Rq1 q2

1/2 ,

(5.1)

with the minimum lubrication film thickness h min and the root-mean-square (rms) surface roughnesses Rq1 and Rq2 of the base body and counterbody is in the range Λ < 3, in boundary lubrication with Λ < 1 and for dry friction both the apparent contact area and the real contact areas must be allowed for (Fig. 5.4). When there are contacts between the friction bodies, interactions occur in the real contact areas and in the near-surface zones. Atomic/molecular interactions occur on the one hand and mechanical interactions on the other. Whereas the former cause adhesion on solid–solid boundary layers or are extremely important technically in the form of physisorption and chemisorption on solid–fluid boundary layers, the latter lead to elastic and plastic contact deformations and to the development of the real contact areas. The type of interaction that primarily occurs depends greatly on the friction state. Thus, when a lubricant is present the atomic/molecular interaction can be disregarded more often than the mechanical. Friction and wear in a given TTS ultimately depend on the interactions between the elements. The friction state, the effective mechanisms of friction and wear, and the contact state can be used to describe the interactions. The tribological loads occurring in the real contact areas produce tribological processes. These subsume the dynamic physical and chemical mechanisms of fric-

tion and wear and boundary-layer processes that can be attributed to friction and wear. Operating Variables (Input Variables) According to [5.1], the operating variables are: type of motion, the time sequence of motions of the elements contained in the system structure, and a number of technical-physical load parameters, which act on the system structure when the function is executed. The operating variables originate from:

• • • • •

Type of motion and time sequence of motions Load Velocities Temperatures Loading time

The type of motion can frequently be attributed to one of the basic types of motion sliding, rolling, spin, impact or flowing or can be composed from these. The time sequence of motions can occur regularly, irregularly, back and forth, or intermittently. The sequence of motions frequently also consists of different components. As a rule, the normal force Fn is decisive for the load. Both the relative velocity between the friction bodies and the entraining velocity of the lubricant in the contact and the slippage as a ratio of the relative velocity to the average circumferential velocity play a role for the velocities. The friction body temperatures and the effective contact temperature produced in operation are critically important for the temperature variables. It is normally not possible to measure the contact temperatures. Apart from these desired input variables, which as a rule are specified by a technical function, disturbance variables such as vibrations or dust particles must be considered under certain circumstances. Output Variables (Useful Variables) The TTS provides output variables for subsequent utilization. These useful variables reflect the performance of a function of the TTS. The useful variables can differ over extremely wide ranges depending on the main task of the TTS. In an energy-determined system, for example, the following output variables may be desired:

• • • • •

Force Torque Velocity Motion Mechanical energy

Tribology

Particular material or signal variables could be interesting as useful variables in a material- or signaldetermined TTS.

5.1.2 Friction General Friction can be ascribed to the interactions between bodies’ material zones that are in contact or moving relative to one another; it counteracts relative motion. External and internal friction are differentiated. When friction is external, the different friction bodies’ material zones are in contact; when friction is internal, material zones that are in contact belong to one friction body or the interfacial medium. A number of parameters can characterize friction. Thus, depending on the application, friction is characterized by the friction force Ff , the friction torque Mf or the coefficient of friction f . Instead of f the symbol μ is also frequently used for the coefficient of friction. The coefficient of friction f is formed from the ratio of the friction force Ff to the normal force Fn Ff f = . (5.2) Fn The work of friction or friction energy Wf is used to calculate the frictional heat or the amount of deformation of the friction force in solid friction. It is calculated as

Wf = Ff sf ; ,

(5.3)

with the friction distance sf . The friction power Pf is of interest for an energy balance or efficiency calculation. The friction power is a power loss and, disregarding signs, the following applies Pf = Ff Δv,

(5.4)

301

with the relative velocity Δv. (The power loss is frequently defined negatively). Types of Friction Friction can be classified according to various features. Types of Friction are distinguished depending on the type of relative motion between the friction bodies. Figure 5.5 presents the most important types of friction with samples applications. There are three main types of friction:

• • •

Sliding friction Rolling friction Spin friction

Apart from these three kinematically defined types of friction, there can be overlaps (mixed forms), namely:

• • •

Sliding–rolling friction (rolling friction) Sliding–spin friction Rolling–spin friction

Along with the types of friction shown in Fig. 5.5, another type of friction is impact friction, which applies when a body strikes another body perpendicular or oblique to the contact surface and possibly withdraws again. The angular contact ball bearing is a machine element in which sliding and rolling and spin friction appear. Friction States Various friction states can be defined if friction is classified as a function of the aggregate state of the material zones involved. To illustrate this, Fig. 5.6 presents different states of friction based on the Stribeck curve using a radial sliding bearing as an example. Generally, the following friction states are differentiated:

• • • •

Solid friction Mixed friction Fluid friction Gas friction

In solid friction the friction acts between material zones that exhibit solid properties and are in direct contact. If the friction occurs between solid boundary layers with modified properties compared with the bulk material, e.g., between reaction layers, then this is boundary-layer friction. If the boundary layers on the contact surfaces each consist of a molecular film coming from a lubricant, then this is called boundary

Part B 5.1

Loss Variables The loss variables of a TTS are essentially represented by friction and wear. While friction leads to losses of force, torque or energy, wear means a progressive loss of material. The energy losses produced when there is friction are converted into heat for the most part. This process is irreversible and is called energy dissipation. Along with the conversion of friction into heat and the generation of wear particles, the tribological process generates other tribologically induced loss variables such as vibrations that frequently become apparent through sound waves, photon emission (triboluminescence), electron, ion emission, etc.

5.1 Tribology

Tribology

5.1 Tribology

faces are not moving. When the volumetric flow of lubricant into the lubricating pocket is constant, the minimum lubrication film thickness is proportional to the cube root of the ratio of the average lubricant viscosity in the lubrication gap and the load, i. e., the minimum lubrication film thickness is less dependent on the viscosity and the load than is the case in hydrodynamic lubrication. Hydrostatic lubrication is mainly used: where the friction partners’ surfaces do not have any metallic contact, i. e., wear may not occur, not even when ramping up and ramping down a machine or at low speed; where as low a friction coefficient as possible must be produced at low speeds; and where, as a result of less effective lubricant entraining velocities in the lubrication gap, the wedge effect cannot produce any bearing lubricating film hydrodynamically.

Soft EHL. Elastohydrodynamics for soft surfaces (soft EHL) refers to materials with low moduli of elasticity, e.g., rubber. In soft EHL, sizeable elastic deformations occur even at low loads. The maximum occurring pressures in soft EHL are typically 1 MPa, in contrast to 1 GPa for hard EHL. This low lubricating film pressure only negligibly influences the viscosity during the flow through the lubrication gap. The minimum lubrication film thickness is a function of the same parameters as in hydrodynamic lubrication with the addition of the effective modulus of elasticity E ∗ . The minimum lubricating film thickness in soft EHL is typically 1 μm. Applications for soft EHL are seals, artificial human joints, tires and nonconformal contacts in which rubber is used. A common feature that hard and soft EHL exhibit is the generation of coherent lubricating films as a result of local elastic deformations of the friction bodies and thus the prevention of interactions between asperities. Hence, only the lubricant’s shear generates frictional resistance to motion.

Boundary Lubrication In boundary lubrication, the friction bodies are not separated by a lubricant, the hydrodynamic lubricating film effects are negligible, and there are extensive asperity contacts. The physical and chemical properties of thin surface films of molecular thickness control the lubricating mechanisms in the contact. The base lubricant’s properties are of little importance. The coefficient of friction is on the whole independent of the lubricant’s viscosity. The frictional characteristic is determined by the properties of the solids involved in the friction process and the boundary layers forming on the material surfaces, which primarily depend on the lubricant’s properties, particularly the lubricant additives, as well as the material surfaces’ properties. These boundary layers are formed by physisorption, chemisorption, and/or tribochemical reaction. The thickness of the surface boundary layer varies between 1 and 10 nm, depending on the molecule size. In physisorption, additives contained in the lubricant [e.g., antiwear (AW) additives] such as saturated and unsaturated fatty acids, natural and synthetic fatty acid esters, and primary and secondary alcohols are adsorbed on the tribologically loaded surfaces. Such materials have in common a high dipole moment because of at least one polar group in the molecule (Fig. 5.14). The coverage of the surfaces follows the laws of adsorption and is dependent on temperature and concentration. A prerequisite for the adsorption of polar groups is that the material surface exhibits a polar character so that van der Waals bonds can form. This is usually attained for metallic materials by oxide films

Hydrostatic Lubrication. In hydrostatic lubrication of

friction bodies, a pocket or recess is incorporated in one friction body’s loaded surface into which a fluid is forced from outside at constant pressure. A pump outside the bearing generates the lubricant pressure. Hence, the lubricant pump and the lubricating pocket into which the lubricant is fed under pressure are the most important features of hydrostatic lubrication. The lubricating pocket is normally positioned opposite the external load. The load-carrying capacity of a contact with hydrostatic lubrication is also assured when sur-

Part B 5.1

lubrication, but these must be augmented by the effective modulus of elasticity E ∗ and the lubricant’s viscosity–pressure coefficients α. Table 5.8 indicates that, in the relationship for the minimum lubrication film thickness, the exponent for the normal load in hard EHL is approximately seven times smaller than it is in hydrodynamic lubrication. This means that, in contrast to hydrodynamic lubrication, the load only marginally influences the lubrication film thickness in hard EHL. The reasons are to be found in the increase of the contact area as the load increases in hard EHL, as a result of which a larger lubrication area is provided to bear the load. The exponent for the lubricant entraining velocity in hard EHL is greater than in hydrodynamic lubrication. Typical applications for hard EHL are toothed gears, rolling element bearings, and cam–follower pairs.

313

316

Part B

Applications in Mechanical Engineering

Table 5.10 Comparison of the properties of natural and synthetic base oils for lubricants (after [5.16]) A

B

C

D

E

F

G

H

I

J

K

Part B 5.1

Viscosity–temperature – + ◦ + + ◦ –– –– ++ ++ – behavior (viscosity index, VI) Low-temperature –– ◦ ++ ++ + ◦ –– – ++ + ◦ performance (pour point) Oxidation stability (aging test) – –– + ◦ + –– + ◦ + + ++ Thermal stability (heating – – – ◦ + ◦ ++ – + ◦ + under absence of oxygen) Volatility (evaporating loss) – ◦ ◦ ++ ++ ◦ ◦ + + ◦ ◦ Finish compatibility ++ – ++ – – – – –– ◦ – ◦ (effect on coatings) Water resistance (hydrolysis test) ++ –– ++ – – ◦ ++ – ◦ – + Antirust properties (corrosion test) ++ ++ ++ – – ◦ – – ◦ –– + Seal compatibility ◦ – ++ – – ◦ ◦ –– ◦ ◦ – (swelling behavior) Flame resistance –– –– –– – – – – ++ ◦ – ++ (ignition temperature) Additive solubility (dissolving ++ ◦ + –– ◦ – + ◦ –– ◦ – of larger concentrations) Lubricity (load-carrying ability) ◦ ++ ◦ + + ◦ ++ ++ –– – ++ Biodegradability – ++ ◦ ++ ++ ++ –– + –– – –– (degradability test) Toxicity ◦ ++ ++ ◦ ◦ + ◦ –– ++ – + Miscibility (formation of ++ ++ ++ + + –– ◦ – –– – –– a homogenous phase) Price ratio to mineral oil 1 3 4 7 8 8 350 7 65 25 350 Weighting: 1: ++; 2: +; 3: ◦; 4: –; 5: – – A – Mineral oil (solvent neutral); B – Rape oil; C – Polyalphaolefin; D – Carboxylic acid ester; E – Neopentyl polyol esters; F – Polyalkylenglycol (polyglycol); G – Polyphenyl ether; H – Phosphoric acid ester; I – Silicon oil; J – Silicate ester; K – Fluorine-chlorine-carbon oil (chlorotrifluoroethylene)

which can cause corrosion of machine parts. This can be prevented in part by admixing additives (e.g., antioxidants, detergent, and dispersant agents). More information on their effect and the use of additives can be found in the section on “Additives.” Synthetic Oils. Synthetic-base lubricating oils are produced by chemical synthesis from chemically defined structural elements (e.g., ethylene). Their development has made it possible to systematically satisfy even extreme requirements (e.g., lubricant temperature > 150 ◦ C). According to their chemical composition, synthetic lubricants are subdivided into synthetic hydrocarbons, which only contain carbon and hydrogen [e.g., polyalphaolefines (PAO), dialkylbenzenes (DAB), polyisobutenes (PIB)], and synthetic fluids (e.g., polyglycols, carboxylic acid esters, phosphoric acid esters, sil-

icon oils, polyphenyl ethers, fluorine–chlorine–carbon oils). Typical characteristics of synthetic oils are provided in Table 5.9 and a comparison of the properties of synthesis oils with those of mineral oil is presented in Table 5.10. Synthetic oils have a number of advantages over mineral oils. They have better resistance to aging (thermal and oxidative stability) and thus their useful life is three to five times longer. They exhibit a more favorable viscosity–temperature behavior (with a significantly lower dependence of viscosity on temperature), display better flow properties at low temperatures and lower volatility at high temperatures, can cover applications operating at a substantially expanded range of temperature, and are radiation and flame resistant. Moreover, synthetic lubricants can be used to obtain specific frictional properties, e.g., lower friction coeffi-

Tribology

5.1 Tribology

317

Table 5.11 Examples of use of the most important synthetic lubricants (after [5.17]) Examples of use

Polyalphaolefins (synthetic hydrocarbons)

– High-performance oils for diesel engines – Multigrade engine oils – Gear lubrication at high thermal stress – Compressor oils – Aircraft engine oils – Fuel economy oils (low-friction engine oils) – Base oil for high- and low-temperature greases – Applications requiring good and fast biodegradability – Applications similar to those for carboxylic acid esters but especially wherever oxidation stability and better additive solubility are required – Metalworking fluids – Gear oils (worm gears) – Hydraulic fluids (flame resistant) – Lubricant for compressors and pumps – High-temperature lubricants (up to 400 ◦ C) – Applications requiring resistance to ionizing radiation (γ rays and thermal neutrons) – Plasticizers – Flame-resistant hydraulic oils – Safety lubricants for air and gas compressors – EP additives – Special lubricants for high temperatures – Base oil for lifetime lubricating greases (e.g., for clutch release bearings for motor vehicle clutches, starters, brakes, and axle components) – Hydraulic oils for lower temperatures – Heat exchange fluids – Lubricants for oxygen compressors and for pumps for aggressive fluids

Carboxylic acid esters

Neopentyl polyol esters Polyalkylglycols (polyglycols)

Polyphenyl ethers Phosphoric acid esters

Silicone oils

Silicate esters Fluorine-chlorine-carbon oils

cients to minimize power loss in ball bearings or gears, or higher friction coefficients to increase the transmittable torque in friction gears. On the other hand, synthetic lubricants often cannot be used as universally as mineral oils since they have been developed for specific properties. In addition, they are more strongly hydroscopic (water attracting), display only slight air release characteristics (risk of foaming), mix poorly or not at all with mineral oils, are toxic to a large extent, and are characterized by poor compatibility with other materials (risk of chemical reaction with seals, paints, and nonferrous metals) and by poor solubility for additives. They are not always available, most notably in certain viscosity classes, and they frequently cost substantially more. Table 5.11 details examples of typical areas of application of synthetic oils. Biodegradable Oils. Environmentally compatible lubri-

cating oils are increasingly being used, for example,

in motor vehicles and equipment in water protection areas and in hydraulic engineering, in vehicles for agriculture and forestry, and in openly running gears with loss lubrication (excavators, mills). They are readily and rapidly degradable, have a low water hazard class, and are toxicologically harmless. Their base substances have to be degraded in a degradability test (e.g., CEC L-33-T-82) by a defined amount within a specified time and the additives used (up to a maximum of 5%) should be potentially degradable. Native oils and native base synthetic esters as well as fully synthetic esters and polyglycols are used. Native oils (e.g., rape oil and natural esters) are unsuitable for high temperatures (> 70 ◦ C) and additionally have low thermal stability and resistance to aging. The synthetic oils suitable for continuous high temperatures are often used as hydraulic oils in agricultural and forestry machines. Polyglycols are used, for example, as readily biodegradable oils in water engineering.

Part B 5.1

Product group

318

Part B

Applications in Mechanical Engineering

Table 5.12 Additives, typical types of additives, applications, and active mechanisms (after [5.18])

Part B 5.1

Additive

Types of additive

Application

Active mechanisms

Antiwear (AW) additive

Zinc dialcyldithiophosphates, tricresylphosphates

Extreme pressure (EP) additives

Sulfurized greases and olefines, chlorohydrocarbons, lead salts of organic acids, aminophosphates

Reaction with metal surfaces produces layers that are plastically deformed and improves the contact pattern Reaction with metal surfaces produces new bonds with lower shear resistance than the base metal. There is constant shearing off and reformation

Friction modifiers

Fatty acids, fat amines, solid lubricants

Decrease of inordinate wear metal surfaces Prevention of microwelding between metal surfaces at high pressures and temperatures Reduction of friction between metal surfaces

Viscosiy index improvers

Polyisobutylenes, polymethylacrylates, polyacrylates, ethylenepropylene, styrene maleic acid esters, copolymers, hydrogenated styrenebutadiene-copolymers Paraffin-alkylated naphthalenes and phenols, polymethylacrylates Normal or alkaline calcium, barium or magnesiumsulfinates, phenates or phosphonates Polymers such as nitrogenous polymethylacrylates, alkyl succunimides and succinate esters, high molecular weight amines and amides Inhibited phenols, amines, organic sulfides, zinc dithiophosphates

Pour point depressants Detergent additives

Dispersant additives

Oxidation inhibitors

Corrosion inhibitors

Rust inhibitors

Zinc dithiophosphates, sulfurized terpenes, phosphorized, sulfurized olefines Amine phosphates, sodium, calcium, and magnesium sulfates, alkyl succinic acid, fatty acids

Reduction of dependence of viscosity on temperture

Highly polar molecules are absorbed on metal surfaces and seperate the surfaces, solid lubricants form friction-reducing surface film Polymer molecules are strongly balled in cold oil (poor solvent) and take on greater volume in warm oil (good solvent) by unballing. This produces a relative thickening in oil

Decrease of pour point of the oil

Encasing prevents the agglomeration of paraffin crystals

Reduction or prevention of deposits in engines at high operating temperatures Prevention or delay of the development and deposition of sludge at low operation temperatures

Reaction with the oxidation products controls the formation of coating and sludge. Products are produced that are oil soluble or suspendet in oil

Minimization of the formation of resin, coating, sludge, acid, and polymer-like compounds Protection of bearing and other metal surfaces against corrosion Protection of ferrous surfaces against rust

Reducing the organic peroxides ends the oxidation chain reaction. reduced oxygen intake by the oil decreases the acid formation. Catalytic reactions are prevented Acts as an anticatalyst; film forms on metal surfaces as protection against attacks from acids and peroxides Metal surfaces prefer to adsorb polar molecules and they serve as a barrier against water neutralization by acids

Additives. Additives are substances that either give new

characteristics to mineral, synthesis or vegetable oils or enhance already existing positive properties. The quantity of additive used differs greatly. Thus, circulating or hydraulic oils may only contain 0.1%, whereas special engine and gear oils may contain up to 30% additives. All properties of lubricants cannot be changed by additives. However, using additives a clear improvement in lubrication can be obtained by modifying some properties. Thus, for example, heat dissipation, viscosity–density properties, and temperature resistance cannot be influenced by additives. Improvements

Dispersantshave a pronounced affinity for impurities and encase these with oil soluble molecules that suppress the agglomeration and deposition of sludge in the engine

brought about by additives are obtained for lowtemperature performance, aging stability, viscosity– temperature properties, and corrosion protection. Only additives can attain good cleaning performance, favorable dispersion behavior, antiseizing properties, and foam inhibition. Additives have to be matched to the base oil in terms of quantity and composition and the presence of other additives since they respond differently to the base oil and are not mutually compatible in every case. For example, there are antagonistic effects between viscosity index improves and antifoam additives, between detergent/dispersant additives and antiwear, antiseizing, and

Tribology

5.1 Tribology

319

Table 5.12 (cont.) Types of additive

Application

Active mechanisms

Metal deactivators

Triarylphosphate, sulfur compounds, diamines, dimercaptothiadiazop deriviatives Silicon polymers, tributylphosphates

Suppression of the catalytic influence on oxidation and corrosion Protection of the development of stable foam

Soaps, polyisobutylenes and polyacrylate polymers Sodium salts of sulfonic acids and other organic acids, fat amine salts Anionic sulfon acid compounds (dinonylnaphthalinsulfonat) Phenols, chlorine compounds, formaldehyde derivatives

Increase of the oils’s adhesive ability Emulsification of oil in water

A protective film is adsorbed an metal surfaces, which inhibits the contact between the bases metal and the corrosive substance Attacking the oil film surrounding every air bubble reduces the boundary surface stress. As a result smaller bubbles coalesce into larger bubbles that rise to the surface Viscosity is increased. Additives are viscous and sticky Adsorbing the emulsifier in the oil/water boundary surface reduces boundary surface stress, as a result of which one fluid disperse into another A boundary layer develops between water and oil form substances active in the boundary surface

Foam inhibitors

Adhesion improvers Emulsifier

Demulsifier

Bactericide

Demulsification of water Increase of the emulsion’s working life, prevention of unpleasent odors

antifoam additives, and between corrosion inhibitors and antiwear and antiseizing additives [5.16]. A difference can be made between additives that form surface layers and those that change the properties of the lubricant itself. Additives forming surface layers act as a lubricating film above all when there is insufficient lubrication, as a result of which friction is reduced and the load-carrying capacity of sliding–rolling pairs is improved. Among others, this group of additives includes antiwear (AW) additives, extreme pressure (EP) additives, and friction modifiers. Adding additives that form surface layers also has drawbacks though. Thus, lubricants with additives oxidize faster than normal mineral oils and corrosive acids and insoluble residues frequently form. Hence these additives should only be used when necessitated by the operating conditions. Additives that modify lubricants influence, for example, foaming behavior, corrosion behavior, sludging, and pour point. Table 5.12 provides an overview of the most important types of additives and their applications. During operation, the effectiveness of some additives can decrease (exhaustion) since reaction with the materials or the atmospheric oxygen causes their concentration to drop. Once the concentration of the additive falls below a certain value, an oil change is necessary. Consistent Lubricants (Lubricating Greases) Consistent lubricants have a flow limit. No movement occurs below a shear stress that is specific to the lu-

The growth of microorganisms is prevented or delayed

bricant. Only when this flow limit has been exceeded does the viscosity drop from a virtually infinitely high to a measurable value. Lubricating greases consist of three components: a base oil (75–96 wt %), a thickener (4–20 wt %), and additives (0–5 wt %). Suitable thickeners can be dispersed both in mineral oils and in synthetic or vegetable oils so that consistent lubricants are produced. By far, most greases are manufactured using soaps (metallic salts from fatty acids) as thickeners. Thus, fatty acids are dissolved in the base oil at relatively high temperatures and a suitable metal hydroxide (e.g., hydroxides of sodium, lithium, and calcium or to a lesser extent barium and aluminum) is added subsequently. Longchain fatty acids come from vegetable or animal oils and can be hydrogenated. Occasionally, not only long-chain fatty acids but also short-chain acids such as acetic, propionic, benzoic acid, etc. are used. Then so-called complex soaps are produced [5.16]. Most soap compounds form a fibrous matrix of interlocking particles, which retains the base oil (Fig. 5.17). By contrast, aluminum soaps contain a spherical gel structure. The grease’s lubricating action is based on the base oil being dispensed slowly and sufficiently in operation under load. The delivery of the base oil depends strongly on the temperature. The lubricating grease releases less and less oil as the temperature drops and the grease becomes stiffer and stiffer (consistency). Beyond a certain temperature limit, this eventually leads to insufficient lubrication in the friction contact. As the

Part B 5.1

Additive

Tribology

5.1 Tribology

321

Table 5.14 Areas of application of synthetic lubricating greases [5.16] Mineral oil (benchmark)

PAO

Ester oils

turn, bentonite grease is incompatible with all other types of grease.

Alkoxyfluorine oils

250 −75 ––– +++ +++ ++ +++ +++ ++ +

250 −30 – +++ +++ +++ +++ +++ +++ ++

imides], soft nonmetals (lead sulfide, iron sulfide, lead oxide, and silver iodide), soft nonferrous metals (gold, silver, lead, copper, and indium), and reaction layers on the surface (oxide, sulfide, nitride, and phosphate layers) are used as solid lubricants. Graphite needs water to adhere and to reduce shear strength (low friction) and hence is unsuitable for use in a dry atmosphere or vacuum. Molybdenum disulfide (MoS2 ) adheres well to all metal surfaces with the exception of aluminum and titanium. It is a highly suitable solid lubricant for temperatures up to 350 ◦ C but costs more than graphite. Polytetrafluoroethylene (PTFE or Teflon) exhibits a low friction factor at low speeds and high loads and is suitable for temperatures from −250 ◦ C to +250 ◦ C. Their high proportion of solid lubricants (graphite, molybdenum disulfide or PTFE) distinguishes lubricating varnishes from decorative industrial varnishes. They can be used as a dry film at temperatures between −180 ◦ C and +450 ◦ C. Lubricating varnishes with oilresistant binders can also be used in oily systems and are suitable, for example, for bypassing the critical breakin phase without damage or for shortening the break-in time.

Solid Lubricants Solid lubricants are used especially whenever fluid and consistent lubricants cannot provide the lubricating action required. This is frequently the case under the following operating conditions: low sliding speeds, oscillating motions, high specific loads, high or low operating temperatures, extremely low ambient pressures (vacuum), and aggressive ambient atmospheres. Solid lubricants are also used to improve particular properties of fluid and consistent lubricants, i. e., as additives, for example, to minimize friction and wear and to guarantee antiseizure performance. Solid lubricants in the form of powders, pastes or lubricating varnishes contribute directly to the build up of the lubricating film on the one hand or improve the lubricating properties in oils, greases or bearing materials on the other hand. Substances with a layer lattice structure (graphite, the sulfides MoS2 and WS2 ), selenides (WSe2 ), organic substances [polytetrafluoroethylene (PTFE), amides,

Table 5.15 Compatibility of types of lubricating grease [5.16] Grease type

Na

Na grease Li grease – Ca grease – Ca complex – Ba complex + Al complex – Bentonite – + compatible; – incompatible

Li

Ca

Ca complex

Ba complex

Al complex

Bentonite

–

– +

– + –

+ + + +

– – – – +

– – – – – –

+ + + – –

+ + – –

+ – –

+ –

–

Part B 5.1

Upper limit of application (◦ C) 150 200 200 Lower limit of application (◦ C) −40 −70 −70 Lubrication of metals ++ ++ +++ Lubrication of plastics ◦ ++ ◦ Hydrolysis resistance ++ ++ ◦ Chemical resistance + + –– Elastomer compatibility ◦ + ◦ Toxicity – + + Flammability ––– ––– + Radiation resistance –– –– – +++ excellent; ++ very good; + good; ◦ moderate; – adequate; – – limited; – – – poor

Silicon oils

Tribology

5.1 Tribology

325

Table 5.17 NLGI consistency classes and applications of lubricating greases (after [5.2]) (NLGI – National Lubricating

Grease Institute) NLGIclass

Penetration 0.1 mm

000 00 0 1 2 3 4

445–475 400–430 355–385 310–340 265–295 220–250 175–205

Consistency

+ +

Ball bearings

+ + +

Centralized lubricating systems

Gears

+ + + +

+ + + +

Water pumps

Block greases

+ + +

viscosity–pressure coefficient, and pu is the ambient pressure; α has a new characteristic value for every lubricant and is chiefly influenced by the composition (paraffin–naphthene–hydrocarbons and aromatics content) as well as the base oil’s physical properties but less by chemical additives (Table 5.16). Reference [5.1] provides an expression that simultaneously reproduces the dependence of the dynamic viscosity η on the state variables pressure p and temperature T ⎡  ⎤   D+E B C+T p − pu B ⎦. +1 η(T, p) = A exp ⎣ C+T 2000 (5.12)

The dependence of the dynamic viscosity on the temperature is represented by the coefficients A, B, and C (Vogel equation) and the dependence on the pressure is described by the coefficients D and E. Tests are employed to determine the coefficients A–E. Figure 5.22 presents the viscosity of a lubricating oil as a function of pressure and temperature. Dependence of Viscosity on Shear Rate. When the rheological properties are independent of time, the flow properties of viscous lubricants can be easily described. Then the shear stress τ in the lubricant is a simple function of the local shear rate γ˙ , i. e., τ = f (γ˙ ). If this function is linear so that the shear stress is proportional to the shear rate, then a Newtonian fluid exists and the proportionality coefficient is the dynamic viscosity, which also remains constant when shear rates vary (Fig. 5.23a). Pure mineral oils generally exhibit

Newtonian properties up to relatively high shear rates of 105 –106 s−1 . At higher shear rates, which occur relatively often in tribotechnical contacts such as toothed gears, ball bearing, cam-follower pairs, etc., the viscosity’s constancy frequently disappears and the viscosity decreases as the shear rate increases. The lubricant begins to behave like a non-Newtonian fluid, i. e., the viscosity now depends on the shear rate. Pseudoplastic behavior, also known as shear thinning, is characterized by a decrease of viscosity as the shear rate increases (Fig. 5.23a). Dilatant fluids manifest the opposite of pseudoplastic behavior, i. e., thickening of the lubricant as the shear rate increases (Fig. 5.23a). Dilatant fluids are normally suspensions with a high solid content. The flow properties of greases can be compared with those of a Bingham substance. In order to generate a flow, a threshold shear stress must first be overcome (Fig. 5.23b). This means that grease behaves like a solid at first. Once the threshold shear stress τ0 is exceeded, the lubricating grease then flows, for example, with constant viscosity like a Newtonian fluid or even pseudoplastically or dilatantly. Consistency of Lubricating Greases. The behavior

of a lubricating grease is frequently described by its consistency (plasticity). Penetration according to ASTM D-217 and ASTM D-1403 is used as a characteristic. To determine the penetration, the penetration depth of a standard cone with predetermined dimensions into the surface of a lubricating grease is measured in a penetrometer after a penetration time of 5 s at a temperature of 25 ◦ C (in units of 1/10 mm). A difference

Part B 5.1

Almost fluid Semifluid Extra soft Very soft Soft Medium Relatively firm 5 130–160 Firm 6 85–115 Very firm + Primary fields of application

Sliding bearings

326

Part B

Applications in Mechanical Engineering

is made between unworked and worked penetration. Unworked penetration is measured in the unused lubricating grease, whereas worked penetration in measured in already sheared grease that has been worked under

standardized conditions in a standard lubricating grease mixer. The higher the worked penetration, the softer the grease. Table 5.17 shows the relationship between penetration and consistency class.

References 5.1

5.2

Part B 5

5.3

5.4

5.5

5.6 5.7 5.8

5.9

5.10 5.11

Gesellschaft für Tribologie e.V.: GfT Arbeitsblatt 7: Tribologie - Verschleiß, Reibung, Definitionen, Begriffe, Prüfung (GfT, Moers 2002), in German H. Czichos, K.-H. Habig: Tribologie-Handbuch; Reibung und Verschleiß, 2nd edn. (Vieweg, Wiesbaden 2003), in German S. Engel: Reibungs- und Ermüdungsverhalten des Rad-Schiene-Systems mit und ohne Schmierung, Dissertation (Universität Magdeburg 2002), in German A. Gervé, H. Oechsner, B. Kehrwald, M. Kopnarski: Tribomutation von Werkstoffoberflächen im Motorenbau am Beispiel des Zylinderzwickels, FVV-Heft R, 497 (1998), in German J.A. Greenwood, J.B.P. Williamson: The contact of nominally flat surfaces, Proc. R. Soc. A 295, 300–319 (1966) B.J. Hamrock: Fundamentals of Fluid Film Lubrication (McGraw-Hill, New York 1994) J.W. Kragelski: Reibung und Verschleiß (VEB Technik, Berlin 1971), in German K.-H. Habig: Tribologie. In: Dubbel – Taschenbuch für den Maschinenbau, 21st edn., ed. by K.-H. Grote, J. Feldhusen (Springer, Berlin, Heidelberg 2004), in German G. Fleischer, H. Gröger, H. Thum: Verschleiß und Zuverlässigkeit (Verlag Technik, Berlin 1980), in German K. Wächter: Konstruktionslehre für Maschineningenieure (Verlag Technik, Berlin 1989), in German H. Thum: Verschleißteile (Verlag Technik, Berlin 1992), in German

5.12

5.13 5.14

5.15

5.16 5.17

5.18

5.19

5.20 5.21

D. Bartel: Berechnung von Festkörper- und Mischreibung bei Metallpaarungen, Dissertation, Universität Magdeburg (2001), in German O.R. Lang, W. Steinhilper: Gleitlager (Springer, Berlin, Heidelberg 1978), in German P. Deyber: Möglichkeiten zur Einschränkung von Schwingungsverschleiß,. In: Reibung und Verschleiß von Werkstoffen, Bauteilen und Konstruktionen, ed. by H. Czichos (Expert-Verlag, Grafenau 1982), p. 149, in German G. Poll: Wälzlager: Dubbel – Taschenbuch für den Maschinenbau, 21st edn. (Springer, Berlin, Heidelberg 2004), in German U.J. Möller, J. Nassar: Schmierstoffe im Betrieb, 2nd edn. (Springer, Berlin, Heidelberg 2002), in German G. Niemann, H. Winter, B.-R. Höhn: Maschinenelemente Band 1; Konstruktion und Berechnung von Verbindungen, Lagern, Wellen, 3rd edn. (Springer, Berlin, Heidelberg 2001), in German W.J. Bartz: Additive – Einführung in die Problematik Kontakt und Studium. In: Additive für Schmierstoffe, Vol. 433, ed. by W.J. Bartz (Expert, RenningenMalmsheim 1994), in German G.W. Stachowiak, A.W. Batchelor: Engineering Tribology, 2nd edn. (Butterworth-Heinemann, Boston 2001) Gesellschaft für Tribologie e.V.: GfT-Arbeitsblatt 5: Zahnradschmierung (GfT, Moers 2002), in German D. Klamann: Schmierstoffe und verwandte Produkte. Herstellung-Eigenschaften-Anwendung (VCH, Weinheim 1982), in German

327

Design of Ma 6. Design of Machine Elements

Oleg P. Lelikov

6.1

6.2

Mechanical Drives ................................. 329 6.1.1 Contact Stresses .......................... 331 6.1.2 Nature and Causes of Failure Under the Influence of Contact Stresses ... 332 Gearings .............................................. 6.2.1 Basics ........................................ 6.2.2 Accuracy of Gearings.................... 6.2.3 Gear Wheel Materials................... 6.2.4 The Nature and Causes of Gearing Failures ......................

334 334 336 336 338

6.2.5 Choice of Permissible Contact Stresses Under Constant Loading Conditions.................................. 6.2.6 Choice of Permissible Bending Stresses Under Constant Loading Conditions.................................. 6.2.7 Choice of Permissible Stresses Under Varying Loading Conditions . 6.2.8 Typical Loading Conditions ........... 6.2.9 Criteria for Gearing Efficiency........ 6.2.10 Calculated Load ..........................

339

341 342 343 344 345

6.3 Cylindrical Gearings .............................. 6.3.1 Toothing Forces of Cylindrical Gearings ................. 6.3.2 Contact Strength Analysis of Straight Cylindrical Gearings ..... 6.3.3 Bending Strength Calculation of Cylindrical Gearing Teeth .......... 6.3.4 Geometry and Working Condition Features of Helical Gearings ......... 6.3.5 The Concept of the Equivalent Wheel............... 6.3.6 Strength Analysis Features of Helical Gearings ...................... 6.3.7 The Projection Calculation of Cylindrical Gearings .................

348

6.4 Bevel 6.4.1 6.4.2 6.4.3 6.4.4 6.4.5 6.4.6

Gearings ..................................... Basic Considerations .................... The Axial Tooth Form ................... Basic Geometric Proportions ......... Equivalent Cylindrical Wheels ....... Toothing Forces........................... Contact Strength Analysis of Bevel Gearings ........................ 6.4.7 Calculation of the Bending Strength of Bevel Gearing Teeth .... 6.4.8 Projection Calculation for Bevel Gearings .......................

364 364 365 365 366 366

6.5 Worm Gearings..................................... 6.5.1 Background ................................ 6.5.2 Geometry of Worm Gearings ......... 6.5.3 The Kinematics of Worm Gearings .

372 372 373 375

348 348 350 352 354 354 355

367 368 368

Part B 6

A machine generally consists of a motor, a drive, and an actuating element. The mechanical power driving a machine constitutes the rotary motion energy of a motor shaft. Electric motors, internal-combustion motors, or turbines are the most common types of motors. The mechanical power transmission from the motor to the actuating element is accomplished by various driving gears. These include gearings, worm gearings, belt drives, chain drives, and friction gears. Some examples of actuating elements are car steering wheels, work spindles, and screw propellers of ships. This chapter covers the advanced design of machine elements, in particular all common types of gearings and the needed machine components. The in-depth description including stress and strength analysis, materials tables and assembly recommendations allows for a comprehensive and detailed calculation and design of these most important drives. Shafts and axles, shaft-hub assemblies and bearings are included with design guidelines and machining options. Single machine elements, such as specific information about bolts and bolted joints, springs, couplings and clutches, friction drives and also sliding bearings are dealt with only where needed for the benefit of a more general view. The chapter provides the practicing engineer with a clear understanding of the theory and applications behind the fundamental concepts of machine elements.

328

Part B

Applications in Mechanical Engineering

6.5.4 Slip in Worm Gearings ................. 6.5.5 The Efficiency Factor of Worm Gearings ....................... 6.5.6 Toothing Forces........................... 6.5.7 Stiffness Testing of Worms ............ 6.5.8 Materials for Worms and Worm-Wheel Rings ............... 6.5.9 The Nature and Causes of Failure of Worm Gearings ....................... 6.5.10 Contact Strength Analysis and Seizing Prevention ................ 6.5.11 Bending Strength Calculation for Wheel Teeth .......................... 6.5.12 Choice of Permissible Stresses ....... 6.5.13 Thermal Design ........................... 6.5.14 Projection Calculation for Worm Gearings ......................

Part B 6

6.6 Design of Gear Wheels, Worm Wheels, and Worms..................... 6.6.1 Spur Gears with External Toothing. 6.6.2 Spur Gears with Internal Toothing . 6.6.3 Gear Clusters .............................. 6.6.4 Bevel Wheels .............................. 6.6.5 Gear Shafts................................. 6.6.6 Worm Wheels ............................. 6.6.7 Worms ....................................... 6.6.8 Design Drawings of Gear and Worm Wheels: The Worm ....... 6.6.9 Lubrication of Tooth and Worm Gears ......................... 6.7

375 376 377 378 378 378 379 380 380 381 383 388 388 391 391 392 393 394 396 397 398

Planetary Gears .................................... 6.7.1 Introduction ............................... 6.7.2 Gear Ratio .................................. 6.7.3 Planetary Gear Layouts ................ 6.7.4 Torques of the Main Units ............ 6.7.5 Toothing Forces........................... 6.7.6 Number Matching of Wheel Teeth.. 6.7.7 Strength Analysis of Planetary Gears ....................... 6.7.8 Design of Planetary Gears.............

399 399 401 401 402 402 403

6.8 Wave Gears .......................................... 6.8.1 Arrangement and Operation Principles of Wave Gears .............. 6.8.2 Gear Ratio of Wave Gears ............. 6.8.3 Radial Deformation and the Transmission Ratio .......... 6.8.4 The Nature and Causes of Failure of Wave Gear Details.................... 6.8.5 Fatigue Strength Calculation of Flexible Wheels ....................... 6.8.6 Design of Wave Gears ..................

412

406 406

413 415 416 416 417 418

6.8.7 Thermal Conditions and Lubrication of Wave Gears...... 425 6.8.8 Structure Examples of Harmonic Reducers .................. 426 6.9 Shafts and Axles ................................... 6.9.1 Introduction ............................... 6.9.2 Means of Load Transfer on Shafts .. 6.9.3 Efficiency Criteria for Shafts and Axles..................... 6.9.4 Projection Calculation of Shafts ..... 6.9.5 Checking Calculation of Shafts ...... 6.9.6 Shaft Design ............................... 6.9.7 Drafting of the Shaft Working Drawing .....................................

426 426 428

6.10 Shaft–Hub Connections ......................... 6.10.1 Key Joints................................... 6.10.2 Spline Connections ...................... 6.10.3 Pressure Coupling........................ 6.10.4 Frictional Connections with Conic Tightening Rings .........

449 449 451 453

6.11 Rolling Bearings ................................... 6.11.1 Introduction ............................... 6.11.2 Classifications of Rolling Bearings . 6.11.3 Main Types of Bearings ................ 6.11.4 Functions of the Main Bearing Components ............................... 6.11.5 Materials of Bearing Components .. 6.11.6 Nomenclature ............................. 6.11.7 The Nature and Causes of Failure of Rolling Bearings ...................... 6.11.8 Static Load Rating of Bearings....... 6.11.9 Lifetime Testing of Rolling Bearings 6.11.10 Design Dynamic Load Rating of Bearings................................. 6.11.11 Design Lifetime of Bearings .......... 6.11.12 The Choice of Bearing Classes and Their Installation Diagrams .... 6.11.13 Determination of Forces Loading Bearings ........... 6.11.14 Choice and Calculation of Rolling Bearings ...................... 6.11.15 Fits of Bearing Races....................

460 460 461 461

6.12 Design of Bearing Units......................... 6.12.1 Clearances and Preloads in Bearings and Adjustment of Bearings................................. 6.12.2 Principal Recommendations Concerning Design, Assembly, and Diagnostics of Bearing Units ... 6.12.3 Design of Bearing Units................

483

429 429 430 436 440

459

464 465 465 467 467 468 470 471 472 474 477 482

483

486 490

336

Part B

Applications in Mechanical Engineering

Part B 6.2

and mass, and operate more smoothly due to the higher contact ratio and the fact that teeth contacting at convex and concave surfaces have a larger equivalent curvature radius. Moreover, they have a lower slip velocity. Bevel gearings transmit mechanical power between shafts with intersecting axes. Normally, Σ = δ1 + δ2 = 90◦ (Fig. 6.14a). The toothing of the bevel wheels can be considered as a rolling of the pitch circular cones of the pinion and the wheel. The main characteristics of bevel gearings are the angles of the pitch cones, δ1 and δ2 , and the external cone distance Re . Intersection lines of the teeth side faces with the pitch cone surface are called teeth lines. Depending on the form of the tooth line there are gearings with straight teeth (Fig. 6.14b), where teeth lines go through the vertex of the pitch cone, and circular teeth (Fig. 6.14c), which are circular arcs d0 . Bevel wheels with circular teeth are characterized by the tooth line tilt in the middle section according to the width of the gear ring. The tilt angle βn is the acute angle between the tangent to the tooth line and the generation of the pitch cone (Fig. 6.14c). Another version of bevel gearings is the hypoid gearing, where the rotation axes of the gear wheels do not intersect but cross.

6.2.2 Accuracy of Gearings The working capacity of gearings depends considerably on the production accuracy of the gear wheels. Production errors are unavoidable due to: deviation in pitch, profile, tooth direction; radial run-out of the gear ring; deviation from parallelism and misalignment of the gear wheel axes; center distance variation; etc. These errors result in increased noise, loss of rotational accuracy of the driven wheel, failure of precision and smooth toothing, torsional vibration, dynamic increase and decrease of distribution evenness along the contact line acting in the load toothing, and other detrimental effects. Standards regulate the accuracy of gear wheels as well as cylindrical and bevel gearings. Twelve degrees of accuracy are specified and are designated in decreasing accuracy order by the numbers from 1 to 12. Most often, degrees 6, 7, and 8 are applied, where degree 6 corresponds to high-accuracy speed gears, degree 7 corresponds to gears with a normal grade of accuracy that operate with high speed and moderate load, or with moderate speed and large load, and degree 8 corresponds to low-accuracy gears. Gears rated for manufacture according to the sixth degree of accu-

racy can have a mass of the gear set that is 30% less than that required with the eighth degree of accuracy. For each degree of accuracy there are three standards of tolerances, which are detailed below. The standard for kinematic accuracy regulates the difference between the actual and nominal rotation angles of the driven gear wheel. The indices of kinematic accuracy influence external gearing dynamics and the positional accuracy of the output shaft with respect to the input shaft. Because of the risk of torsional and resonance oscillations, and noise, these are important in the pitch circuits of machines, control systems, and high-speed power trains. The standard for smooth operation regulates rotary speed fluctuations per wheel revolution, which cause high-frequency variable, dynamic loads, and noise. The standard for teeth contact regulates the teeth adjacency in the mounted gearing and the degree of load distribution in contact lines, and determines the efficiency of power trains. The gearing side clearance is also regulated. This is the distance between the teeth side faces, which determines the free rotation of one of the gear wheels by a fixed double gear wheel. Side clearance is required to avoid teeth seizing in the gearing as a result of their expansion at the working temperature, as well as to provide a location for lubricant and for the provision of free-wheel rotation. Side clearance is provided in conjunction with tolerances of teeth thickness and the axle base. The clearance dimension is specified by a coupling type of gear wheel in the gearing: H = 0 clearance, E = small, D and C = reduced, B = standard, A = increased. Mostly coupling types B and C are applied. For reverse gears it is recommended to use couplings with reduced clearances. An example of the accuracy designation of a cylindrical gearing with grade 7 according to the standards of kinematic accuracy, grade 6 according to the standards of drive operation smoothness, grade 6 in accordance with the standards of teeth contact, and with coupling type C is 7-6-6-C.

6.2.3 Gear Wheel Materials The choice of the gear wheel material is made to provide contact strength and teeth bending resistance for the functioning gearing under its operating conditions. Steel is the most commonly used material in power trains. In some cases cast iron and plastic are also used. The important criteria for the selection of materials are the mass and dimensions of the gearing.

Design of Machine Elements

Nitrocementing (nitrocarburizing) of the teeth surface layers in a gaseous medium with subsequent quenching provides high contact and bending strength, wear, and sliding strength. Steel grades 5120 (ASTM), 20CrMo5 (DIN), and 30MnCrTi (DIN) are applied. The nitrocarburizing layer thickness is 0.1–1.2 mm. Warpage (tooth distortion) is insignificant, and subsequent grinding is not required. The hardness of the tooth surface is 58–64 HRC Nitriding (surface diffusion nitrogen saturation) provides particularly high hardness of the teeth surface layers. It is characterized by insignificant warpage and enables the production of teeth of high accuracy without development operations. Nitrided wheels are not used under impact loads (because of the risk of cracking the hardened case). Steel grades 41CrAlMo7 and 40NiCrMo4KD (EN) (hardness 58–65 HRC) are applied for nitrided wheels. Strengthening heat treatment is carried out before nitriding, i. e., quenching with subsequent hightemperature tempering. The teeth are not ground after nitriding and nitrocementing because of the minimum warpage. This is why these kinds of chemicothermal hardening can be successfully used for wheels with internal teeth and in cases when teeth grinding is difficult to carry out. Nitriding is not used as often as cementation and nitrocementing due to the long process involved (several tens of hours) and the resulting thin layer (0.2–0.8 mm). Wheel teeth with hardness H > 45 HRC are cut before heat treatment. Teeth finishing (grinding, etc.) is carried out after the heat treatment, as required. Gearings with hard (H > 45 HRC) work surfaces of the teeth run in badly. Throughout surface heat or chemicothermal treatment of the teeth, previous heat treatment (refining) defines the mechanical characteristics of the tooth core. The load-carrying capacity of gearings corresponding to the contact strength is higher when the surface teeth hardness is higher. Thus it is advisable to use surface thermal or chemicothermal hardening. These kinds of hardening allow one to increase the load-carrying capacity of the gearing several fold in comparison with refined steels; for example, the allowable contact stresses [σ ]H of cemented gear wheels are twice as high as the values of [σ ]H of heat-refined wheels, which allows one to decrease their mass by four times. However when defining the hardness of the teeth work surfaces, it must be borne in mind that higher hardness corresponds

337

Part B 6.2

The materials used for gear wheel production in Russia are discussed below. The correspondence between Russian and foreign materials is provided in Appendices 6.A and 6.B. Steel: Gearings with steel gear wheels have the lowest mass and dimensions. Moreover, the mass and dimensions decrease with greater hardness of the teeth effective area, which in turn depends on the steel grade and the heat treatment applied. Heat refining treatment is a combination of quenching and high-temperature tempering; it provides the most favorable combination of hardness, viscosity, and plasticity. Heat refining treatment is carried out before teeth cutting. Materials for the wheels are carbon steel grades C36, C35, C46, C45 (EN), 50Γ, and alloy steel grades 37Cr4 (DIN), 5145 (ASTM), 40NiCr6 (DIN), etc. The hardness of the tooth core and the tooth effective area are equal for improved wheels, 235–302 HB. Wheel teeth made from refined steel have good running in ability and are not subject to fracture failure, although they have restricted load-carrying capacity. They are applied in lightly and medium loaded gearings. High hardness (H > 350 HB) of the surface layer with viscous core preservation is achieved using thermal or chemicothermal surface hardening of previously refined gear wheels. This includes surface hardening, cementation, nitrocementing with tempering, and nitriding. Surface hardening of teeth with high-frequency current heating is appropriate for gear wheels with module values > 2 mm. For low modules a small tooth is annealed through, which results in warpage and embrittlement of the tooth. Steel grades C46, C45 (EN), 37Cr4 (DIN), 40NiCr6 (DIN), and 34CrMo4KD (DIN) are applied for quenching with high-frequency current heating; their surface hardness is 45–53 HRC. For H > 350 HB material hardness is measured according to the C-Rockwell scale. The tooth core hardness corresponds to the heat refining treatment. Cementation (surface diffusion carburizing) with subsequent quenching along with high surface hardness also provides a high bending strength for the teeth. For gear wheels of medium size, the carburized case constitutes 15% of the tooth thickness (but not more than 1.5–2 mm). Only the surface layer saturated with hydrocarbon is annealed. Steel grades 5120 (ASTM), 14NiCr10 (5732) (DIN), and 20MnCr5G (DIN) (hardness of the tooth surface 56–63 HRC) are used for cementation.

6.2 Gearings

358

Part B

Applications in Mechanical Engineering

the case of polishing (large values are obtained by refining and after quenching with heating by means of high-frequency currents). The factor YA takes the influence of double-sided load application (reversing gears) into account. For one-sided load application YA = 1. For reverse loading and an equal load and number of loading cycles in the forward and backward direction (e.g., the teeth of the satellite in planetary gearing) YA = 0.65 for normalized and refined steels, YA = 0.75 for hardened and cemented steel, and YA = 0.9 for nitrided steel.  (mm) 4. The tentative value of the axle base is aw  = K (u ± 1) 3 T1 /u , aw

Part B 6.3

where the plus sign applies for external toothing, and the minus sign applies for internal toothing. T1 is the torque on the pinion (the highest of longacting), in N m, and u is the gear ratio. The factor K , which depends on the surface hardnesses H1 and H2 of the teeth of the pinion and the wheel, respectively, takes the following values: Table 6.7 Coefficient K for the cylindrical gearings Hardness H

Factor K

H1 ≤ 350 HB

H2 ≤ 350 HB

10

H1 ≥ 45 HRC

H2 ≤ 350 HB

8

H1 ≥ 45 HRC

H2 ≥ 45 HRC

6

The circumferential velocity v (m/s) is determined from the formula  n 2πaw 1 ν= . 6 × 104 (u ± 1)

The accuracy degree is taken from Table 6.6. The previously determined value of the axle base is specified according to the formula  K H T1 , aw = K a (u ± 1) 3 ψba u[σ]2H where K a = 450 applies for spurs and K a = 410 applies for helical and herring-bone gears (N/mm2 )1/3 ; and [σ]H is in N/mm2 . ψba is a width ratio taken from the sequence of standard numbers: 0.1, 0.125, 0.16, 0.2, 0.25, 0.315, 0.4, 0.5, and 0.63 depending on the wheel position relative to the bearings. Its value is as

follows ⎧ ⎪ 0.315–0.5 symmetrical arrangement ⎪ ⎪ ⎪ ⎪ ⎨0.25–0.4 unsymmetrical arrangement ⎪ ⎪ 0.2–0.25 console arrangement of one ⎪ ⎪ ⎪ ⎩ or both wheels . For herring-bone gearings ψba = 0.4–0.63, for gear-boxes ψba = 0.1–0.2, and for gearings of internal toothing ψba = 0.2(u + 1)/(u − 1). Lower values ψba are obtained for gearings with teeth hardness H ≥ 45 HRC. The load factor in contact strength calculations is K H = K HV K Hβ K Hα . The factor K HV takes the internal dynamics of the loading into consideration. The values K HV are taken from Table 6.8 and depend on the accuracy degree of the gearing according to the smoothness standards, the circumferential velocity, and the hardness of the working surfaces. The factor K Hβ takes the unevenness of the load distribution along the length of the contact lines into account. The teeth of the gear wheels can grind, and thus the unbalance factors are considered during the initial working 0 and after grinding K . period K Hβ Hβ 0 are taken from Table 6.9 Values of the factor K Hβ and depend on the coefficient ψbd = b2 /d1 , the gearing layout, and the teeth hardness. As the wheel width and pinion diameter have not yet been determined, the value of the coefficient ψbd is calculated approximately as ψbd = 0.5ψba (u ± 1) . The factor K Hβ is determined from the formula

0 − 1 K Hw , K Hβ = 1 + K Hβ where K Hw is the factor taking into account teeth grinding; its values are computed depending on the circumferential velocity of the gear wheel with lower hardness (Table 6.10). The factor K Hα , which takes into consideration the load distribution between the teeth, is determined from the formula

0 − 1 K Hw , K Hα = 1 + K Hα where K Hw is the factor considering teeth grinding; its values are found depending on the circumferential

Design of Machine Elements

6.3 Cylindrical Gearings

359

Table 6.8 Coefficients K HV of the internal dynamics of loading in contact stress analysis. The values for the spurs are

given in the numerator and the values for the helical wheels are given in the denominator Accuracy degree according to GOST 1643-81

Hardness on the teeth surface > 350 HB

6

≤ 350 HB > 350 HB

7

≤ 350 HB > 350 HB

8

≤ 350 HB > 350 HB

9

1

3

5

8

10

1.02 1.01 1.03 1.01 1.02 1.01 1.04 1.02 1.03 1.01 1.05 1.02 1.03 1.01 1.06 1.02

1.06 1.03 1.09 1.03 1.06 1.03 1.12 1.06 1.09 1.03 1.15 1.06 1.09 1.03 1.12 1.06

1.10 1.04 1.16 1.06 1.12 1.05 1.20 1.08 1.15 1.06 1.24 1.10 1.17 1.07 1.28 1.11

1.16 1.06 1.25 1.09 1.19 1.08 1.32 1.13 1.24 1.09 1.38 1.15 1.28 1.11 1.45 1.18

1.20 1.08 1.32 1.13 1.25 1.10 1.40 1.16 1.30 1.12 1.48 1.19 1.35 1.14 1.56 1.22

◦ along the contact lines Table 6.9 Imbalance factors K Hβ

ψbd

Hardness on the surrface of the wheel teeth

0.4

≤ 350 HB > 350 HB ≤ 350 HB > 350 HB ≤ 350 HB > 350 HB ≤ 350 HB > 350 HB ≤ 350 HB > 350 HB ≤ 350 HB > 350 HB ≤ 350 HB > 350 HB

0.6 0.8 1.0 1.2 1.4 1.6

◦ for the gearing layout according to Fig. 6.37 The values K Hβ

1

2

3

4

5

6

7

1.17 1.43 1.27 – 1.45 – – – – – – – – –

1.12 1.24 1.18 1.43 1.27 – – – – – – – – –

1.05 1.11 1.08 1.20 1.12 1.28 1.15 1.38 1.18 1.48 1.23 – 1.28 –

1.03 1.08 1.05 1.13 1.08 1.20 1.10 1.27 1.13 1.34 1.17 1.42 1.20 –

1.02 1.05 1.04 1.08 1.05 1.13 1.07 1.18 1.08 1.25 1.12 1.31 1.15 –

1.02 1.02 1.03 1.05 1.03 1.07 1.04 1.11 1.06 1.15 1.08 1.20 1.11 1.26

1.01 1.01 1.02 1.02 1.02 1.04 1.02 1.06 1.03 1.08 1.04 1.12 1.06 1.16

Table 6.10 Run-in coefficients K Hw of gearings Hardness on the teeth surface

Values K Hw in v (m/s) 1 3

5

8

10

15

200 HB 250 HB 300 HB 350 HB 43 HRC 47 HRC 51 HRC 60 HRC

0.19 0.26 0.35 0.45 0.53 0.63 0.71 0.80

0.22 0.32 0.41 0.53 0.63 0.78 1.00 1.00

0.27 0.39 0.50 0.64 0.78 0.98 1.00 1.00

0.32 0.45 0.58 0.73 0.91 1.00 1.00 1.00

0.54 0.67 0.87 1.00 1.00 1.00 1.00 1.00

0.20 0.28 0.37 0.46 0.57 0.70 0.90 0.90

Part B 6.3

≤ 350 HB

Values of K HV in ν (m/s)

360

Part B

Applications in Mechanical Engineering

where K m = 3.4 × 103 for spur gears and K m = 2.8 × 103 for helical gears, and instead of [σ ]F the lowest of the values of [σ ]F2 and [σ ]F1 is substituted. The load factor in the bending stress analysis is

Part B 6.3

velocity of the gear wheel with the lower hardness (Table 6.10). 0 is determined depending The value of the factor K Hα on the accuracy degree (n ac = 5, 6, 7, 8, 9) according to smoothness standards: 0 =1 – For spur gears K Hα 0 = 1 + A(n − 5) – For helical gearings K Hα ac where A = 0.12 for gear wheels with hardness H1 and H2 > 350 HB, and A = 0.06 for H1 and H2 ≤ 350 HB or H1 > 350 HB, and H2 ≤ 350 HB. In the case of large-scale manufacture of reduction gears the computed value aw is approximated to the nearest standard value: 50, 63, 71, 80, 90, 100, 112, 125, 140, 160, 180, 200, 224, 250, 260, 280, 300, 320, 340, 360, 380, and 400 mm. 5. The preliminary basic wheel dimensions are: – Pitch diameter d2 = 2aw u/(u ± 1) – Width b2 = ψba aw 6. The gear module. The maximum allowed module m max (mm) is determined from the condition of no teeth undercutting at the root

K F = K FV K Fβ K Fα . The factor K FV takes the internal loading dynamics into account. The values of K FV are taken from Table 6.12 and depend on the accuracy degree according to the smoothness standards, the circumferential velocity, and the hardness of the working surfaces. The coefficient K Fβ , which considers the unevenness of the stress distribution at the teeth root along the face width, is evaluated in accordance with 0 . K Fβ = 0.18 + 0.82K Hβ

The coefficient K Fα , which considers the influence of manufacturing errors in the pinion and the wheel on the load distribution between the teeth, is determined in the same way as in contact strength 0 . analysis: K Fα = K Hα From the given range (m min –m max ) of the modules the lowest value m is taken, adjusting it with stan-

m max ≈ 2aw /[17(u ± 1)] . The minimum value of the module m min (mm) is determined from the strength condition m min =

K m K F T1 (u ± 1) , aw b2 [σ]F

Table 6.12 Coefficients K FV of the internal dynamics of loading in bending stress analysis. The values for the spurs are given in the numerator, and the values for the helical wheels are in the denominator Accuracy degree according to GOST 1643-81

Hardness on the surface of the wheel teeth

6

> 350 HB ≤ 350 HB

7

> 350 HB ≤ 350 HB

8

> 350 HB ≤ 350 HB

9

> 350 HB ≤ 350 HB

The values K FV in v (m/s) 1

3

5

8

10

1.02 1.01 1.06 1.03 1.02 1.01 1.08 1.03 1.03 1,01 1.10 1.04 1.03 1.01 1.11 1.04

1.06 1.03 1.18 1.09 1.06 1.03 1.24 1.09 1.09 1.03 1.30 1.12 1.09 1.03 1.33 1.12

1.10 1.06 1.32 1.13 1.12 1.05 1.40 1.16 1.15 1.06 1.48 1.19 1.17 1.07 1.56 1.22

1.16 1.06 1.50 1.20 1.19 1.08 1.64 1.25 1.24 1.09 1.77 1.30 1.28 1.11 1.90 1.36

1.20 1.08 1.64 1.26 1.25 1.10 1.80 1.32 1.30 1.12 1.96 1.38 1.35 1.14 – 1.45

Design of Machine Elements

Nonfulfillment of these inequalities means that the material of the details and the heat treatment method must be changed. 12. Contact stress testing of wheel teeth The calculated value of the contact stress is determined from (6.6). If the calculated stress σH is lower than the allowable stress [σ]H by 15–20%, or if σH is higher than [σ]H by 5% or less, then the earlier accepted parameters of the gearing are taken as final. Otherwise recalculation is required. 13. Forces in toothing (Fig. 6.29) are given by peripheral Ft = 2 × 103 T1 /d1 ; radial Fr = Ft tan α/ cos β , (for the standard angle α = 20◦ tan α = 0.364) ; axial Fa = Ft tan β .

σF2 =

K F Ft YFS2 Yβ Yε ≤ [σ]F2 , b2 m

and in the pinion teeth σF1 = σ F2 Y FS1 /YFS2 ≤ [σ]F1 . The value of the coefficient YFS takes into account the form of the tooth and stress concentration depending on the reduced number z v = z/ cos3 β of the teeth. The coefficient x of the displacement for external toothing is taken according to Table 6.14.

For internal toothing it is as follows: Table 6.15 Coefficient YFS for internally toothing z

YFS

40 50 63 71

4.02 3.88 3.80 3.75

The value of the coefficient Yβ , which considers the tilt angle of the tooth in helical gearings, is determined from (β in degrees) Yβ = 1 − εβ β/120 , under the condition that Yβ ≥ 0.7. Yε is a coefficient that takes teeth overlap into account. For spur gears Yβ = 1; Yε = 1 in the case of accuracy degrees 8 or 9; Yε = 0.8 applies for accuracy degrees 5–7. For helical gearings one has Yε = 0.65. 15. Checking strength calculation of teeth under peak load The aim of this calculation is prevention of residual strains or brittle fracture of the surface layer or the teeth under the action of the maximum torque Tmax . The action of peak loads is evaluated by means of the overload factor K load = Tmax /T , where T is the nominal torque. For prevention of residual strains or brittle fracture of the surface layer the contact stress σH max must not exceed the allowable stress [σ]H max σH max = σH K load ≤ [σ ]H max , where σH is the contact stress under the action of the nominal torque T .

Table 6.14 Coefficients YFS of the tooth form and stress concentration z or z v

Values of YFS for the coefficient of displacement x of the tools −0.6 −0.4 −0.2 0 +0.2

+0.4

+0.6

12 14 17 20 25 30 40 60 80 100 200

– – – – – – 4.37 3.98 3.80 3.71 3.62

3.67 3.62 3.58 3.56 3.52 3.51 3.51 3.52 3.53 3.53 3.59

– 3.30 3.32 3.34 3.37 3.40 3.42 3.46 3.49 3.51 3.56

– – – – – 4.38 4.06 3.80 3.71 3.66 3.61

– – – – 4.22 4.02 3.86 3.70 3.63 3.62 3.61

– – 4.30 4.08 3.91 3.80 3.70 3.62 3.60 3.59 3.59

363

– 4.00 3.89 3.78 3.70 3.64 3.60 3.57 3.57 3.58 3.59

Part B 6.3

14. Bending stress testing of wheel teeth The calculated bending stress in the wheel teeth is

6.3 Cylindrical Gearings

368

Part B

Applications in Mechanical Engineering

where ϑH is the ratio taking into consideration the influence of the gearing of the bevel wheel type (i.e., straight or circular teeth) on the load-carrying capacity. The gear ratio of the equivalent cylindrical gearing is then uv =

dv2 dm2 cos δ1 u cos δ1 = = . dv1 cos δ2 dm1 cos δ2

Considering that cos δ1 = sin δ2 (Fig. 6.40) and tan δ2 = u, we have u v = u sin δ2 / cos δ2 = u 2 . The diameter of the equivalent spur pinion is dv1 = dm1 / cos δ1 . Substituting the cosine function for the tangent function we obtain cos δ1 = 1/ 1 + tan2 δ1 .

Part B 6.4

Bearing in mind that tan δ1 = 1/u and dm1 = 0.857de1 we can write dv1 = dm1 / cos δ1 = dm1 1 + tan2 δ1

  = dm1 u 2 + 1 /u 2 = 0.857de1 1 + u 2 /u . Substituting the values u v and dv1 into (6.8) and √replacing Ft = 2 × 103 T1 /(0.857de1 ), b = 0.143de1 1 + u 2 , subject to the strength condition σH ≤ [σ]H we obtain the formula for checking analysis of steel bevel gearings  K H T1 4 ≤ [σ]H , (6.9) σH = 6.7 × 10 3 uϑ de1 H where T1 is in N m, de1 is in mm, and σH and [σ ]H are in N/mm2 . The load factor K H for bevel gearings is K H = K A K Hβ K HV . The values of the ratio K A are set in the same way as for cylindrical gearings. The factor K Hβ takes the unevenness of load distribution along the contact lines into account. K HV considers internal dynamic load. Checking Analysis Having solved (6.9) relative to de1 we obtain the checking analysis formula for steel bevel gearings as  K H T1 , de1 = 1650 3 u [σ]2H ϑH

where de1 is an outer pitch diameter of the pinion (mm), T1 is in N m, and [σ]H is in N/mm2 .

6.4.7 Calculation of the Bending Strength of Bevel Gearing Teeth Similarly as for straight cylindrical gearings, the bending strength condition is checked for the teeth of the pinion and the wheel K F Ft YFS1 ≤ [σ ]F1 ; σF1 = bm n ϑF YFS2 σF1 ≤ [σ ]F2 , σF2 = YFS1 where K F is the load factor, m n is the normal module in the mean section of the bevel wheel, YFS is the ratio of the tooth form and stress concentration of the equivalent wheel [YFS is chosen according to z v (z vn )], and ϑF is the ratio that takes into account the influence of the bevel-wheel gearing on the load-carrying capacity. The load factor K F for bevel gearings is K F = K A K Fβ K FV . The values of the coefficient K A are obtained in the same way as for the cylindrical gearings. K Fβ is the ratio that considers the unevenness of the stress distribution at the teeth root along the face width, and K FV is a coefficient for the internal dynamic load. The choice of the allowable stresses [σ ]F1 and [σ ]F2 was explained above.

6.4.8 Projection Calculation for Bevel Gearings The following basic data are considered: T1 (the torque on the pinion measured in N m), typical loading conditions, n 1 (the rotational frequency of the pinion measured in min−1 ), u (the gear ratio), L h (the operation time of the gearing, i.e., the lifetime, measured in hours), and the gearing layout, and gear wheel type. The choice of materials, heat treatment method, and the determination of the allowable stresses are given in Sect. 6.3.7. Diameter of the Outer Pitch Circle of the Pinion The tentative value of the outer pitch circle diameter of the pinion (mm) is  T1  =K 3 , de1 uϑH

where T1 is the torque on the pinion (N m) and u is the gear ratio. The factor K , which depends on the surface hardnesses H1 and H2 of the teeth of the pinion and the wheel, have the following values, respectively:

370

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Applications in Mechanical Engineering

ψbd is computed approximately from ψbd = 0.166 u 2 + 1 .

is substituted into the design formula. Rounding off of the computed module value to the standard value can be ignored.

Cone Radius and Face Width The angle of the pitch pinion cone is

Teeth Number of the Pinion and the Wheel For the pinion with straight teeth one has z 1 = de1 /m e , whereas with circular teeth one has z 1 = de1 /m te . The teeth number of the wheel is z 2 = z 1 u. The given values are rounded to the whole number. In practice, there is another method to determine the teeth number and wheel module. The tentative value of the teeth number of the pinion (z 1 ) is chosen depending on its diameter de1 and gear ratio u in accordance with one of the diagrams graphed for straight bevel wheels (Fig. 6.47) or wheels with circular teeth (Fig. 6.48), with the teeth hardness of the wheel and the pinion ≥ 45 HRC. z 1 is specified, taking into account the teeth hardness of the pinion and the wheel by:

δ1 = arctan(1/u) . The external cone distance is Re = de1 /(2 sin δ1 ) and the face width is b = 0.285Re . The Gearing Module The exterior end module of the gearing (m e for bevel wheels with straight teeth, m te for wheels with circular teeth) is

m e (m te ) ≥

14K FV K Fβ T1 . de1 bϑF [σ]F

Part B 6.4

The value of the internal dynamic load factor K FV for straight bevel wheels is chosen from Table 6.12, conditionally taking their accuracy as one degree rougher than the actual degree. For bevel wheels with circular teeth the value of K FV is taken from Table 6.12, as for helical wheels. The factor K Fβ takes the unevenness of the stress distribution at the teeth root along the face width into account. For bevel gearings with straight teeth one has  ; for wheels with circular teeth one uses K Fβ = K Fβ

 , K Fβ = K Fβ  = 0.18 + on the condition that K Fβ ≥ 1.15, where K Fβ 0 0.82K Hβ . For spurs the coefficient ϑF is taken equal to 0.85 and for wheels with circular teeth it is taken from Table 6.17. Instead of [σ]F the lesser of [σ]F1 and [σ ]F2

Table 6.19 Correction of the pinion tooth number z 1 Hardness H

Teeth number z 1

H1 ≤ 350 HB

H2 ≤ 350 HB

1.6z 1

H1 ≥ 45 HRC

H2 ≤ 350 HB

1.3z 1

H1 ≥ 45 HRC

H2 ≥ 45 HRC

z 1

The teeth number of the wheel is z 2 = z 1 u. Calculated values of the teeth number of the pinion and the wheel are rounded to whole numbers. The exterior end module of the gearing is calculated (m e for bevel wheels with straight teeth, m te for wheels with circular teeth) by using m e (m te ) = de1 /z 1 .

Table 6.18 Coefficients of displacement xe1 for bevel pinions with straight teeth z1

xe1 for gear ratio u: 1.0

1.25

1.6

2.0

2.5

3.15

4.0

5.0

12

–

–

–

–

0.50

0.53

0.56

0.57

13

–

–

–

0.44

0.48

0.52

0.54

0.55

14

–

–

0.34

0.42

0.47

0.50

0.52

0.53

15

–

0.18

0.31

0.40

0.45

0.48

0.50

0.51

16

–

0.17

0.30

0.38

0.43

0.46

0.48

0.49

18

0.00

0.15

0.28

0.36

0.40

0.43

0.45

0.46

20

0.00

0.14

0.26

0.34

0.37

0.40

0.42

0.43

25

0.00

0.13

0.23

0.29

0.33

0.36

0.38

0.39

30

0.00

0.11

0.19

0.25

0.28

0.31

0.33

0.34

40

0.00

0.09

0.15

0.20

0.22

0.24

0.26

0.27

Design of Machine Elements

6.4 Bevel Gearings

371

Table 6.20 Coefficients of displacement xn1 for bevel pinions with circular teeth z1

xn1 for the gear ratio u: 1.0

1.25

1.6

2.0

2.5

3.15

4.0

5.0

12

–

–

–

0.32

0.37

0.39

0.41

0.42

13

–

–

–

0.30

0.35

0.37

0.39

0.40

14

–

–

0.23

0.29

0.33

0.35

0.37

0.38

15

–

0.12

0.22

0.27

0.31

0.33

0.35

0.36

16

–

0.11

0.21

0.26

0.30

0.32

0.34

0.35

18

0.00

0.10

0.19

0.24

0.27

0.30

0.32

0.32

20

0.00

0.09

0.17

0.22

0.26

0.28

0.29

0.29

25

0.00

0.08

0.15

0.19

0.21

0.24

0.25

0.25

30

0.00

0.07

0.11

0.16

0.18

0.21

0.22

0.22

40

0.00

0.05

0.09

0.11

0.14

0.16

0.17

0.17

Uncut Wheel Dimensions The dimensions of the billets are computed for the bevel pinion and the wheel (mm) (Fig. 6.39b) as

Final Values of Wheel Dimensions The pitch cone angles of the pinion and the wheel are

The values of Dblank and Sblank determined from calculations are then compared with the limit dimensions Dmax and Smax detailed in Table 6.1. The conditions for suitability of the billets are

δ1 = arctan(1/u r );

δ2 = 90◦ − δ1 .

The pitch diameters of the wheels are with straight teeth de1 = m e z 1 , de2 = m e z 2 ;

Dblank = de1 + 2m e (m te ) + 6 mm , Sblank = 8m e (m te ) .

Dblank ≤ Dmax ; Sblank ≤ Smax .

with circular teeth de1 = m te z 1 , de2 = m te z 2 . The outer diameters of the wheels are with straight teeth dae1 = de1 + 2(1 + xe1 )m e cos δ1 , dae2 = de2 + 2(1 + xe2 )m e cos δ2 ; with circular teeth

Toothing Forces (Fig. 6.44) The circumferential force on the mean diameter dm1 of the pinion is

Ft = 2 × 103 T1 /dm1 ,

where

dm1 = 0.857de1 .

The axial force on the pinion is

dae1 = de1 + 1.64(1 + xn1 )m te cos δ1 ,

with straight teeth

Fa1 = Ft tan αw sin δ1 ,

dae2 = de2 + 1.64(1 + xn2 )m te cos δ2 .

with circular teeth

Fa1 = γa Ft .

The coefficients xe1 and xn1 for straight and helical pinions are taken from Tables 6.18 and 6.20. For gearings with z 1 and u that differ from those given in Tables 6.18 and 6.20, the values xe1 and xn1 are rounded up. The coefficient of tool displacement for the wheel is xe2 = −xe1 ;

xn2 = −xn1 .

The radial force on the pinion is with straight teeth

Fr1 = Ft tan αw cos δ1 ,

with circular teeth

Fr1 = γr Ft .

The axial force on the wheel is Fa2 = Fr1 , and the radial force on the wheel is Fr2 = Fa1 .

Part B 6.4

The Actual Gear Ratio ur = z2 /z1 The calculated value of u r must not differ from the target value by more than 3% for bevel reduction gears, 4% for bevel-cylindrical double-reduction gears, and 5% for three-stage (or greater) bevel-cylindrical reduction gears.

372

Part B

Applications in Mechanical Engineering

The coefficients γa and γr for the angle βn = 35◦ are determined from the formulas γa = 0.44 sin δ1 + 0.7 cos δ1 , γr = 0.44 cos δ1 − 0.7 sin δ1 . The calculated coefficients γa and γr are substituted into the formulas with their corresponding signs. Teeth seizing will not occur if the force Fa1 is directed towards the base of the pitch cone of the drive pinion. Thus the rotating sense of the pinion (seen from the direction of the pitch cone point) and the dip direction of the teeth are chosen to be identical; e.g., for the drive pinion with a left tooth dip the sense of rotation is counterclockwise.

Part B 6.5

Contact Stress Analysis of Wheel Teeth The rated contact stress is  4 K HV K Hβ T1 ≤ [σ]H . σH = 6.7 × 10 3 ϑ u r de1 H

Bending Stress Analysis of Wheel Teeth The bending stress in the teeth of the spur is

2.72 × 103 K FV K Fβ T1 YFS2 ≤ [σ ]F2 . bde1 m e (m te ) ϑF For gearings with circular teeth the module m e is substituted for the module m te in this formula. The bending stresses in the teeth of the pinion are σF2 =

σF1 = σ F2 YFS1 /YFS2 ≤ [σ ]F1 . The values of the factors YFS1 and YFS2 , considering tooth form and stress concentration, are taken from Table 6.14 and depend on the coefficient of displacement and the given number of teeth

z v2 = z 2 / cos3 βn cos δ2 ,

z v1 = z 1 / cos3 βn cos δ1 . For the checking strength analysis of teeth under the action of peak loads see Sect. 6.3.7.

6.5 Worm Gearings 6.5.1 Background Worm gearings are used for transmission of rotational motion between shafts, the axes of which intersect in space. In most cases, the intersection angle is 90◦ (Fig. 6.49). The drive is worm 1, representing a gear wheel with a small number (z 1 = 1–4) of teeth (coils), which is similar to an acme screw or an approximate thread. To increase the contact line length in the toothing with the worm, the teeth of worm wheel 2 have the form of an arc in axial section. The worm gearing is a tooth-screw gear, the motion of which is transformed according to the principle of the screw pair with its inherent increased slip [6.38–47]. Depending on the form of the external worm surface gearings can have a cylindrical worm (Fig. 6.49a) or a globoidal worm (Fig. 6.49b). The quality of globoidal gears is higher, but they are complicated to manufacture and assemble, and are sensitive to the axial displacement caused by, e.g., wear of the bearings. In practice, gearings with cylindrical worms are most often applied. The advantages of worm gearings are: 1. The availability of a high gear ratio u in one stage (up to 80).

2. Compactness and moderate mass of the structure. 3. Operation smoothness and silence. 4. The availability of self-stopping gearings, i. e., permitting motion only from the worm to the wheel. This self-stopping of the worm gearing allows a mechanism without a braking device, preventing reverse rotation of the wheels (e.g., under the action of a lifted load gravity). 5. The availability of exact and slight displacements. Their disadvantages are: 1. A relatively low efficiency factor because of increased slip of the worm coils on the wheel teeth, and as a result considerable heat release in the toothing zone 2. The need for expensive antifriction materials for the ring of the worm wheels 3. Increased wear and tendency to seizing 4. The necessity for adjustment of the mesh (the mean plane of the worm wheel ring must coincide with the axis of the worm) Worm gearings are widely used in vehicles, liftingand-shifting machines with low and mean capacity (the lifting mechanism of elevators, winch, power hoist;

378

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Applications in Mechanical Engineering

The direction of the force Ft2 always coincides with the sense of rotation of the wheel, and the force Ft1 is directed towards the side opposite the worm rotation.

6.5.7 Stiffness Testing of Worms

Part B 6.5

Hardness analysis of the worm body under the action of the forces in the toothing is carried out in order to prevent excessive load concentration in the contact area. Flexing due to the constituents Ft1 and Fr1 in the worm bearing section, where the most important toothing area is located, have maximum values. Flexing in this section due to the torque produced by the axial force Fa1 is zero (Fig. 6.57a). Flexing f of the worm due to the resultant radial force R leads to an increase of the axle base and an increase of the pitch cylinder radius of the worm. The angle of the coil dip on the deformed worm does not equal the angle of the teeth dip of the worm wheel; toothing precision is broken, which causes load concentration in the toothing. Thus, worm flexing f (mm), in the mean section is limited to the allowed values [ f ] = (0.005–0.008)m (where m is the toothing module, mm)

2 × l3 Ft12 + Fr1   ≤ f , f= 48E Je where l is the distance between the worm bearings (mm) (in predesigns, l ≈ 0.9d2 can be used), E is the coefficient of elasticity of the worm material (N/mm2 ), Je (mm4 ) is the equivalent moment of inertia (the moment of inertia of the cylindrical bar, which is distortion equivalent to the worm),   πd 4f 1 da1 . 0.36 + 0.64 Je = 64 df1

6.5.8 Materials for Worms and Worm-Wheel Rings Worms and wheels must have sufficient strength and form a well-ground antifriction pair in view of the considerable slip velocities in the toothing. Worms are manufactured from medium-carbon steels of grades C 46, C 45 (EN), C 53, and C 50 E (EN) or alloy steels of grades 37 Cr 4, 41 Cr 4 (EN), and 40 NiCr 6 (DIN) with surface hardening or volume quenching up to hardnesses of 45–54 HRC and subsequent grinding of work coil surfaces. Worms from cemented steels of grades 20 MnCr 5 G (DIN) and 20 CrS 4 (DIN) with hardness

after quenching of 56–63 HRC ensure good operation (Appendix 6.A Table 6.95). Materials for worm-wheel rings can be classified into three groups according to decreasing scoreresistance and antifriction behavior, as recommended for application slip velocities (Appendices 6.A Table 6.95, Table 6.97). Group I Tin bronze is applied for high slip velocities (vsl = 5–25 m/s). This material has good score resistance, but low strength. Group II Tinless bronze and brass are used with intermediate slip velocities (vsl = 2–5 m/s). Most often aluminum bronze is applied. This bronze has high mechanical strength, but low score resistance, so it is used together with quenched (> 45 HRC) ground and polished worms. Group III Grey iron of grades ISO 150 and ISO 200 are applied for low slip velocities (vsl < 2 m/s) in hand-driven devices.

6.5.9 The Nature and Causes of Failure of Worm Gearings In gearings with wheels made of tin bronze (a soft material) fatigue spalling of the work surfaces of the wheel teeth is the most dangerous failure mode, because of the increasing contact stress and increasing fatigue limit of metal for the given loading cycle number. Seizing is also possible as a result of the considerable slip velocities of the contact surfaces in combination with the boundary lubrication rate (lack of a separating oil layer). Seizing of soft materials is shown as a smearing (diffusion transfer) of bronze on the worm; the teeth section decreases gradually, but the gearing continues to operate for some time, determined by the wear rate. Seizing in gear rings made of tinless bronze, brass, and iron (a hard material) results in the formation and subsequent fracture of a microwelded bridge with a jump of the friction coefficient and catastrophic wear, which results in wheel teeth damage with scales after microwelding onto the worm coils. To prevent seizing it is recommended that surfaces of the coils and teeth be thoroughly treated, and that materials with high antifriction behavior and oils with load-carrying and antiscoring additives be used.

380

Part B

Applications in Mechanical Engineering

values Ft2 = 2 × 103 T2 /d2 ; dw1 = m(q + 2x); d2 = mz 2 ; m = 2aw /(z 2 + q + 2x), and also using a strength condition σH ≤ [σ]H , we obtain σH =

5350 (q + 2x) z  2   z 2 + q + 2x 3 × KT2 ≤ [σ]H , aw (q + 2x)

(6.10)

Part B 6.5

where σH is the rated contact stress in the toothing area (N/mm2 ), aw is the axle base (mm), T2 is the torque on the wheel (N m), and [σ]H is the allowable contact stress (N/mm2 ). Worm gearings with nonlinear worms are characterized by a more favorable ratio of curvature radii of the worm and the wheel, as well as a greater total length of the contact lines, which leads to increased load-carrying capacity. Contact stresses in gearings with nonlinear worms can be determined approximately from (6.10) with substitution of the numerical coefficient of 5350 for the value 4340. Assuming the worm to be rigid, one obtains q = 0.25z 2 and x = 0. Solving (6.10) for aw we obtain the verification analysis formula for worm gearings

aw ≥ K a 3 KT2 / [σ]2H , where K a = 610 for linear worms and K a = 530 for nonlinear ones, aw is in mm, [σ]H is in N/mm2 , and T2 is in N m. Substituting the parameters of worm gearings into the initial dependence for σH , we obtain a formula for the verification analysis  98Z E cos γw KT2 (6.11) ≤ [σ]H , σH = d2 dw1 ξ 2 where

 σH is a rated contact stress (N/mm ), Z E = 1/ π[(1 − ν12 )/E 1 + (1 − ν22 )/E 2 ] is a coefficient taking into account the stress–strain properties of the worm and worm wheel, (N/mm2 )0.5 ; T2 is the torque on the wheel (N m), d2 and dw1 are the pitch diameter and the initial diameter, respectively, of the wheel and the worm (mm). ξ is a coefficient that takes into account the influence of the worm gear class on the load-carrying capacity; for linear worms one uses ξ = 1, whereas for nonlinear worms ξ = 1.06 + 0.057νsl on the condition that ξ ≤ 1.65, and [σ]H is the allowable contact stress (N/mm2 ). In short-cut calculations seizing prevention is provided in contact stress analysis by the choice of the allowable stress. In more precise calculations the worst

case is supposed, i. e., when the load-carrying capacity reduction of the oil film results in immediate surface seizing. The critical temperature ϑcr of oil film breakdown has been determined experimentally for the main oil grades (ϑcr = 100–350 ◦ C). The criterion for lack of seizing is represented in the form ϑ = (ϑ + ϑmom ) < ϑcr , where ϑ is the temperature of the friction surface before the contact (the oil temperature in the reduction gear), ϑmom is the instantaneous temperature on contact (temperature flash), which can be determined from a special calculation by solving the differential thermal conductivity equation while taking into account the specific characteristics of the behavior of the thermal process during the contact. To achieve the total temperature ϑ the critical value ϑcr can be determined experimentally.

6.5.11 Bending Strength Calculation for Wheel Teeth This calculation is carried out for the teeth of the worm wheel, because the coils of the worm are considerably tougher. A bending calculation is performed according to the formulas for helical wheels, writing included values in terms of the parameters of the worm gearing and taking into consideration the greater teeth bending strength of worm wheels due to their arched form (Fig. 6.52). Taking into account these features, we obtain the formula for checking the bending stress analysis of worm-wheel teeth K Ft2 YF2 cos γw ≤ [σ ]F , (6.12) σF = 1.3m2 (q + 2x) where σF is the design bending stress in the weakest section of the tooth (N/mm2 ), YF2 is the form factor of the wheel tooth, chosen depending on the equivalent tooth number z v2 (where greater values correspond to lower values of the tooth number), and [σ ]F is the allowable bending stress for the wheel teeth (N/mm2 ). The equivalent tooth number z v2 , similarly to a helical wheel with dip angle γw , of the tooth becomes z v2 = z 2 / cos3 γw .

6.5.12 Choice of Permissible Stresses Permissible stresses are determined from empirical formulas depending on the material of the wheel teeth, the

384

Part B

Applications in Mechanical Engineering

The factor 0.9 is used for worms with hard (H ≥ 45 HRC), ground and polished coils. The factor 0.75 is used for worms with hardness ≤ 350 HB, and σt is taken from Table 6.21. The service life ratio is K HL = 8 107 /NHE , under the condition that K HL ≤ 1.15. Here NHE = K HE Nk is an equivalent loading cycle number for the worm-wheel teeth for the whole lifetime of the gearing. If NHE > 25 × 107 , it is assumed that NHE = 25 × 107 . The total cycle number of stress change is Nk = 60n 2 L h , where L h is the service lifetime of the gearing (h). The values of the equivalence factors K HE for typical loading conditions are given in Table 6.23. The coefficient Cv takes the material wear rate of the wheel into account. It is assumed to depend on the slip velocity vsl :

Table 6.23 Coefficients of equivalence for the typical

loading conditions of worm gearings Typical condition

Equivalence factors K HE K FE

0 I II III IV V

1.0 0.416 0.2 0.121 0.081 0.034

1.0 0.2 0.1 0.04 0.016 0.004

where σF0 is a fatigue bending point for 106 stress change cycles. For materials of groups I and II σF0 = 0.25σy + 0.08σt , whereas for materials of group III

Part B 6.5

σF0 = 0.22σbs . Table 6.22 The values of the coefficient Cv depending on the slip velocity vsl vsl (m/s)

Cv

5 6 7 ≥8

0.95 0.88 0.83 0.80

or in accordance with the formula Cv = 1.66vsl−0.352 on the condition that Cv ≥ 0.8. Group II – Permissible Contact Stresses.

[σ]H = σH0 − 25vsl . Here σH0 = 300 N/mm2 for worms with hardness on the coil surface ≥ 45 HRC, whereas σH0 = 250 N/mm2 for worms with hardness ≤ 350 HB. Group III – Permissible Contact Stresses.

[σ]H = σH0 − 35vsl . Here σH0 = 200 N/mm2 for worms with hardness on the coil surface ≥ 45 HRC, whereas σH0 = 175 N/mm2 for worms with hardness ≤ 350 HB. Allowable Bending Stresses Allowable bending stresses are calculated for the teeth material of the worm wheel according to

[σ]F = K FL σF0 ,

The service life ratio is

9 K FL = 106 /NFE . Here NFE = K FE Nk is an equivalent loading cycle number for the worm-wheel teeth, and Nk is the total number of stress change cycles for the whole lifetime of the gearing. If NFE < 106 , it is assumed that NFE = 106 . If NFE > 25 × 107 , it is assumed that NFE = 25 × 107 . The values of the equivalence factors K FE for typical loading conditions are given in Table 6.23. Overload Stress Capacity The overload stress capacity on the maximum static or unit peak load for materials is

[σ ]F max = 0.8σ y . Group I: [σ ]H max = 4σy ; Group II: [σ ]H max = 2σy ; [σ ]F max = 0.8σ y . Group III: [σ ]H max = 1.65σbs ; [σ ]F max = 0.75σbs . The Axle Base The axle base (mm) is

aw ≥ K a 3 K HV K Hβ T2 / [σ ]2H ,

where K a = 610 for involute, Archimedean, and convolute worms; K a = 530 for nonlinear worms. K HV is a coefficient of internal dynamics, taking the value K HV = 1 for v2 ≤ 3 m/s, and K HV = 1–1.3 for v2 > 3 m/s, where v2 is the circumferential velocity of

386

Part B

Applications in Mechanical Engineering

which is recommended for gearings with the following worms Involute (Z I ) −1 ≤x ≤ 0 , Formed by a torus (ZT ) 0.5 ≤x ≤ 1.5 , Archimedean (Z A), convolute (Z N) , Formed by a cone(ZK) 0 ≤x ≤ 1.0 . For the helix angle of the coil worm line on the cylinder The pitch angle γ = arctan(z 1 /q) , The starting angle γw = arctan[z 1 /(q + 2x)] , The base angle (for the wormZI) γb = arccos(0.940 cos γ ) .

Part B 6.5

With the exception of those cases caused by drive kinematics, the worms of gearings have a coil line of the right direction. The actual gear ratio is u r = z 2 /z 1 . The calculated value u r must not differ from the target value by more than 4%; for standardized reduction gears for machine-building applications the tolerances are 6.3% for single gearing and 8% for double gearing . Dimensions of the Worm and the Wheel The dimensions of the worm and the wheel are as follows (Figs. 6.51 and 6.52): The pitch diameter of the worm

d1 = qm . The diameter of the coil crests da1 = d1 + 2m . The diameter of the roots df1 = d1 − 2.4m . The pitch diameter of the wheel d2 = z 2 m . The diameter of the tooth tops da2 = d2 + 2m(1 + x) . The socket diameter for gearings with Z I worms df2 = d2 − 2m(1 + 0.2 cos γ − x) . The socket diameter for gearings with Z N, Z A, Z K , and ZT worms: d f 2 = d2 − 2m(1.2 − x) .

The largest diameter of the wheel dae2 ≤ da2 + 6m/(z 1 + k) , where k = 2 for gearings with Z I , Z A, Z N, and Z K worms; and k = 4 for gearings with ZT worms. The length b1 of the cut worm part is

b1 = 2 (0.5dae2 )2 − (aw − 0.5da1 )2 + 0.5πm . The face width b2 of the worm wheel for the gearings is:

•

for Z I , Z A, Z N, and Z K worms b2 = 0.75da1 b2 = 0.67da1

•

for z 1 ≤ 3 , for z 1 = 4

and for ZT worms b2 = (0.7 − 0.1x)da1

Checking Strength Analysis of Gearings The slip velocity in the toothing is

vsl = vw1 / cos γw , where vw1 = πn 1 m(q + 2x)/60 000. Here vw1 is the circumferential velocity on the starting diameter of the worm (m/s), n 1 = n 2 u r , (min−1 ), m is in mm, and γw is the initial helix coil angle. The allowable stress [σ ]H is specified according to the rated value vsl . The design stress is determined from (6.11) by specifying the load factor as the value of K = K HV K Hβ . The circumferential velocity of the worm wheel (m/s) is v2 = πn 2 d2 /60 000. In the case of common manufacturing accuracy and under the condition of worm rigidity it is assumed that K HV = 1 for v2 ≤ 3 m/s. For v2 > 3 m/s the value of K HV is assumed to be equal to the coefficient K HV (Table 6.8) for helical gearings with a hardness of the working tooth area ≤ 350 HB and the same accuracy degree. The load concentration coefficient K Hβ is K Hβ = 1 + (z 2 /θ)3 (1 − X), where θ is the coefficient of worm strain (Table 6.29); X is a coefficient that takes into account the influence of the operating gearing mode on the grind of the worm-wheel teeth and the worm coils. The values of X for typical loading conditions and cases, when the rotational frequency of the worm-wheel shaft does not change with load modification, are detailed in in Table 6.30.

Design of Machine Elements

6.5 Worm Gearings

387

Table 6.29 Deformation coefficients θ of worms z1

θ for coefficient q of the worm diameter 8 10 12.5

14

16

20

1 2 4

72 57 47

176 140 122

225 171 137

248 197 157

108 86 70

154 121 98

Table 6.30 Influence coefficients X in operating mode on running-in of worm gearings X

Typical conditions

0

1.0

I

0.77

II

0.5

III

0.5

IV

0.38

V

0.31

Toothing Forces (Fig. 6.57) The peripheral force on the wheel, which is equal to the axial force on the worm, is

Ft2 = Fa1 = 2 × 103 T2 /d2 . The peripheral force on the worm, which is equals to the axial force on the wheel, is Ft1 = Fa2 = 2 × 103 T2 /(dw1 u 2 η) . The radial force is Fr = Ft2 tan α/ cos γw . For the standard angle α = 20◦ , Fr = 0.364Ft2 / cos γw .

η = tan γw / tan(γw + ρ) , where γw is a helix angle of the coil line on the pitch cylinder, and ρ is a modified friction angle determined experimentally, taking into account the relative capacity loss in the toothing, in the bearings, and due to oil stirring. The value of the friction angle ρ between a steel worm and a bronze (brass, iron) wheel depends on the slip velocity vsl :

Bending Stress Analysis of Wheel Teeth The calculated bending stress is determined from (6.12), where K is a load factor, the values of which are computed in the paragraph Checking Strength Analysis of Gearing, and YF2 is the form factor of the wheel tooth, which is chosen depending on the equivalent tooth number z v2 = z 2 / cos3 γw :

Table 6.31 Angle friction values ρ depending on the slip

Table 6.28 Tooth form coefficient YF2

velocity vsl

z v2

YF2

vsl (m/s)

ρ

0.5

3◦ 10

3◦ 40

1.0

2◦ 30

3◦ 10

1.5

2◦ 20

2◦ 50

2.0

2◦ 00

2◦ 30

2.5

1◦ 40

2◦ 20

3.0

1◦ 30

2◦ 00

4.0

1◦ 20

1◦ 40

7.0

1◦ 00

1◦ 30

10

0◦ 55

1◦ 20

15

0◦ 50

1◦ 10

20 24 26 28 30 32 35 37 40 45 50 60 80 100 150 300

1.98 1.88 1.85 1.80 1.76 1.71 1.64 1.61 1.55 1.48 1.45 1.40 1.34 1.30 1.27 1.24

The lower value of ρ is for tin bronze and the higher one is for tinless bronze, brass, and iron.

Part B 6.5

The Efficiency Factor of Gearings The efficiency factor for worm gearings is

404

Part B

Applications in Mechanical Engineering

b from (6.16) transmission ratio u ah

b −1 . z b = z a u ah

pinion number. The coefficient is specified as c = (u − 1)z a /z b .

The tooth number z g of the planetary pinion g is determined according to the coaxiality condition, in compliance with which the axle bases aw of the gear sets with external and internal toothing are to be equal (Fig. 6.90) aw = 0.5(da + dg ) = 0.5(db − dg ) ,

(6.17)

where d = mz is the pitch diameter of the appropriate gear wheel. As the toothing modules of the planetary gear are equal, (6.17) takes the form z g = 0.5(z b − z a ) .

Part B 6.7

where c is assumed to depend on the transmission ratio, according to: Table 6.38 The value of factor c depending on the gear

ratio u c 1.4 1.5 1.6 1.8

z g = cz f .

For every layout the calculated tooth numbers are rounded to whole numbers. Furthermore, in accordance with Table 6.39, the coefficients of displacement x1 of the pinion and x2 of the wheel are chosen, and the coefficient B is determined as B = 1000xsum /(z a + z g ) , where xsum = x1 + x2 .

Example Determine the toothing angle with z a + z g = 18 + 27 = 45.

z b = z a (u − 1)/c ,

10 12 14 16

z f = (z b − z a )/(c + 1) and

According to the nomogram (Fig. 6.94) the toothing angle αw of the gear is found.

Layout according to Fig. 6.91b z a is assumed. Then we have

u

Then we have

Solution According to Table 6.39 we have x1 = 0.4 and x2 = 1.02, and consequently, xsum = x1 + x2 = 0.4 + 1.02 = 1.42. Then

B = 1000xsum /(z a + z g ) = 1000 × 1.42/(18 + 27) = 31.55 .

The tooth number z b after the calculation is rounded to a whole number that is divisible by the planetary

According to the nomogram (Fig. 6.94) we determine αw = 26◦ 55 . As the force calculation is not done and the modules of the toothing are unknown, for the layout in Fig. 6.91b

Table 6.39 Coefficients of displacement x1 and x2 of the pinions and the wheel in planetary gears zg

18 22 28 34 42 50 65 80 100 125

Values of the coefficients of displacements x1 and x2 with z a 12 15 18 22 x1 x2 x1 x2 x1 x2 x1

x2

28 x1

x2

34 x1

x2

0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 –

– 0.68 0.94 1.20 1.48 1.60 1.80 1.99 2.19 2.43

– – 0.86 0.80 0.72 0.64 0.70 0.75 0.80 0.83

– – 0.86 1.08 1.33 1.60 1.84 2.04 2.26 2.47

– – – 1.01 0.90 0.80 0.83 0.89 0.94 1.00

– – – 1.01 1.30 1.58 1.79 1.97 2.22 2.46

0.61 0.66 0.88 1.03 1.30 1.43 1.69 1.96 2.90 –

0.34 0.38 0.26 0.13 0.20 0.25 0.26 0.30 0.36 –

0.64 0.75 1.04 1.42 1.53 1.65 1.87 2.14 2.32 –

0.54 0.60 0.40 0.30 0.29 0.32 0.41 0.48 0.52 –

0.54 0.64 1.02 1.30 1.48 1.63 1.89 2.08 2.31 –

– 0.68 0.59 0.48 0.40 0.43 0.53 0.61 0.65 0.75

Design of Machine Elements

13.0 12.0 11.0

23° 20' 23°10' 23°

26.0

39.0 25° 50'

25.0

25° 40'

24.0

22°50' 10.0 9.0

22° 40' 22° 30'

25° 30'

23.0

7.0

22°10' 22°

22.0

5.0

21° 40' 21° 30'

21.0

25°

3.0

1.0 0

B αw

36.0 35.0

27° 30'

34.0

27° 20'

24° 50'

33.0

19.0

24° 40'

32.0

27°

18.0

24° 30'

31.0

26° 50'

30.0

26° 40'

29.0

26° 30'

24° 20' 24° 10'

16.0

24°

15.0

23° 50'

28.0

26° 20'

14.0

23° 40'

27.0

26° 10'

13.0

23° 30' B αw

26

sum of the central wheels (z a + z b ) is divisible by the number of planetary pinions n w (usually n w = 3), i. e., (z a + z b )/n w = γ , where γ is any whole number. Layout according to Fig. 6.91b The Coaxiality Condition (z a + z g )/ cos αwa = (z b − z f )/ cos αwb .

Hence

20.0

17.0

405

26° B αw

Fig. 6.94 Chart for the determination of the angle of ac-

tion

the modules of both steps are assumed to be equal. Tooth numbers z a , z g , and z b calculated in this way are checked according to the conditions of mounting and adjacency. Layouts according to Fig. 6.90 and Fig. 6.91a The Condition of Coaxiality (z a + z g ) cos αwa = (z b − z g )/ cos αwb ,

where αwa and αwb are toothing angles of the gear with external (index a) and internal (index b) toothing. From this condition   cos αwa cos αwb zb za − . zg = cos αwb cos αwa cos αwa + cos αwb The mounting condition requires coincidence of the teeth with tooth slots to have place in all the toothings of the central wheels with planetary pinions, otherwise the gear cannot be mounted. It is determined that, with a symmetrical arrangement of the planetary pinions, the mounting condition is met when the tooth

z f = (z b / cos αwb − z a / cos αwa ) /(c/ cos αwa + 1/ cos αwb ) ; z g = cz f . If, in the strength analysis of the gears according to the layout in Fig. 6.91b, different modules for the gears with external (z a − z g ) and internal (z f − z b ) toothing are assumed, the coaxiality condition for such a gearing is (z a + z g )m a / cos αwa = (z b − z f )m b / cos αwb . Hence z b m b / cos αwb − z a m a / cos αwa , cm a / cos αwa + m b / cos αwb where the tooth number z g = cz f . Sometimes for fulfillment of the coaxiality condition it is convenient for one gear to be helical. The coaxiality condition in this case becomes zf =

(z a + z g )m a /(cos β cos αwa ) = (z b − z f )m b / cos αwb . The required tilt angle β of the tooth is determined from this condition. The mounting conditions of the gear are then z a /n w = γ and z b /n w = γ . For all layouts of planetary gears control of the adjacency condition is carried out, which requires that the planetary pinions do not touch the teeth. To this end the sum of the top crest radii, which is dga = m(z g + 2), must be less than the distance l between their axes (Fig. 6.92), i. e., dga < l = 2aw sin(180◦ /n w ) ,

(6.18)

where aw is an axle base. For the layouts in Figs. 6.90 and 6.91a the axle base forms aw = 0.5m(z a + z g ) , and in accordance with (6.18) the adjacency condition is fulfilled if (z g + 2) < (z a + z g ) sin(180◦ /n w ) .

Part B 6.7

2.0

21°10' 21° 20°50' 20° 40' 20° 30' 20° 20' 20°10' 20°

27° 40'

27° 10'

21° 20' 4.0

27° 50' 37.0

25° 10'

21°50' 6.0

38.0

25° 20'

22° 20' 8.0

28°

6.7 Planetary Gears

406

Part B

Applications in Mechanical Engineering

The axle base of the gear, which is produced according to any layout, is aw = (z a + z g )m a cos α/(2 cos β cos αwa ) . The actual values of the transmission ratios of reduction gears must not differ from the nominal values by more than 4% for single-reduction units, 5% for double-reduction units, and 6.3% for triple-reduction units.

6.7.7 Strength Analysis of Planetary Gears

Part B 6.7

The first calculation phases for planetary gears (choice of material and heat treatment, determination of allowable stresses) are performed in the same way as for traditional cylindrical gearings (Sect. 6.3.7). Strength analysis is carried out for all toothings according to the formulas for traditional gearings. For example, for the gearing shown in Fig. 6.90 it is necessary to calculate the external toothing of the wheels a and g, and the internal toothing of the wheels g and b. The modules and forces of these toothings are equal and internal toothing is faster in accordance with its behavior, and therefore when the same material is used for the wheels it is sufficient to calculate only the external toothing. Only the main characteristics of the calculation for planetary gears are examined below. For the determination of the allowable stresses [σ]H and [σ]F the service life ratios Z N and YN are found according to the equivalent loading cycle numbers NHE = μH Nk and NFE = μF Nk . The number of stress cycles Nk of the teeth for the whole lifetime is calculated only for wheel rotation relatively to each other. For the central pinion Nka = 60n w n a L h , where n w is the number of planetary pinions, L h is the total operating lifetime of the gearing (h), n a = (n a − n h ) is the relative rotational frequency of the drive central pinion, and n a and n h are the rotational frequencies of the central pinion and the carrier (min−1 ). According to n a the circumferential velocity is determined, in compliance with which the accuracy degree of the gear is set and the coefficients K HV , K FV are chosen. For planetary pinions Nkg = 60n t n g L h , where n t is the loading number of the tooth per revolution and n g = n a z a /z g is the relative rotational frequency of the planetary pinion.

The tooth of the planetary pinion is loaded twice per revolution in the toothing with wheels a and b. However, by determination of the cycle number it is assumed that n t = 1, because the contact strength analysis takes into account that the tooth of the planetary pinion works with wheels a and b with different flanks. By determination of the allowable bending stresses [σ ]Fg for the teeth of the planetary pinion the coefficient YA is set, taking into consideration the double-sided application of the load (under a symmetrical loading cycle). The values YA are assumed to be YA = 0.65, 0.75, and 0.9, respectively, for refined, quenched with radiofrequency (RF) current heating (or cemented), and nitrided steels. The axle base aw of a spur planetary gear train for the wheel set of the external toothing (of the central pinion with the planetary pinion) is determined as     3 K H T1 kw , aw = 450 u + 1 ψba u  [σ ]2H n w where u  = z g /z a is a gear ratio of the calculated wheel set, kw = 1.05–1.15 is an unbalance factor between the planetary pinions, T1 = Ta is the torque on the shaft of the drive central pinion (N m), n w is the number of planetary pinions, ψba is the coefficient of the face width of the wheel, with ψba = 0.4 for wheel hardness H ≤ 350 HB, ψba = 0.315 for H ≤ 50 HRC, and ψba = 0.25 for H > 50 HRC. The width bb of the central wheel b is bb = ψba aw . The width bg of the planetary pinion ring is assumed to be 2–4 mm more than the value of bb , and the width ba of the central pinion is assumed to be ba = 1.1bg . The toothing module is m = 2aw /(z g + z a ). The calculated module is rounded to the nearest standard value and then the axle base is specified as aw = m(z g + z a )/2. Bending analysis is performed according to (6.7) as for standard gearings.

6.7.8 Design of Planetary Gears Figure 6.95 shows the construction of a single-reduction epicyclic unit produced according to the layout of Fig. 6.90. In this construction the central drive pinion is a floating link. In the radial direction the pinion self-installs along the planetary pinions. In the axial direction the pinion is fixed from one side with a pin butt (1) and from the other side with a toothed coupling (2) with spring rings (3) installed in it. The pitch diameter of the toothed coupling (2) is assumed, for simplicity of manufacture, to be equal to the diameter d1 of the central pinion. The coupling diameter is dc ≥ d1 + 6 m,

412

Part B

Applications in Mechanical Engineering

Table 6.40 Recommended values of the coefficient a23 Bearings

Values of the coefficient a23 for use conditions 1 2 3

Ball (except spherical) Roller with cylindrical rollers, ball spherical double-row Roller tapered Roller spherical double-row

0.7 – 0.8 0.5 – 0.6 0.6 – 0.7 0.3 – 0.4

Part B 6.8

The input and output shafts of reduction gears are loaded with the force F acting from the side of the toothing and the cantilever force FC (from the sleeve, belt drive, or chain gear). The assigned rolling bearings are calculated based on a set lifetime according to the action on the support reaction (Fr1 or Fr2 ). Taking into account the largest possible unevenness distribution of the total torque to the flows, the force F (N) acting on the shaft from the side of the toothing is determined from the following formulas: For the input shaft (layout in Fig. 6.111a) F = 0.2 × 103 T1 /d1 , where T1 is the torque on the shaft (N m) and d1 is the pitch diameter of the toothed coupling teeth (2) (mm), which connects the input shaft to the drive pinion (Fig. 6.95). For the output shaft (layouts in Fig. 6.111b,c and Figs. 6.95 and 6.100a) F = 0.1 × 103 Th /aw , where Th is the torque on the output shaft (the carrier) (N m), Th = T1 uη, and aw is the axle base of the gear (mm). The bearings of the planetary pinions are the most heavily loaded Fr max ≈ 2Ft max , where Ft max is the peripheral force (N) and Ft max = 2 × 103 kw T1 max /(n w d1 ). Here, T1 max = T1 is the maximum of the long-acting (nominal) torque on the drive pinion (N m) and d1 is the pitch diameter of the drive pinion (mm).

1.0 0.8 0.9 0.6

1.2 – 1.4 1.0 – 1.2 1.1 – 1.3 0.8 – 1.0

Table 6.41 Values of the coefficient a1 Safety Pt (%)

Lifetime designation

Values of the coefficient a1

90 95 96 97 98 99

L 10a L 5a L 4a L 3a L 2a L 1a

1 0.62 0.53 0.44 0.33 0.21

The equivalent radial force for the bearing calculation under typical varying loading conditions is Fr = K E Fr max , where K E is an equivalence coefficient. The required radial dynamic load rating Cr, re (N) of the planetary pinion bearings is determined from the formula  L  n a z a 60 , Cr, re = Pr k sah a1 a23 106 z g where Pr = VFr K dy K t is an equivalent radial load (N), V = 1.2 (the outer race rotates relative to the radial load), and L sah is the required bearing lifetime with given safety (h); n a = (n a − n h ) and z a is the relative rotational frequency and tooth number of the central drive pinion, z g is the tooth number of the planetary pinion, a1 is a safety factor (Table 6.41), a23 is a use environment coefficient (Table 6.40: for spherical double-row ball-bearings a23 = 0.5–0.6, for spherical double-row roller bearings a23 = 0.3–0.4), k = 3 for ball bearings, and k = 10/3 for roller bearings.

6.8 Wave Gears The wave gear is a power transmission in which rotation is transmitted by traversal of the deformation area of

a flexible elastic section. A mechanical wave harmonic drive can be frictional and geared.

Design of Machine Elements

6.8.2 Gear Ratio of Wave Gears As with planetary gears, wave gears have three main elements that take external torques. Any main unit can be stopped. 1. The generator is stopped (ωh = 0). Rotation is transmitted from the flexible wheel with tooth number z g to the rigid one (z b ), a common internal mesh ωg zb u hgb = = . ωb zg There is a plus sign in the formula, because the rotational directions ωg and ωb coincide. 2. The rigid wheel is stopped, ωb = 0 (Fig. 6.115a). This is the most frequent case (the standard wave gear). Let us consider a differential wave gear with all three movable elements having angular velocities

415

ωg , ωb , and ωh . Let us choose a coordinate system that is quiescently bound to the generator. To do this assume that the angular velocity is (−ωh ) for the whole system. Then the elements have relative angular velocities ω g − ωh ;

ωb − ω h ;

ωh − ωh = 0 ,

i. e., both wheels seem to rotate relative to the stationary generator. Then, as in the first case, we can write ω g − ωh zb h = = . u gb ωb − ω h zg If the rigid wheel is stopped, movement is transmitted from the generator to the flexible wheel and, therefore, u bhg = ωh /ωg is determined. Supposing that ωb = 0 in the formula for the differential gear we have ω g − ωh zb = ; 0 − ωh zg ωg zb − +1 = ; ωh zg ωh 1 1 = = u bhg = ωg (ωg /ωh ) 1 − z b /z g zg =− . zb − z g The minus sign shows that the sense of rotation of the flexible wheel is opposite to that of the generator. 3. The flexible wheel is stopped, ωg = 0 (Fig. 6.115b,c). Rotation is transmitted from the generator to the g rigid wheel. It is necessary to find u hb = ωh /ωb . Supposing ωg = 0 in the formula for the differential gear we have 0 − ωh ωb − ω h −ωh /ωb 1 − ωh /ωb ωh − ωb ωh ωb

zb ; zg zb = ; zg z b z b ωh = − ; z g z g ωb −z b /z g = ; (z g − z b )/z g =

Then g

u hb =

ωh zb = . ωb zb − z g

The senses of rotation of the generator and the rigid wheel coincide. The difference in the number of wheel

Part B 6.8

radial force Fr . The reactions Ft and Fr act on the tooth of the flexible wheel. If the generator is driving (ωh = 0), and the rigid wheel is fixed (ωb = 0), under the action of the force Ft the flexible wheel rotates (ωg = 0) in the direction opposite to the generator rotation, as indicated by the minus sign in the formula for the transmission ratio, and as will be demonstrated hereinafter. If the flexible wheel is stationary (ωg = 0), the rigid wheel rotates (ωb = 0) under the action of the force Ft in the direction of the generator rotation (ωh = 0), as indicated by a plus sign in the formula for the transmission ratio. Figure 6.115c shows the layout of a wave gear with a stationary flexible wheel. Wave gears are the only power transmission that can transmit rotation through the wall, from a sealed space into a vacuum, without applying a rotatory seal. The flexible wheel g has the form of a blind sleeve with a flange, with which the wheel is fixed on the wall that separates the different media. The gear ring of the flexible wheel is in the middle sleeve part. In wave gears each of the three primary elements can be driving. Thus, for example, in the case of a fixed flexible wheel and rotation of the rigid wheel in the counterclockwise direction, the flexible wheel acts upon the generator with a force Fr (Fig. 6.116). The line of force action Fr is along the normal to the curve that circumscribes the straining form of the flexible wheel. Under the action of the torque T = 2Fr e (where 2 is the number of strain waves) the generator rotates in the same direction as the rigid wheel.

6.8 Wave Gears

416

Part B

Applications in Mechanical Engineering

teeth is divisible by the wave number (as in planetary gears it is divisible by the planetary pinion number) (z b − z g )/n w = K z , where K z is a whole number, with u ≥ 70K z = 1, n w is a wave number, and for the two-wave gear n w = 2. Then zb − z g = 2 . Example g Determine the transmission ratios u bhg and u hb for z g = 200 and z b = 202

zg ωh 200 =− =− = −100 , ωg zb − z g 202 − 200 ωh zb 202 g u hb = = = = 101 . ωb zb − z g 202 − 200

u bhg =

Part B 6.8

6.8.3 Radial Deformation and the Transmission Ratio From Fig. 6.112 it follows that 2W0 = db − dg . For tooth wave gears with module m we have 2W0 = db − dg = m(z b − z g ) . Since z b − z g = 2, the radial deformation W0 for wheels cut without displacement of the basic profile is W0 = m. For standard wave gears zg mz g =− u bhg = − zb − z g mz b − mz g dg dg =− =− . db − d g 2W0 In other words, the transmission ratio in wave gears is equal to the ratio of the driven wheel radius to the difference of the radii of the rigid wheel and the flexible wheel or to the deformation dimension W0 . It follows that higher values of the transmission ratio u can be reached for low values of W0 , i. e., by small modules m. Major deformation dimensions W0 correspond to lower values of u, for which the curvature of the flexible wheel and, therefore, bending stresses increase considerably in the toothing area. The allowable range of the transmission ratio of the wave gear is 70 < u < 320 . The lower limit on u is provided by the limit on the strength of the flexible wheel under bending stresses,

whereas the upper limit is provided by the minimal module values (m ≥ 0.15 mm). Advantages of Wave Gears 1. The availability of a higher transmission ratio on one grade with a comparatively high value of the efficiency factor η. For one grade u up to 320 with η = 0.7–0.85. 2. The capability to transmit higher torques for smaller dimensions and mass due to the large number of teeth that engage simultaneously. 3. Operating smoothness and low kinematic inaccuracy due to two-zone and multipair toothing. 4. Rotation transmission from a sealed space without the use of rotatory seals. 5. Low loads on the shafts and bearings as a consequence of construction symmetry. 6. Operation with little noise. Disadvantages 1. Production complexity of the thin-walled flexible wheel and the wave generator. 2. The need for special gear-shaping equipment to apply the small modules. 3. Limited rotational frequencies of the wave generator, leading to increased vibration. Applications Wave gears are applied in industrial robots and manipulators, in mechanisms with high transmission ratio, and also in devices with increased requirements of kinematic accuracy or tightness.

6.8.4 The Nature and Causes of Failure of Wave Gear Details Some of the causes of failure of wave gear details are: 1. Fracture of the flexible wheel as a result of fatigue cracks in the tooth sockets, as the wheel is exposed to alternate bending stresses. 2. Bearing fracture of the wave generator as a consequence of the toothing force action and the resistance of the flexible wheel to deformation. 3. Skipping of the wave generator (rotation of the generator shaft without rotation of the output shaft) as a result of insufficient radial rigidity and great resilience of the wave generator and the stiff wheel for the transmission of high torques. Thereupon the teeth at the toothing entry rest with their tops against

418

Part B

Applications in Mechanical Engineering

Obviously, the bending stresses depend on the deformation law of the flexible wheel. By deformation according to the law W = W0 cos(2ϕ), which is similar to that for an ellipse, we have Eh (−4W0 cos (2ϕ) + W0 cos (2ϕ)) . 2r 2 It follows that the bending stresses vary, and that they reach maximum values for ϕ = 0 and 90◦ . For ϕ = 0◦ σF = −

3 EhW0 . 2 r2 For ϕ = 90◦ σF =

3 EhW0 . 2 r2 In the general case we can write σF = −

EhW0 , r2 where Aσ is a coefficient that depends on the form of the deformation. This is particularly so for deformation of flexible wheels with a cam generator with a flexible bearing Aσ = 1.75. The characteristics of the cycle of alternating symmetric changes of bending stresses are its amplitude σa = σF and mean value σm = 0. The availability of the gear ring and the tension under the action of the forces Fl distinguish the real flexible wheel from the smooth ring. Both result in an increase of the acting stresses. Thus, the coefficient K σ , which takes into account the influence of the gear ring and its tension on the strength of the flexible wheel, is applied to the rated relation (K σ = 1.5–2.2; higher values correspond to lower module values and lower values of the rounded radii in the sockets between the teeth). Upon installation the generator distorts the flexible wheel from only one side. Under the action of the torque the initial form and size of the deformation change in a real gear. This is due to the adjustment of the radial clearance in the supple bearing, the clearances between the bearing cup and flexible wheel, and the contact deformations in the supple bearing and deformations of the stiff wheel. This change in the initial form and deformation size results in an increase of acting stresses, which is taken into consideration through the insertion of the coefficient K s = 1.3–1.7 into the design formula. The loading of the flexible wheel with torque T and intersecting forces Q that cause the action of the shearing stresses is taken into account by means of insertion of the coefficient K τ = 1.2–1.3 into the design relation. σF = Aσ

Thus, the formula for calculation of the equivalent stresses in flexible wheels has the form EhW0 Kσ Ks Kτ . σa = Aσ r2 The safety factor according to the fatigue strength of the flexible gear ring is determined from the formula SF = σ−1 /σa ,

(6.20)

where σ−1 is the endurance limit of the material used for the flexible wheel. The strength condition of the flexible wheel (checking calculation) is SF ≥ [S]F ,

(6.21)

Part B 6.8

where [S]F = 1.6–1.7. Higher values indicate a probability of nonfracture of greater than 99%. In the case of the design calculation the diameter d of the flexible wheel opening is determined according to the fatigue strength criterion of the flexible ring (Sect. 6.8.6). Bearing Calculation of Wave Generators An operational peculiarity of wave generators is the fact that they rotate with high frequency of the input element reacting to high loads of the output elements. The cam wave generator is optimum in terms of loadcarrying capacity. The required dynamic load rating of flexible bearings is determined according to the standard method for rolling bearings (Sect. 6.11.14). Wear of the teeth is insignificant and does not limit the gear lifetime in the case of correctly chosen mesh geometry, materials, heat treatment, and lubrication parameters.

6.8.6 Design of Wave Gears Choice of Mesh Parameters Tooth Profile. Involute teeth are used in the wave gears,

with well-known technological advantages such as the availability of existing tools and the ability to provide sufficiently high multipair toothing under load. To cut involute teeth a tool with a 20◦ angle of the basic rack profile is used. It should be noted that the stresses in the rim of the flexible gear wheel reduce when the socket width is increased to a size that is similar to or greater than the tooth thickness. Involute teeth with a wide socket can be cut with a tool with a reduced pitch line depth. The profile of involute teeth with a wide socket is accepted as the basis for the standard series of harmonic reducers for machine-building applications.

Design of Machine Elements

6.9 Shafts and Axles

433

Table 6.47 Influence factors K dσ and K dτ of the absolute dimensions of the shaft cross-section Stress condition and material

K dσ (K dτ ) with shaft diameter d (mm) 20 30 40

50

70

100

Bend for carbon steel Twist for all the steels and bend for alloy steel

0.92 0.83

0.81 0.70

0.76 0.65

0.71 0.59

0.88 0.77

0.85 0.73

Table 6.48 Influence factors K Fσ and K Fτ of the finished treatment Type of machining

Roughness parameter Ra (μm)

K Fσ for σt (N/mm2 )

K Fτ for σt (N/mm2 )

≤ 700

> 700

≤ 700

> 700

Fine grinding Fine turning Finish grinding Finish turning

≤ 0, 2 0.2 – 0.8 0.8 – 1.6 1.6 – 3.2

1 0.99 –0.93 0.93 –0.89 0.89 –0.86

1 0.99– 0.91 0.91– 0.86 0.86– 0.82

1 0.99–0.96 0.96–0.94 0.94–0.92

1 0.99– 0.95 0.95– 0.92 0.92– 0.89

where Sσ and Sτ are safety factors for the normal and shearing stresses Sσ = σ−1D /σa , Sτ = τ−1D /(τa + ψτ D τm ) . Here σa and τa are stress amplitudes, τm is a mean stress (Fig. 6.139), and ψτ D is an influence factor of the stress cycle unbalance for the shaft section concerned. Stresses in the weak sections are determined from the formulas σa = 103 Mc /W , τa = 103 Mt /(2Wt ) , τm = τa ,

where Mc = ( Mx2 + M y2 + M) is a resultant bending moment (N m), Mt is a twisting moment (Mt = T ) (N m), and W and Wt are modules of the shaft section for bending and twisting (mm3 ). The influence factor ψτD of the stress cycle imbalance for the shaft section concerned is ψτD = ψτ /K τD , where ψτ is a sensitivity index of material to the stress cycle unbalance (Table 6.45). The endurance limits of the shaft in the section are σ−1D = σ−1 /K σD , τ−1D = τ−1 /K τD , where σ−1 and τ−1 are the endurance limits of the smooth specimens in the completely reversed cycle of

bending and twist (Table 6.45), and K σD and K τD are reduction factors for the endurance limit. The values K σD and K τD are determined from the relations K σD = (K σ /K dσ + 1/K Fσ − 1)/K v , K τD = (K τ /K dτ + 1/K Fτ − 1)/K v , where K σ and K τ are effective stress concentration factors of bending and twist. The influence on the endurance limit of the shaft form change in the axial direction or the cross section is also taken into account (transition area, key groove, splines, thread, etc.). Pressure at the installation point of the details mounted with interference (gear wheels, rolling bearings) is also a stress concentrator. Stress concentration decreases the endurance limit. K dσ and K dτ are influence factors of the dimensions of the absolute cross-section (Table 6.47). The higher the absolute dimensions of the cross section of the detail, the lower the endurance limit. K Fσ and K Fτ are influence factors of the surface finish (Table 6.48). With increasing surface roughness the endurance limit of the detail is lowered. The development of corrosion considerably reduces the endurance limit during operation. K v is an influence factor of surface hardening (Table 6.49). Surface hardening of the detail increases the endurance limit considerably. Surface hardenings are more effective than volumetric ones, which are often accompanied by impact strength reduction and an increase in the stress concentration sensitivity. For example, case-hardening and quenchhardening increase the fatigue strength by 30–40% or more in comparison with volume quenching for the same hardness. The values of the coefficients K σ and K τ are taken from tables. For a step junction with a hollow chamfer

Part B 6.9

For each of the fixed presumably weak sections the general load factor S is calculated as

S = Sσ Sτ / Sσ2 + Sτ2 ≥ [S] ,

Design of Machine Elements

Table 6.51 Effective stress concentration factors K σ and K σ by groove execution with a milling cutter end disk

Kτ

500 700 900 1200

1.8 2.0 2.2 2.65

1.4 1.7 2.05 2.4

1.5 1.55 1.7 1.9

the gears and bearings. Elastic shaft displacements have little influence on the operation of gears with flexible couplers. In gearings they produce mutual warp of the wheels and separation of the axles, which is especially adverse for Novikov gears. For the involute gearings of reduction gears the allowable wrap angles [θ] (radians) can be determined from the formula

Designation of the gear layout in Fig. 6.141

Coefficient Kp

Designation of the gear layout in Fig. 6.141

Coefficient Kp

1 and 2 3

1.2 0.8

5 and 6 7 and 8

0.4 0.1

4

0.6

where K p is a coefficient taking into account the influence of the gear wheel position relative to the bearings (Table 6.54), ψba is a width coefficient, and HBme is the mean hardness of the work tooth surface of the lowspeed wheel.

Table 6.52 Effective stress concentration factors K σ and K τ for spline and thread sections of the shaft

500 700 900 1200

K σ for Splines

Thread

K τ for splines Straight-sided

Involute

1.45 1.6 1.7 1.75

1.8 2.2 2.45 2.9

2.25 2.5 2.65 2.8

1.43 1.49 1.55 1.6

K τ for thread 1.35 1.7 2.1 2.35

Table 6.53 Ratios K σ /K dσ and K τ /K dτ for the estimation of the stress concentration at the installation sites of the components with interference on the shaft K σ /K dσ by σt (N/mm2 )

K τ /K dτ by σt (N/mm2 )

Shaft diameter d (mm)

500

700

900

1200

500

700

900

1200

30 40 50 60 70 80 90 100

2.6 2.75 2.9 3.0 3.1 3.2 3.3 3.35

3.3 3.5 3.7 3.85 4.0 4.1 4.2 4.3

4.0 4.3 4.5 4.7 4.85 4.95 5.1 5.2

5.1 5.4 5.7 5.95 6.15 6.3 6.45 6.6

1.5 1.65 1.75 1.8 1.85 1.9 1.95 2.0

2.0 2.1 2.2 2.3 2.4 2.45 2.5 2.55

2.4 2.6 2.7 2.8 2.9 3.0 3.05 3.1

3.05 3.25 3.4 3.55 3.7 3.8 3.9 3.95

Part B 6.9

The rigidity of the shafts rotating in the bearings must provide ease and smoothness of rotation, as well as sufficient stress distribution in contact, which finally will influence the lifetime of the bearings. The total tolerance on the coaxiality of the cone and the outer race of the rolling bearings, which is caused by an unfavorable combination of various kinds of machining errors, assembly and deformation of the bearings, and the shaft and case details under the action of the load, is estimated from the maximum permissible angle θmax of the mutual wrap between the axles of the bearing racers that is mounted on the bearing unit. The maximum permissible angle θmax of mutual warp of the bearing racers is defined, for which the lifetime can be proved to be not less than the required time. The values of the maximum permissible angle

[θ] = 10−3 K p ψba HBme /600 ,

σt (N/mm2 )

435

Table 6.54 Influence factors K c of position of the gear wheels relative to the supports

K τ for a key groove σt (N/mm2 )

6.9 Shafts and Axles

Design of Machine Elements

6.9 Shafts and Axles

437

Table 6.56 Allowable torques transmitted with the cylindrical ends of the shafts. The values of the torques for the shafts with a diameter of less than 6 mm are not regulated Allowable torques T (N m) for the coefficient K (N/mm2 ) 2.0 2.8 4.0 5.6 8.0

11.2

16.0

22.4

6 7 8 9 10 11 12 14 16 18 – 20 22 – 25 28 30 32 35, 36 – 40 – 45 – 50 – 55 60 63 – 70,71 – 80 – 90 – 100 – 110 – 125 – 140 – 160 – 180

0.5 0.71 1.0 1.4 2.0 2.8 4.0 5.6 8.0 11.2 12.5 16.0 22.4 25.0 31.5 45.0 50.0 63.0 90.0 100 125 140 180 200 250 280 355 400 500 560 710 800 1000 1120 1400 1600 2000 2500 2800 3150 4000 4500 5600 6300 8000 9000 11 200

2.8 4.0 5.6 8.0 11.2 16.0 22.4 31.5 45.0 63.0 71.0 90.0 125 140 180 250 280 355 500 560 710 800 1000 1120 1400 1600 2000 2240 2800 3150 4000 4500 5600 6300 8000 9000 11 200 12 500 16 000 18 000 22 400 25 000 31 500 35 500 45 000 50 000 63 000

4.0 5.6 8.0 11.2 16.0 22.4 31.5 45.0 63.0 90.0 100 125 180 200 250 355 400 500 710 800 1000 1120 1400 1600 2000 2240 2800 3150 4000 4500 5600 6300 8000 9000 11 200 12 500 16 000 18 000 22 400 25 000 31 500 35 500 45 000 50 000 63 000 71 000 90 000

5.6 8.0 11.2 16.0 22.4 31.5 45 63.0 90.0 100 140 180 250 280 355 500 560 710 1000 1120 1400 1600 2000 2240 2800 3150 4000 4500 5600 6300 8000 9000 11 200 12 500 16 000 18 000 22 400 25 000 31 500 35 500 45 000 50 000 63 000 71 000 90 000 100 000 125 000

– – – – – – – – – – 19 – – 24 – – – – – 38 – 42 – 48 – 53 56 – – 65 – 75 – 85 – 95 – 105 – 120 – 130 – 150 – 170 –

0.71 1.0 1.4 2.0 2.8 4.0 5.6 8.0 11.2 16.0 18.0 22.4 31.5 35.5 45.0 63.0 71.0 90.0 125 140 180 200 250 280 355 400 500 560 710 800 1000 1120 1400 1600 2000 2240 2800 3150 4000 4500 5600 6300 8000 9000 11 200 12 500 16 000

1.0 1.4 2.0 2.8 4.0 5.6 8.0 11.2 16.0 22.4 25.0 31.5 45.0 50.0 63.0 90.0 100 125 180 200 250 280 355 400 500 560 710 800 1000 1120 1400 1600 2000 2240 2800 3150 4000 4500 5600 6300 8000 9000 11 200 12 500 16 000 18 000 22 400

1.4 2.0 2.8 4.0 5.6 8.0 11.2 16.0 22.4 31.5 35.5 45.0 63.0 71.0 90.0 125 140 180 250 280 355 400 500 560 710 800 1000 1120 1400 1600 2000 2240 2800 3150 4000 4500 5600 6300 8000 9000 11 200 12 500 16 000 18 000 22 400 25 000 31 500

2.0 2.8 4.0 5.6 8.0 11.2 16.0 22.4 31.5 45.0 50.0 63.0 90.0 100 125 180 200 250 355 400 500 560 710 800 1000 1120 1400 1600 2000 2240 2800 3150 4000 4500 5600 6300 8000 9000 11 200 12 500 16 000 18 000 22 400 25 000 31 500 35 500 45 000

Part B 6.9

Diameter d (mm) 1st row 2nd row

Design of Machine Elements

relevant for bearing units working with contaminated lubricants, for which abrasion is typical. If the shaft has rolling bearings, the diameter and length of the shaft journals for the bearing are determined from the dimensions of the chosen bearing. Technical requirements (roughness, deviation of the form and position) for the mounting and bearing front faces must meet the requirements for ball and roller bearings. Tolerance ranges for the diameters of the mounting shaft surfaces, as well as the fit for the bearing joint with the shafts (axles), are fixed according to the accuracy grades of the bearings. The nature of the mating of the bearing with the shaft and the choice of the fit depend on whether the inner race of the bearing rotates or not relative to the radial load that affects it, and on the direction and value of the acting load intensity, etc. When fastening the inner races of the rolling bearings on the shaft in the axial direction structural measures must be taken to provide the correct mounting, dismantling, and required maintenance of the bearings in operation. As a result of the temperature increase during operation of the product, the shaft can become elongated, which is why fixing of the shaft from the axial displacement must be done such that the shaft elongation does not cause jamming of the bearings or lead to the occurrence of secondary stress. The method of shaft fastening from the axial displacement is chosen depending on the kind of bearings that are mounted on the shaft (adjustable or nonadjustable), and on the working conditions of other components that mate with the shaft. The machining accuracy of the journals (necks) for friction and rolling bearings is of great consequence. Because of the different component types that are set on the shafts and the axles, the greatest demands are made on the mounting of gear and worm wheels and pulleys of high-speed belt drives with regard to the coaxiality of the shaft sections bearing these components relative to the journals (necks). For gears with toothing this results from the necessity of providing the standards of kinematic accuracy and of contact; for pulleys it is necessary to decrease imbalance and, consequently, dynamic loads and vibrations. Thus, for example, the coaxiality tolerance of a mounting shaft surface with a diameter of 56 mm for gear wheels, a pitch diameter of 240 mm with kinematic accuracy degree 7 of the gear is 0.025 mm. Certain accuracy demands, if necessary, can also be made for other sections or structural shaft components;

439

Part B 6.9

The spline connection reduces the fatigue strength of the shaft less than the key joint. Component fastening on the shaft using lock screws, adjusting nuts, cutting rings, etc., increases stress concentration and consequently reduces the fatigue strength of the shaft. Thus it is advisable to use axial fastening for the components. When an opening application for the lock screws or pins, nut threads, grooves for the elastic rings, etc., cannot be avoided, measures should be adopted to decrease stress concentration at these points. Shaft hardening by structural means at the positions of the transverse openings can be carried out by the following methods: countersinking the hole, removal of a flat along the hole, and insertion of a bronze (a material with a lower coefficient of elasticity) bushing into the hole. These measures can decrease the stress concentration by 20–40% or more. The thread is characterized by considerable stress concentration. The stress concentration factor for the thread substantially depends on the thread veeradius R between the threads. For high-duty shafts it is recommended to use a thread with vee-radius R = (0.125–0.144)P, where P is the thread pitch. Another reason for stress concentration is fretting wear (friction corrosion) that results from the slightly varying relative displacements of the shaft and the mated component, which are in turn caused by flexural or torsional strain. The stress concentration is especially strong in those cases in which the component is set on the shaft with interference and when it transmits loads to the shaft. The fatigue strength of the shafts under the hubs can be raised with plastic forming (breaking-in with a roller), chemicothermal treatment (nitriding), surface hardening, and treatment with a laser beam and plasma. The quality of the surface layer in the weak sections distinctly affects the fatigue strength of the shaft, especially at stress concentration sites. The structure of the journals is caused by the type of shaft bearing applied (rolling bearing or sleeve bearing). The journal diameter of the friction bearing is chosen depending on the required strength and rigidity of the shaft and the overall dimensions of the whole structure. To increase the reliability of the friction bearing it is usually helpful to increase the journal diameter, but it must be borne in mind that journals are end faces of the shaft and according to the assembly conditions they are designed to have a smaller diameter than the middle parts of the shaft. To decrease wear the journals are heat treated or chemicothermally treated (hard-surfacing, cementing, nitriding), leaving the core viscous. Above all this is

6.9 Shafts and Axles

440

Part B

Applications in Mechanical Engineering

for example, the tolerances on the symmetry and parallelism of the key groove of the shaft axles are fixed in order to provide the possibility of assembling the shaft with the component mounted on it and to provide even contact of the key and shaft surfaces.

6.9.7 Drafting of the Shaft Working Drawing Introduction Dimensioning. In the working drawings the minimum

number of dimensions must be set, but they must be sufficient for the production and control of the component. The dimensions given in the drawings can be classified as being:

•

Part B 6.9

• •

Functional, determining qualitative product indexes: dimensions of the assembly measuring chains, mating dimensions, diameters of the shaft sites for gear and worm wheels, couplings, bearings and other components, and thread dimensions on the shafts of the adjusting nuts Free (dimensions of the nonjoining surfaces) Reference

Functional dimensions are set in the working drawings of the components, having been taken from the drawing of the assembly unit (reduction gear, gearbox) and from the layouts of the dimensional chains. Free dimensions are set, taking into account the fabrication technique and control convenience. Reference dimensions are not subjected to execution according to the given working drawings and are not controlled during component manufacture. Reference dimensions are marked with an asterisk and a notation such as “* Dimensions for reference” is added in the standards. Extreme Dimensional Deviations For all the dimensions given in the working drawings extreme deviations are indicated in millimeters. It is permissible not to indicate extreme deviations of dimensions that fix areas of different roughness and accuracy of the same surface, of the heat-treated zone, the coat-

ing and knurling zone, as well as the diameters of the knurled surfaces. In these cases, the sign “≈” is marked directly on such dimensions. If necessary extreme deviations of the rough or very rough accuracy degree according to the Russian standard [6.55] (Table 6.57) are set for these dimensions instead of using this sign. If extreme deviations (tolerances) are not given individually for the appropriate nominal dimensions, the overall dimensional tolerances according to the Russian standard [6.55] are applied, fixed according to four accuracy degrees: accurate f , mean m, rough c, and very rough v (Table 6.57). For the choice of the accuracy degree the common accuracy of the corresponding industry is taken into account. The overall dimensions are applied for the following dimensions with undisclosed individually extreme deviations:

• • •

For linear dimensions (e.g., outer and inner diameters, radii, distances, shoulder dimensions, dimensions of the dull edges, outer rounded radii and chamfer dimensions) For angular dimensions, including angular dimensions that are usually undisclosed, i. e., right angles or angles of regular polygons For linear and angular dimensions, which are obtained by ready-mounted component machining

References to the overall tolerances of the linear and angular dimensions are given in the standards, indicating the number of the standard and the letter symbol of the accuracy degree required, e.g., for the accuracy degree mean: “Overall tolerances according to GOST 30893.1-m” or “GOST 30893.1-m”. The individual extreme deviation of the linear dimensions is indicated according to one of the three following methods:

• •

Reference designations of the tolerance ranges, e.g., 63H7 Values of the extreme deviations, e.g., 64+0.030

Table 6.57 Extreme deviations of the linear dimensions according to [6.55] Extreme deviations for the intervals of the dimensions (mm) 0.5–3 > 3 –6 > 6 –30 > 30– 120

> 120– 400

> 400–1000

Accurate f Mean m

±0.05 ±0.10

±0.05 ±0.10

±0.1 ±0.2

±0.15 ±0.30

±0.2 ±0.5

±0.3 ±0.8

Rough c Very rough v

±0.20 –

±0.30 ±0.50

±0.5 ±1.0

±0.80 ±1.50

±1.2 ±2.5

±2.0 ±4.0

Accuracy degree

Design of Machine Elements

•

Reference designation of the tolerance ranges with indication of the extreme values in brack  deviation ets to the right: 18P8 −0,018 −0,045

The first method is recommended in the case of nominal dimensions, which are included in the series of standard numbers [6.83]. The second method is used in the case of nonstandard numbers on the nominal dimensions, and the third is used with standard numbers, but with inadvisable tolerance ranges. Extreme deviations of chain dimensions are assigned according to the results of the probabilitytheoretical calculation of the corresponding dimensional chains. Approximately extreme deviation of the chain dimensions can be taken according to the compensation method:

•

•

Extreme deviations of the thread diameters are shown in the component working drawings in accordance with the fits of the threaded connections that are given in the working drawings of the assembly units, for example, for the threads in the openings M20-7H, M16-3H6H, M30 ×1.5-2H5C, and for the threads on the shafts M42-8g, M16-2m, M30 ×1.5-2r. Form Tolerances and Tolerances on the Surface Position During machining of the components errors arise not only in the linear dimensions, but also in the geometry, as well as the errors in the relative position of the axles, surfaces, and structural components of the details. These errors can exert an unfavorable influence on the efficiency of the machinery, producing vibrations, dynamic loads, and noise. The first group of accuracy requirements is caused by the installation of the rolling bearings (Russian standard [6.89]). It is important for rolling bearings that the rolling paths of the racer are not distorted. Racers are very compliant and on installa-

441

tion they adopt the form of the mounting surfaces of the shafts and cases. To decrease the shape defects of the rolling paths form, tolerances are set for the mounting surfaces of shafts and cases. The relative warp of the outer and inner races of the bearings increases shaft rotation and power waste resistance, and reduces the lifetime of bearings. Race warp can be caused by:

• • •

Axial deviations of the mounting surfaces of the shafts and the case Perpendicularity deviations of the datum faces of the shaft and case Deformations of the shaft and case in the working unit

To limit these deviations the tolerances on the mounting surface position of the shaft and case are set in the working drawings. The second group of accuracy requirements results from the necessity to abide by kinematic accuracy standards and contact standards of tooth and worm gears [6.28, 29, 41]. The achievement of the requisite accuracy depends on the positional accuracy of the mounting surfaces and the datum faces of the shafts, as well as the mounting openings and the datum faces of the wheels. Thus, the tolerances on the datum face position are set in the working drawings of the shafts, gear, and worm wheels. The third group of accuracy requirements is caused by the need for limitation of possible component unbalance. Allowable imbalance values are defined in [6.86] depending on the kind of product and its operating conditions. The standards of allowable imbalance are described by the equation en = const., where e is a specific imbalance (g mm/kg), which is numerically equal to the displacement of the mass center from the rotation axles (micrometer), and n is a rotational frequency (min−1 ). In this respect it is convenient to make demands on the single component surfaces in the form of the coaxiality tolerances in the working drawings. Base axles and surfaces are indicated in the working drawings with equilateral hatched triangles connected with a frame, where the designation of the base is written with a capital letter. If the tolerance on the form or the position is not given individually for the appropriate element of the detail, overall tolerances on the form and position according to [6.56] are applied, being fixed for three accuracy degrees (in decreasing accuracy order): H, K , and L. By the choice of the accuracy degree, the com-

Part B 6.9

•

If compensator is a component that is scraped or ground according to the results of the measurement by assembly, with a view to decreasing the machining allowance of the tolerance ranges of the chain dimensions should be assumed: of the openings H9, of the shafts h9, others ± IT9/2. If a gasket package serves as a compensator, the tolerance ranges of the chain dimensions are assumed to be H11, h11, ± IT11/2. If a thread pair serves as a compensator, as a consequence of its wide compensating possibilities, the tolerance dimensional ranges are assumed to be: H14, h14, ±IT14/2.

6.9 Shafts and Axles

Design of Machine Elements

6.9 Shafts and Axles

443

Table 6.59 Recommended values of roughness Ra

Type of surface

1.25 2.5 2.5 3.2 2.5 0.8

1.6 3.2 0.32 1.6 6.3 3.2 6.3 1.6 3.2

1.6 0.8 0.8 0.4 3.2

1.6 0.8 1.6 0.8 3.2

Part B 6.9

Mounting surfaces of the shafts and the cases from steel for the rolling bearings of the normal accuracy degree for: d or D up to 80 mm d or D over 80 mm Mounting surfaces of the cases from iron for the rolling bearings of the normal accuracy degree for: D up to 80 mm D over 80 mm Pin shoulder faces of the shafts and the cases for stationing of the rolling bearings of the normal accuracy degree Shaft surfaces for interference joints Pin shoulder faces for positioning of the gear, worm wheels with the ratio of the opening hub length to its diameter: l/d < 0.7 l/d ≥ 0.7 Shaft surfaces for cup-type seals Case (cover) surfaces for cup-type seals Grooves, bevels, hollow chamfer radii on the shafts Surfaces of the key grooves on the shafts: effective noneffective Surfaces of the key grooves in the openings of the wheels, pulleys: effective noneffective Spline surfaces on the shafts: – tooth surface of the joint: fixed sliding – cylindrical surfaces, centering joining: fixed sliding – cylindrical surfaces, noncentering joining Spline surfaces in the openings of the wheels, pulleys, chainwheels: – tooth surface of the joint: fixed sliding – cylindrical surfaces, centering joining: fixed sliding – cylindrical surfaces, noncentering joining

Ra (μm)

444

Part B

Applications in Mechanical Engineering

Table 6.59 (cont.)

Part B 6.9

Type of surface

Ra (μm)

Opening surfaces of the hubs with interference connections Hub faces of gear, worm wheels positioned along the pin shoulder face of the shaft with the ratio of the opening length to its diameter l/d < 0.7 l/d ≥ 0.7 Hub faces of gear, worm wheels, along which the rolling bearings of the accuracy degree normal are positioned Free (noneffective) faces of gear, worm wheels Working tooth surfaces of gear wheels with external toothing: With the module ≤ 5 mm With the module > 5 mm Working surfaces of the worm coils; cylindrical concave Working tooth surfaces of worm wheels Cusp surfaces of the wheel teeth, worm coils, chain wheel teeth Bevels and recesses on the wheels Opening surfaces in the covers for the rubber glands Working surface of the belt pulleys Working tooth surface of the chainwheels Opening surfaces for bolts, screws, stud-bolts Bearing surfaces for bolt, screw, and nut heads

1.6

Technical requirements are located above the main inscription, and if there is not enough space they are placed to the left of the main inscription. Technical requirements are written in the following order: 1. Requirements for the material, workpiece, heat treatment, and the material properties of the finished part (HB, HRC) 2. Guidelines about dimensions (dimensions for references, rounded radii, angles, etc.) 3. Overall tolerances on the dimensions, forms, and positions 4. Tolerances on the forms and mutual surface position, for which there are no conventional graphic characters in [6.80] 5. Surface quality requirements (guidelines about finish, coating, roughness)

1.6 3.2 1.6 6.3 1.25 2.5 0.63 1.25 1.6 6.3 6.3 1.6 2.5 3.2 12.5 6.3

6. Units of measurement that have to be indicated for the dimensions and extreme deviations given in the technical requirements Performance of the Shaft Working Drawing Dimensions and Extreme Deviations. In the shaft

working drawings the mating, chain, and overall and free dimensions are set. Figure 6.143 shows a method for axial dimensioning of the shaft. The dimensions are indicated in this figure: C1 and C2 are the matings (lengths of the key grooves); G and P are overall and chain dimensions, K 1 and K 2 coordinate the position of the key grooves, which is convenient for the control with a vernier caliper or with a trammel; l1 is the length of the shaft extension (conjunctive dimension), l2 and l3 are the lengths of the mating surfaces. The dimensions l1 , l2 , l3 , and l4 correspond to the consecutive phases of the shaft turning. In this example, the dimen-

446

Part B

Applications in Mechanical Engineering

Table 6.60 Recommendations concerning the determination of the form tolerances and position tolerances of the shaft

surfaces

Position in Fig. 6.145

Tolerance

1, 2 3 4

Tci ≈ 0.5t, where t is a surface dimension tolerance Tso according to Table 6.61 depending on the bearing type Tso on the diameter d according to Table 6.62. The tolerance accuracy degree is according to Table 6.63 Tso ≈ 60/n for n > 1000 min−1 ; tolerance is in mm Tpr on the diameter d0 according to Table 6.64. Tolerance accuracy degree by bearing positioning: ball bearings – 8, roller bearings – 7 Tpr on the diameter ds by l/d < 0.7 according to Table 6.64. Tolerance accuracy degree is according to Table 6.65 Tpa ≈ 0.5tsp ; Tsi ≈ 4tsp , where tsp is a width tolerance of the key groove

5 6 7 8

Table 6.61 Tolerances of coaxiality Tsow and Tsok for mounting surfaces of the shaft and the case in bearing units. Tsow

Part B 6.9

and Tsok are coaxiality tolerances of the mounting surface of the shaft and the case with length B = 10 mm in diametral form. For length B1 of the slot the tabulated value should be multiplied by 0.1B1 . θ is the allowable angle of mutual warp of the racers, caused by deformations of the shaft and the case in the working unit Bearing type Radial ball, single-row Radial-thrust ball, single-row Radial with short cylindrical rollers: without modified contact with modified contact Taper roller: without modified contact with modified contact Needle roller single-row without modified contact with modified contact Radial ball and roller double-row spherical

Tsow (μm) 4 3

θ (angle min) 1.6 1.2

Tsok (μm) 8 6

1 3

2 6

0.4 1.2

1 2

2 4

0.4 0.8

1 4 12

0.2 0.8 2.4

0.5 2 6

Table 6.62 Coaxiality tolerances according to [6.88] Dimension range (mm)

Coaxiality tolerance (μm) for tolerance accuracy degree: 5 6 7 8

9

over 18 up to 30 Over 30 to 50 Over 50 to 120 Over 120 to 250 Over 250 to 400

10 12 16 20 25

60 80 100 120 160

16 20 25 30 40

be controlled: roundness accuracy tolerance, tolerance of the longitudinal section profile, diameter variability tolerance in the cross and longitudinal section).

25 30 40 50 60

•

40 50 60 80 100

The tolerance on cylindrical shape (position 2) of the mounting shaft surfaces is set in their installation sites with interference of gear and worm wheels to limit pressure concentration.

Design of Machine Elements

6.9 Shafts and Axles

447

Table 6.63 Recommended accuracy degrees of coaxiality tolerance. The accuracy degree of the coaxiality tolerances of

the slots are for the wheels of tooth (numerator) and worm (denominator) gears Kinematic accuracy

Accuracy degree of the coaxiality tolerance with the diameter of the pitch circle (mm)

degree of the gear

over 50 up to 125

over 125 up to 280

over 280 up to 560

6

5/6

5/6

6/7

7

6/7

6/7

7/8

8

7/8

7/8

8/9

9

7/8

8/9

8/9

Table 6.64 Tolerances of parallelism and perpendicularity in compliance with GOST 24643-81 Dimension range (mm)

Parallelism, perpendicularity tolerance (μm) for tolerance accuracy degree: 5

6

7

8

9

10

4

6

10

16

25

40

Over 25 to 40

5

8

12

20

30

50

Over 40 to 63

6

10

16

25

40

60

Over 63 to 100

8

12

20

30

50

80

Over 100 to 160

10

16

25

40

60

100

Over 160 to 250

12

20

30

50

80

120

Over 250 to 400

16

25

40

60

100

160

Table 6.65 Recommended accuracy degrees of perpendicularity tolerance Wheel type

Accuracy degree of the perpendicularity tolerance by accuracy degree of the gear according to the contact standards 6 7 and 8 9

Gear wheels

5

6

7

Worm wheels

6

7

8

• • •

•

The coaxiality tolerance of the mounting surfaces for rolling bearings relatively to their mutual axles (position 3) is set to limit the warp of the rolling bearing racers. The coaxiality tolerance of the mounting surface for the gear and worm wheel (position 4) is specified to guarantee kinematic accuracy standards and contact standards of tooth and worm gears. The coaxiality tolerance of the mounting surface for half-coupling, pulley, chainwheel (position 5) is set to decrease the imbalance of the shaft and the components installed on this surface. The coaxiality tolerance according to position 5 is set by a rotational frequency of more than 1000 min−1 . The perpendicularity tolerance of the datum shaft face (position 6) is specified to decrease the warp

•

•

of the racers and geometry distortion of the rolling path of the inner race. The perpendicularity tolerance of the datum shaft face (position 7) is set only when mounting narrow gear wheels (l/d < 0.7) on the shaft. The tolerance is set to guarantee execution of the contact standards of the teeth in the gear. Symmetry and parallelism tolerances of the key groove (position 8) are specified to guarantee the possibility of shaft assembly with the component installed on it and an even contact surface between the key and the shaft.

The tables referred to in Table 6.60 are given below. The values of θ according to Table 6.61 are used by shaft rigidity checking. Figure 6.146 shows an example of a shaft drawing.

Part B 6.9

Over 16 up to 25

450

Part B

Applications in Mechanical Engineering

The key length l = lc + b with chamfered l = lc or with flat ends is chosen from the standard series. The hub length lhu is fixed by ≈ 10 mm more than the key length. To decrease the unevenness of the stress distribution along the height and the length of the key the joint length is limited: lhu ≤ 1.5d. If the hub length lhu > 1.5d is obtained according to the results of the key joint calculation, so it is advisable to apply a spline connection or an interference connection instead of a key joint. The strength condition according to shearing stresses is τsh = 2 × 103 T/(dblc ) ≤ [τ]sh ,

Part B 6.10

where b is the key width (mm) and [τ]sh is the allowable shearing stress (N/mm2 ). A semicircular key represents a disk part with the diameter D and the thickness b. The key height h ≈ 0.4D and the length l ≈ 0.95D. The groove on the shaft for the semicircular key is made with a disk cutter; in the hub it is made with a broaching cutter or a shaping cutter. Such a fabrication method provides ease of installation and removal of the key, with interchangeability of the connection. A manual fit is usually not needed. The key in the shaft groove self-installs and does not require extra fastening to the shaft. The disadvantage of such a connection is a weakening of the shaft cross-section with a deep groove, which decreases the fatigue strength of the shaft. Thus, semicircular keys are applied by transmission of relatively low torques. Semicircular keys, like straight ones, work with the side faces (Fig. 6.148). The keys are standardized; for every shaft diameter d the values b, h, t1 , t2 and D are given in the standard. The keys are checked for strength according to bearing stresses σst and shearing stresses τsh in compliance with the formulas given for straight keys; lc ≈ l. Materials of Keys and the Choice of Allowable Stresses Medium-carbon steels with tensile stress σt ≥ 590 N/mm2 serve as the material for the keys (e.g. steel grades E 355 (EN), C 46, C 45 (EN), C 50 E (EN), Appendix 6.A Table 6.95). The values of the allowable stresses of the steel shaft for the key joints are chosen depending on the load condition and operating conditions of the connection from Table 6.66 (the shaft is made of steel). Higher values are taken under constant load, lower ones are under varying load and operation with impacts. In the case of reverse load [σ]st is reduced 1.5

Table 6.66 Allowable stresses [σ ]st for key joints (steel

shaft) Connection type, hub material Fixed, steel hub Fixed, hub is iron or steel casting Sliding without load, steel hub

[σ ]st (N/mm2 ) 130–200 80 –110 20 –40

times. The allowable stress on the key shearing is [τ]sh = 70–100 N/mm2 . The higher value is taken under constant load. The key joint is labor-intensive in manufacture. By the torque transmission considerable local deformations of the shaft and the hub characterize it, which results in uneven pressure distribution on the contact area of the mounting surfaces of the shaft and the hub, as well as on the active faces of the key and the key grooves, which in turn decreases the fatigue shaft strength. Thus, application of the key joints must be limited. They should be used only an interference fit, for the given torque cannot be made in consequence of insufficient material strength of the wheel. With torque transmission through the key joint, application of the wheel fits on the shaft with clearance is prohibited, and the transition fits are undesirable. If there is a clearance in the connection, the shaft rotation runs with surface slipping of the shaft and the wheel opening, which results in wear-out. This is why the interference should by made with the torque transmission with the key on the mounting surfaces of the shaft and the wheel opening, which guarantees nonopening of the junction. With the torque transmission with the key joint the fits for the wheels can be assumed according to the following recommendations: Cylindrical straight Cylindrical helical and worm Bevel Gearboxes

H7/ p6(H7/r6), H7/r6(H7/s6), H7/s6(H7/t6), H7/k6(H7/m6).

The fits with a great interference are given in brackets for the wheels of reverse gears. For the cases that do not have jointing planes along the shaft axes (e.g. in gearboxes), the choice of the wheel fits is determined by the assembly technique. Assembly is carried out inside the case in the straightened conditions, which is why transition fits are applied for the wheels of gearboxes. When mounting the gear wheels on the shafts with interference it can be difficult to match the key groove

Design of Machine Elements

6.10 Shaft–Hub Connections

453

Table 6.67 Allowable stresses [σ ]st for spline connections Type of joint Fixed Sliding without load (pinion unit of a gearbox) Sliding under load (joint of a driveshaft)

σst = 2 × 103 TK t /(dm zhlc ) ≤ [σ]st , where T is a rated torque (the highest of the long-acting torques under varying loading conditions) (N m), K t is an irregularity ratio of load distribution between the teeth (that depends on the manufacturing accuracy, the errors of the pitch angles of the cusps and mating sockets, the value of the radial clearance, and the working conditions), K t = 1.1–1.5, dm is the mean diameter of the joint (mm), z is a cusp number, h is a working cusp height (mm), lc is a working joint length (mm), and [σ]st is the allowable bearing stress (N/mm2 ). In Table 6.67 the values of [σ]st are given for products of general engineering and hoist transport systems that are intended for a long lifetime. Higher values are assumed for easy loading conditions.

≥ 40 HRC

60–100 20–30 –

100–140 30–60 5 –15

Through the projection calculation of the spline connections the length of the cusps lc is determined after the choice of the section dimensions according to the standard. If lc > 1.5d is obtained, the dimensions and heat treatment are changed or another kind of joint is assumed. The length of the hub is assumed to be lhu = lc + (4–6)mm or more, depending on the joint structure. Adjusted bearing and wearing calculations are worked out for straight-sided spline connections and load conditions; the design philosophy of the joint, the working surface grind, the required lifetime, etc., are taken into account. The component fits of the spline connections are regulated by standards. Mostly the fits of the straightsided splines according to Table 6.68 and involute ones according to Table 6.69 are used.

6.10.3 Pressure Coupling Load-Carrying Capacity of Pressure Coupling Interference connections are widely used in practice for the transmission of torque, axial forces, and bending moments. Connections along the cylindrical surfaces are primarily spread. The nature of the joint is such that the shaft is connected to a bushing that has a hole diameter slightly smaller than that of the shaft. At the junction site the components strain elastically and a contact pressure p arises on the surface of the contact, leading to frictional forces on the joint surface that are

Table 6.68 Fits of the elements of straight-sided spline connections Centering along the surface

Joint

Gear

Surface fits Centering

Lateral

D

Fixed

Irreversible Reversible Irreversible Reversible Irreversible Reversible Irreversible Reversible

H7/ js6 H7/n6 H7/ f 7 H7/h7 H7/h7 H7/ js6 H7/ f 7 H7/g7

F8/ f 7 F8/ js7 D9/d9 F8/ f 8 H9/h10 F10/ js7 H9/d10 H9/ f 9

Sliding d

Fixed Sliding

Part B 6.10

quence of resiliency under the action of the radial force and torque, or a mismatch of the rotation axes (because of the presence of clearances, and errors of production and assembly). Joint parameters are chosen from standard tables depending on the shaft diameter, and then the efficiency criterion calculation is carried out. To provide the required efficiency a checking analysis is carried out. Bearing and wear of the work surfaces are due to the bearing stresses σst acting on the surfaces. The short-cut (approximate) calculation is based on the limitation of the bearing stresses σst by the allowable values [σ]st , which are fixed on the basis of field experience with similar structures

[σ ]st (N/mm2 ) with hardness ≤ 350 HB

Design of Machine Elements

of gear or worm wheels, pulleys, chainwheels, and the inner race of bearings, etc. The efficiency conditions of the interference connection are the lack of relative displacement of the components under the action of the axial force Fa and the lack of relative component turning under the action of the torque T . The shafts rotate relative to the loads acting on them. This is why stresses change cyclically in some ranges at any contact point per revolution of the shaft. Stress cycling results in the effect of surface layer fatigue of the component material, in microslip of the mounting surfaces, and as a result, in wear, i. e., in so-called contact corrosion. The interference of the joint in this case is progressively decreased and there comes a point at which the hub turns relative to the shaft. To prevent contact corrosion, or to reduce its influence in interference connections, a definite traction reserve K should be included, which is assumed to be: For the wheels of the output shafts of reduction gears, on whose ends there is A joint sleeve: K =3 A chain wheel: K = 3.5 A belt drive sheave: K = 4

•

For the wheels of the countershafts of reduction gears: K = 4.5

Calculation of Pressure Coupling Loaded with a Torque and an Axial Force The purpose of the calculation is to match the interference fit. The basic data are as follows: required for transmission rotatory torque T (N m), axial force Fa (N), as well as d – the joint diameter (mm), d1 – the diameter of the central axial hole of the shaft (mm), d2 – the passage outer diameter of the bushing (of the wheel hub, the outer diameter of the rim, etc.) (mm), l – the mating length (mm), and materials of the connecting components, and the roughness parameters of the mating surfaces. Matching of the fit is carried out in the following order:

1. Average contact pressure (N/mm2 ) p = K F/(πdl f ) ,

where K is a traction safety factor; F = Fa2 + Ft2 is a relative total peripheral force (N), Ft = 2 × 103 T/d is a peripheral force (N), and f is a traction coefficient (friction).

455

Table 6.70 Recommended values of the traction coeffi-

cient f Material pair

f when mounting by Insertion Heating

Steel–iron Steel–steel Steel–bronze (brass) Iron–bronze (brass)

0.08 0.08 0.05 0.05

0.14 0.14 0.07 0.07

2. Component deformation (μm) δ = 103 pd(C1 /E 1 + C2 /E 2 ) , where C1 , C2 are stiffness factors C1 = [1 + (d1 /d)2 ]/[1 − (d1 /d)2 ] − ν1 , C2 = [1 + (d/d2 )2 ]/[1 − (d/d2 )2 ] + ν2 , where E is a coefficient of elasticity (N/mm2 ), being for steel 2.1 × 105 , iron 0.9 × 105 , tin bronze 0.8 × 105 , for tinless bronze, and for brass 105 ; ν is Poisson’s ratio: being for steel 0.3, for iron 0.25, and for bronze and brass 0.35. 3. Allowance for pressing down of microasperities (μm) u = 5.5(Ra1 + Ra2 ) , where Ra1 and Ra2 are the arithmetic-mean deviations of the surface profile of the shaft and the hole, respectively. Generally, Ra1 = 0.8 μm and Ra2 = 1.6 μm. 4. Allowance for thermal deformation (μm) By fit matching in mating of the components, which heat in operation to relatively high temperatures, thermal deformations that loosen the interference are calculated according to the formula δt = 103 d[(t2 − 20 ◦ C)α2 − (t1 − 20 ◦ C)α1 ] . Here t1 and t2 are the average volumetric temperatures of the shaft and the bushing, respectively; α1 , α2 are the linear expansion coefficients (1/◦ C) of the shaft and the bushing, respectively, being for steel α = 12 × 10−6 , for iron α = 10 × 10−6 , and for bronze and brass α = 19 × 10−6 . 5. Minimum interference (μm), required for load transmission, [N]min = δ + u + δt . 6. Maximum interference (μm), permissible with the component strength (of the hub, ring, etc.), [N]max = [δ]max + u .

Part B 6.10

•

6.10 Shaft–Hub Connections

Design of Machine Elements

6.10 Shaft–Hub Connections

457

Table 6.73 Stochastic minimum Nmin and maximum Nmax interferences of fits Diameter d (mm)

Over 30 up to 40 Over 40 up to 50 Over 50 up to 65 Over 65 up to 80 Over 80 up to 100 Over 100 up to 120 Over 120 up to 140 Over 140 up to 160

Over 180 up to 200 Over 200 up to 225 Over 225 up to 250 Over 250 up to 280 Over 280 up to 315

H7 p6 7 36 7 36 9 44 9 44 10 51 10 51 12 59 12 59 12 59 14 69 14 69 14 69 15 77 15 77

H7 r6 15 44 15 44 18 53 20 55 24 65 27 68 32 79 34 81 37 84 41 95 44 98 47 101 53 115 57 119

from Fig. 6.153 that covering increases the displacement force by a factor of 2–4.5. The load-carrying capacity of joints assembled by means of shaft cooling exceeds the strength of the connection assembled by means of insertion in by a factor of 2 for joints without coating and by factors of 1.2–1.3 for joints with soft coatings (Cd, Cu, and Zn). For joints with hard coatings (Ni and Cr) the load-carrying capacity is lower when assembled with cooling than when assembled with insertion. The traction increase by electroplated coatings is caused by interdiffusion in the case of high pressure of the coating and parent metal, which is accompanied by the formation of the intermediate structures. This explains the close approximation to one value of the traction coefficient f (the right ordinate in Fig. 6.153), which actually represents the shearing resistance of the intermediate metal layer.

H7 t6 29 58 35 64 43 78 52 87 64 105 77 118 91 138 103 150 115 162 130 184 144 198 160 214 177 239 199 261

H8 u8 32 88 42 98 55 119 70 134 86 162 106 182 126 214 155 243 166 254 185 287 207 309 233 335 258 372 293 407

H7 u7 42 78 52 88 66 108 81 123 99 149 119 169 142 193 171 227 182 238 203 269 225 291 251 317 278 352 313 387

H8 x8 52 108 69 125 90 154 114 178 140 216 172 248 204 292 236 324 266 354 299 401 334 436 374 476 418 532 468 582

H8 z8 84 140 108 164 140 204 178 242 220 296 272 348 320 410 370 460 420 510 469 571 524 626 589 691 653 767 733 847

H8 za8 120 175 152 207 193 258 241 306 297 373 362 438 425 514 490 579 555 644 619 721 689 791 769 871 863 977 943 1057

Application of soft coatings and assembly with shaft cooling increase the load-carrying capacity of the joints by a factor of 3–4 in comparison with joints without coating assembled by means of insertion. Consequently, for a set external load there is the possibility of using fits with lower interferences and corresponding lower tension stresses in the female part (bushing) and compression in the male part (shaft). Moreover, electroplated coatings protect contact surfaces from corrosion and avoid welding. Calculation of Interference Connections Loaded with a Bending Moment In some cases, the interference joints, e.g., the connections of gear wheels with shafts, are subjected to loading by a bending moment. Considering the shaft to be absolutely hard, it can be imagined that the shaft rotates around the axis, which is

Part B 6.10

Over 160 up to 180

Nmin (μm) for the fits Nmax H8 H7 H7 s7 s6 s7 13 24 25 59 53 61 13 24 25 59 53 61 18 30 32 72 65 74 24 36 38 78 71 80 29 44 46 93 85 96 37 52 54 101 93 104 43 61 64 117 108 120 51 69 72 125 116 128 59 77 80 133 124 136 66 86 89 152 140 155 74 94 97 160 148 163 84 104 107 170 158 173 95 117 121 191 179 195 107 129 133 203 191 207

Interference values

Design of Machine Elements

6.10 Shaft–Hub Connections

459

Table 6.74 Basic characteristics of conic interference-fit rings D (mm)

L (mm)

l (mm)

Ft1 (kN)

Ft2 (kN)

T (N m)

Fa (kN)

12E7 14E7 15E7 16E7 18E7 20E7 22E7 24E7 25E7 28E7 30E7 32E7 35E7 36E7 38E7 40E8 42E8 45E8 48E8 50E8 55E8 56E8 60E8 63E8 65E8 70E8

15 f 7 18 f 7 19 f 7 20 f 7 22 f 7 25 f 7 26 f 7 28 f 7 30 f 7 32 f 7 35 f 7 36 f 7 40 f 7 42 f 7 44 f 7 45e8 48e8 52e8 55e8 57e8 62e8 64e8 68e8 71e8 73e8 79e8

4.5 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3 7.0 7.0 7.0 8.0 8.0 10.0 10.0 10.0 10.0 12.0 12.0 12.0 12.0 14.0

3.7 5.3 5.3 5.3 5.3 5.3 5.3 5.3 5.3 5.3 5.3 5.3 6.0 6.0 6.0 6.6 6.6 8.6 8.6 8.6 8.6 10.4 10.4 10.4 10.4 12.2

6.95 11.20 10.75 10.10 9.10 12.05 9.05 8.35 9.90 7.40 8.50 7.85 10.10 11.60 11.00 13.80 15.60 28.20 24.60 23.50 21.80 29.40 27.40 26.30 25.40 31.00

7.5 12.6 13.5 14.4 16.2 18.0 19.8 21.6 22.5 25.2 27.0 28.8 35.6 36.6 38.7 45.0 47.0 66.0 70.0 73.0 80.0 99.0 106.0 111.0 115.0 145.0

10 19.6 22.5 25.5 32.4 40 48 58 62 78 90 102 138 147 163 199 219 328 373 405 490 615 705 780 830 1120

1.67 2.80 3.00 3.19 3.60 4.00 4.40 4.80 5.00 5.60 6.0 6.4 7.9 8.2 8.6 9.95 10.4 14.6 15.6 16.2 17.8 22.0 23.5 24.8 25.6 32.0

where dm and l are, respectively, the mean diameter and the joint length (mm), f is a traction coefficient (friction) ( f ≈ 0.12), and α is a gradient angle of the cone generatrix to the shaft axis. For the shaft ends the taper 1 : 10 is the most commonly used, α = 2◦ 51 45 , tan α = 0.05. The torque T (N m) which the connection can transmit is T ≤ 0.5 × 10−3 Ft dm f r , where fr is a surface friction factor fr = f/(tan α + f ). The required pull force for transmission through the joint for a set torque T becomes Ft = 2 × 103 KT/(dm fr ) , where K = 1.3–1.5 is a traction safety factor. Along with these tightening joints, tapered connections are used in dead joints and rarely in dismantled structures, where the interference is formed without application of thread pieces, but, e.g. by, means of insertion with a standardized impact or insertion on the

rated axial displacement, or by means of heating of the female part (cooling of the male part). Recommended tapers for such connections are 1 : 50 to 1 : 30.

6.10.4 Frictional Connections with Conic Tightening Rings Frictional connections with conic tightening rings are used for the installation of components such as gear wheels, pulleys, chainwheels, and half-couplings on shafts. These connections transmit torques and axial forces due to the frictional forces on the contact surfaces of the shaft and the hub with conic rings installed in the annular gap between the shaft and the hub (Fig. 6.156). In Russia the rings are produced from spring steel 55 Si (EN), etc. (Appendix 6.A Table 6.95). By tightening the nut on the shaft (Fig. 6.156a) or the screw in the hub (Fig. 6.156b) the conic rings are elastically deformed and pull against one another. Then the outer rings are

Part B 6.10

d (mm)

Design of Machine Elements

467

6.11.7 The Nature and Causes of Failure of Rolling Bearings 1. Fatigue flaking of the work surfaces of the races and solids of revolution in the form of bubbles or flaking-off under the action of fluctuating contact stresses. Nonmetallic inclusions in the steel, deep grinding marks, and microasperities are the main sources of crack nucleation. Fatigue flaking is the main fracture mode of bearings with good lubrication and ingress protection of the abrasive particles. It is usually observed after a long operation time. 2. Bearing of the work surfaces of the rolling paths and solids of revolution (formation of dimples and hollows) as a consequence of local plastic strains under the action of vibrational, impact, or considerable dead loads. 3. Abrasion owing to poor protection of the bearing from penetration of abrasive particles (constructionsite engines, road and agricultural machines, looms). Application of perfect seal structures in bearing units decreases wear of the work-bearing surfaces. 4. Cage fracture due to the action of centrifugal forces and the influence of solids of revolution with different dimensions on the cage. This fracture mode is a principal cause of efficiency loss in high-speed bearings. 5. Fracture of the races and solids of revolution as a consequence of race warp and impact overloads (chipping of the ledges, splitting of the races, etc.). In the case of qualitative assembly and correct operation, component fracture of the bearings should not take place. Outward signs of abnormal operation are the following: loss of rotational accuracy, increased noise and vibration, increased rotation, and temperature resistance. The main efficiency criteria for rolling bearings are contact fatigue strength and static contact strength.

6.11.8 Static Load Rating of Bearings At initial point contact (ball bearings) touching of the bodies under load occurs along an elliptic area; at initial linear contact (roller bearings) it is along a rectangular area. The corresponding values of the contact stresses are determined from Hertz’s formulas for point and linear contact. The ratio of the curvature radii at the contact points is such that the contact stresses σh in the contact of the

Part B 6.11

The characters defining an accuracy rating (0, normal, 6X, 6, 5, 4, T , 2, Appendix 6.B), a group for radial clearance (0, 1, 2–9; for radial-thrust ball bearings the grade of preinterference is indicated by 1, 2, and 3), a row for the frictional moment (1, 2–9) and a bearing class (A, B, and C) are marked to the left of the main designation. The accuracy ratings are listed in ascending order of accuracy. In general engineering bearings of the accuracy ratings normal and 6 are used. In products with high accuracy or running with high rotational frequency (spindle units of high-speed machines, high-speed motors, etc.) bearings of classes 5 and 4 are applied. Bearings of accuracy rating 2 are used in gyroscopic devices. The characters are located in recitation order rightto-left from the main designation of the bearing and are attached to it by a dash, e.g., A125-3000205, where 3000205 is the main designation, 5 is an accuracy rating, 2 is the group for radial clearance, 1 is a row of frictional moment; and A is the bearing class. For all bearings except tapered ones the character “0” is used to designate the normal accuracy rating. For tapered bearings the character “0” is used to designate accuracy rating 0, the character “N” is for the normal accuracy rating, and the character “X” is for accuracy rating 6X. In our example the bearing 7208 has accuracy rating 0. Depending on the presence of extra requirements for vibration level, deviations of shape and rolling surface position, frictional moment, etc., there are three bearing classes: A, increased regulated standards; B, regulated standards; and C, without extra requirements. Possible characters to the right of the main designation are the following: A – increased dynamic load rating; E – the cage is made of plastic materials (polymers, textolite); P – the components of the bearing are made from heat-resistant steels; C1–C28 – closed class for filling with a lubricant; T (T1–T5) – temperature requirements of tempering of the bearing components, etc. An example of the reference designation of a bearing with extra characters is A75-3180206ET2C2, i.e., a ball radial single-row bearing (0) with a double-sided seal (18) and a hole diameter of 30 mm (06), a diameter series 2, a width series 3, an accuracy rating 5, a radial clearance according to group 7, in the case of a requirement failure in the frictional moment, class A, with a cage made from plastic material (E), and the temperature of the regulating race tempering is 250 ◦ C (T2), filled with a lubricant by the manufacturer (C2).

6.11 Rolling Bearings

468

Part B

Applications in Mechanical Engineering

solid of revolution with the inner race are higher than in the contact zone of the solid of revolution with the outer race for all bearing types (except spherical ones). Thus, e.g., contact stresses σH (N/mm2 ) for ball radial single-row bearings in contact with the inner race are



  2 ≈ 1035 3 5F / z D2 , (6.22) σH ≈ 1035 3 F0 /Dw r w while for the outer race



  2 ≈ 827 3 5F / z D2 , σH ≈ 827 3 F0 /Dw r w

Part B 6.11

where F0 is a force acting on the most heavily loaded solid of revolution by the loading of the bearing with the radial force Fr (N), z is the number of solids of revolution, and Dw is the diameter of the solid of revolution (mm). The basic static load rating of the bearing is a static load in N, which corresponds to the rated contact stress in the center of the most heavily stressed contact zone of the solid of revolution and the rolling path of the bearing. According to the relevant ISO standard the following are assumed as design contact stresses σH for bearings: Radial and radial-thrust ball (except self-installed): Radial ball self-installed: Radial and radial-thrust roller: Thrust and thrust-radial ball: Thrust and thrust-radial roller:

σH = 4200 N/mm2 σH = 4600 N/mm2 σH = 4000 N/mm2 σH = 4200 N/mm2 σH = 4000 N/mm2

The total residual strain in the solid of revolution and the rolling path of the race arising by these contact stresses is approximately equal to 0.0001 of the diameter of the solid of revolution. The static load rating for radial and radial-thrust bearings corresponds to the radial force Fr causing purely radial displacement of the races relative to each other. For thrust and thrust-radial bearings this corresponds to the central axial force Fa . The basic static load rating is designated in the following way: radial – C0r , axial – C0a . With static loading, damage of the bearings appears in the form of the working surface plastic strain. In strength analysis the acting contact stress σH should be limited to σH ≤ [σ]H , where [σ]H is the allowable contact stress.

The derivation of this formula is shown for the calculation of the basic static load rating using the example of a ball single-row radial bearing. The strength condition for the most loaded point on the inner race of the bearing is, according to (6.22),

  2 ≤ [σ ] . σH = 1035 3 5Fr / z Dw H From this the allowable radial load is     1 [σ ]H 3 2 [F]r = z Dw . 5 1035 Designating the expression in square brackets on the right-hand side by f 0 and writing [F]r = C0r we obtain the formula to calculate the basic static load rating C0r (N), for radial and radial-thrust ball bearings: 2 C0r = f 0 iz Dw cos α ,

where f 0 is a coefficient depending on the bearing class, material, and geometry of the bearing components, their manufacturing accuracy, and the assumed value of the design contact stress (Table 6.78); i is the number of rows of the solids of revolution, z is the number of solids of revolution in a row, Dw is the ball diameter (mm), and α is the nominal contact angle (degrees). Design dependencies for the calculation of the static load rating for other bearing classes are given in the standard [6.111]. The values of the basic static load rating C0r (C0a ) for all bearings are calculated in advance and given in the manufacturer’s catalog.

6.11.9 Lifetime Testing of Rolling Bearings The lifetime is the running time of the bearing until the appearance of signs of material fatigue on the solids of revolution or the races. The bearing lifetime is designated by L (life) and is expressed in terms of the number of millions of revolutions of one race relative to another or in terms of working hours. The main design dependencies for matching of bearings are obtained on the basis of a pilot study of specimen and full-scale bearings. Figure 6.165 shows a contact stress-cycle diagram of specimens manufactured according to the standards of the bearing industry technology. The ordinate axis shows contact stresses σH , which were determined according to Hertz’s theory; the abscissa shows the lifetime, expressed by the number N of stress change cycles to fracture. Stress-cycle diagrams are plotted for the different probability levels Q of fracture: 0.01, 0.10, 0.30,

Design of Machine Elements

6.11 Rolling Bearings

469

Table 6.78 Values of the coefficient f 0 for ball bearings. The values f 0 are determined from Hertz’s formulas obtained from the condition of initial point contact with a modulus of elasticity of 2.07 × 105 N/mm2 and Poisson’s ratio of 0.3. The values of f 0 are calculated for the case of common external force distribution between the solids of revolution, when the load on the most loaded ball in ball radial and radial-thrust bearings is equal to 5Fr /(z cos α), and in ball thrust and thrust-radial bearings it is Fa /(z sin α). f 0 for the intermediate values Dw cos α/Dpw is calculated by linear interpolation f0 for ball bearings Radial and radial-thrust

Self-installed

Thrust and thrust-radial

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25 0.26 0.27 0.28 0.29 0.30 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 0.39 0.40

14.7 14.9 15.1 15.3 15.5 15.7 15.9 16.1 16.3 16.5 16.4 16.1 15.9 15.6 15.4 15.2 14.9 14.7 14.4 14.2 14.0 13.7 13.5 13.2 13.0 12.8 12.5 12.3 12.1 11.8 11.6 11.4 11.2 10.9 10.7 10.5 10.3 10.0 9.8 9.6 9.4

1.9 2.0 2.0 2.1 2.1 2.1 2.2 2.2 2.3 2.3 2.4 2.4 2.4 2.5 2.5 2.6 2.6 2.7 2.7 2.8 2.8 2.8 2.9 2.9 3.0 3.0 3.1 3.1 3.2 3.2 3.3 3.3 3.4 3.4 3.5 3.5 3.6 3.6 3.7 3.8 3.8

61.6 60.8 59.9 59.1 58.3 57.5 56.7 55.9 55.1 54.3 53.5 52.7 51.9 51.2 50.4 49.6 48.8 48.0 47.3 46.5 45.7 45.0 44.2 43.5 42.7 41.9 41.2 40.5 39.7 39.0 38.2 37.5 36.8 36.0 35.3 34.6 – – – – –

Part B 6.11

Dw cos α/Dpw

Design of Machine Elements

subjected to excessive changes of temperature and rotational frequency. The basic dynamic design load rating is designated in the following way: radial – Cr , axial – Ca . The values Cr (Ca ) for each bearing are calculated in advance and indicated in the manufacturer’s catalog. The development of the formula for calculation of the basic dynamic radial load rating is shown by using the example of a ball radial single-row bearing. The calculation is based on the use of experimental stress-cycle diagrams (Fig. 6.165) described by a dependence q

σHi Ni = const. ,

(6.25)

where q = 9 for ball bearings, and const. is a constant that corresponds to the experimental environment. With bearing loading with a radial force Fr and inner race rotation and a nonrotating outer race, the number of loading cycles for L million revolutions is where z is the number of solids of revolution, K ef < 1 is an equivalence coefficient taking into account the uneven load distribution between the solids of revolution, and K 1 = 0.5(Dpw + Dw cos α)/Dpw . Here Dpw is the diameter of the circle going through the centers of the solids of revolution, Dw is the ball diameter, and α is the contact angle. In accordance with (6.25) we have

   2 9 0.5 × 106 zK K L = const. 1035 3 5Fr / z Dw 1 ef The left- and the right-hand sides of this expression are raised to a power of one-third and, after transformation, we have   const1/3 1/3 Fr L = 1/3  10353 × 5 0.5 × 106 K 1 K ef 2 × z 2/3 Dw .

The expression in square brackets is designated f c . In accordance with (6.24) for P = Fr we have Fr L 1/3 = Cr . After appropriate changes and some corrections we obtain the formula for the calculation of Cr (N), the basic dynamic radial design load rating for ball radial and radial-thrust bearings 1.8 , Cr = bm f c (i cos α)0.7 z 2/3 Dw by Dw ≤ 25.4 mm ; 1.4 Cr = 3.647bm f c (i cos α)0.7 z 2/3 Dw , by Dw > 25.4 mm ,

471

where bm is a coefficient characterizing the behavior of steel, taking into account its method of manufacture and depending on the bearing class and structure; f c is a coefficient depending on the geometry of the bearing components and their production accuracy; i is the number of rows of solids of revolution; and z is the number of solids of revolution in a row. Design dependencies for the calculation of the dynamic load rating are given in standards for other bearing classes. By definition, the basic dynamic load rating represents a very large load corresponding to the theoretical area of the stress-cycle diagram, that is not achievable in practice.

6.11.11 Design Lifetime of Bearings The basic design lifetime L 10 in millions of revolutions is determined by 90% safety (as indicated by the figure 10 in the designation; i.e., 10 = 100 − 90)  k C , (6.26) L 10 = P where C is the base dynamic load rating of the bearing (radial Cr or axial Ca ) (N), P is the equivalent dynamic load (radial Pr or axial Pa ) (N), and k is an exponent that is chosen in accordance to the outcomes of experiments to be k = 3 for ball bearings and k = 10/3 for the roller bearings. The formula for the lifetime calculation is correct if Pr (or Pa ), and for varying loads Pr max (or Pa max ), does not exceed 0.5Cr (or 0.5Ca ). The applicability of this formula is also limited to rotational frequencies from 10 min−1 to the limiting values stated in the manufacturer’s catalog. From the given formula the basic design lifetime L 10 for bearings that are produced from standard bearing steels according to standard technology and exploited under common conditions is calculated. For different material properties or operating conditions from the standard ones, as well as for increased safety requirements and to take into account special bearing properties, the corrected design lifetime L sa is determined in millions of revolutions as L sa = a1 a2 a3 L 10 ,

(6.27)

where a1 is a coefficient correcting the lifetime depending on the safety Pt (Table 6.41), a2 is a coefficient adjusting the lifetime depending on the special bearing properties, and a3 is a coefficient correcting the lifetime depending on the operating conditions of the bearing.

Part B 6.11

N = 0.5 × 106 zK 1 K ef L ,

6.11 Rolling Bearings

472

Part B

Applications in Mechanical Engineering

The corrected design lifetime of the bearing in operating hours is L sah = 106 L sa /(60n) , (min−1 ).

where n is the rotational frequency of the race Sometimes it is more convenient to express the bearing lifetime of vehicles (the bearings of wheel hubs and half-axes) in units of distance. The corrected design lifetime in millions of kilometers is L sas = (π D/1000)L sa ,

Part B 6.11

where D is the wheel diameter in meters. The rolling bearing calculation for an increased probability of nonfailure during operation is carried out for important units by using a safety factor of 91– 99%. Instead of the index s, the value of the difference (100 − Pt ) is written in the lifetime designation, where Pt is the safety used for the lifetime determination. Thus, for 90% safety one writes L 10a (L 10ah ) and for 97% safety one writes L 3a (L 3ah ). The bearing can obtain special properties, resulting in a different lifetime, following the application of special materials (e.g., steels with a particularly low content of nonmetallic inclusions) or special production processes, or are of a special structure. The values of the coefficient a2 are fixed by the bearing manufacturer. Working conditions, which are additionally taken into account with the help of the coefficient a3 – it is a conformity of the lubricant viscosity with the required value (taking into account rotational frequencies and temperatures), the presence of foreign particles in the lubricant, as well as conditions causing material property change of the bearing components (e.g., high temperature causes hardness to decrease). Calculation of the basic lifetime is built upon the fact that the thickness of the oil film in the contact zones rolling element race is equal to or a little more than the total roughness of the contact surfaces; Therefore a3 = 1. The bearing producer provides recommendations concerning the values of the coefficient a3 for other conditions. For the choice of the bearing dimension and the calculation of the corrected lifetime for specific operating conditions it is supposed that the bearings correspond to the required accuracy grade and that the required strength and rigidity of the shafts and cases are provided. Application of the values a2 > 1 and a3 > 1 in the formula of the corrected lifetime will be valid.

6.11.12 The Choice of Bearing Classes and Their Installation Diagrams Each bearing class has particular features due to its structure. For the choice of bearing class a few different comparative factors must be appreciated. Thus, it is impossible to formulate a general law for bearing choice. The most significant factors are given below:

• • • • • •

Value and direction of the load (radial, axial, combined) Load conditions (constant, varying, vibrational, impact) Rotational frequency of the bearing race Required lifetime (in hours or millions of revolutions) Environmental conditions (temperature, humidity, dust level, acidity, etc.) Particular requirements for the bearing, which are made with a unit structure (the necessity for bearing self-installation into the support for warp compensation of the shaft or the case; the ability to allow shaft displacement in the axial direction; bearing assembly directly onto the shaft, on the clamping or clamping-tightening sleeve; the necessity to adjust the radial and axial clearance of the bearing, increase of support rigidity and accuracy of the shaft rotation, decrease of the frictional moment, noisiness; desired overall dimensions of the unit, requirements for safety; price of the bearing and of the entire unit)

With the choice of bearing type the common practice in machine design and operation of the fixed machine class can be headed for. Thus, for example, ball radial bearings are mostly used for shaft supports of spurs and helical wheels, reduction gears, and gearboxes. Tapered roller bearings are applied as shaft supports of spur gears where the dimensions of the ball bearings are excessively large. Bevel and worm wheels must be precisely and rigidly fixed in the axial direction. Ball radial bearings are characterized by low axial rigidity. Thus, in power trains, tapered roller bearings are used for shaft supports of bevel and worm wheels. For the shaft supports of the bevel pinion tapered roller bearings are applied from the same considerations. For high rotational frequency of the gear shaft (n > 1500 min−1 ) ball radial-thrust bearings are used. Worm supports in power worm gears are loaded with considerable axial forces, which is why tapered roller bearings are mainly applied as supports for worm

Design of Machine Elements

6.11 Rolling Bearings

475

Table 6.79 Formulas for the calculation of the coefficients X, Y , and e for ball radial and radial-thrust bearings. For

single-row bearings with Fa /Fr ≤ e it is assumed that X = 1 and Y = 0. In the formulas given in the table C0r is a static load rating of the bearing; for the double-row bearings C0r is a static load rating of a row (half of the static load rating of the double-row bearing) Bearing class

α (◦ )

Axial loading coefficient e



f 0 Fa C0r

0.23

Single-row bearing

Double-row bearing

Fa /Fr > e X

Y

Fa /Fr ≤ e X

Y

Fa /Fr > e X

Y

0.56

0.44/e

1.0

0

0.56

0.44/e

0.45

0.55/e

1.0

0.62/e

0.74

0.88/e

0.44

0.56/e

1.0

0.63/e

0.72

0.91/e

Radial

0

0.28

Radialthrust

12

0.41

15

0.46

18 25 26 36 40

0.57 0.68

0.43 0.41

1.0 0.87

1.0 1.0

1.09 0.92

0.70 0.67

1.63 1.41

0.95 1.14

0.37 0.35

0.66 0.57

1.0 1.0

0.66 0.55

0.60 0.57

1.07 0.93

 

f 0 Fa C0r f 0 Fa C0r

0.17 0.11

Determination of Axial Reactions By the installation of a shaft on two nonadjustable radial ball or radial-thrust bearings the axial force Fa load-

ing the bearing is equal to the external axial force FA acting on the shaft. The force FA supports the bearing, which limits the axial displacement of the shaft under the action of this force. By determination of the axial forces loading adjustable radial-thrust bearings the axial forces that arise under the action of the radial load Fr as a consequence of the tilt of the contact area with respect to the hole axis of the bearing should be taken into account. The values of these forces depend on the bearing class, contact angle, and the radial forces, as well as on how the bearings are adjusted. If the bearings are assembled with a large clearance, only one or two balls or rollers take the whole load. The axial load component equals Fr tan α for transmission through only one solid of revolution. The working conditions of the bearings are unfavorable with large clearances, so such clearances are not permissible. Bearings are usually adjusted in such a way that the axial clearance is about zero under fixed temperature conditions. In this case, about half of the solids of revolution are under the action of the radial load Fr , and the total axial component for all the loaded

Table 6.80 Values of the coefficients X, Y , and e for roller radial-thrust bearings (α = 0◦ ) Bearing classes

X Fa /Fr ≤ e

Y

X Fa /Fr > e

Y

e

Single-row Double-row

1.0 1.0

0 0.45 cot α

0.4 0.67

0.4 cot α 0.67 cot α

1.5 tan α 1.5 tan α

Part B 6.11

the solids of revolution and the cage, as well as friction in the lubricant, can negatively influence rolling conditions in the bearing and cause creep of the balls and rollers along the rolling path. As a general recommendation it is assumed that the loads that affect the roller bearings must be 0.02C and those on the ball bearings must be 0.01C, where C is the dynamic load rating. The weight of the components supported by the bearing with the external forces often exceeds the required minimum load. Otherwise the bearing must be loaded by an extra radial or axial force. It is easier to provide such a force, e.g., in systems with radial and radial-thrust ball bearings, and tapered roller bearings, by means of prior axial loading made by adjustment of the relative position of the inner and outer races with spacing racers, pads, or springs. Extra radial force can be applied in the same way, e.g., by means of increased belt tension.

Design of Machine Elements

6.11.14 Choice and Calculation of Rolling Bearings

Calculation of the Static Load Rating of Bearings A static load rating calculation checks whether the equivalent static load P0r (P0a ) on the bearing exceeds the static load rating C0r (C0a ) given in the manufacturer’s catalog

P0r ≤ C0r

or

P0a ≤ C0a .

The equivalent static radial (or axial P0a ) load P0r is a static radial (or axial) load that causes the same contact stress in the most heavily loaded contact zone as in the conditions of actual loading. The static equivalent radial load for ball radial and radial-thrust, and roller radial-thrust (α = 0◦ ) bearings is equal to the greater of the two values determined from the expressions P0r = X 0 Fr + Y0 Fa ; P0r = Fr , where Fr and Fa are, respectively, the radial and axial loads on the bearing (N), and X 0 and Y0 are, respectively, the coefficients of the static radial and static axial loads (Table 6.81). For roller radial bearings α = 0◦ , which supports only a radial load, P0r = Fr . The static equivalent axial load for ball and roller thrust-radial bearings (α = 90◦ ) is determined from P0a = 2.3Fr tan α + Fa . For ball and roller thrust bearings (α = 90◦ ) one has P0a = Fa . For the calculation of the static equivalent radial load for two identical single-row radial ball, radial-thrust ball, and roller bearings installed together on the same shaft positioned with the wide or narrow faces towards one other, making a mutual bearing unit, the values X 0 and Y0 for double-row bearings are used, and the values Fr and Fa are assumed to form a combined load acting on the whole set. For the choice and calculation of the bearings it should be borne in mind that the allowable static equivalent load P0 can be lower than, equal to, or higher than the basic static load rating. The value of this load depends on the requirements of run smoothness (e.g., of

Table 6.81 Values of the coefficients X 0 and Y0 . The values Y0 for the intermediate contact angles are obtained by means of linear interpolation Bearing class Ball radial Ball radial-thrust angle α (◦ )

with

contact

Ball and roller self-installed, α = 0 Roller radial-thrust tapered

12 15 20 25 30 35 40 45

477

Single-row bearings X0 Y0 0.6 0.5 0.5 0.47 0.46 0.42 0.38 0.33 0.29 0.26 0.22 0.5 0.22 cot α 0.5 0.22 cot α

Double-row bearings X0 Y0 0.6 0.5 1.0 0.94 0.92 0.84 0.76 0.66 0.58 0.52 0.44 1.0 0.44 cot α 1.0 0.44 cot α

Part B 6.11

Let us assume that the type and configuration of the bearing installation have been chosen previously. The dimensions of the bearing selected for the application can be chosen on the basis of estimation of its loading rate in accordance with the corresponding acting loads, rotational frequency, required lifetime, and safety. The values of the dynamic and static load ratings are given in the manufacturer’s catalog. Calculations on the static and/or dynamic load ratings are now to be performed. The static load rating is not only used to calculate the parameters for nonrotating bearings or those rotating with low rotational frequencies (n < 10 min−1 ), or those performing slow oscillatory rotations, but also for bearings rotating with frequency n ≥ 10 min−1 and those subjected to the action of short-term impact loads or substantial overloads. The static load rating of bearings that run with low rotational frequencies and are designed for a short lifetime are also checked in this way. Calculations of the dynamic load rating (specified lifetime calculation) are performed for the entire load range. Testing is additionally carried out under the assumption of the application of the highest loads.

6.11 Rolling Bearings

478

Part B

Applications in Mechanical Engineering

Table 6.82 Values of the coefficients X and Y for ball thrust-radial bearings. The values X, Y , and e for the contact

angles α not mentioned in the table are determined from the given formulas. The ratio Fa /Fr ≤ e is not used for single bearings. With Fa /Fr > e it is assumed that Y = 1 α (◦ )

45 50 55 60 65 70 75 80 85 α = 90◦

For single bearings with Fa /Fr > e X>

For double bearings with Fa /Fr ≤ e X Y

Fa /Fr > e X

0.66 0.73 0.81 0.92 1.06 1.28 1.66 2.43 4.80 1.25 tan α × (1 − 2 sin α/3)

1.18 1.37 1.60 1.90 2.30 2.90 3.89 5.86 11.75 20 tan α/13 × (1 − sin α/3)

0.66 0.73 0.81 0.92 1.06 1.28 1.66 2.43 4.80 1.25 tan α × (1 − 2 sin α/3)

Part B 6.11

the machines), noise level (for electric motors), constancy of the friction moment (for measuring apparatus and test equipment), or the value of the initial friction under load (for cranes), as well as on the actual geometry of the contact surfaces. The higher the listed requirements, the lower the value of the allowable static equivalent load. If a high run smoothness is not needed, a short-term increase P0r (P0a ) up to 2C0r (2C0a ) is possible. With increased requirements of run smoothness, noise level, and constancy of the friction moment it is recommended that the allowable static equivalent load P0r (P0a ) be reduced to C0r /S0 (C0a /S0 ). The safety factor S0 = 1.5 for thrust bearings of crane hooks and brackets, S0 = 2 for precise instrumental equipment, and S0 = 4 for important heavily loaded supports and turntables. Specified Lifetime Calculation of Bearings The basic data for this calculation are: Fr1 and Fr2 , the radial loads (radial reaction) of every support of the double-seat shaft (N); FA , the external axial force acting on the shaft (N); n, the rotational frequency of the race (as a rule the rotational frequency of the shaft) (min−1 ); d the diameter of the mounting shaft surface, which is taken from the layout diagram (mm); L sa and L sah , the required lifetime during which the probability of bearing operation failure is less than the appropriate probability, in millions of revolutions or hours, respectively; and the loading and operating conditions of the bearing unit (possible overload, working temperature, etc.). Working conditions of the bearings are rather varied and can differ in terms of short-term overloads, work-

e

0.59 0.57 0.56 0.55 0.54 0.53 0.52 0.52 0.51 10/13 × (1 − sin α/3)

1.25 1.49 1.79 2.17 2.68 3.43 4.67 7.09 14.28 1.25 tan α

ing temperature, rotation of the inner or outer race, etc. The influence of these factors on the bearing efficiency is taken into account by means of the insertion of the equivalent dynamic load into the calculation. As an equivalent dynamic radial (or axial Pa ) load Pr one assumes a constant value that results in the same lifetime under the actual loading conditions. The equivalent dynamic load is:

•

Radial, for ball radial and ball or roller radial-thrust bearings Pr = (VX Fr + YFa )K dy K t

•

Radial, for the roller radial bearings Pr = Fr VK dy K t

•

(6.30)

Axial, for ball and roller thrust bearings Pa = Fa K dy K t

•

(6.29)

(6.31)

Axial, for ball and roller thrust-radial bearings Pa = (X Fr + YFa )K dy K t

(6.32)

Here Fr and Fa are radial and axial loads on the bearing (N), X and Y are coefficients of the radial and axial dynamic loads, V is a coefficient of rotation (V = 1 for rotation of the inner race relative to the vector direction of the radial load, or V = 1.2 for rotation of the outer race), K dy is a dynamic coefficient (Table 6.85); K t is a temperature coefficient, its values are assumed depending on the operating temperature toper of the bearing: For operation under increased temperatures

Design of Machine Elements

Table 6.83 Values of the coefficient K t toper (◦ C)

Kt

≤ 100 125 150 175 200 225 250

1.0 1.05 1.10 1.15 1.25 1.35 1.4

bearings with a special stabilizing heat treatment or produced from heat-resistant steels are applied. The quality of the operation of the bearing under increased temperatures also depends on whether the lubricant used retains

6.11 Rolling Bearings

479

its properties, and on whether the materials of the seal and the retainer are chosen correctly. The values X and Y depend on the class and structural features of the bearing, as well as on the ratio of the axial and radial loads. The limit value of the ratio Fa /Fr is a coefficient e of the axial loading. For ball bearings with contact angle α < 18◦ the values of e are determined from the formulas given in Table 6.79 depending on the ratio f 0 Fa /C0r . The values of the coefficient f 0 depending on the geometry of the bearing components and on the stress levels used in the calculation of the basic static radial load rating are given in Table 6.78 for ball radial and radial-thrust bearings. The values of the coefficients X, Y , and e are assumed according to the data given in Table 6.79 for the

Table 6.84 Values of the coefficients X and Y for roller thrust-radial bearings (α = 90◦ ). The ratio Fa /Fr ≤ e is not used

for the single bearings

Single Double

Fa /Fr ≤ e X

Y

Fa /Fr > e X

Y

– 1.5 tan α

– 0.67

tan α tan α

1.0 1.0

e 1.5 tan α 1.5 tan α

Table 6.85 Recommended values of the dynamics factor K dy

Load nature

K dy

Application field

Quiet load without impulses

1.0

Light impulses, short-time overloads up to 120% of the nominal load

1.0–1.2

Moderate impulses, vibrational load, short-time overloads up to 150% of the nominal load

1.3–1.5

Short-time overloads up to 180% of the nominal load

1.5–1.8

Loads with substantial impulses and vibrations; short-time overloads up to 200% of the nominal load Load with strong impacts, short-time overloads up to 300% of the nominal load

1.8–2.5

Low-power kinematic reduction gears and drives. Mechanisms of hand cranes, units. Power hoists, hand winches. Operating gears Precise gearings. Cutting machines (except planing, slotting, and grinding machines). Gyroscopes. Lifting mechanisms of cranes. Telphers and monorail carriers. Winches with a mechanical drive. Electric motors with low and average power. Light fans and blowers Gearings. Reduction gears of all types. Travel mechanisms of crane trolleys and swing-out mechanisms of cranes. Bushes of rail mobile trains. Boom changing mechanisms of cranes. Spindles of grinding machines. Electric spindles Centrifuges and separators. Boxes and propulsion engines of electric locomotives. Mechanisms and running wheels of cranes and road machines. Planers and slotting machines. Powerful electric machines Gearings. Breaking machines and impact machines. Crank mechanisms. Rollers of rolling mills. Powerful fans

2.5–3.0

Heavy forging machines. Log frames. Working roller conveyors of heavy section mills, blooming and slab mills. Refrigerating equipment

Part B 6.11

Bearing classes

Design of Machine Elements

3.

4.

6. 7.

where C is a basic dynamic load rating of the bearing (radial Cr or axial Ca ) (N), P is an equivalent dynamic load (radial Pr or axial Pa , and under varying loading conditions PEr or PEa ) (N), k is

an exponent that takes on the value k = 3 for ball bearings and k = 10/3 for roller bearings, n is the rotational frequency of the race (min−1 ), a1 is the coefficient adjusting the lifetime depending on the required safety (Table 6.41), and a23 is a coefficient adjusting the lifetime depending on special properties of the bearing, which it obtains, e.g., as a consequence of the application of special materials or special production processes or special structure, as well as its working conditions (conformity of the lubricant characteristics with the required ones, the presence of the foreign particles causing behavioral changes of the material). The basic design lifetime is confirmed based on the test results of the bearings on special machines and in certain conditions characterized by the presence of a hydrodynamic oil film between the contact surfaces of the races and the solids of revolution and by the absence of increased warp of the bearing races. Under real operating conditions deviations from these conditions are possible, which are approximately estimated by using the coefficient a23 (Table 6.40). With the choice of the coefficient a23 the following use conditions of the bearing are distinguished: a) Common (material of usual fusion, presence of the race warps, absence of a safe hydrodynamic oil film, and presence of foreign particles) b) The presence of the elastic hydrodynamic oil film in the contact between the races and the solids of revolution, the absence of increased warps in the unit; standard production steel. c) The same as in item (b), but the races and the solids of revolution are manufactured from steel of electroslag or vacuum-arc refining. Design formulas for lifetime are correct for rotational frequencies over 10 min−1 to the limit frequencies according to the manufacturer’s catalog, and also if Pr (or Pa ), and with varying loads Pr max (or Pa max ) does not exceed 0.5Cr (or 0.5Ca ). In some cases, the allowable load Pr (or Pa ) is determined from the formula for the lifetime calculation. For bearings running with low rotational frequencies and those intended for a short lifetime the allowable load calculated in such a way can exceed the static load rating, which is inadmissible. Thus, adaptability of the formulas is restricted by the condition Pr ≤ C0r (or Pa ≤ C0a ). 8. The fitness of the planned dimension type of the bearing is estimated. The bearing is suitable if the design lifetime L sah is more than or equal to the

481

Part B 6.11

5.

– The value Cr for ball radial-thrust bearings with contact angle α ≥ 18◦ , and the values of the coefficients of the X radial, Y axial loads, the coefficient e of the axial loading from Table 6.79. – The values Cr , Y , and e for tapered roller single-row bearings; X = 0.4 is also assumed (Table 6.80). The axial forces Fa1 and Fa2 are determined from the equilibrium condition of the shaft and that of the minimum level of the axial loads on radial-thrust bearings. For ball radial bearings, as well as for ball radialthrust bearings with contact angle α < 18◦ the values X, Y , and e are determined according to Table 6.79, depending on the ratio f 0 Fa /C0r . The values of the coefficient f 0 are given in Table 6.78 depending on the ratio Dw cos α/Dpw , where Dw is the ball diameter, α is the contact angle (for radial bearings α = 0◦ ), Dpw is the circle diameter of the center ball position: Dpw = (d + D)/2. In the absence of tabulated values the ball diameter can be calculated according to the height of the effective cross-section H = (D − d)/2: – For bearings from series 200, 300, and 400 for d ≤ 40 mm for the especially easy series Dw = 0.6H. – For bearings from series 200, 300, and 400 for d > 40 mm Dw = 0.635H. – For compact and high-speed bearings Dw = 0.55H. – For bearings of increased load rating Dw = 0.64H. The ratio Fa /Fr is compared with the coefficient e, and the values of the coefficients X and Y are finally assumed: for Fa /Fr ≤ e it is assumed that X = 1 and Y = 0, for Fa /Fr > e for ball radial and radialthrust, and roller bearings the earlier (under points 2 and 4) values of the coefficients X and Y are finally assumed. The equivalent dynamic load is calculated ((6.29)– (6.32)). The design lifetime of the bearing, which has been corrected according to the safety level and use conditions, is determined (h)  k 6 10 C , L sah = a1 a23 P 60n

6.11 Rolling Bearings

482

Part B

Applications in Mechanical Engineering

Table 6.87 Recommended values of the design lives of machines and equipment

Part B 6.11

Machines, equipment, and their operating conditions

Lifetime (h)

Devices and equipment used occasionally (demonstration equipment, domestic appliances, devices, technical plants for medicine purposes) Mechanisms used during a short period of time (agricultural machines, lifting cranes in assembly workshops, light conveyors, construction machines and mechanisms, electric hand tools) Important mechanisms running with breaks (auxiliaries in power stations, conveyors for flowline production, lifts, not often used metal-working machines) Machines for one-shift operation with underload (fixed electric motors, reduction gears of general industrial function, rotor crushing plants) Machines running under full load during one shift (working machines, woodworkers, machines for general engineering, lifting cranes, separators, centrifuges, fans, conveyors, graphic arts equipment) Machines for round-the-clock use (gear-drives of roller mills, compressors, mine hoists, fixed electric machines, ship drive, pumps, textile equipment) Wind power plants, including the main shaft, gearboxes, generator drives Hydroelectric power plant, rotating furnaces, machines for high-speed cable winding, motors for ocean liners Continuously running machines with high load (equipment for paper-making plants, electric power plants, mine pumps, equipment of merchant ships, rotary furnaces)

300–3000

required one L sah ≥

L sah

3000–8000

8000–12 000 10 000–25 000 20 000–30 000

40 000–50 000 30 000–100 000 60 000–100 000 ≈ 100 000

6.11.15 Fits of Bearing Races .

In some cases, two identical radial or radial-thrust single-row bearings are installed together in one support. If the bearings are manufactured precisely and assembled so that they run as a unit, this pair is considered as one double-row bearing. For the lifetime determination from the formula of item (7) the basic dynamic radial load rating Cr sum of the set of two bearings is substituted for Cr , taking the value Cr sum = 1.625Cr for ball bearings and Cr sum = 1.714Cr for roller bearings. The basic static radial load rating of this set is equal to twice the nominal load rating of a single-row bearing C0r sum = 2C0r . For the determination of the equivalent load Pr the values of the coefficients X and Y are assumed as for double-row bearings: for ball bearings according to Table 6.79; for roller bearings according to Table 6.80. If the bearing unit comprises two self-contained bearings, which are substituted independently of each other, these premises are not applicable. The recommended values of the bearing lifetime of different machines and equipment are given in Table 6.87.

Bearing races can be classified into the following categories: local, circulating, and oscillatory. Local loading applies when when the resulting radial load acting on the bearing is always supported by the same limited section of the rolling path of the race and is transmitted to a corresponding part of the mounting surface of the shaft or the casing. Circulating loading applies when the resulting radial load acting on the bearing is supported and transmitted through the solids of revolution to the rolling path in a rotational process in sequence along its whole length and, therefore, along the whole mounting surface of the shaft or the case. Oscillatory loading applies when the fixed race of a bearing is subjected to the influence of the resulting radial load, which therefore performs periodic oscillatory motion. For circulating loading the connection of the races with the shaft or the case should be made through interference, which prevents turning and running of the mated component with the race and consequently beading of the mounting surfaces, contact corrosion, galling, decrease of rotational accuracy, and imbalance.

486

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Applications in Mechanical Engineering

Table 6.90 Recommended axial clearances (μm) for radial-thrust roller tapered single-row bearings. Installation configurations of the bearings: 1 – two in a support; 2 – one in every support

Over

To

Axial clearance by contact angle α (◦ ) 10–16 Configuration 1 Configuration 2 Min Max Min Max

– 30 50 80 120 180 260 360

30 50 80 120 180 260 360 400

20 40 50 80 120 160 200 250

Hole diameter of the bearing d (mm)

40 70 100 150 200 250 300 350

Part B 6.12

the product most often by means of axial displacement of the outer and inner races or (rarely) by means of radial deformation of the inner race by its fit onto the cylindrical or bevel surface of the shaft. A radial preload is usually used in roller bearings with cylindrical rollers, double-row radial-thrust ball bearings, and sometimes in radial ball bearings. For example, the preload is applied with the help of the interference fit of a sufficient size of one or two races of the bearing, where the initial radial inside clearance in the bearing decreases to zero. As a result in operation the clearance becomes negative, i. e., a preload appears. Bearings with a flare are the most convenient for applying a radial preload, as the force of the preload can be adjusted rather exactly by moving the bearing along its bevel mounting surface (on the shaft journal, clamping sleeve, or tightening bushing). The axial force of the preload required for singlerow radial-thrust ball bearings, tapered roller bearings, and radial ball bearings is made by means of the displacement of one of the races relative to the other along the axis by a distance corresponding to the required force of the preload. Two fundamentally different main adjusting methods are applied: individual and combined adjustment. With individual adjustment each bearing unit is regulated separately with the help of nuts, washers, spacing, deformable sleeves, etc.; changing and checking allow the nominal value of the preload force to be maintained with the lowest possible deviations. The following measuring procedures of the preload are used:

•

According to displacement, which is determined by means of the component measurement of the bearing unit, taking into account the thermal expansion

40 50 80 120 200 250 – –

• •

70 100 150 200 300 350 – –

25– 29 Configuration 1 Min Max – 20 30 40 50 80 – –

– 40 50 70 100 150 – –

of the components in operation and a certain force loss of the preload during some operation time, i. e., taking into account the resiliency in the system. According to the frictional moment with the use of the known ratio between the bearing load and frictional moment in it. This method is universal, requires little time, and can be easily automatized. According to the directly measured force, which can be made or changed by adjustment.

In practice, the first two methods are used more often due to their simplicity and availability. For combined adjustment all of the components of the bearing unit must be completely interchangeable, which in the end results in a tightening of their dimensional tolerances. The advantage of individual adjustment is that single unit components can be manufactured according to free tolerances (e.g., corresponding to the 9th–14th accuracy degree) and the preload is applied with a comparatively high degree of accuracy.

6.12.2 Principal Recommendations Concerning Design, Assembly, and Diagnostics of Bearing Units Design Recommendations The design of a product should be adapted for convenient assembly, and precise installation and dismantling of the bearing units. The mounting surfaces of shafts and cases should have hollow chamfers or contact lead-ins with a small taper angle to guarantee precise prior centering, decrease shearing and bearing microasperity, and a smooth insertion force increase with assembly.

Design of Machine Elements

•

•

The possibility of substantial initial (after assembly) axial race displacement s, which is not compensated later. Errors in the dimensions l, L, b1 , and b2 cause this displacement and also the fact that the axial shaft position depends on the axial position of the engaged wheels, which has an accidentally wide spacing in values. The need for comparatively precise production of the components according to the dimensions L and l. These dimensions (shown in Fig. 6.221a) along with other dimensions form a dimensional chain. The errors in the component manufacture according to these dimensions result in axial displacement of the bearing races.

The advantages of this configuration are the following:

• •

•

•

Easy shaft floating because of the low axial force. The possibility of adjustment of the initial value of s – the axial displacement of the races – to the minimum. This is achieved by means of matching of the compensatory gaskets K mounted under the flanges of both bearing caps. The production of the components according to the dimensions l, L, and h in compliance with free tolerances (e.g., of accuracy degree 14). Possibly accumulated errors are eliminated with the compensatory gaskets K . The absence of stops for the outer bearing races in the case holes, which makes their machining easier.

The disadvantage of this configuration, as with the previous one, is that its application is limited to stiff shafts and high manufacturing accuracy of both the shafts and the case holes.

Diagram in Fig. 6.221c In this configuration, in the supports radial ball singlerow, ball, or roller double-row spherical bearings are applied. The choice of one or another bearing class is defined by the required load rating and shaft stiffness. The inner bearing races are fastened onto the shaft, whereas the outer races are free and can move along the holes of the case. The displacement value is restricted by the clearances z set on assembly by matching the compensatory gaskets K . Axial shaft floating, if its value is not more than the axial clearance in the bearings, occurs at the expense of this clearance relative to the fixed outer bearing races. If the axial shaft displacement exceeds the axial clearance in the bearings, by floating of the shaft the outer bearing races slide in the holes of the case, which results in wear of the hole surface. To decrease this wear tempered-steel bushings are sometimes placed into the holes of the case. The advantage of this configuration is than it can be applied for nonrigid shafts and low coaxiality grade of the mounting surfaces of the shaft and the case. The absence of stops for the outer bearing races in the holes of the case can also be considered an advantage.

The disadvantages of this configuration are the following:

• • •

The presence of kinetic friction of the outer bearing races along the holes of the case. The necessity of the application of substantial axial force for realization of the shaft floating. The use of tempered-steel bushings makes the supports more expensive and reduces the positioning accuracy of the shaft.

Examples of the Embodiment of Floating Shaft Units Figure 6.222 shows structures of the input shafts of a single-reduction gear unit with chevron gears made according to the configuration shown in Fig. 6.221a,b. The shafts are floating. The axial position of the floating shaft is determined by the teeth of the semichevrons, which are inclined in different directions. The conjugated shafts are fixed relative to the case. The outer race of the bearing without ledges (Fig. 6.222a) is tightened with a face of the clamp-on cap to ring (1). This ring can be solid if the jointing plane of the case goes through the shaft axis. If the case is made without a split, (1) is a spring planar thrust inner ring. In the floating support shown in Fig. 6.222a it is recommended to fasten the inner bearing race from

509

Part B 6.12

Diagram in Fig. 6.221b The outer races have some freedom from axial displacement. Displacement into the case is restricted to the ledges of both bearing races; towards the bearing caps it is restricted by a clearance z. The value of the clearance z = 0.5–0.8 mm depends on the unit dimensions and manufacturing accuracy of the teeth of the mated chevron gears, and their assembly accuracy. With axial floating of the shaft the inner races of the bearings with roller sets shift relative to the outer races. At the start of axial shaft floating the rollers of the bearings displace the outer races towards the caps in such a way that the races find their place and are fixed later.

6.12 Design of Bearing Units

512

Part B

Applications in Mechanical Engineering

Part B 6.12

semisolid lubricant behaves like a solid; it does not spread under its own weight and is retained on tilted and vertical surfaces. Lubricants with calcium and lithium thickeners are used for bearings. Mineral and synthetic oils with a kinematic viscosity of 15–500 mm2 /s at 40 ◦ C are applied as a dispersion medium. For the lubrication of rolling bearings semisolid lubricants of classes 2 (predominantly) and 3 according to the National Association of Lubricating Grease Institute (NLGI) standards are recommended. Most often lubricants with a lithium base are applied, which are resistant to water and are corrosion protected. One type of lubrication method has a permanent quantity of lubricant that is intended for the entire lifetime of the bearing. The other requires periodic addition and changes of the lubricant. In the first case, the lifetime of the lubricant is equal to or greater than the lifetime of the bearings or the maintenance cycle of machines with built-in bearings. Closed bearings filled with a lubricant on manufacture with safety washers or with contact seals belong to this class. Bearings with built-in safety washers are applied in units where contamination is not high and water, vapor, etc., do not Table 6.94 Classification of kinematic viscosities in com-

pliance with ISO 3448 Viscosity class

Kinematic viscosity (mm2 /s) at 40 ◦ C Average

Minimum

Maximum

ISO VG 2

2.2

1.98

2.42

ISO VG 3

3.2

2.88

3.52

ISO VG 5

4.6

4.14

5.06

ISO VG 7

6.8

6.12 9.00

7.48

ISO VG 10

10

11.0

ISO VG 15

15

13.5

16.5

ISO VG 22

22

19.8

24.2

ISO VG 32

32

28.8

35.2

ISO VG 46

46

41.4

50.6

ISO VG 68

68

61.2

ISO VG 100

100

90.0

ISO VG 150

150

135

165

ISO VG 220

220

198

242

ISO VG 320

320

288

352

ISO VG 460

460

414

506

ISO VG 680

680

612

748

ISO VG 1000

1000

900

1100

ISO VG 1500

1500

1350

1650

74.8 110

penetrate, or in units where the absence of friction in this noncontact seal in the case of high rotational frequencies or high temperatures is important. Bearings with built-in contact seals are applied in units where it is impossible to ensure an external seal due to a lack of space, where the possibility of contamination is normal and ingress of moisture is possible, or if it is necessary to guarantee a long lifetime without maintenance. As a liquid lubricant refined mineral (petroleum) oils are mostly used for bearings. Liquid synthetic oils (diether, polyalkylen-glycol, fluorine-carbonic, silicone) in comparison with mineral oils demonstrate better stability, viscosity, and pour point. They are used at high or low temperatures, and high rotational frequencies. The choice of lubricating oil is determined by the viscosity required to ensure effective lubrication at the operating temperature. The dependence of the oil viscosity on the temperature is characterized by the viscosity index (VI). A higher VI indicates less viscosity dependence on temperature. The wider the range of operating temperatures, the greater the viscosity index of the oil used should be. For lubrication of rolling bearings oils with VI of 85 and higher should be used. Table 6.94 shows a classification of kinematic viscosities in accordance with the recommendations ISO 3448. To increase the performance characteristics of the oil various additives are used. The most common additives are antioxidants, anticorrosives, antifoams, antideterioration, and antiscoring. Preference is given to oil used in the conjugate units (bearings and gear wheels are usually lubricated from a common oil reservoir). The use of oil with higher viscosity is advisable in the case of high loads and low velocities. Efficiency of lubrication depends on the degree of separation of contact surfaces by the lubrication layer. To form an appropriate layer the lubricant must have a certain minimum viscosity, ν1 , at the operating temperature. The value of the minimum required kinematic viscosity ν1 can be determined from the nomogram shown in Fig. 6.226, depending on the mean diameter dm (mm) of the bearing and its rotational frequency n (min−1 ). This nomogram corresponds to the results of the latest research in the field of the tribology of rolling bearings. If the operating temperature of the bearing is known from field experience, or can be determined by other means, the kinematic oil viscosity ν at the base temper-

520

Part B

Applications in Mechanical Engineering

6.22 6.23 6.24 6.25 6.26

6.27

6.28

6.29 6.30

Part B 6

6.31

6.32

6.33

6.34

6.35

6.36

6.37

6.38 6.39 6.40

6.41

6.42

G. Pahl, W. Beitz, J. Feldhusen, K.-H. Grote: Konstruktionslehre, 3rd edn. (Springer, London 1997) I.E. Shigley: Mechanical Engineering Design (McGrawHill, New York 1977) E.B. Vulgakov (Ed.): Aviation Gearings and Reduction Gears (Mashinostroenie, Moscow 1981), in Russian E.B. Vulgakov: Coaxial Gearings (Mashinostroenie, Moscow 1987), in Russian V.P. Kogaev, I.V. Gadolina: Summation of fatigue damages by probability calculation of service life, Vestn. Mashinostr. 7, 3–7 (1989), in Russian GOST 25.587-78 Calculations and strength tests in mechanical engineering. Test methods of contact fatigue (Standards Publishing House, Moscow 1978) GOST 1643-81 Principal standards of interchangeability. Cylindrical gearings. Tolerances (Standards Publishing House, Moscow 1981) GOST 1758-81 Bevel and hypoid gears. Tolerances (Standards Publishing House, Moscow 1981) GOST 9563-60 Principal standards of interchangeability. Gear wheels. Modules (Standards Publishing House, Moscow 1960) GOST 13754-81 Principal standards of interchangeability. Bevel gearings with straight teet. Original profile (Standards Publishing House, Moscow 1981) GOST 13755-81 Principal standards of interchangeability. Involute gears. Original profile (Standards Publishing House, Moscow 1981) GOST 19326-73 Bevel gearings with circular teeth. Calculation of geometry (Standards Publishing House, Moscow 1973) GOST 19624-74 Bevel gearings with straight teeth. Calculation of geometry (Standards Publishing House, Moscow 1974) GOST 21354-87 Cylindrical involute gearings of external toothing. Strength analysis (Standards Publishing House, Moscow 1987) GOST R 50891-96 Reduction gears of machinebuilding application. General technical conditions (Standards Publishing House, Moscow 1996) GOST R 50968-96 Reduction gearmotors. General technical conditions (Standards Publishing House, Moscow 1996) E.L. Airapetov, M.D. Genkin, T.N. Melnikova: Static of Globoidal Gears (Nauka, Moscow 1981), in Russian G. Niemann, H. Winter: Machinenelemente, 2nd edn. (Springer, Berlin Heidelberg 1983), in German V.V. Shults: Natural Wear-and-Tear of Machine Components and Tools (Mashinostroenie, Leningrad 1990), in Russian GOST 3675-81 Principal standards of interchangeability. Worm cylindrical gearings. Tolerances (Standards Publishing House, Moscow 1981) GOST 16502-83 Principal standards of interchangeability. Globoidal gears. Tolerances (Standards Publishing House, Moscow 1983)

6.43 6.44

6.45

6.46

6.47

6.48

6.49

6.50

6.51 6.52

6.53

6.54

6.55

6.56

6.57 6.58 6.59 6.60 6.61

GOST 17696-89 Globoidal gears. Calculation of geometry (Standards Publishing House, Moscow 1989) GOST 19036-94 Principal standards of interchangeability. Worm cylindrical gearings. Original worm and original productive worm (Standards Publishing House, Moscow 1994) GOST 19650-97 Worm cylindrical gearings. Calculation of geometry (Standards Publishing House, Moscow 1997) GOST 19672-74 Worm cylindrical gearings. Modules and coefficients of the worm diameter (Standards Publishing House, Moscow 1974) GOST 24438-80 Globoidal gears. Original worm and original productive worm (Standards Publishing House, Moscow 1980) P.F. Dunaev, O.P. Lelikov: Design of Units and Components of Machines, 9th edn. (Academy, Moscow 2006), in Russian P.F. Dunaev, O.P. Lelikov: Calculation of Dimensional Tolerances, 4th edn. (Mashinostroenie, Moscow 2006), in Russian P.F. Dunaev, O.P. Lelikov: Components of machines, 5th edn. (Mashinostroenie, Moscow 2007), in Russian P.F. Dunaev, O.P. Lelikov, L.P. Varlamova: Tolerances and Fits (Vysshaya shkola, Moscow 1984), in Russian GOST 2.309-73 (edn. 2003) Uniform system of design documentation. Designations of surface roughness and marking regulations in the drawings of products (Standards Publishing House, Moscow 2003) GOST 25346-89 Uniform system of tolerances and fits. General provisions, series of tolerances and principal deviations (Standards Publishing House, Moscow 1989) GOST 25347-82 Uniform system of tolerances and fits. Tolerance ranges and advisable fits (Standards Publishing House, Moscow 1982) GOST 30893.1-2002 (ISO 2768-1-89) Principal standards of interchangeability. General tolerances. Extreme deviations of linear and angular dimensions with non-specified tolerances (Standards Publishing House, Moscow 2002) GOST 30893.2-2002 (ISO 2768-2-89) Principal standards of interchangeability. General tolerances. Tolerances of form and position of surfaces nonspecified individually (Standards Publishing House, Moscow 2002) E.L. Ayrapetov, M.D. Genkin: Dynamics of Planetary Trains (Nauka, Moscow 1980), in Russian E.G. Ginzburg: Wave Gears (Mashinostroenie, Leningrad 1969), in Russian M.N. Ivanov: Wave Gears (Vysshaya Shkola, Moscow 1981), in Russian V.N. Kudriavtsev: Planetary Gears (Mashinostroenie, Moscow, Leningrad 1966), in Russian V.N. Kudriavtsev, Y.N. Kirdiashev (Eds.): Planetary Gears: Reference Book (Mashinostroenie, Moscow 1977), in Russian

Design of Machine Elements

6.62

6.63

6.64

6.65 6.66

6.67

6.68

6.70 6.71 6.72

6.73

6.74

6.75

6.76

6.77

6.78

6.79

6.80

6.81

6.82

6.83 6.84

6.85

6.86

6.87

6.88

6.89

6.90 6.91 6.92

6.93

6.94

6.95

6.96

6.97

6.98

6.99

GOST 25.504-82 Calculations and strength testing. Calculation methods of fatigue strength characteristics (Standards Publishing House, Moscow 1982) GOST 2789-73 Surface roughness. Parameters and characteristics (Standards Publishing House, Moscow 1973) GOST 6636-69 Normal linear dimensions (Standards Publishing House, Moscow 1969) GOST 12080-66 Cylindrical shaft ends. Basic dimensions, allowable torsional moments (Standards Publishing House, Moscow 1966) GOST 12081-72 Tapered shaft ends with a taper 1:10. Basic dimensions, allowable torsional moments (Standards Publishing House, Moscow 1972) GOST 22061-76 Machines and processing equipment. System of balancing accuracy classes (Standards Publishing House, Moscow 1976) GOST 24266-94 Shaft ends of reduction gears and reduction gearmotors. Basic dimensions, allowable torsional moments (Standards Publishing House, Moscow 1994) GOST 24643-81 Principal standards of interchangeability. Tolerances of form and surface positions. Values (Standards Publishing House, Moscow 1981) GOST 3325-85 Rolling bearings. Tolerance ranges and technical requirements for mounting surfaces of the shafts and cases. Fits (Standards Publishing House, Moscow 1985) GOST 23360-78 Feather keys. Dimensions, tolerances and fits (Standards Publishing House, Moscow 1978) G.A. Bobrovnikov: Strength of Force Fits Attained by Cooling (Mashinostroenie, Moscow, 1971), in Russian E.S. Grechishchev, A.A. Il’iashenko: Joints with Interference (Mashinostroenie, Moscow 1981), in Russian K. Ootsuka, K. Simidzu, Y. Sudzuki: Alloys with an Effect of Shape Memory, ed. by H. Funakubo (Metallurgia, Moscow 1990), in Russian A.A. Illin: Alloys with an effect of shape memory. Totals of science and technology, Phys. Met. Heat Treat. 25, 3–39 (1991) D.N. Reshetov, Y.V. Krasnov: Statistical analysis of friction coefficient in the joints with interference, Isvestia Vuzov. Mashinostr. 4, 15–19 (1985), in Russian GOST 1139-80 Principal standards of interchangeability. Straight-sided spline connections. Dimensions and tolerances (Standards Publishing House, Moscow 1980) GOST 6033-80 Principal standards of interchangeability. Involute spline connections with a profile angle 30◦ . Dimensions, tolerances and measurable values (Standards Publishing House, Moscow 1980) GOST 21425-75 Straight-sided serrated (spline) joints. Calculation methods of load-carrying ability (Standards Publishing House, Moscow 1975) GOST 24071-80 Principal standards of interchangeability. Key joints with semicircular keys. Dimen-

521

Part B 6

6.69

GOST 9587-81 Principal standards of interchangeability. Gearings Original profile of fine-module gear wheels (Standards Publishing House, Moscow 1981) GOST 10059-80 Fine-module finishing gear-shaping cutters. Technical conditions (Standards Publishing House, Moscow 1980) GOST 23179-78 Radial ball single-row flexible rolling bearings. Technical conditions (Standards Publishing House, Moscow 1978) GOST 25022-81 Planetary gearboxes. Critical parameters (Standards Publishing House, Moscow 1981) GOST 26218-94 Harmonic reduction gears and reduction gearmotors. Parameters and dimensions (Standards Publishing House, Moscow 1994) GOST 26543-94 Planetary reduction gearmotors. Critical parameters (Standards Publishing House, Moscow 1994) GOST 30078.1-93 Wave gears. General technical requirements (Standards Publishing House, Moscow 1993) GOST 30078.2-93 Wave gears. Types. Critical parameters and dimensions (Standards Publishing House, Moscow 1993) V.L. Biderman: Theory of Mechanical Oscillations (Vysshaya Shkola, Moscow 1980), in Russian V.V. Bolotin: Vibration in Engineering: Handbook, Vol. 1–6 (Mashinostroenie, Moscow 1978), in Russian O.P. Lelikov: Shafts and Supports with Frictionless Bearings (Mashinostroenie, Moscow 2006), in Russian G.S. Maslov: Calculation of the Vibration of Shafts, 2nd edn. (Mashinostroenie, Moscow 1980), in Russian S.V. Serensen, M.B. Groman, V.P. Kogaev, R.M. Shneiderovich: Shafts and Axles (Mashinostroenie, Moscow 1970), in Russian S.V. Serensen, V.P. Kogaev, R.M. Shneiderovich: Load-Carrying Ability and Strength Analysis of the Machine Components, 3rd edn. (Mashinostroenie, Moscow 1975), in Russian W. Steinhilper, R. Röper: Maschinenelemente, Vol. 13, 4th edn. (Springer, Berlin Heidelberg 1994), in German W. Weaver, S.P. Timoshenko, D.H. Young: Vibration Problems in Engineering (Wiley Interscience, New York 1985) R50-83-88 Recommendations: Calculations and Strength Testing. Strength Analysis of Shafts and Axles (Publishing House of Standards, Moscow 1989) GOST 2.307-68 Uniform system of design documentation. Marking of dimensions and extreme deviations (Standards Publishing House, Moscow 1968) GOST 2.308-79 Uniform system of design documentation. Indication of form and surface position tolerances in the drawings (Standards Publishing House, Moscow 1979)

References

522

Part B

Applications in Mechanical Engineering

6.100

6.101 6.102 6.103 6.104 6.105

6.106

6.107 6.108

Part B 6

6.109

sions of keys and groove sections. Tolerances and fits (Standards Publishing House, Moscow 1980) J. Brändlein, P. Eschmann, L. Hasbargen, K. Weigang: Wälzlagerpraxis (Vereinigte Fachverlage GmbH, Mainz 1995), in German P. Eschmann, L. Hasbargen, K. Weigang: Ball and Roller Bearings (Wiley, New York 1985) T.A. Harris: Rolling Bearing Analysis, 4th edn. (Wiley, New York 2000) L.Y. Perel, A.A. Filatov: Rolling Bearing (Mashinostroenie, Moscow 1992), in Russian SKF Cataloque 6000EN, November 2005 (SKF, Schweinfurt 2005) D.N. Reshetov, O.P. Lelikov: Calculation of rolling bearings by varying loads, Isvestia Vuzov Mashinostr. 12, 15–19 (1984) GOST 520-2002 Rolling bearings. General technical conditions (Standards Publishing House, Moscow 2002) GOST 3189-89 Ball and roller bearings. Nomenclature (Standards Publishing House, Moscow 1989) GOST 3395-89 Rolling bearings. Classes and embodiments (Standards Publishing House, Moscow 1989) GOST 13942-86 Spring thrust planar outer eccentric rings and grooves for them. Structure and dimensions (Standards Publishing House, Moscow 1986)

6.110 GOST 13943-86 Spring thrust planar inner eccentric rings and grooves for them. Structure and dimensions (Standards Publishing House, Moscow 1986) 6.111 GOST 18854-94 (ISO 76-87) Rolling bearings. Static load rating (Standards Publishing House, Moscow 1994) 6.112 GOST 18855-94 (ISO 281-89) Rolling bearings. Dynamic rated load rating and design life (Standards Publishing House, Moscow 1994) 6.113 GOST 20226-82 Collars for installation of rolling bearings. Dimensions (Standards Publishing House, Moscow 1982) 6.114 GOST 24810-81 Rolling bearings. Clearances. Dimensions (Standards Publishing House, Moscow 1981) 6.115 ISO 5593-84 Rolling bearings. Terminological dictionary 6.116 E.A. Chernyshov: Casting Alloys and their Foreign Analogs (Mashinostroenie, Moscow 2006), in Russian 6.117 O.E. Osintsev, V.N. Fedotov: Copper and Copper Alloys. Russian and Foreign Brands (Mashinostroenie, Moscow 2004), in Russian 6.118 A.S. Zubchenko (Ed.): Grades of Steels and Alloys, 2nd edn. (Mashinostroenie, Moscow 2003), in Russian

523

Manufacturin 7. Manufacturing Engineering

Thomas Böllinghaus, Gerry Byrne, Boris Ilich Cherpakov (deceased), Edward Chlebus, Carl E. Cross, Berend Denkena, Ulrich Dilthey, Takeshi Hatsuzawa, Klaus Herfurth, Horst Herold (deceased), Andrew Kaldos, Thomas Kannengiesser, Michail Karpenko, Bernhard Karpuschewski, Manuel Marya, Surendar K. Marya, Klaus-Jürgen Matthes, Klaus Middeldorf, Joao Fernando G. Oliveira, Jörg Pieschel, Didier M. Priem, Frank Riedel, Markus Schleser, A. Erman Tekkaya, Marcel Todtermuschke, Anatole Vereschaka, Detlef von Hofe, Nikolaus Wagner, Johannes Wodara, Klaus Woeste 7.1

Casting ................................................ 7.1.1 The Manufacturing Process ............ 7.1.2 The Foundry Industry.................... 7.1.3 Cast Alloys ................................... 7.1.4 Primary Shaping .......................... 7.1.5 Shaping of Metals by Casting ......... 7.1.6 Guidelines for Design ................... 7.1.7 Preparatory and Finishing Operations ..............

525 525 525 527 536 538 548

7.2

Metal Forming...................................... 7.2.1 Introduction ................................ 7.2.2 Metallurgical Fundamentals .......... 7.2.3 Theoretical Foundations................ 7.2.4 Bulk Forming Processes ................. 7.2.5 Sheet Forming Processes ............... 7.2.6 Forming Machines ........................

554 554 557 560 568 585 599

7.3

Machining Processes ............................. 7.3.1 Cutting........................................ 7.3.2 Machining with Geometrically Nondefined Tool Edges ................. 7.3.3 Nonconventional Machining Processes.....................

606 606

7.4

Assembly, Disassembly, Joining Techniques ............................... 7.4.1 Trends in Joining – Value Added by Welding ............... 7.4.2 Trends in Laser Beam Machining .... 7.4.3 Electron Beam ............................. 7.4.4 Hybrid Welding ............................ 7.4.5 Joining by Forming....................... 7.4.6 Micro Joining Processes ................. 7.4.7 Microbonding .............................. 7.4.8 Modern Joining Technology – Weld Simulation ..........................

553

636 647 656 657 668 675 682 686 697 702 706

Part B 7

Manufacturing is the set of activities converting raw materials into products in the most possible cost effective way, including design of goods, manufacturing parts and assembling them into products (subassemblies) using various production methods and techniques, the sale of products to customers, servicing, maintaining the product in good working order, and eventually recycling materials and parts. Whilst the design stage costs about 10-15% of all manufacturing costs, its effect on all other activities is enormous. The designed product has to be easy to make, easy to assemble, maintainable at a competitive cost level, and finally it should be economically recyclable. This is why concurrent engineering (CE) is a systematic approach integrating the design stage and manufacturing stage of products with a view to optimizing all elements involved in the life cycle of a product. Due to the vast complexity of manufacturing engineering it can only be dealt with in a number of different chapters. The sections in this chapter illustrate the most important manufacturing processes from casting to assembly, from the first shape giving process to the last component integrative process. In between the reader will find a variety of manufacturing processes, including the most recent technologies, e.g. microbonding, nanotechnology, and others. Chapter 10 describes the front end of manufacturing, i. e. design, and Chap. 16 is allocated to quality assurance in manufacturing engineering. Finally, Chap. 17 is devoted to manufacturing logistics and manufacturing system analysis.

526

Part B

Applications in Mechanical Engineering

There are very few restrictions with regard to the geometry of castings. All that can be drawn is also castable, but it is sometimes difficult to draw what is easy to cast. High quality casting designs increasingly result from the incorporation of numerical simulation of mold filling and solidification, rapid prototyping, and simultaneous engineering. This takes place through close cooperation between foundrymen and designers. In the future it is expected that bionic and biological designing will provide new impulses for shaping. This will enable a large amount of freedom in the choice, thereby leading to full utilization of modern computer technology in the foundry industry.

Part B 7.1

Properties of Castings Castings are produced from the following material groups: iron alloys (cast steel, cast iron), aluminum, magnesium, titanium, copper, zinc, tin, nickel, and cobalt alloys. All of these are cast alloys. Independent of the type of production process, in the manufacture of metallic components by casting differentiation is always to be made between the material properties and the properties of the casting itself. In order to achieve a prescribed component characteristic the material and the geometry determine and complement each other in the properties of the component. These properties depend on the following:

• • • • • • • • •

The geometry of the part The chemical composition of the cast material The treatment of the melted material (inoculation, modification, desulfurization, deoxidation, magnesium treatment, grain refinement, etc.) The type of molding and casting process The rate of cooling from casting to the ambient temperature The subsequent heat treatment The subsequent treatment of the outer layer (chemical-thermal process, surface deformation, surface alloying, surface remelting, etc.) Changes in the surface layer through machining The type of coating (painting, galvanizing, enameling etc.)

During the past decades the properties of cast alloys have also been further developed and considerably improved. For example, whereas in the 1950s only steel casting was able to achieve tensile strengths of more than 400 N/mm2 , today the designer has the choice of three higher strength groups of ferrous materials, i. e.

spheroidal graphite cast iron, malleable cast iron, and cast steels. In many cases, this has enabled the highly economical substitution of forged and rolled steels. There have also been further developments in nonferrous metal cast alloys, especially in the fields of aluminum and magnesium materials, which increasingly enable the use of these alloys in automotive manufacturing. Consequently, the last decade has seen substantial rates of growth in the production of spheroidal graphite cast iron, as well as in aluminum and magnesium alloy castings. This is directly associated with the efforts towards light construction but also towards the reduction of total production costs. The trend towards light construction is not only being realized with less dense cast materials, e.g. aluminum, but is also being achieved with higher density materials, e.g. spheroidal graphite cast iron. This is the result of the combined effect of material and shape as well as further development of casting technology. In the selling of castings the material properties were traditionally (and often still are) taken as a basis for the contract, i. e. such material characteristics as yield strength, tensile strength, elongation at fracture, fatigue strength etc., which were determined from separately quasi simple geometrical samples. However, these samples only partially reflect the capabilities of the cast materials. Cast components are increasingly being designed on the basis of fracture mechanics. This shows that cast components are frequently unbeatable. The Development of Casting Processes The development of molding and casting processes during recent decades has led to the fact that the casting more and more approaches the shape of the finished part. The best results have been achieved with investment casting (lost wax molding process) and high pressure die casting, which can produce almost finished parts. These often require only minimum machining, e.g. fine machining of operating surfaces. Additionally, the development of weldable aluminum pressure die castings has enabled further possibilities of use. Mechanical machining requires a relatively high amount of energy, the generation of 1 t of chips requiring the same amount of energy as that for the melting of 1 t of material. The chips produced in machining the casting to the complete product, which can often result in a material utilization of less than 50%, should now be a thing of the past. The future lies in the production of near net shape castings with the resultant large savings in energy.

Manufacturing Engineering

• • • • •

The reduction of wall thicknesses as a result of better pouring possibilities The use of higher strength materials Optimal casting design with, for example, ribbing or realization of hollow structures The reduction of machining allowances Material substitution, e.g. spheroidal graphite cast iron instead of forged steel and aluminum alloys instead of cast iron

These savings in materials reduce the weight of the components as well as the amount of machining. They also result in energy savings and thus preservation of the environment. Overall consideration of component manufacture from the raw material to the finished part and taking account of recycling of metallic materials, i. e. an economic balance, illustrated that, by comparison with the other main production processes, the manufacture and use of castings results in substantial energy savings and thus ecological advantages, e.g. the reduction of CO2 .

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From case studies, it is a well-known fact that, by comparison with other process variants, near net shape castings are clearly advantageous with regard to specific energy requirements for the finished components, especially with respect to machining from solid semiproducts. Component manufacture by casting is also clearly preferential when considering ecological aspects such as CO2 emission. Foundries pursue objective environmental management and confront public option with declarations of their achievements.

7.1.3 Cast Alloys Cast alloys are metallic materials manufactured by primary shaping in a foundry. Cast alloys can be classified in two main groups: cast ferrous materials (cast irons and cast steels) and cast nonferrous materials (cast aluminum, cast magnesium, cast copper, and cast zinc alloys). Cast Iron Alloys Cast iron alloys can be classified into seven groups:

• • • • • • •

Gray cast iron Spheroidal graphite cast iron Ausferrite spheroidal graphite cast iron Compacted graphite cast iron Malleable cast iron Austenitic cast iron Abrasion resisting alloyed cast iron

Cast Iron. The term cast iron designates an entire family of metallic materials with a wide variety of properties. It is a generic term like steel, which also designates a family of metallic materials. Steels and cast irons are both primarily iron with carbon as the main alloying element. Steels contain less than 2%, while all cast irons contain more than 2% carbon. About 2% is the maximum carbon content at which iron can solidify as a single phase alloy with all of the carbon in solution in austenite. Thus, the cast irons by definition solidify as heterogeneous alloys and always have more than one constituent in their microstructure. In addition to carbon, cast irons also must contain appreciable silicon, usually from 1 to 3%, and thus they are actually iron-carbon-silicon alloys. The high carbon content and the silicon in cast irons make them excellent casting alloys. Their melting temperatures are appreciably lower than those of steel. Molten cast irons are more fluid than molten steel and less reactive with molding

Part B 7.1

In many cases, groups of parts were and are being assembled from numerous individual components (turned, milled, and sheet metal components) by means of welding, riveting, bolting, etc. This type of assembly not only necessitates expensive manufacture of individual parts but also gives rise to considerable assembly costs. The casting of integral components (one-piececastings), through which the numerous previously necessary individual parts are combined in one casting, is an ideal way towards a new generation of parts. These integral castings can additionally better incorporate specific functional elements, resulting in considerable savings in material and energy. Recycling is understood to be the return of material into the production process. In doing so, the aim is not to leave industrial production open-ended but, as with nature, to close the circuit, here material flows. Recycling is in no way a new term for metallic materials but is rather a thousands of years old practice of returning metallic waste into the production process. Recycling of cast steel, cast iron, and cast nonferrous metals is a worldwide normal practice. Recycling of metallic materials leads to the saving of energy, preservation of our raw materials reserves, and thus to relief of our environment. Development of the properties of the cast materials and the improvement of the molding and casting processes in the foundry industry have not only led to higher productivity but also material saving through:

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Part B 7.1

materials. Formation of lower density graphite in cast iron during solidification reduces the change in volume of the metal from liquid to solid and makes production of more complex castings possible. The various types of unalloyed cast irons cannot be designated by chemical composition because of similarities between the types. Unalloyed cast irons are designated by their mechanical properties. High-alloy cast irons are designated by their chemical composition and mechanical properties. These have a wide range in chemical composition and also contain major quantities of other elements. The presence of certain minor elements is also vital for the successful production of each type of cast iron. For example, nucleating agents, called inoculants, are used in the production of gray cast iron to control the graphite type and size. Trace amounts of bismuth and tellurium in the production of malleable cast iron, and the presence of a few hundredth of a percent of magnesium causes the formation of spheroidal graphite cast iron. In addition, the composition of a cast iron must be adjusted to suit particular castings. Small castings and large castings of the same grade of cast iron cannot be made from the same composition of alloy. For this reason, most cast iron castings are purchased on the basis of mechanical properties rather than composition. The common exception is for castings that require special properties such as corrosion resistance or elevated temperature strength. The various types of cast iron can be classified according to their microstructure. This classification is based on the form and shape in which the major portion of carbon occurs in the cast irons. This system provides for five basic types of gray cast iron, spheroidal graphite cast iron, malleable cast iron, compacted graphite cast iron, and white cast iron. Each of these types may be moderately alloyed or heat treated without changing its basic classification. The high-alloyed cast irons, generally containing over 3% of added alloying element, can also be individually classified as gray or spheroidal graphite cast iron or white cast iron, but the high-alloyed cast irons are classified as a separate group. Gray Cast Iron. When the composition of a molten cast

iron and its cooling rate are appropriate, the carbon in the cast iron separates during solidification and forms separate graphite flakes that are interconnected within each eutectic cell (EN 1561). The graphite grows edgewise into the liquid and forms the characteristic flake shape. When gray cast iron is broken, most of the frac-

ture occurs along the graphite, thereby accounting for the characteristic gray color of the fractured surface. Because the large majority of iron castings produced are of gray cast iron, the generic term is often improperly used to mean gray cast iron specifically. The properties of gray cast iron are influenced by the size, amount, and distribution of the graphite flakes, and by the relative hardness of the matrix metal around the graphite. These factors are controlled mainly by the carbon and silicon contents of the metal and the cooling rate of the casting. Slower cooling and higher carbon and silicon contents tend to produce more and larger graphite flakes, a softer matrix structure, and lower strength. The flake graphite provides gray cast iron with unique properties such as excellent machinability at hardness levels that produce superior wear-resisting characteristics, the ability to resist galling, and excellent vibration damping. The amount of graphite present, as well as its size and distribution, are important to the properties of the cast iron. Wherever possible, it is preferable to specify the desired properties rather than the factors that influence them. Microscopically, all gray cast irons contain flake graphite dispersed in a iron-silicon matrix. How much graphite is present, the length of the flakes, and how they are distributed in the matrix directly influence the properties of the cast iron. The basic strength and hardness of the cast iron is provided by the metallic matrix in which the graphite occurs. The properties of the metallic matrix can range from those of a soft, low-carbon steel to those of hardened, high-carbon steel. The matrix can be entirely ferritic for maximum machinability, but the cast iron will have reduced wear resistance and strength. An entirely pearlitic matrix is characteristic of high-strength gray cast iron, and many castings are produced with a matrix microstructure of both ferrite and pearlite to obtain intermediate hardness and strength. Alloying element additions and/or heat treatment can be used to produce gray cast iron with very fine pearlite or with an acicular matrix structure. Graphite has little strength or hardness, so it decreases these properties of the metallic matrix. However, graphite provides several valuable characteristics to gray cast iron: the ability to produce sound castings economically in complex shapes, good machinability, even at wear-resisting hardness levels and without burring, dimensional stability under different heating, high vibration damping, and borderline lubrication retention.

Manufacturing Engineering

Spheroidal Graphite Cast Iron. Spheroidal graphite cast iron or ductile iron (EN 1563) is characterized by the

fact that all of its graphite occurs in microscopic spherolites. Although this graphite constitutes about 10% by volume of this material, its compact spheroidal shape minimizes the effect on mechanical properties. The difference between the various grades of spheroidal graphite cast irons is in the microstructure of the material around the graphite, which is called the matrix. This microstructure varies with the chemical composition and the cooling rate of the casting. It can be slowly cooled in the sand mold for a minimum hardness as-cast condition or, if the casting has sufficiently uniform sections, it can be shaken out of the mold while still at a temperature above the critical and normalized. The matrix microstructure and hardness can also be changed by heat treatment. The high ductility grades are usually annealed so that the matrix structure’s ferrite is entirely free of carbon. The intermediate grades are often used in the as-cast condition without heat treatment and have a matrix structure of ferrite and pearlite. The ferrite occurs as rings around the graphite spheroids. Because of this, it is called bull-eye ferrite. The high-strength grades are usually given a normalizing heat treatment to make the matrix all pearlite, or they are quenched and tempered to form a matrix of tempered martensite. However, spheroidal graphite cast iron can be moderately alloyed to have an entirely pearlitic matrix as-cast condition. The chemical composition of spheroidal graphite cast iron and the cooling rate of the casting directly affect its tensile properties by influencing the type of matrix structure that is formed. All of the regular grades of the spheroidal graphite cast iron can be made from the same cast iron provided that the chemical composition is appropriate so that the desired matrix microstructure can be obtained by controlling the cooling rate of the casting after it is poured or by subsequent heat treatment. For most casting requirements, the chemical composition of the spheroidal graphite cast iron is primarily a matter of facilitating production. Table 7.1 Mechanical properties of gray cast iron Tensile strength (N/mm2 ) Brinell hardness

100– 350 155– 265

Table 7.2 Mechanical properties of spheroidal graphite

cast iron Tensile strength (N/mm2 ) Yield strength (N/mm2 ) Elongation (%) Brinell hardness

350– 900 220– 600 6 – 22 130– 330

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The properties of gray cast iron primarily depend on its chemical composition. The lower strength grades of gray cast iron can be produced consistently by simply selecting the proper melting stock. Grey cast iron castings in the higher strength grades require close control of their processing and chemical composition. The majority of the carbon in gray cast iron is present as graphite. Increased amounts of graphite result from an increased total carbon content in the gray cast iron. This decreases the strength and hardness of the gray cast iron, but increases other desirable characteristics. An appreciable silicon content is necessary in gray cast iron because this element causes the precipitation of the graphite in the material. The silicon also contributes to the distinctive properties of the gray cast iron. It maintains a moderate hardness level, even in the fully annealed condition, and thus assures excellent machinability. Also, silicon imparts corrosion resistance at elevated temperature and oxidation resistance in gray cast iron. Gray cast iron can be alloyed to increase its strength and hardness as-cast or its response to hardening by heat treatment. A very important influence on gray cast iron properties is the effective section thickness in which it is cast. The thicker the wall and the more compact the casting, the lower the temperature at which liquid metal will solidify and cool in the mold. As with all metals, slower solidification causes a larger grain size to form during solidification. In gray cast iron, slower solidification produces a larger graphite flake size. Gray cast iron is commonly classified by its minimum tensile strength or by hardness (Table 7.1). The mechanical properties of gray cast iron are determined by the combined effect of its chemical composition, processing technique in the foundry, and the solidification and cooling rates. Thus, the mechanical properties of the gray cast iron in a casting will depend on its shape, size and wall thickness as well as on the gray cast iron that is used to pour it. Five grades of gray cast iron are classified by their tensile strength in EN 1561. The grades of gray cast iron also can be specified by Brinell hardness only. The chemical composition and heat treatment, unless specified by the purchaser, shall be left in the direction of the manufacturer, who shall ensure that the casting and heat treatment process is carried out with the same process parameters.

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The common grades of spheroidal graphite cast iron differ primarily in the matrix structure that obtains the spheroidal graphite. These differences are the result of differences in the chemical composition, in the cooling rate of the casting, or the result of heat treatment. 13 grades of spheroidal graphite cast iron are classified by their tensile properties or hardness in EN 1563 (Table 7.2). The common grades of spheroidal graphite cast iron also can be specified by only Brinell hardness. The method of producing spheroidal graphite, the chemical composition and heat treatment unless will be specified by the purchaser.

Table 7.3 Mechanical properties of ausferrite spheroidal

graphite cast iron Tensile strength (N/mm2 ) 800– 1400 Yield strength (N/mm2 ) 500– 1100 Elongation (%) 1 – 10 Brinell hardness 250– 480 Abrasion resistant spheroidal graphite ausferritic cast irons Tensile strength (N/mm2 ) 1400– 1600 Yield strength (N/mm2 ) 1100– 1300 Elongation (%) 0–1 Vickers hardness 400– 500

Part B 7.1

Ausferrite Spheroidal Graphite Cast Iron. This group of

Table 7.4 Mechanical properties of compacted graphite

spheroidal graphite cast iron (ISO/WD 17804, ASTM 897-90) is well known as ADI (austempered cast iron), and recently as ausferrite spheroidal graphite cast iron. The development of ausferrite spheroidal graphite cast iron has given the design engineer with a new group of cast ferrous materials that offer the exceptional combination of mechanical properties equivalent to cast and forged steels and production costs similar to those of conventional spheroidal graphite cast iron. Ausferrite spheroidal graphite cast iron provides a wide range of properties, all produced by varying the heat treatment (austempering) of the same castings. Austempering is a special heat treatment process, which consists of three steps:

cast iron

• • •

Austenitize in the temperature range of 840–950 ◦ C for a time sufficient to produce a fully austenitic matrix that is saturated with carbon. Rapidly cool the entire part to an austempering temperature in the range of 230–400 ◦ C without forming pearlite or allowing the formation of ausferrite to begin. Isothermally treat at the austempering temperature to produce ausferrite with an austenite carbon content in the range of 1.8–2.2%.

After heat treatment (austempering) the matrix consists of acicular ferrite and residual austenite without carbides. Six grades of ausferrite spheroidal graphite cast iron are classified by their tensile properties in ISO/WD 17804 and two abrasion resistant grades are classified by Vickers hardness. Compacted Graphite Cast Iron. Compacted graphite cast iron (vermicular graphite cast iron, VDG-sheet W50) is a recent addition to the family of commercially produced cast irons (Table 7.4). Its characteristics are

Tensile strength (N/mm2 ) Yield strength (N/mm2 ) Elongation (%) Brinell hardness

300– 500 220– 380 0.5 – 1.5 140– 260

between of the gray cast iron and spheroidal graphite cast iron. The graphite in compacted graphite cast iron is in the form of interconnected flakes. The short span and blunted edges of graphite in this material provide improved strength, some ductility and a better machined finish than gray cast iron. The interconnected compacted graphite cast iron provides slightly higher thermal conductivity, more damping capacity, and better machinability than those obtained with spheroidal graphite cast iron. Compacted graphite cast iron provides similar tensile and yield strengths to ferritic spheroidal graphite cast iron and malleable cast iron, although the ductility is less. Malleable Cast Iron. The starting point is a cast iron in

which the carbon and silicon contents are arranged so that the casting is graphite-free after solidification, the entire carbon content being bonded to the iron carbide (cementite). If the casting is then heat-treated (tempered), the cementite decomposes without residue. Two kinds of malleable cast iron are distinguished:

• •

White malleable cast iron, which is decarbonized during heat treatment; and black malleable cast iron, which is not decarbonized during heat treatment

White malleable cast iron (EN 1562) is produced by heating for 50–80 h at about 1050 ◦ C in a decarburizing atmosphere (CO, CO2 , H2 , H2 O). In this process carbon

Manufacturing Engineering

Table 7.5 Mechanical properties of malleable cast iron White malleable cast iron Tensile strength (N/mm2 ) Yield strength (N/mm2 ) Elongation (%) Brinell hardness Black malleable cast iron Tensile strength (N/mm2 ) Yield strength (N/mm2 ) Elongation (%) Brinell hardness

350– 500 170– 350 3 – 16 200– 250 300– 800 200– 600 1 – 10 150– 320

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Nickel-alloyed cast iron owes its excellent corrosion resistance to the presence of nickel in concentrations of 12.0–36.0%, a chromium content of 1.0–5.5% and, in one type, s copper content of 5.5–7.5%. These cast irons have an austenitic matrix. Ten grades of austenitic cast iron with spheroidal graphite and two grades of austenitic cast iron with flake graphite are classified in EN 13835 by chemical composition and mechanical properties, like austenitic steels. The mechanical properties of austenitic cast iron with spheroidal graphite and with flake graphite are shown in Table 7.6.

Table 7.6 Mechanical properties of austenitic cast iron With flake graphite Tensile strength (N/mm2 ) Elongation (%) Brinell hardness With spheroidal graphite Tensile strength (N/mm2 ) Yield strength (N/mm2 ) Elongation (%) Brinell hardness

140– 220 2 120– 150 370– 500 210– 290 1 – 45 120– 255

Austenitic Cast Iron. High-alloy cast iron is used to produce components that require resistance to corrosives in the operating environment such as seawater, sour well oils, commercial organic and inorganic acids, and alkalis. The ability to easily cast it into complex shapes and the ease of machining some types of this material, make high-alloy cast iron an attractive material for the production of components for chemical processing plants, petroleum refining, food handling, and marine service. Two types dominate high alloy corrosion resistant cast iron: nickel-alloyed cast iron (austenitic cast iron, EN 13835) and high-Si cast iron.

Part B 7.1

is removed from the casting, so that after cooling a purely ferritic microstructure is in the casting. White malleable cast iron with small cross sections is welds well. Black malleable cast iron is produced by heating in a neutral atmosphere, first for about 30 h at 950 ◦ C. In this process the cementite of the ledeburite decomposes into austenite and graphite (temper carbon), which is precipitated in fluky clusters. In a second step of the heat treatment the austenite is converted during slow cooling from 800 to 700 ◦ C into ferrite and temper carbon or transformed during quick cooling into pearlite and temper carbon. In EN 1562 five grades of white malleable cast iron and nine grades of black malleable cast iron are classified by tensile strength.

Abrasion Resisting Alloyed Cast Iron. High-alloy white cast iron (EN 12513) is specially qualified for abrasionresistant applications. The predominant carbides in its microstructure provide the high hardness necessary for crushing and grinding other materials without degradation. The supporting matrix structure may be adjusted by alloy content and/or heat treatment to develop the most cost-effective balance between resistance to abrasive wear and the toughness required to withstand repeated impact loading. High-alloy white cast iron is easily cast into shapes required for crushing and grinding or the handling of abrasive materials. Abrasion resistance concerns the conditions under which a metal or alloy is used. The ability of a part to resist a weight loss due to abrasion depends upon its microstructure, the actual mechanical operations of the part, and the kind and size of material being moved, crushed or ground. Most of the white cast iron designated for abrasionresistant applications falls within the high-alloy cast iron category, but unalloyed white cast iron is common and provides satisfactory service where the abrading material is not fine or where replacement is not frequent or expensive. All alloyed cast iron contains chromium to prevent the formation of graphite and to ensure the stability of the carbides in the microstructure. Alloy white cast iron also may contain nickel, molybdenum, copper, or a combination of these alloying elements to prevent or minimize the formation of pearlite in the microstructure. Unalloyed white cast iron castings develop hardnesses in the range 350–550 BHN. Their microstructures consist of primary iron carbides with a microhardness of 900–1200 VHN in a pearlitic matrix with a microhardness of 220–300 VHN. Alloyed martensitic white cast iron, however, develops Brinell hardnesses in the 500–700 range. The carbide hardness remains 900–1200 VHN, but martensitic, always associated

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with some retained austenite, exhibits a microhardness of 600–700 VHN. For many abrasion-resistant applications; the more costly alloyed white cast iron with martensitic matrix structures provide the most economical service. EN 12513 covers the composition and hardness of abrasion-resistant white cast iron. Martensitic white cast iron falls into two major groups: • The low-chromium group with 1–4% chromium and 3–5% nickel • The high-chromium white cast iron containing 14– 28% chromium with 1–3% of molybdenum, often alloyed further with additions of nickel and copper A third but minor category comprise the straight 25–28% chromium white cast iron. Cast Steel Cast steels can be classified into four groups: • Cast carbon and cast low-alloy steel • Cast high-alloy steel • Cast stainless steel • Cast heat-resisting steel

Part B 7.1

Cast Carbon and Cast Low-Alloy Steel. This group of cast steels consists of many subgroups: steel castings for general purposes (DIN 1681, EN 10293 steel casting for general engineering uses), steel casting for pressure purposes (partially EN 10213), steel castings with improved weldability and toughness for general purposes (DIN 17182, EN 10293 steel castings for general engineering uses, draft), quenched and tempered steel castings for general purposes (DIN 17205, EN 10293 steel castings for general engineering uses, draft), steel castings for use at room temperature and elevated temperatures (EN 10213-2), and steel castings for use at low temperatures (EN 10293-3). Carbon steel is considered to be steel in which carbon is the principal alloying element. Other elements that are present and that, in general, must be reported are manganese, silicon, phosphorus, and sulfur. In a sense, all of these elements are residuals from the raw materials (coke, iron ore) used in the manufacture of the steel, although the addition of manganese is often made during the steelmaking process to counter the deleterious effect of sulfur. Low-alloy cast steels are considered to be those steels to which elements (other than carbon) are added deliberately to improve mechanical properties. For all cast carbon and cast low-alloy steels, the mechanical properties are controlled by the chemical

composition, the heat treatment and the microstructure of these cast steels. Among the exceptions are the effect of carbon on increasing hardness, the effect of nickel on increasing toughness, and the effect of combinations of chromium, molybdenym, vanadium, and tungsten on increasing elevated temperature strength. The major reason for using alloying elements in low-alloy cast steels is to make the role of heat treatment on increasing strength effective over a wide range of material thickness by quenching and tempering. This effectiveness is termed hardenability. 30 grades of steel castings for general engineering uses (5 grades of carbon cast steels, 20 grades of low alloy cast steels, and 5 grades of high alloy cast steels) are classified by their chemical composition, heat treatment processes (austenitizing, air cooling/austenitizing, quenching, tempering), and mechanical properties in EN 10293 (Table 7.7). EN 10213 consists of steel castings for pressure purposes, in specially cast steel grades for use at room temperature and elevated temperatures (carbon cast steels, low alloy cast steels, high alloy cast steels), cast steel grades for use at low temperatures (low alloy cast steels, high alloy cast steel), and cast austenitic and austeniticferritic steel grades (high alloy cast steel grades). High-Alloy Cast Steel. There are two main groups of high-alloy cast steels: cast stainless steels and cast heatresisting steels. Cast Stainless Steel. Cast stainless steels (EN 10213, EN 10283, SEW 410) are distinguished by special resistance to chemically corrosive substances; in general, they have a chromium content of at least 12 wt %. The cast stainless steels in EN 10213, EN 10283, and SEW 410 are subdivided into martensitic, ferritic-carbidic, ferritic-austenitic, austenitic, and full austenitic steels. Cast stainless steels are suitable for welding. Their resistance to intercrystalline corrosion in mill finish is an important property of cast stainless steels. A special kind of cast stainless steels are the duplexsteels (dual phase steels) with about 50% austenite and 50% soft martensite, in which the two phases fulfil different functions: the austenite guarantees corrosion Table 7.7 Mechanical properties of steel castings for gen-

eral engineering uses Tensile strength (N/mm2 ) Yield strength (N/mm2 ) Elongation (%)

380– 1250 200– 1000 7 – 25

Manufacturing Engineering

protection, e.g. seawater resistance in this case, the soft martensite guarantees component strength. In EN 10213, EN 10283, and SEW 410 44 grades of cast stainless steels are classified by chemical composition and mechanical properties. The main alloying elements are chromium, nickel, and molybdenum. Heat-Resisting Cast Steel. The chief requirement for

Cast Nonferrous Alloys The cast nonferrous alloys are classified into four main groups:

• • • •

Cast aluminum alloys Cast magnesium alloys Cast copper alloys Cast zinc alloys

There are other groups: for example, cast titanium alloys, cast tin alloys, cast lead alloys, cast nickel alloys, cast cobalt alloys, etc. Cast Aluminum Alloys. The specification of a cast aluminum alloy (EN 1706) for a cast component is based

upon the mechanical properties it can achieve. These properties are obtained from one particular combination of cast alloy, melt treatment (grain refining, modification) foundry practice, and thermal treatment. In all cast aluminum alloys the percentage of alloying elements and impurities must be carefully controlled. The main alloying elements of the cast aluminum alloys are copper, silicon, magnesium, and zinc. Grain refiners, which are usually materials that liberate titanium, boron, or carbon, are generally added in the form of master-alloy to the melt. In casting alloy this is a well-proven method to influence the nucleation conditions in a melt, so that it solidifies with as finegrained and dense a structure as possible. Hypereutectic aluminum-silicon alloys can be grain-refined with additions that release phosphorus, which promotes the nucleation of primary silicon. Modifying aluminumsilicon alloys of eutectic and hypereutectic composition means treating the melt to binder primary silicon from precipitating to form coarse, irregularly shaped particles. The melt can be modified by adding capsules of metallic sodium or compounds that release sodium. Alternatively, the addition of strontium has proved successful in castings. In contrast to sodium, which burns off and is lost fairly quickly, strontium lasts longer. Industrial casting processes consist of traditional sand casting, low-pressure sand casting, investment casting, lost-foam casting, permanent mold casting, high pressure die casting, low-pressure permanent mold casting, back-pressure die casting, vacuum die casting, squeeze casting, and thixocasting. Sand and permanent mold castings may be heat treated to improve mechanical and physical properties. The following thermal treatments are industrially used:

• •

Stress relief or annealing Solution heat treatment and quenching, artificial aging

Table 7.8 Mechanical properties of cast stainless steels Tensile strength (N/mm2 ) Yield strength (N/mm2 ) Elongation (%)

430– 1100 175– 1000 5 – 30

Table 7.9 Mechanical properties of heat-resistant cast steel at room temperature Tensile strength (N/mm2 ) Yield strength (N/mm2 ) Elongation (%)

400– 440 220– 230 5 – 15

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heat-resisting cast steels (EN 10295, SEW 471, SEW 595) is not especially good high-temperature strength but sufficient resistance to hot gas corrosion in the temperature range above 550 ◦ C. The highest temperature at which a heat-resisting steel can be used depends on operational conditions. Recommended temperatures for air and hydrogen atmospheres are up to 1150 ◦ C depending on the chemical composition. The scaling limit temperatures for the heat-resisting steels is defined as the temperature at which the material loss in clean air is 0.5 mg cm−2 h−1 . The scale resistance of heat-resisting cast steels is based on the formation of dense, adhesive surface layers of oxides of the alloying elements chromium, silicon, and aluminum. The protective effect starts when the chromium content is 3 to 5%, but chromium contents up to 30% can be alloyed. The protective effect of these layers is limited by the corrosive low-meltingpoint eutectics and by carburizing. To increase the heat resistance the alloying element nickel is added in addition to chromium (Cr + Ni = 25–35%). In EN 10295, SEW 471, and SEW 595 25 grades of heat-resistant cast steels are classified by the chemical composition and the mechanical properties. The main alloying elements are chromium, silicon, and nickel. The creep behavior with the creep rupture strength and the creep limit in the temperature range of 600 up to 1100 ◦ C is the most important.

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Table 7.10 Mechanical properties of aluminum cast alloys (sand molding – 1, permanent mold casting – 2, high pressure die casting – 3, investment casting – 4) Casting technology

1

2

3

4

Tensile strength (N/mm2 ) Yield strength (N/mm2 ) Elongation (%) Brinell hardness

140–300 70–210 1 –5 40–100

150–330 70–280 1–8 45–100

200–240 120–140 1–2 55–80

150–300 80 –240 1–5 50 –90

• •

Solution heat treatment, quenching and natural aging and Solution heat treatment, quenching, and artificial overaging (for the groups 1, 2 and 4 in Table 7.10)

In EN 1706 37 grades of cast aluminum alloys are classified by their chemical composition and mechanical properties (Table 7.10). The mechanical properties depend on the chemical composition of the cast aluminum alloys, the casting technology, and the heat treatment process.

Following are some of the advantages magnesium alloys offer casting designers:

• • •

Cast Magnesium Alloys. Magnesium combines a den-

Part B 7.1

sity two-thirds that of aluminum and only slightly higher than that of fiber-reinforced plastics with excellent mechanical and physical properties as well as processability and recyclability. Cast magnesium alloys (EN 1753) can be divided into two groups: the sand-casting alloys that have a fine grain structure due to a melt treatment with small additions of zirconium, and the die casting alloys, in which aluminum is the principal alloying element. The alloys can also be classified as general purpose, high ductility, and high temperature alloys. Most of the alloys are produced as high-purity versions to reduce potential corrosion problems associated with higher levels of iron, nickel, and copper. Aluminum improves the mechanical strength, corrosion properties, and castability of the castings. Ductility and fracture toughness are gradually reduced with increasing aluminum content. Manganese is added to control the iron content of the alloys. The level of manganese additions varies from one alloy to the next, depending on the mutual solubilities of iron and manganese in the presence of other alloying elements. A basic requirement of high-purity alloys is that the iron content of diecast parts is limited to a maximum of 0.005 wt %. Other impurities like nickel and copper also must be strictly controlled. Other alloying elements are zinc, manganese, silicon, copper, zirconium, and rare earth elements.

• • • • •

Light weight – The lightest of all structural alloys, magnesium alloys preserves the light weight of a design without sacrificing strength and rigidity. High stiffness to weight ratio – This characteristic is important where resistance to deflection is desired in a light-weight component. Damping capacity – Magnesium is unique among metals because of its ability to absorb energy inelastically. This property yields the vibration absorption capacity to ensure quieter operation of equipment. Dimensional stability – Annealing, artificial aging or stress-relieving treatments normally are not necessary to achieve stable final dimensions. Impact and dent resistance – The elastic energy absorption characteristics of magnesium alloys result in a good impact and dent resistance and energy management. Anti-galling – Magnesium alloys possess a low galling tendency and can be used as a bearing surface in conjunction with shaft hardness above 400 HB. High conductivity – Magnesium alloys have a high thermal conductivity and a good electrical conductivity. Wall thickness – Magnesium alloy die castings are commonly produced with a wall thickness from 0.15 to 0.4 cm.

Magnesium alloys can be cast by a variety of methods, including high-pressure die casting, low pressure permanent mold casting, sand casting, plaster/investment casting, and thixocasting and squeeze casting. Different alloys may be specified for the different processes. In cases where the same alloy is used with different casting processes, it is important to note that the properties of the finished castings will depend on the casting method. The most prevalent casting method

Manufacturing Engineering

7.1 Casting

535

Table 7.11 Mechanical properties of cast magnesium alloys Casting method Sand casting Tensile strength (N/mm2 ) Yield strength (N/mm2 ) Elongation (%) Brinell hardness

140– 250 90– 175 2–8 50– 90

Table 7.12 Mechanical properties of cast copper alloys Tensile strength (N/mm2 ) Yield strength (N/mm2 ) Elongation (%) Brinell hardness

150– 750 40– 480 5 – 25 40– 190

Cast Copper Alloys. Cast copper alloys (EN 1982) are known for their versatility. They are used in a wide range of applications because they are easily cast, have a long history of successful use, are readily available from a multitude of sources, can achieve a range of physical and mechanical properties, and are easily machined, brazed, soldered, polished, or plated. The following lists the physical and mechanical properties common to cast copper alloys:

• •

•

Good corrosion resistance, which contributes to the durability and long-term cost-effectiveness. Favorable mechanical properties ranging from pure copper, which is soft and ductile, to manganesebronze, which rivals the mechanical properties of quenched and tempered steel. In addition, all cast copper alloys retain their mechanical properties, including impact toughness at low temperatures. High thermal and electrical conductivity, which is greater than any metal except silver. Although the conductivity of copper drops when alloyed, cast copper alloys with low conductivity still conduct both heat and electricity better than other corrosionresistant materials.

High-presure diecasting

160–250 90 –175 2–8 50 –90

150–260 80–160 1 –18 50–85

Table 7.13 Mechanical properties of cast zinc alloys Tensile strength (N/mm2 ) Yield strength (N/mm2 ) Elongation (%) Brinell hardness

•

•

•

•

• •

220– 425 200– 370 2.5 – 10 83– 120

Bio-fouling resistance, as copper inhibits marine organism growth. Although this property (unique to copper) decreases upon alloying, it is retained at a useful level in many alloys, such as coppernickel. Low friction and wear rates, such as with the high-leaded tin-bronzes, which are cast into sleeve bearings and exhibit lower wear rates than steel; good castability, as all cast copper alloys can be sand cast and many can be centrifugally, continuously, and permanent mold cast, as well as diecast. Good machinability, as the leaded copper alloys are free-cutting at high machining speeds, and many unleaded alloys such as nickel-aluminum bronze are readily machinable at recommended feeds and speeds with proper tooling. Ease of post-casting processing, as good surface finish and high tolerance control is readily achieved. In addition, many cast copper alloys are polished to high luster, and platting, soldering, and welding also are routinely performed. Large alloy choice, since several alloys may be suitable candidates for any given application depending upon design loads and corrosivity of the environment. Comparable costs to other metals due to their high yield, low machining costs, and little requirement for surface coatings such as paint.

In EN 1982 the cast copper alloys are divided into cast copper, cast copper-chromium, cast copper-zinc, cast copper-tin, cast copper-tin-lead, cast copper-aluminum, cast copper-manganese-aluminum, and cast coppernickel alloys.

Part B 7.1

for magnesium alloys is die casting. In this process, thin-walled parts are produced at high production rates with reduced tool wear compared to aluminum alloys, due to the lower heat content per volume of molten metal. Both hot chamber and cold camber machines are currently used for magnesium alloys. Thixocasting is another casting method that has shown progress with magnesium alloys. There are seven cast magnesium alloys in EN 1753.

Permanent mould casting

536

Part B

Applications in Mechanical Engineering

35 grades of cast copper alloys are classified by their chemical composition and mechanical properties in EN 1982. Cast Zinc Alloys. Cast zinc alloys (EN 1774 and EN 12844) are assigned to three alloy groups. The first group of alloys have 4% aluminum as the primary alloying element with 0.099% or less magnesium to control intergranular corrosion. Another alloying element is copper. The alloys with the highest copper content have the highest hardness. The mechanical properties can be improved with 0.005 to 0.2% nickel as alloying element. The second group has higher aluminum contents (8 to 27%) These alloys have superior hardness, wear and creep resistance that increase with the aluminum content. The third group is a cast zinc alloy that has copper as the primary alloying element. Castings of the cast zinc alloys are manufactured by the high pressure die casting. In EN 12844 8 grades of cast zinc alloys are classified by their chemical composition and mechanical properties.

7.1.4 Primary Shaping Part B 7.1

According to DIN 8580 [7.1], primary shaping is the manufacturing of a solid body from a shapeless material by creating cohesion. Thus primary shaping serves to give a component made from a material in shapeless condition an initial form. Shapeless materials are gases, liquids, powders, fibers, chips, granules, solutions, melts, and the like. Primary shaping may be divided into two groups with regard to the form of the products and their further processing:

•

•

Products produced by primary shaping, which will be further processed by forming, severing, cutting, and joining. The final product no longer resembles the original product of primary shaping in form and dimensions, i. e. a further material change in shape and dimensions is accomplished by means of other main groups of manufacturing processes. Products produced by primary shaping, which essentially have the form and dimensions of finished components (e.g. machine parts) or end-products, i. e. their shape essentially corresponds to the purpose of the product. The attainment of the desired final form and dimensions usually requires only operations that fall into the main process group cutting (machining).

Most powders are produced by primary shaping, whereby the powders are atomized out of the melt, and rapid solidification is followed. From powder, sintering parts are produced as a result of powder metallurgical manufacturing. The production of cast parts from metallic materials in the foundry industry (castings), from metallic materials in powder metallurgy (sintered parts), and from high-polymer materials in the plastics processing industry has major advantages for economic efficiency. The production of cast parts is the shortest route from the raw material to the finished part. It bypasses the process of forming and all the associated expense. The final form of a finished component with a mass ranging from a few grams to several hundred tonnes is practically achieved in one direct operation. The production of cast parts by primary shaping from the liquid state allows the greatest freedom of design. This cannot be achieved by any other manufacturing process. Primary shaping also enables processing of materials that cannot be achieved by means of other manufacturing methods. The direct route from the raw material to the preform or the end-product results in a favorable material and energy balance. The continual further development of primary shaping processes increasingly permits the production of components and end-products with enhanced practical characteristics, i. e. cast parts with lower wall thicknesses, lower machining allowances, narrower dimensional tolerances, and improved surface quality. In the following, primary shaping of metallic materials from the liquid state in foundry technology, of metallic materials from the solid state in powder metallurgy, and of high-polymer materials (plastics) from the plasticized state or from solutions is discussed on a common basis with regard to the fundamental technological principles. The discussion is restricted to subjects relevant to mechanical engineering. For a better appreciation of the relevant principle of action, many detailed technological operations are omitted, which although vital to the specific manufacturing technology, are of minor importance. Furthermore, when discussing the specific primary shaping processes, only products with a simple form are referred to, because the diversity of the possible geometric forms cannot be described here. Only the most important primary shaping processes are selected, as the large number of technological processes and process variables means that it is impossible to provide anything like a complete description. The

Manufacturing Engineering

processes are selected first according to their technical importance and second according to the principle of action. Materials technology problems will only be mentioned briefly, although they are vital in order to understand the technological processes, their applicability and efficiency, and the changes in material properties brought about by the technological processes. Process Principle in Primary Shaping In the processes of primary shaping, the technological manufacturing process essentially comprises the following steps:

• • • • •

Supply or production of the raw material as an amorphous substance Preparation of a material state ready for primary shaping Filling of a primary shaping tool with the material in a state ready for primary shaping Solidification of the material in the primary shaping tool Removal of the product of primary shaping from the primary shaping tool

Material State Ready for Primary Shaping In primary shaping of metallic materials from the liquid state, the raw materials (pig-iron, scrap, ferroalloys and the like) are melted in a metallurgical melting furnace by means of thermal energy. The melting furnaces are usually physically separated from the primary shaping tool. The molten metal is carried by means of transfer vessels (ladles) to the primary shaping tools, termed molds in the foundry industry, and cast there. In primary shaping of high-polymer materials from the plasticized state, bulk raw materials (granules, powder) are fed after proportioning into a preparation device, which is usually integral with the primary shaping tool. There, thorough mixing, homogenizing and plasticizing of the material to be processed are accomplished under the action of heat and pressure. When solutions are used, these are produced in a mixing unit and then poured into the primary shaping tool. In primary shaping of metallic and also high-polymer materials from the solid state, the bulk raw materials (metal powder, plastic powder, or plastic granules) are poured straight into the primary shaping tool, where they sinter, or first become plastic and then solidify under the action of pressure and thermal energy.

Primary Shaping Tools The primary shaping tool contains a hollow space which, with the allowance for contraction, usually corresponds to the form of the product (unmachined part) to be manufactured, but may be smaller or larger than the resulting unmachined part. Furthermore, primary shaping tools often contain systems of channels (runners) for feeding the material in the state ready for primary shaping. The allowance for contraction corresponds to the dimensional changes that occur in the material to be processed from the moment of solidification to its cooling to room temperature. In the production of cast parts, a distinction is made between primary shaping tools for once-only use and those for repeated use. Primary shaping tools for onceonly use are only used for primary shaping of metallic materials from the liquid state in foundry technology. They are termed expendable or dead molds. Only one product (casting) can be manufactured, as the mold is subsequently destroyed. However, primary shaping tools for repeated use (permanent molds) are also used in foundry technology. A larger quantity of cast parts can be produced. The primary shaping technologies for processing of high-polymer materials and powder metallurgy use only primary shaping tools for repeated use. Primary shaping tools for repeated use are usually made of metallic, and more rarely of nonmetallic, materials. Primary shaping tools for once-only use (dead molds) are made with the aid of patterns. Filling the Primary Shaping Tools Filling of the primary shaping tools with the material ready for primary shaping may be accomplished by means of the following principles of action: under the influence of gravity, elevated pressure or centrifugal force and by displacement. The material to be processed can be put into the primary shaping tools in solid, pourable form (e.g. powder), as molten metal in the case of metallic materials, or in plasticized condition, as a solution or as a paste in the case of high-polymer materials. Change of State Ready for Primary Shaping Shaping into the Solid State of Aggregation. Liquid

metallic materials (molten metals) change by crystallization to the solid state of aggregation on cooling owing to the removal of heat. Thermoplastics are cooled in the primary shaping tool after forming. As a result of temperature reduction, which is accomplished either by heat removal in cooled tools or in downstream equipment

537

Part B 7.1

These individual steps are discussed in the following section.

7.1 Casting

566

Part B

Applications in Mechanical Engineering

Table 7.20 Typical values for coefficient of friction and friction factor Process

Coefficient of friction μ

Friction factor m

Cold forging (steel, stainless steel, Cu-alloys, brass) Cold forging (Al-, Mg-alloys) Wire drawing (steel, stainless steel, Cu-alloys, brass) Wire drawing (Al-, Mg-alloys) Hot forging Forging of Ti and Ni alloys Hot rolling Deep drawing (steel) Deep drawing (stainless steel) Deep drawing (Cu-alloys, brass) Deep drawing (Al-, Mg-alloys) Ironing (steel) Ironing (stainless steel) Ironing (Cu-alloys, brass) Ironing (Al- and Mg-alloys)

0.05– 0.10 (lower values for phosphated workpieces) 0.05 0.05– 0.10

0.05–0.10

0.03– 0.10 Use not recommended Use not recommended Use not recommended 0.05– 0.10 0.10 0.05– 0.10 0.05 0.05– 0.10 0.05 0.10 0.05

– 0.20–0.40 0.10–0.30 (glass lubrication) 0.70–1.00 (no lubrication) Use not recommended Use not recommended Use not recommended Use not recommended Use not recommended Use not recommended Use not recommended Use not recommended

Part B 7.2

which friction is specified, and Af is the workpiece area on which forces are specified. To apply the upper bound method the plastic region has to be estimated, the constant flow stress has to be estimated in the plastic region, friction stresses must be constant and hence described by the constant shear model, and finally, a kinematically admissible velocity field or appropriate shear planes have to be assumed. Lower bound methods lead to forces that are always lower than the actual forces. Here, a statically admissible stress field has to be guessed that fulfils the equilibrium equations and the stress boundary conditions. Ideally, for an analysis the force can be limited between an upper and lower bound. Yet, the application of the lower bound method is much more difficult since the guess of an admissible stress field is not straightforward. Furthermore, in practical applications an upper bound for the forming forces are sufficient. The upper bound property for the forming force is given if and only if the material’s flow stress is correct and the friction stresses are correct. Otherwise, the computed upper bound may also be lower than the actual physical forces. The Slip Line Field Solution. The slip line field solution

also assumes rigid perfectly plastic material behavior. Furthermore, the plane strain state is assumed. Moreover, the processes have to be frictionless. If these assumptions are fulfilled, then the theory supplies the

0.05–0.10 –

exact solution. The slip line field solution is based on the governing equations including the flow condition, the volume constancy equation, the flow rule, and the equilibrium equations for the plane strain state. These equations build up a hyperbolic system of partial differential equations that can be solved by the method of characteristics. If the stresses are expressed in terms of the hydrostatic stress and the orientation of the stress element in the maximum shear stress direction, the two characteristics lines are orthogonal to each other (α and β-slip lines) and correspond to the directions of maximum shear stress; therefore they are called slip lines. The governing equations can be written as ordinary differential equations along each slip line. These equations can be summarized as the Hencky equations for the stresses σh − 2kφ = constant along the α-slip line, σh + 2kφ = constant along the β-slip line,

(7.39)

and the Geiringer equations in terms of the particle velocities dφ dνα = νβ along α-slip line, ds ds dνβ dφ (7.40) = να along β-slip line, ds ds where φ is the inclination of the slip line and s is distance along the slip line. Constructing the slip line field from known boundary conditions, using (7.39) and

568

Part B

Applications in Mechanical Engineering

These functionals can be easily discretized by assuming shape functions for the velocities over the element domain. After the standard discretization procedure the resulting finite element equations read   e (7.45) KD + KeH ν e = f e . f e is the nodal force vector of the element compatible with the nodal velocity vector ν e . The nonlinear deviatoric stiffness matrix is given by KeD and the linear hydrostatic stiffness matrix by KeH . The resulting nonlinear (w.r.t. nodal velocities) equations (7.45) can be solved by standard numerical methods. The common ones applied are the direct iteration and the Newton– Raphson method. Both methods are iterative and are applied in increments. The time integration is performed explicitly in most commercial software. Implicit Static Elasto-Plastic Finite Element Formulations. These formulations usually assume an additive

composition of the elastic and plastic strain rate tensors pl

εij ≈ εijel + εij .

(7.46)

Part B 7.2

This is based on so-called hypoelastic models. Also models based on hyperelasticity are used that lead to a multiplicative split of elastic and plastic deformations. For the elastic strain rates the generalized Hooke’s law and for the plastic strain rates the Levy–Mises equations are used. These then lead to the modified Prandtl–Reuss equations between the objective (frame-invariant) rate of the stress tensor and the strain rates σˆ ij = Cijmn ε˙ mn .

(7.47)

Various types of objective rates can be used such as the Jaumann rate, the Truesdell rate, or generally any Lie-derivative of the true stress tensor. The constitutive fourth order tensor contains the elastic constants and the plastic properties such as the normal of the flow surface and the slope of the flow curve. For consistent linearization (7.47) has to be modified slightly. The elasto-plastic field equations are derived from the principle of virtual work supplying (neglecting inertial forces)     ∂u j dV − ti δu i dA = 0 . σij δ (7.48) ∂xi V

A

Equation (7.48) must be fulfilled at the unknown current configuration. Linearization of this equation about the last known state and space discretization supply the

nonlinear finite element equations. Time integration is performed primarily implicitly. Explicit Dynamic Elasto-Plastic Finite Element Formulations. The explicit dynamic finite element formu-

lations are based on the virtual work principle to which an inertia term is added     ∂u j dV − ti δu i dA σij δ ∂xi V A  + ρu¨ i δu i dV = 0 , (7.49) V

where u¨ i is the acceleration vector and ρ the density. Discretization of (7.49) leads to Mu¨ = F − I .

(7.50)

Here, M is the mass matrix, F the external force vector, and I the internal force vector at the current time. Time discretization by a central difference scheme and by adding a damping term C supplies the fundamental equations for the formulation " ! 1 M ut+Δt (Δt)2   t  M u − ut−Δt = Ft − I t + −C . (7.51) 2Δt Δt Here Δt is the time increment for the computation and must satisfy the stability condition L , (7.52) Δt ≤ cd where cd is the current dilatational wave speed of the material (speed of sound in that material) and L is the characteristic element dimension, which can be taken as the minimum distance between any two nodes of an element. The elastic wave speed can be found from # 2G(1 − ν) (7.53) . cd = (1 − 2ν)ρ

7.2.4 Bulk Forming Processes This section describes the basic bulk forming processes. Upsetting A workpiece of initial diameter d0 and initial height h 0 is reduced between two flat dies to a specimen with final diameter d1 and final height h 1 (Fig. 7.50). This process is also called open die forging or free forming.

602

Part B

Applications in Mechanical Engineering

ter of energy controlled presses is the nominal energy E nom . Hammers and screw presses are two typical representatives of this group. Different from hammers, screw presses have drives and frame elements under load, so that for these in addition to the nominal energy also a nominal force has to be specified for which these machine elements are designed. Force controlled presses provide independent of the stroke a given force that is the obtained by the hydraulic pressure p multiplied by the cylinder cross-sectional area A (Fig. 7.120b). The basic parameter for these presses is therefore the maximum allowable force Fnom . The typical representative of this group is the hydraulic press. Finally, stroke controlled presses (Fig. 7.120c) provide ram force for each ram position depending on the kinematics of the mechanical drive. The characteristic parameters, therefore, are the ram force as a function of the stroke and the maximum ram force Fnom . Typical representatives are crank and toggle presses. Transient Parameters. The basic time-dependent pa-

Part B 7.2

rameters are the effective stroke rate, the contact time of the tools with the workpiece under the forming load, and finally the speed of the press. The effective stroke rate determines the economic efficiency of the press. This parameter is related to the failing height in case of hammers, to the speed during the load free stroke in case of hydraulic presses and to the speed and total stroke in case of crank presses. The contact time under pressure is especially important for warm and hot forming processes since it determines the cooling amount of the workpiece. Typical contact times for various machines are given in Table 7.33 For stroke controlled presses the contact time under pressure is larger the softer the frame and tool system are (i. e. the lower C is). Another important parameter is the speed of the ram of the press. This directly influences the strain rates during forming. Especially in warm and hot forming, the higher the strain rates, the higher the flow stress, and hence the higher the forming loads. In hammers the speed is given during the forming process by the power balance, whereas for stroke driven presses the ram speed is a function of the ram position. For the latter, it must be noted that the true ram speed depends on the stiffness of the frame-tool system. Accuracy Parameters. The accuracy parameters of presses are related to geometric errors of the workpiece, such as position errors during impact, eccentricity of the product, dimensional errors in product height, the angle

Table 7.33 Order of magnitude for contact times for various press types (after [7.22, 23]) Press type

Contact times under pressure (s)

Hammers Screw presses (with fly-wheel) Stroke controlled presses Hydraulic presses

10−3 – 10−2 10−2 – 10−1 10−1 – 5 × 10−1 10−1 – 1

of twist of the product, etc. These errors are caused either by inaccuracies of the presses in the idle state, such as excessive clearance of the guides or skewness of the lower die and upper die leading to position errors during impact, or by inaccuracies of the press under load, such as elastic deformations leading to height errors in the tool. The latter errors are strongly dependent on the stiffness of the press, so that this characteristic parameter is the key parameter for the press specification. In presses generally the frame, the upper tool, the lower tool, and the drive system deflect elastically. In the case of hammers, only the lower tool deflects elastically. Other Parameters. Finally, parameters such as stroke

length, tooling space, space requirements of the press, weight of the press, and necessary power supply can be listed as other characteristic parameters. Energy Controlled Presses Energy controlled presses provide a certain predetermined amount of energy for the forming process. Force as well as displacement is not controlled directly. There are basically two types of energy controlled presses: Hammers and screw presses. Hammers. There are basically three types of hammers (Fig. 7.121): Drop hammers provide the energy by a freely falling ram including the upper die. In doubleacting hammers the ram is accelerated by a fluid such as steam, air, or hydraulic oil acting through a cylinder and piston. Finally, in counter-blow hammers upper and lower dies are accelerated towards each other. The first two types transmit the forging force to the ground, whereas for the counter-blow hammer the ground is practically not effected by the forming load. The properties of these hammers are given in Table 7.34. Hammers are basically used in hot forging operations, so that the impact speeds are important for determining the strain rates for the forming process.

614

Part B

Applications in Mechanical Engineering

Table 7.36 Values for ferrous materials kc1.1 and 1 − m c Cutting conditions Cutting speed Depth of cut Cutting material Cutting edge geometry

vc = 100 m/min ap = 3.0 mm Cemented carbide P10

Steel Cast iron

α 5◦ 5◦

γ 6◦ 2◦

λ 0◦ 0◦

ε 90◦ 90◦

κ 70◦ 70◦

rε 0.8 mm 0.8 mm

Part B 7.3

Material

Material number

Rm (N/mm2 )

Specific machining forces ki1.1 kc1.1 1 − mc kf1.1

1 − mf

kp1.1

1 − mp

St 50-2 St 70-2 Ck45N Ck45V 40Mn4V 37MnSi5V 18CrNi8BG 34CrNiMo6V 41Cr4V 16MnCr5N 20MnCr5N 42CrMo4V 55NiCrMoV6V 100Cr6 GG30

1.0050 1.0070 1.1191 N 1.1191 V 1.1157 V 1.5122 V 1.5920 BG 1.6582 V 1.7035 V 1.7131 N 1.7147 N 1.7225 V 1.2713 V 1.2067 JL1050

559 824 657 765 755 892 618 1010 961 500 588 1138 1141 624 HB = 206

1499 1595 1659 1584 1691 1656 1511 1686 1596 1411 1464 1773 1595 1726 899

0.30 −0.07 0.51 0.27 0.31 0.31 0.27 0.37 0.27 0.37 0.24 0.43 0.21 0.14 0.09

274 152 309 282 244 249 242 284 215 312 300 252 198 362 164

0.51 0.10 0.60 0.57 0.55 0.67 0.46 0.72 0.52 0.50 0.58 0.49 0.34 0.47 0.30

0.71 0.68 0.79 0.74 0.78 0.79 0.80 0.82 0.77 0.70 0.74 0.83 0.71 0.72 0.59

351 228 521 364 350 239 318 291 291 406 356 354 269 318 170

Table 7.37 Correction factors for cutting force calculation Cutting speed correction factor

Rake angle correction factor Cutting material correction factor

Tool wear correction factor Cutting fluid correction factor

Workpiece shape correction factor

Kv =

2.023 vc0.153

for vc < 100 m/min

Kv =

1.380 vc0.07

for

vc > 100 m/min

K γ = 1.09–0.015 ◦ (steel) K γ = 1.03–0.015 ◦ (cast iron) K CM = 1.05 (HSS) K CM = 1.0 (cemented carbide) K CM = 0.9 – 0.95 (ceramic) K TW = 1.3–1.5 K TW = 1.0 for sharp cutting edge K CL = 1.0 (dry) K CL = 0.85 (non-water soluble coolant) K CL = 0.9 (emulsion-type coolant) K WS = 1.0 (outer diameter turning) K WS = 1.2 (inner diameter turning)

Here, T0 and vc are reference values. T0 is normally set at T0 = 1 min. C is the cutting speed for an operating period of T0 = 1 min.

The Taylor straight line is plotted on the basis of a wear/tool life turning test according to ISO 3685. With these tests suitable settings for high-speed steel,

Manufacturing Engineering

7.3 Machining Processes

619

Table 7.39 Cutting force components for drilling Material

Mat. No.

Rm (N/mm2 )

1 − mc

kc1.1 (N/mm2 )

1 − mf

kf1.1 (N/mm2 )

18CrNi8 42CrMo4 100Cr6 46MnSi4 Ck60 St50 16MnCr5 34CrMo4 Grey cast iron

1.5920 1.7225 1.2076 1.5121 1.1221 1.0531 1.7131 1.7220

600 1080 710 650 850 560 560 610

0.82 ± 0.04 0.86 ± 0.06 0.76 ± 0.03 0.85 ± 0.04 0.87 ± 0.03 0.82 ± 0.03 0.83 ± 0.03 0.80 ± 0.03

2690 ± 230 2720 ± 420 2780 ± 220 2390 ± 250 2200 ± 200 1960 ± 160 2020 ± 200 1840 ± 150

0.55 ± 0.06 0.71 ± 0.04 0.56 ± 0.07 0.62 ± 0.02 0.57 ± 0.03 0.71 ± 0.02 0.64 ± 0.03 0.64 ± 0.03

1240 ± 160 2370 ± 230 1630 ± 300 1360 ± 100 1170 ± 100 1250 ± 70 1220 ± 120 1460 ± 140

Up to G-22 Over G-22

– –

– –

0.51 0.48

0.56 0.53

356 381

or at an angle to the axis of rotation of the tool. The cutting edge is not continuously in engagement with the workpiece. Therefore, it is subject to alternating thermal and mechanical stresses. The complete machine-tool– workpiece-fixture system is dynamically stressed by the interrupted cutting action. Milling processes are classified according to DIN 8589 on the basis of the following:

• • •

The nature of the resulting workpiece surface The kinematics of the cutting operation The profile of the milling cutter

Milling Classification of Milling Processes. In milling, the

Milling can be used to produce a practically infinite variety of workpiece surfaces. A distinguishing feature of a process is the cutting edge (major or minor) that produces the workpiece surface (Fig. 7.146): in face milling the minor cutting edge is located at the face of the milling cutter, while in peripheral milling the major cutting edge is located on the circumference of the milling cutter. A distinction can be made on the basis of the feed direction angle ϕ (Fig. 7.147): in down-milling the feed direction angle ϕ is > 90◦ , thus the cutting edge of the milling cutter enters the workpiece at the maximum undeformed chip thickness, while in up-milling the feed direction angle ϕ is < 90◦ , thus the cutting edge enters at the theoretical undeformed chip thickness h = 0. This initially results in pinching and rubbing. A milling operation may include both up-milling and down-milling. The principal milling processes are summarized in Fig. 7.148.

necessary relative motion between the tool and the workpiece is achieved by means of a circular cutting motion of the tool and a feed motion perpendicular to

Plain Face Milling with End Milling Cutters. The kinematics of cutting and the relationship of the cutting

Short-Hole Drilling. Short-hole drilling with drilling

depths of L < 2D covers a large proportion of bolt hole drilling, through hole drilling and tapping. For this, short-hole drills with indexable inserts may be used for diameters from 10 to over 120 mm. Their advantage compared with twist drills is the absence of a chisel edge, and the increase in cutting speed and feed rate achieved with indexable cemented carbide or ceramic inserts. Due to the asymmetrical machining forces, the use of short-hole drills requires rigid tool spindles similar to those found on common machining centers and milling machines. The higher rigidity of the tool enables pilot drilling of inclined or curved surfaces with accuracy of IT7.

Part B 7.3

Values are given in Table 7.39. The feed forces are strongly dependent on the shape of the chisel edge. They can be lowered significantly by web thinning [7.56]. Wear causes them to reach twice their original value or more. Surface quality in drilling with twist drills corresponds to roughing with Rz = 10–20 μm. The surface roughness can be reduced by reaming with increased dimensional accuracy. The application of solid cemented carbide drills provides another solution. When drilling solid metal, surface qualities, dimensional accuracy, and accuracy of shape like those obtained with reaming are achieved. Most of the drilling tools are further improved by suitable coatings.

504 535

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7.3 Machining Processes

629

Table 7.41 Properties of some coatings of HSS tools Properties

Coating materials TiN TiCN

Hardness (HV) 2200–2600 Critical load before 70 –80 coating failure (N) Maximum coating thickness (μm) 10 Deposition speed (μm/h) 6–8 Stability against oxidation (◦ C)b 550 Friction coefficient 0.67 (against steel 100Cr6) a For composition: 50%Ti-50%Cr; 50%Ti-50%Al; b Heating on air during 1 h

3200–3300 65–75 10 6 –7 550 –

TiCrNa

TiAlNa

2450– 2900 40– 50

3000–3200 60–70

3000– 3300 50– 60

20 4–5 650–700 –

10 4–6 800 0.67–0.75

50 2–4 700 0.57

by CVD or PVD techniques. They are used to achieve longer tool lives or higher cutting speeds. They broaden the range of use of a grade. Coated cemented carbides should not be used for nonferrous metals, high-nickel ferrous materials or, because of the edge rounding caused by the coating process, for precision or ultraprecision machining (cermets are better suited for this purpose). Intermittent cutting and milling requires coatings of especially high bonding strength, which can be influenced by process control during coating. The application areas of carbides fall into six groups as shown in Table 7.42. The classification is based on the properties of each grade and the machining conditions, type of material being machined, and chip formation. Ceramics. Ceramic cutting tool materials are single-

phase or multiphase sintered hard materials based on metal oxides, carbides, or nitrides. In contrast to cemented carbides, no metallic binders are needed and the material provides high hardness even at temperatures above 1200 ◦ C. Ceramic inserts are generally suitable for machining at high cutting speeds, usually exceeding 500 m/min. The use of aluminum oxide ceramic is restricted by its lower bending strength and fracture toughness compared with cemented carbide. In intermittent cutting with alternating mechanical and thermal stresses, microcracking, crack growth with microchipping or total fracture can occur. This effect greatly depends on the nature and composition of the ceramic. The change from single-phase materials (Al2 O3 ) to multiphase materials has improved toughness considerably: today Al2 O3 containing 10–15% ZrO2 (transformation toughening), Al2 O3 with TiC (dispersion strengthening) or Al2 O3 reinforced with SiC whiskers (high

Part B 7.3

tungsten carbide (WC: α-phase), titanium carbide and tantalum carbide (TiC, TaC: γ -phase). The binder is cobalt (Co; β-phase) with a content of 5–15%. Nickel and molybdenum binders (Ni, Mo) are also used in so-called cermets (also cemented carbides). A higher β-phase content increases toughness, while a higher α-phase content increases wear resistance and a higher γ -phase content enhances wear resistance at high temperature. Cermets have high edge strength and cutting edge durability. They are suitable for finishing under stable cutting conditions. The manufacturing of cemented carbides by powder metallurgy permits considerable freedom in the choice of constituents (in contrast to casting). Cemented carbides retain their hardness up to over 1000 ◦ C (Fig. 7.158). They can therefore be used at higher speeds (by a factor of three or more) than highspeed steels. According to standards (DIN 4990/ISO 513) cemented carbides are classified into the metal cutting application groups P (for long-chipping, ductile ferrous materials), K (for short-chipping ferrous materials), M (for ductile cast iron and for ferritic and austenitic steels), N (for nonferrous metals such as aluminum and copper alloys), S (for superalloys and titanium alloys), and H (for hardened materials, such as steels and cast irons). Each group is subdivided due to toughness and wear resistant grades by adding a number. For example, P02 stands for very hard-wearing cemented carbide and P40 stands for tough cemented carbide. The metal cutting application groups do not correspond to grades of cutting tool material, but to the application areas of the finished cutting tools. Most cemented carbide cutting tools are coated with titanium carbide (TiC), titanium nitride (TiN), aluminum oxide (Al2 O3 ), or chemical or physical combinations of these substances. The coatings are applied

CrN

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7.3 Machining Processes

631

Table 7.43 Properties of oxide ceramics Properties

Al2 O3

Al2 O3 -ZrO2

Al2 O3 -TiC

Al2 O3 with SiC whiskers

Hardness (30 HV) Young’s modulus (GPa) Bending strength σB (MPa) Fracture toughness K 1C (MPa m1/2 ) Coefficient of thermal expansion α (10−6 K−1 ) Thermal conductivity λ (W/(m K))

2000 390 350 4.5 7.5

2000 380 600 5.8 7.4

2200 400 600 5.4 7.0

2400 390 600–800 6 –8 –

30

28

35

wear. Si3 N4 is suitable for turning and milling of gray cast iron, for highly intermittent cutting actions, and for the turning of high-nickel content materials. The properties of some oxide ceramic materials are given in Table 7.43.

for machining of steels. PCBN is manufactured as either a carbide-backed or solid material. Different grades of PCBN are used for the machining of gray, white, and high-alloy cast irons, and hardened steels. Coatings on PCBN tools are becoming increasingly popular as with cemented carbides. Monocrystalline diamond tools are used for high-precision and ultraprecision machining of aluminum, copper, electroless nickel, glass, plastic, and silicon where, for example, surface finish requirements of several nm and form errors of less than 0.1 μm are common [7.76]. Being a single crystal material, it is possible to produce an extremely sharp cutting edge, within the range of 10–100 nm. Thick-film CVD diamond is generally considered as lying between monocrystalline and polycrystalline diamond, in terms of properties and behavior in application. In Table 7.44 conditions of cutting parameters and application areas of PCB and PCD tools are shown.

Table 7.44 Application of and cutting parameters for PCB and PCD tools Work material PCB Structural and tool steels (without thermal treatment) (< 30 HRC) Hardened steels (35 –55 HRC) Hardened steels (55 –70 HRC) Grey iron, high strength cast iron (150– 300 HB) White cast iron and hardened cast iron (400– 650 HB) PCD Aluminum and aluminum alloys Al-Si-alloys (Si < 20%) Copper and copper alloys Composed nonmetallic materials and plastics Wood WC-Co carbides

Cutting speed (m/min) Turning

Milling

–

400–900

50– 200 40– 120 300– 1000 40– 200

200–400 80 –300 600–3000 150–800

600– 3000 500– 1500 300– 1000 200– 1000 – 15– 30

600–6000 500–2500 300–2000 200–2000 2000–4000 15 –45

Part B 7.3

Superhard Cutting Tool Materials. Superhard cutting tool materials include polycrystalline diamond (PCD), polycrystalline cubic boron nitride (PCBN), monocrystalline diamond (MCD), and various forms of chemical vapor deposition diamonds (both thin-film coatings and self-supporting thick-films). The polycrystalline diamond is typically manufactured as a backed 0.5–2.0 mm layer of superhard composite on a cemented carbide substrate. PCD is used to machine nonferrous metals, including metal-matrix composites (MMC), wood, composites, stone, and certain cast irons. Due to a well-defined maximum operating temperature of between 700–800 ◦ C, it cannot be used

35

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651

gion of 30–40% and 20–25% when it is supplied under pressure. When machining sintered carbides, USM can be combined with electrochemical anodic dissolution. Processes of rough and finishing ultrasonic operations can be carried out on one machine tool. USM can provide a removal speed of up to 5500 m3 /min when machining glass and of up to 500 m3 /min when machining carbides; the corresponding surface finish is Ra = 0.32–0.16 μm. In recent ultrasonic developments the loose abrasive set-up is replaced by a tool with bonded abrasives (see the section Grinding with Rotating Tools). Regarding the kinematics it is an ultrasonic assisted grinding process, but in some cases it is referred to as ultrasonic milling. Besides milling and drilling also ultrasonic assisted turning has gained attention due to the improved wear behavior of the chosen tools [7.138, 139]. Beam Machining Thermoelectric processes utilize concentrated thermal energy to remove material and electrical energy, in some ways, to generate thermal energy. The main characteristics of these processes are high temperatures and high thermal energy densities that can be achieved for material removal up to 109 W/cm2 . The main beam machining processes are: laser beam machining (LBM), electron beam machining (EBM), and plasma beam machining (PBM). Beam machining (BM) can be used for machining both electrically conductive and nonconductive materials.

Table 7.46 Characteristics and application of thermal sources (after [7.135, 136]) Thermal source

Limiting concentration of energy (W/cm2 )

Energy source

Application

Gas flame

8 × 102

Arc plasma

6 × 103

Cutting off, accompanying heating, maximum thickness up to 3 mm Cutting off up to 3 mm, welding, heat treatment, welding

Electron beam

105

CW type laser beam

109

Jet of the heated gas T ≈ 3500 K Gas and the metal steam ionized by electric discharge Electron beam in vacuum Beam of photons in a gas

Pulsed laser beam

1010

Beam of photons in a gas

Cutting off, welding (up to 20 mm/pass), heat treatment, welding Welding (up to 10 mm/pass), heat treatment, welding on, evaporation of layers Evaporation of layers, drilling of apertures, surfaces amorphous, shock hardening

Part B 7.3

and fragile materials, such as glass, ceramics, silicon, ferrite, ruby, sintered carbide, diamond and the like [7.133]. Besides the oscillation from the tool side, ultrasonic movement of the workpiece is also possible [7.134]. It is accepted that material removal results from the combined effects of hammering (impacting) abrasive particles in the work surface, the impact of free abrasive particles on the surface, cavitations, erosion, and the chemical action of the fluid employed. The most important process input parameters controlling the material removal rate, surface roughness, and accuracy are the frequency and amplitude of oscillation, abrasive particle size, and by implication the impact force. During machining abrasive grains enter the machining zone as abrasive suspension. Mechanical vibrations of the tool with ultrasonic frequency are achieved by a suitable electro-mechanical converter. Usually, the converter will consist of magneto-resistive elements with the ability to change their linear size in a variable magnetic field. In some cases, piezoelectric converters are employed in a variable electric field. Tools for USM are made of structural steels, whilst carbides, CBN, silicon, and diamond are used as grits with grain sizes up to 3–10 μm [7.137]. The abrasive slurry moves into the machining zone either freely or under pressure and is removed by suction through the tool or workpiece, which substantially increases machining productivity. Mass concentration of grits in the abrasive slurry at free feed is in the re-

7.3 Machining Processes

Manufacturing Engineering

Plasma Beam Machining. Plasma beam machining is

based on the use of low temperature open plasma, which is applied to increase operational properties of machined components such as wear resistance, corrosion stability, thermal stability, etc. Such an amelioration is carried out in order to attain the formation of functional coatings from corresponding materials, generated by a plasma jet, plasma welding, and plasma depositing. Furthermore plasma is used in some combined plasma-mechanical processes, in particular in plasmamechanical machining.

655

Plasma coating is characterized by a great concentration of the thermal stream and high speed of the plasma jet. For coating fine grained powders are used (40–100 μm). The thickness of the deposited layer is around 0.3–0.5 mm and higher; deposition productivity is 2–4 kg/h. Plasma cutting is characterized by local removal of metal along a cut line by a plasma jet using quality plasma forming gases like argon, nitrogen, hydrogen, air, etc.. It is applied for cut off stainless steels with thicknesses up to 60–80 mm and low-carbon and lowalloying steels with thicknesses up to 30–500 mm. After plasma cutting the surface roughness may reach Rz = 80–160 μm. Combined Methods of Machining For further development of manufacturing technologies a combination of energy sources is possible. With a complex joint use of mechanical, thermal, chemical, or electrical energy an enhanced material removal, better surface quality or improved tool life time can be achieved. Examples for these process combinations are e.g. electrochemical grinding, electro-discharge grinding, ultrasonic-electrochemical, electro-dischargechemical, anodic-mechanical, plasma-mechanical, and laser-mechanical processes. Electrochemical Grinding. Electrochemical grinding (ECG) is carried out by overlapping material removal by microabrasive grains (diamond, CBN) with anodic (electrochemical) dissolution. Anodic dissolution of metallic workpiece materials reduces the microchip thickness and the area of mechanical contact between workpiece and the grinding wheel [7.146]. Furthermore ECG reduces the material resistance against mechanical penetration by means of reduction of the strength of the superficial microlayer. ECG processes work at a voltage of up to Up = 5–10 V (at machining with independent electrode Up = 24 V) and a current density of up to 15–150 A/cm2 . Nitrate/nitrite solutions are often used as working media (dielectric fluid). They contain various passivation additives (soda, glycerin, triethylamine, etc.) for reduction of the corrosion activity. ECG processing is applied on surface ground components of hard, magnetic, heat resisting steels and alloys; surface and cylindrical grinding of thin-walled, nonrigid components; profile grinding; grinding of viscous materials, etc.

Part B 7.3

process is the transformation of electron kinetic energy into thermal energy. The electrons are emitted from a hot cathode and accelerated towards a ring shaped anode with a round opening (Fig. 7.197). The acceleration voltage is around 25–200 kV. The electrons reach the workpiece surface and release their high kinetic energy. The energy density of an electron beam is up to 105 –107 W/cm2 , which is comparable to laser beams. Due to the fact that electrons, unlike photons, have a mass (m e = 9.108 × 10−31 kg) and an electric charge (e = 1.602 × 10−19 A s), the energy transfer and effect on the workpiece surface is different compared to laser processes. To prevent electron collisions with gas molecules, the system is highly evacuated. The focusing of the electron beam is done with magnetic fields, which are generated by so-called magnetic lenses. The electrons can penetrate much more deeply into the workpiece material than laser beams. They transfer their energy via collisions with enveloping electrons. EBM systems are more complex compared to regular laser systems. Due to the limitation of the working chamber this process is dedicated to special applications, where the benefits of high penetration depth, high impulse frequency, and fast beam deflection can be used [7.144]. Thus drilling is a perfect process to elaborate the potential of EBM, e.g. small bores (diameter down to few μm) can be made in thin foils at a rate of up to 10 000 bores/s without moving the target. Typical application fields are combustion-chambers of aircraft turbines (difficult to machine cobalt-based material, several thousand holes) or spinning heads for glass fiber production (6000 holes of 0.8 mm diameter in 5 mm thick material [7.145]). A disadvantage of the technology is related to the fact that X-rays are generated above an acceleration voltage of 80 kV, which makes a severe shielding of the system necessary.

7.3 Machining Processes

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Part B

Applications in Mechanical Engineering

Electro-Discharge Grinding. During electro-discharge grinding (EDG) metal removal is carried out by microcutting of bonded abrasive grains while the grinding wheel working surface is continuously influenced by electroerosion. Electric discharges provide an opening of the grinding wheel topography, allowing new abrasive grains to come into contact, and the removal of adhering chips from the wheel surface to prevent loading. Also just cut chip segments might be directly evaporated in the zone of contact. Discharges occur between the workpiece and the wheel, or between the tool and a specially adapted additional electrode [7.147, 148]. EDG processes can be actively controlled and their intensity can be adjusted to provide substantial increase and stabilization in the lifetime and cutting ability of the grinding wheel. For EDG processes either standard cutting fluid or 3% water soda solution is used as working medium. Current-conducting metal bonded abrasive wheels (or wheels with diamond or CBN grains) are connected to the positive pole and the workpiece is connected to the

negative pole of a pulse voltage source. EDG is applied in tool grinding, surface grinding, and cylindrical internal and external grinding machine tools. Laser-Assisted Machining. Laser-assisted machining

(LAM) has found rising acceptance due to its potential to significantly increase machining efficiency; in particular, in processes of punching and cutting complex shaped workpieces. Laser radiation is employed for two reasons. Firstly, the laser source is used for heating (thus annealing or hardness reduction) of the workpiece material surface layer directly in front of the cutting tool. By this tool lifetime is extended and the productivity is drastically increased. It even opens the possibility of applying cutting technologies to materials that were not machinable in this way before, like laser-assisted turning of ceramics [7.149]. Secondly the laser can be used for final surface formation (for example, a groove after milling by an end mill). Applied in this combination LAM processes increase the accuracy and quality of the machined parts.

Part B 7.4

7.4 Assembly, Disassembly, Joining Techniques Considering manufacture of tomorrow, production process and technology of joining will continue to hold its dominating position worldwide in the production of added value. Figures 7.198 and 7.199 clearly show the increasing economic importance that must be attributed to joining in those industrial branches where it already has been intensively utilized so far – an impor-

Fig. 7.198 Value added by joining industry (2003) [7.150], with

permission

tance as is hardly attributed to any other metal working manufacturing procedure. A large number of bonding methods having evolved within the last one hundred years have gained in importance by developing from a conventional into a high-performance welding procedure. Highly effective joining technologies have been adapted to the specific characteristics of material and structural parts and developed into microjoining or hybrid joining techniques. Today, joining technology in general covers about eighty different modern joining techniques which are in use worldwide, even though with varying intensity. Therefore it cannot be aim of these chapters to provide the international readership, engineers, specialists or students with process engineering descriptions of all joining procedures known. The author and his coauthors agree with the fundamental idea of this book to present even a profound description of joining technology, though with intended restriction to selected state-of-the-art technologies (Fig. 7.200). Thus it seems to be quite reasonable, within the frame of this technology handbook, to point out trends in the chapters presented, and to show the interested reader how an innovative product optimized in its

Manufacturing Engineering

stir welding in which it has been possible to exploit interesting economic applications after a relatively short development time is regarded as an example of this. Further examples are friction spot joining and magneticpulse welding. Figure 7.209 makes a rough assessment of the research fields of joining processes. Before the explanation of the effects of the statements made here about the joining processes in some welding-intensive sectors, the value added generated by welding technology in Germany should be considered. Value Added by Welding Technology in Germany Studies conducted in 2001 [7.150] and in 2005 [7.156] show the economic importance of joining and welding.

•

Investigations conducted by the DVS have indicated that the German market for ancillary supplies for joining technology may be estimated to be about one third of the European market and this in turn one third of the global market. For 2003, it is thus possible to estimate a value of approximately Euro 15 billion per year for the value added generated by ancillary supplies for welding technology all over the world. However, the specified figures do not serve to define the value added by the companies which use joining technology in their fabrication in order to manufacture their products. It is far more difficult to estimate the economic benefit for this sector because welding is just a part of the value added in these companies and only few statistical values are available. A calculation is carried out here on the basis of a macroeconomic model. In this case, the study comes to the following results (Fig. 7.198): The macroeconomic value added by the production and application of welding technology in the investment-goods industry in Germany amounts to around Euro 27 billion (i. e. 4.8% of the value added

663

by the producing sector in Germany). In this respect, around 640 000 employees are directly or indirectly connected with welding technology. Results show that joining technology can hold its own even in a difficult economic environment and is proving to be a cross-sectional technology which, because of the close cooperation with various sectors, is relatively resistant to economic cycles and can open up new sales markets. A comparison of data from 2005 with the data from 2001 shows an increase in the value added of 18% with a simultaneous increase in the numbers of employees of 5% in welding technology. This is indicative of higher productivity. This results from the strategies pursued by the companies in joining technology and by the companies applying it with the three following main focal points:

• • •

Concentration on core competences Adaptation of the production processes Increase in the labour productivity

In Germany, a number of sectors are regarded as welding-intensive, including vehicle construction (road vehicles, rail vehicles, ships and aircraft) as well as metal construction and mechanical engineering. On average 5% of the total value added by these sectors is generated by welding technology (Fig. 7.199). A few joining-technology trends for these sectors are considered below. Trends in Welding-Intensive Sectors in Germany The following statements are essentially based on the results of the cooperative technical-scientific work in the DVS and make no claim to being complete. Joining Technology in Road-Vehicle Construction. In

order to reduce weight, tailored blanks are being used to an increasing extent in bodymaking. The combination of sheets with different materials, material thicknesses and/or surface conditions (as a rule, welded together using the laser beam) serves to achieve better material utilization with regard to the stress-bearing capacity. The tailored blanks allow the increasing use of highstrength ductile steels. The bodies are assembled not only by means of resistance spot welding and adhesive bonding but also by means of mechanical joining and gas-shielded arc welding. In this respect, the latter process is utilized in regions subjected to high and dynamic stresses. Another application is for the attachment of studs in order to fasten built-in and at-

Part B 7.4

•

The production value of the companies providing goods and services for joining in Germany amounts to approximately Euro 3.6 billion. These goods and services include welding machines, appliances required for welding, welding filler materials, adjuvants, gases, protective clothing, testing machines and also the further training of the weldingtechnology personnel. The companies working for this production value employ 37 000 people (converted to full-time staff) and generate a value added amounting to around Euro 1.6 billion.

7.4 Assembly, Disassembly, Joining Techniques

Manufacturing Engineering

creates a steam passage in the melt, the so-called keyhole. Typically, the diameter of such a capillary steam tube shows the magnitude of the beam diameter (0.1 to 1 mm). Characteristic threshold intensities for capillary formation lie in the range of 106 W/cm2 . In laser beam penetration welding, the system of capillary steam tube and surrounding molten bath is led along the assembly line. The molten bath flows around the capillary on both sides, comes together behind it, and, when solidifying, forms a joint (Fig. 7.217b) [7.157].

ity of the laser used. With the rod systems currently used and with their beam quality of 16 mm mrad, only working areas of approx. 150 mm side length could be accommodated when welding within a typical sheet thickness range of 1–2 mm. When working with a disc laser, an area of up to 300 mm side length can be covered without difficulty with the smaller scanner systems. This so-called remote welding procedure makes redundant the otherwise necessary system of axles with which the focusing optical system or the structural component is moved, but it is also of interest when combined with robots [7.160]. In the kilowatt range of performance, predominantly CO2 lasers, longitudinally diode-pumped Yb:YAG lasers, transversally initiated Nd:YAG rod lasers, and Yb:YAG disc lasers are currently used. CO2 lasers differ from other beams by almost diffraction-limited beams even at a performance of several kilowatts (typically M 2 < 2). With a wavelength of λ = 10.6 μm, however, the beam parameter product of a CO2 laser cannot be smaller than 3.4 mm mrad (M 2 = 1). Currently, in the kilowatt range, solid-state lasers do not yet produce diffraction-limited beams, but with 2.8 mm mrad (M 2 = 8) at 1 kW medium performance (rod laser) and 7 mm rad (M 2 = 21) at 4 kW (disc laser) they already offer excellent focusability with their short wavelength, which is ten times shorter than that of other lasers. In addition, diode-pumped solid-state lasers reach a high efficiency of greater than 20% (electrical-optical without cooling). Recently, fiber lasers have also appeared on the market that, by incoherent collimation of several fibers, offer a capacity of several kilowatts as, e.g., 1 kW power output with a beam parameter efficiency of 6 mm mrad (M 2 = 18) or 4 kW with 20 mm mrad (M 2 = 59) [7.161, 162]. The unique advantages of fiber lasers are their unsurpassed efficiency, excellent beam quality, low volume and weight, and outstanding robustness. These advantages can be attributed to their fiber-optical microstructure. Recent investigations have shown that their high performance can be achieved with several evanescent wave guides without impairing the beam quality. With such developments, fiber lasers are also capable of producing beams in the kilowatt range that offer an excellent focusability. The form of the modes can be determined by an appropriate design of the wave guides (distribution of the refraction index) [7.161]. It must be pointed out here that CO2 lasers are available today not only with a 10.6 μm wavelength but also up to a performance of 6 kW, with a 9.3 μm wavelength.

669

Part B 7.4

Trends in Systems Engineering. The motivation behind the development of lasers for industrial material processing has always been the demand for higher performance together with higher quality of beam. With the use of the traditional lamp-pumped Nd:YAG solid-state laser, increased performance of the laser is always connected to a decrease in beam quality, due to the thermal lens formed. By using laser diodes instead of pulsedlight sources, the thermal lens can be reduced; however, the principal decrease in beam quality will remain even if the laser performance is increased. The situation is different with a disc laser. This laser eliminates the thermal lens in the crystal so that a high performance together with a good quality of the beam can be obtained. With this, important new preliminaries for new laser applications are provided by achieving smaller focus diameter, longer distances between the optical machining system and the workpiece, and, last but not least, a higher focus depth of the focused laser beam [7.158]. In welding and cutting, the improved beam quality of the disc laser can directly result in a reduction of the focus diameter, which then causes the power density of the laser beam on the workpiece to increase to the square. The machining threshold moves toward lower performance, and the laser welding penetration effect begins sooner. The range of welding parameters is enlarged, and thus process reliability is increased. By the laser welding penetration effect that comes into play already at lower performances the weld seam width can be kept narrow. From this will result a low heat input and, thus, less distortion of the structural parts. Thus, an efficient and precise welding of thin sheets becomes possible. In addition, considerable penetration depth and welding speed are achieved [7.159]. Also when welding with scanner optical systems, the beam quality may be used to much advantage. Scanner optical systems with their galvo-mirrors deflect the laser beam within a working area. The focus diameter and working distance depend directly on the beam qual-

7.4 Assembly, Disassembly, Joining Techniques

Manufacturing Engineering

• • •

Oxygen laser cutting Fusion laser cutting Evaporative laser cutting

Oxygen Laser Cutting. The laser beam heats the material to ignition temperature. The oxygen injected into the kerf burns the material and expels the slag formed. The combustion process generates additional energy. With the quality of the cut being continuously high, a distinct connection between the purity of the oxygen and the maximum possible cutting speed can be proven. Fusion Laser Cutting. In this version of the procedure,

the material gets fused in the crossover point by laser radiation. The melt is expelled from the kerf by an inert gas. High-pressure fusion laser cutting is proving to be increasingly successful in oxide-free cutting of stainless steels. It is also successfully used in cutting mild steels and aluminum. As a rule, nitrogen is used as the cutting gas. The cutting gas pressure at the cutting nozzle can be 20 bar and above.

beam quality to about 5 mm mrad. At this level, the beam could be launched into an optical wave guide of 100–200 μm core diameter, and a laser would be available for machining that could be very finely focused as is possible with the best CO2 lasers already in use [7.174]. Laser cutting has, until now, been dominated by flatsheet cutting. This is mainly due to four factors: the dynamics and precision of five-axle laser cutting systems have been too poor, and cutting speeds have been much lower than with cutting flat sheets. Programming of five-axle cutting systems is very time consuming and inaccurate. The price of the system is higher than that of two-axle cutting systems. Finally, the market for parts cut in three dimensions is much smaller than that for flat-sheet cutting [7.175]. The use of laser cutting systems becomes especially critical when cutting thick plates. A 4 kW CO2 cutting laser can, e.g., facilitate processing of mild steel plates up to 25 mm thick, using oxygen as the cutting gas. In conventional laser cutting, an increase in the range of cuttable plate thickness can only be reached by further increasing the laser beam performance available. However, with the newly developed LASOX technique (laser-assisted oxygen cutting) it is, given a considerably lower laser beam performance, possible to cut plates more than 50 mm thick with a laser beam performance of 2 kW. This is achieved by modifying process conditions at the front of the kerf. The laser beam is defocused and will heat the workpiece surface only to ignition temperature without melting it. The diameter of the laser beam on the plate surface is larger than the diameter of the cutting oxygen jet. Under these conditions, the cutting process is similar to oxy-gas flame cutting rather than to the conventional laser cutting [7.176, 177]. The increasing availability of high-power lasers above 6 kW of good mode quality, TEM 01 or better, for fusion laser cutting opens up new possibilities for entrepreneurial reorientation. According to laboratory tests, a cut thickness of more than 30 mm is feasible with a laser beam performance of 9 or 12 kW. At present, the perspective limit is considered to be a material thickness of 45 mm [7.178]. In fusion laser cutting in the plate range, the incomplete expulsion of the melt from the joint presents considerable difficulties. By applying liquids instead of gases this problem may be eliminated. In comparison to gas jets, water jets produce a higher impulse response. In this way the material is more effectively removed from the kerf [7.179].

673

Part B 7.4

Evaporative Laser Cutting. In evaporative laser cutting, the material to be cut is evaporated at the crossover point of the laser beam. An inert gas, e.g., nitrogen or argon, expels the byproducts from the kerf. This cutting process is used with materials that have no liquid phase or melt, as is the case with paper, wood, several synthetic materials or plastics, textiles, and ceramics. At present, CO2 lasers with performances of up to 5 kW and Nd:YAG lasers with performances of up to 2 kW are in use for laser cutting. Special CO2 cutting lasers with performances of up to 5000 W allow process-reliable machining of mild steel plates with a thickness of up to 25 mm. With high-speed thin-sheet cutting, cutting speeds of up to 40 mm/min are achieved. New drive mechanics allows positioning speeds of up to 300 m/min [7.173]. So far, CO2 lasers have proven suitable tools for fast 2-D laser cutting of thin sheets due to their good focusability and high laser beam performances. By increasing the beam quality of solid-state lasers through the use of diode-pumped Nd:YAG lasers, with new resonator programs, launching into ever smaller fibers becomes possible with which, in the meantime, suitable focusing for high-speed cutting has become practicable. So, for example, launching of laser beam performances of up to 4 kW in fibers of 300 μm diameter is feasible. The aim of the current development of solidstate lasers in the multikilowatt range is an increase in

7.4 Assembly, Disassembly, Joining Techniques

Manufacturing Engineering

693

alloys are used to match the material of the workpieces and prevent corrosion. Blind rivets can be provided with different coatings. Some criteria on the selection of materials for blind rivets are as follows:

• • •

Avoidance of exposure to corrosion of workpieces Connection strength Cost

Most relevant applications of blind rivets are parts where a two-sided accessibility is not possible, such as closed sectional profiles, e.g., interior pressure-shaped profiles or large-area parts where connections should be set far away from the edges. But blind rivets mostly have a lower shear connection strength than punch rivets or locking ring bolt systems, especially those types of blind rivets where only the rivet body supplies the power between the workpieces. The mechanical properties of blind rivet connections depend on the properties of base materials and the blind rivets used. Overall sheet thickness of workpieces to be joined can vary in a wide range from 0.5 mm to more than 20 mm. Punch Riveting. Until the development of punch riveting for joining two or more parts it was necessary to have premanufactured holes for setting the full or hollow rivets. Holes could be set by drilling, punching, or some other thermal or nonthermal cutting process, such as watercutting. These additional working steps were problematical for increasingly automated production. In particular, hole-congruent positioning of more than two workpieces required high manufacturing precision. The additional process steps reduced the economic efficiency of the whole joining process. With punch riveting workpieces are directly form and force closed and permanently joined without premanufacturing a hole. The cylindrical solid rivet produces the necessary hole itself while joining by punching a small slug out of all workpieces to be joined. The rivet itself is not deformed. Only parts are deformed locally, because the die-side material needs to be deformed in one single or multiple ring grooves of the punch rivet. Workpieces need to have two-sided accessibility for joining. Transmission of connection strength between joined parts happens exclusively by the punch rivet. Because of its simple technology and less surface damage around the joining spot, especially on coated and painted parts, this connection is an economical alternative to resistance spot welding.

Part B 7.4

Along with other developments blind rivets were developed consisting of two or more parts that have different mechanical properties and requirements. Most common blind rivets have two parts, the rivet body and the mandrel, which form the closing head. Blind riveting does not have special requirements for surface preparation like all mechanical joining processes. Different materials can be permanently joined with blind rivets. Releasing the connection is only possible by the destruction of the blind rivet. All parts need to be congruent, predrilled, and fixed to achieve joining with blind rivets. Holes can be drilled, punched, or brought in by another prior manufacturing step. The size and tolerances of the hole depend on the diameter and type of blind rivet. Process steps are very similar for different types of blind rivets and are shown in Fig. 7.255. At first, the blind rivet is introduced into the setting hole and the rivet head is pressed against the set-head material. The mandrel is pulled by the clamping jaw of the setting tool and slips into the rivet body. The workpieces are pressed together by an increasing pulling strength. With this the mandrel head transforms the rivet body and creates a closing head. Depending on the kind of rivet, either the mandrel is pulled completely out of the rivet body or the mandrel breaks at the preset breaking point and is extracted by the setting tool. The required breakload will be determined by the cross section of the mandrel preset breaking point and by the material of the mandrel. Some kinds of rivets surround and fix the mandrel head and prevent it from loosening with vibrating loads. Different types of blind rivets differ in their required joining forces, connection strength, and mechanical properties as well as in costs associated with manufacturing the rivet connection. Blind rivets were developed by the necessity of joining comparable connections of full rivets but having only one-sided accessibility. For that reason blind rivets can join almost every material and material combination without having special requirements of deformability or other material properties. The only precondition is that joining parts must have a premanufactured hole. Important for a good quality of blind rivet connection is the right choice of rivet diameter and rivet length for the joining task. Since the mandrel has to transform the rivet body, it should have a higher tensile strength. For that reason, the mandrel and rivet body mostly consist of different materials. Although rivet bodies used to be made of aluminum because of its better deformability, nowadays also mild steel, stainless steel, and nickel and copper

7.4 Assembly, Disassembly, Joining Techniques

708

Part B

Applications in Mechanical Engineering

Table 7.53 Examples of analytical and numerical temperature field calculations (after [7.283])

Author(s)

Year

Welding procedure and heat source, respectively

Specific features

Norman et al. [7.264] Kondoh, Ohji [7.265]

1998 1998

Laser welding TIG-welding

Hermans, den Ouden [7.266] Suzuki, Trevisan [7.267] Nguyen et al. [7.268]

1998

Kamala, Goldak [7.270] Eagar, Tsai [7.271] Kasuya, Yurioka [7.272]

1993

Jeong, Cho [7.273]

1997

Short-circuit gas-shielded metal-arc welding Multirun arc welding Double-ellipsoidal heat source Double-ellipsoidal heat source Gauss heat source Quasi-stationary, instantaneously active and nonstationary heat source TIG-welding and tubular cored arc welding

Combination of spot and linear source Open- and closed-loop process control by comparison of measured and analytical data Calculation of process-specific parameter using specially developed computational algorithms Temperature distribution for thin sheet metal Analytical solution for a moving doubleellipsoidal high-energy heat source Error assessment of analytical 2-D-models

Sudnik et al. [7.274]

2001

Metal active-gas welding

Nguyen et al. [7.275]

2001

Hybrid double-ellipsoidal heat source

Bonifaz [7.276]

2000

Arc welding

Murugan et al. [7.277] Gu et al. [7.278]

2000 1993

Manual metal-arc welding Arc welding

Murugan et al. [7.279]

1999

Little, Kamtekar [7.280]

1998

Manual metal-arc welding (overlay welding) TIG-welding

Cai et al. [7.281]

2001

Line Gauss source

Zhou et al. [7.282]

2003

Two-side TIG-MIG-welding

Analytical

2000 1999

1983 1991

Determination of the HAZ-geometry Determination of the HAZ-geometry and of the Δt8/5 -times

Part B 7.4

HAZ- and temperature field calculation with the help of a 2-D-normal distribution Gauss heat source Mathematical model of a heat source during metal active-gas welding Superposition of semi-elliptical heat sources for better approximation to the real shape of the melt

Numerical Comparison between experiment and calculations Multirun welding Comparison between static temperature field calculations with transformed Euler’s formulation and calculations with Lagrange formulation Temperature field calculation, microstructure hardness Investigations into the influence of individual temperature-dependent parameters on the simulation results Efficiency improvement with application of the line Gauss source Temperature field calculation, geometry of the melt

710

Part B

Applications in Mechanical Engineering

Table 7.54 Approaches to transverse shrinkage assessment of single-pass butt welds (after [7.297]) Method proposed by Okerblom, Michailov et al. [7.288–290]

Heat input qs , Sy = f (q S )

S y = 2A y

α qs cρ h

Weld cross section A0 , Sy = f (A0 )

(7.180)

Wörtmann and Mohr [7.291] S y = 2A y

α A 0 qm c h

(7.181)

Malisius [7.292] Sy = x Satoh, Ueda et al. [7.293–295]

# S y = h SG α

Watanabe and Satoh [7.296] Sy = C1

TS qm tan c

φ 2

m LE A0 ln + C2 h2 m LE1

A0 + 0.0121b h

(7.182)

(7.183)



A0 h2

(7.184)

Matsui [7.297]

Part B 7.4

Sy =

qs erf ( f ) cρh

(7.185)

Gilde [7.298] S y = 0.24

α qs cρ h

(7.186)

S y = 17.4

qs h

(7.187)

Capel [7.299]

Spraragen and Ettinger [7.300]

A0 h

(7.188)

A0 +m h

(7.189)

S y ≈ 0.25 Richter and Georgi [7.301] Sy = n

for the fabrication process and, in particular, for the inservice behavior of the respective component. It is thus a major goal of analytical and numerical simulations to assess such stresses and strains, in order to predict buckling and load-bearing capacities. Such stresses

and strains should thus be determined in the design phase, when considering the life cycle of a structure or a component. Significant work has been initiated to improve analytical and, in particular, numerical calculations of weld stresses and distortions, and it has to be

716

Part B

Applications in Mechanical Engineering

Thermo-Mechanical-Metallurgical Analysis Diffusion Analysis. Most of the metallurgical phenom-

ena related to welding are dependent on the kinetic process of diffusion, which can be defined as an atomic transport of matter in a metal matrix [7.325, 326]. In welding, diffusion normally occurs under conditions of high stress and temperature gradients. Because most diffusion processes can quite conveniently be numerically simulated, modeling of diffusion will be discussed ahead of the other simulations related to weld metallurgy. With regard to welding applications, diffusion is often used to investigate the transport of interstitials, e.g., monatomic hydrogen or nitrogen moving through a homogeneous metal lattice. Under ideal conditions, i. e., by exclusion of additional effects, the flux of the interstitial atoms passing through a unit plane is proportional to the concentration gradient, where the proportionality constant is the diffusion coefficient. This is Fick’s first law, which in the 1-D case can be written as   ∂C (7.197) , J = −Dx ∂x

Part B 7.4

where J is the flux of the substance passing through the specific plane and C is the concentration of the substance. The diffusion coefficient varies with temperature and can be described by an Arrhenius relationship as   EA (7.198) , Dx = D0 exp − RT where D0 is the diffusion coefficient and E A is the activation energy. Usually, the continuity equation of the conservation of matter is true under such conditions. This means that the time-dependent change in concentration equals the divergence of the flux, and thus for the 1-D case ∂J ∂C =− . ∂t ∂x

(7.199)

The combination of (7.197) and (7.199) gives Fick’s second law in the 1-D version [7.325]  2  ∂C ∂ C ∂C and = Dx = ∇(D∇C) , ∂t ∂t ∂x 2 (7.200) for the multidimensional version. Such diffusion processes can be numerically modeled using the thermal module of commercial finite-element programs by assignment of the heat conductivity K to the so-called effective diffusion coefficient Deff

(K ⇔ Deff ) and by setting the specific heat Cp and the density ρ to unit one (Cp = 1, ρ = 1) [7.327–329]. Modeling by Fick’s laws can be applied in good agreement with experimental results not only for the diffusion of an interstitial like hydrogen, nitrogen, or carbon in a metal lattice, but also for the diffusion of such atoms in homogeneous microstructures, if they are bound at specific sites, but they can all still be activated at the respective thermal conditions. The latter process is generally regarded as reversible trapping. In the case of irreversible trapping, part of the hydrogen will be kept tenaciously so that this fraction will no longer take part in the diffusion process. Beginning with McNabb and Foster, quite a number of researchers have developed models for such trapping processes, in particular for hydrogen, in the past 50 years [7.327–329], but still with a lack of consistency in experimental results. In particular, hydrogen has often been reported to be accumulated in weld regions with high residual stresses and strains. Such attraction of hydrogen in crack-susceptible regions is considered to be based on diffusion-enhancing effects, like hydrogen transport with moving dislocations, etc.. Such diffusion enhancing by mechanical stressing or straining of the microstructure can be modeled by inserting an additional potential field in the 3-D version of Fick’s second law, which has been investigated extensively by Sofronis et al. [7.330]. However, such numerical analyses have not yet been sufficiently verified by experimental results. It has been discovered in the past 10 years that modeling hydrogen diffusion in weld microstructures, in particular for carbon, martensitic, and ferritic steels, can be carried out quite consistently by experimentally validated numerical analyses based on Fick’s laws [7.327–329]. This means that numerical simulation of a hydrogen concentration profile is possible for the most hydrogen-susceptible weld microstructures. The most important results of such modeling procedures are the development of geometrical hydrogen distribution versus time and the determination of respective removal heat treatments. It can only be emphasized that for such calculations the correct temperature diffusion coefficients (Fig. 7.291) for the particular weld microstructures and thermal cycle have to be inserted into such numerical simulations [7.328]. More recently, the numerical calculation of the geometrical and thermal hydrogen distribution in weld microstructures has been extended by simulation of respective crack initiation and propagation [7.329].

Manufacturing Engineering

terdendritic liquid pressure, relating this to an inability to adequately feed solidification shrinkage and thermal contraction [7.374–376]. Although these models were developed for castings, they are equally applicable in principle to welding. Of particular importance to welding, however, is the influence of restraining conditions and their effect on local strain fields around a moving weld pool [7.377]. The ability to simulate these local stress/strain fields is of critical importance for predicting cracking, with several examples published [7.361, 378–380]. An example of one such simulation is given in Fig. 7.299, showing the strain distribution in a modified Varestraint test [7.361]. Porosity. Gas porosity in metals is usually associ-

ated with dissolved interstitial elements: H, N, and O, which form gas (diatomic molecules) during solidification. The conditions necessary for gas pore formation in molten metal have been modeled based upon a simple consideration of Gibbs free energy for nucleation [7.381] ΔG = γ A + Pe V − Pi V ,

(7.203)

r ∗ = −2γ /ΔP ,

(7.204)

where ΔP = (Pe − Pi ). It follows that homogeneous nucleation is promoted by low surface tension, low external pressure, and high internal pressure (e.g., EB welding a nitrogen strengthened stainless steel in a vacuum). However, heterogeneous nucleation is even more likely to occur, allowing this critical radius to be achieved with a smaller volume of gas. Heterogeneous nucleation is favored by conditions where the liquid does not wet the substrate (e.g., oxide inclusions [7.382]). ΔP can be considered as the driving force for nucleation and can thus be expressed in terms of a thermodynamic chemical potential [7.382] ΔP = −

p RT , ln Ω p0

(7.205)

where R is the universal gas constant, T is absolute temperature, Ω is the molar volume, p is the interstitial partial pressure, and p0 is the equilibrium interstitial partial pressure. It follows that there must be a condition of supersaturation (i. e., p > p0 ) in order for nucleation to occur. Thus, in order to understand pore formation in a weld, one must first consider mechanisms to achieve supersaturation. Pores can form in the weld pool if the liquid becomes supersaturated by picking up interstitials from the welding gas, directly under the arc (hot region), and then moving rapidly to cooler regions near the fusion line. The pickup of interstitials at the weld pool surface has been modeled, where it has been shown that dissolved interstitial concentrations exceed Sieverts’ law predictions due to the dissociation of diatomic molecules in the arc plasma [7.383]. It is also possible to form porosity interdendritically, even when the weld pool has not become saturated, due to the partitioning of interstitial elements during solidification. The large drop in solubility between liquid and solid results in a buildup of interstitials in the interdendritic liquid, which leads to supersaturation. Simulations for interdendritic porosity have been used successfully to predict conditions favorable to pore formation in castings [7.384, 385]. Once nucleated, pores may grow, coalesce, become entrapped, or escape the weld pool, depending upon the welding conditions [7.382]. Slow welding speed allows time for pores to escape, aided by the buoyant force of gravity. The use of pool agitation (e.g., current pulsation) also helps in this regard. When welding in the overhead position, most pores become entrapped. Rapid travel speed limits the time available for pore nucleation and growth.

7.4.9 Fundamentals of Magnetic Pulse Welding for the Fabrication of Dissimilar Material Structures One major challenge in welding is to develop fast, reliable, and cost-effective industrial processes to permanently join dissimilar materials, i. e., different metals (including alloys), or metals with plastics or ceramics. For these combinations of materials, the fusion welding processes are inapplicable, as the physicochemical properties of unlike materials are seldom similar or compatible. Alternatively, the colder and solid-state joining processes like magnetic pulse welding (MPW) offer the most potential, particularly for cylindrically symmetrical components including light and ductile

723

Part B 7.4

where ΔG is the change in free energy associated with pore formation, γ A is the energy associated with the creation of gas/liquid interface of surface area A and surface tension γ , Pe V is the positive work done forming a pore of volume V against an external pressure Pe , and −Pi V is the negative work done with the aid of internal vapor pressure Pi . From this it follows that the critical radius needed for homogeneous nucleation of a spherical pore (i. e., r such that ΔG/ dr = 0) takes the following form

7.4 Assembly, Disassembly, Joining Techniques

724

Part B

Applications in Mechanical Engineering

Part B 7.4

metals. MPW is straightforward and in many aspects similar to explosive bonding, except that it has for now only been applied to cylindrically symmetrical components. MPW utilizes the magnetic fields generated by heavy discharge currents into inductive coils. The resulting discharge is a dampened sine wave of consecutive pulses. In proximity to the coils are the components to be welded, or workpieces. The discharge current running through the coils induces Eddy currents in the nearby workpiece. The interactions between the magnetic fields of these two currents results in a strong repel force between coil and workpiece. By necessity, this workpiece must be electrically conductive as well as plastically deformable, and the repel forces must be such that a violent collision will occur, preferentially at a slight angle to form a jetting action similar to that in explosive welding. During MPW, the amount of heat produced is almost nonexistent since the process only lasts small fractions of a second. Parameters such as gap distance (between coil and workpiece, and between the two workpieces), material properties, thickness, as well as welder characteristics determine the properties of the final weld joint. Mechanical interlocking as well as thin and discontinuous intermetallic phases (all resulting from localized melting) will control the final properties of dissimilar-material welds, e.g., static strength, shock and vibration resistance, and vacuum tightness. Magnetic pulse welding (MPW), also referred to as electromagnetic impulse joining or pulsed magnetic welding [7.386], is a four-decade-old process from the Cold War era [7.387]. Just like other governmental programs, the widely developed nuclear programs of the former Soviet Union, the United States, and other military and industrial powers spawned spinoff technologies that have found industrial and manufacturing applications. MPW is said to have been invented at the Kurchatov Institute of Nuclear Physics to seal metal canisters and nuclear fuel pins [7.387]. In the decade following its initial success until recently, the process only found military and aerospace applications, as for flight control rods, artillery shell casings, and bimetallic metal inserts [7.388, 389]. Almost 40 years after being invented, MPW has gained the attention of the private sector, in particular the transportation and refrigeration industries. With weight saving and improved vehicle safety driving the use of an increasing number of dissimilar materials’ joints (e.g., aluminum with steel), the automotive community has emerged as the major player in further developing MPW technology. MPW is indeed one of the rare processes capable of joining dissimilar materials in high-volume production environment. The

actual process lasts less than 100 ms, and the production rates may be readily customized (for instance, be as small as a few seconds).The process has not only been tested and applied to numerous combinations of metals and alloys [7.388–398], but also metals with ceramics or metal-matrix composites [7.399]. In the automotive industry, immediate potential applications for MPW include more conventional metallic materials for air conditioning tubings, tubular spaceframes, driveshafts, struts, shocks, and electrical connections. To date, any joints between round parts such as a tube-to-tube joint, a tube-to-end joint or a wire crimp joint are ideal candidates for magnetic pulse welding. In the near-future, it is conceivable to see magnetic pulse welding, alone or combined with other processes, applied to noncylindrical workpieces like flat sheets. MPW is an extension of magnetic pulse forming, or electromagnetic forming, a process that uses identical technology to manufacture complex shapes in fractions of a second. Process Principles and Parameters MPW can be applied to the same materials as explosive bonding, provided the hollow sections can be accelerated. MPW is identical to explosive bonding in the formation of the joint, but instead of the chemical explosive energy, magnetic fields are used to drive the materials together. In order to weld and in particular achieve a metallurgical bond wherein atoms of the two materials are brought into direct contact, a tremendous amount of energy must be compressed and discharged within an extremely short time. In some systems, the discharge is as high as 2 million amps and lasts less than 100 μs. As a result, the actual energy expenditure is exceptionally low and the components have no time to heat appreciably. A schematic representation for a magnetic pulse welder is illustrated in Fig. 7.300. The welding unit, or welder, simply consists of an LC circuit (i. e., inductance–capacitance) with a high-voltage transformer and some impedance (not represented in Fig. 7.300) so that the discharge current waveform is a dampened sine wave. This discharge current runs through a coil, also called an inductor. This coil is usually positioned all around the workpieces to be welded, but not necessary as discussed later in this chapter. Figure 7.300 illustrates the situation where two concentric workpieces (i. e., an internal and an external workpiece) are welded. The workpieces are positioned coaxially inside the coil with gaps in between, a requirement to produce the Eddy currents and the magnetic force necessary for welding. The electrical currents in the coil

732

Part B

Applications in Mechanical Engineering

Part B 7.4

able. These microhardness changes in the aluminum workpiece can be correlated to microstructural transformations. Because hardness variations were not monotonic, as could have been expected by strain hardening (i. e., materials strengthened as they were deformed), two competing mechanisms acted in the vicinity of the weld interface. Strain hardening clearly occurred further away from the interface, where hardness gradually increased closer to the weld. In sections of the welds where interfacial microconstituents were not seen, the hardening of the aluminum was also greater, and hardness variation was monotonic all through the aluminum wall thickness. Hardening is also greatest when the intermetallic constituents are thin [7.395]. The softening immediately adjacent to the interface, also observed in aluminum-copper welds [7.393–395], indicates that the interfacial heating was simply enough to oppose the hardening due to plastic strains. Figure 7.309 shows that the aluminum softening near the microconstituent could be as high as 30 kg/mm2 (see arrow in Fig. 7.309). As depicted in Fig. 7.309, this decrease in hardness therefore appears to represent as much as 50% of the material initial hardness (thus strength). While eliminating totally the intermetallic phases may reveal difficult in the case of dissimilar joints treated here, magnetic pulse welding more than any other process allows to reduce their thickness. Strengths, especially in the tensile-shear mode of aluminum-copper, aluminum-steel, and aluminumtitanium joints – among other dissimilar-metal joints – have proven to be exceptionally high [7.395]. Welds are often so strong that no other process can outperform MPW. In fact, magnetic pulse welds are often associated with weight reduction, in part because the overlaps do not have to be as long as with other processes (e.g., brazing, adhesive bonding). Since the moving workpiece is usually thin and only accounts for a small cross-sectional area relative to the area associated with the overlap, this workpiece normally fails, in many occasions leaving the joint undisturbed during testing. In applications involving tube-to-tube joints, where fluids flow on the inside of the assembly, resistance to high internal pressures is primary. A variety of tests, including hydrostatic pressure tests and helium leak tests, may be applied to measure weld quality. In some cases (e.g., heat exchanger tubes), weld joints can also be subjected to thermal cycles within a wide range of compositions at the same time they are tested for leaks. Frequently, the

quality of magnetic pulse welds is proven, and magnetic pulse welding provides a hard-to-beat cost-effective engineering solution to large-scale manufacture of tubular structures. Conclusions and Summary MPW is a suitable process for dissimilar materials, particularly metals (including alloys) since they are electrically conductive and Eddy currents can flow in them. The moving workpiece, i. e., the one with Eddy currents, collides with the stationary workpiece with such force that both mechanical interlocking and atomic interactions occur between the two materials. Surfaces of the workpieces do not have to be cleared of surface contaminants because of the phenomenon of jetting. Magnetic pulse weld interfaces are similar to those produced by explosion welding and their properties mainly depend on the collision velocity and the collision angle. MPW possesses numerous advantages and a few disadvantages. Several advantages of MPW are largely tied to the fact that the process can be electrically controlled from the power supply. The parameters are therefore easily controlled, adjusted, and set. This results in a highly repeatable process, which, because of the rapid discharge, is extremely fast. Other advantages of the MPW process are linked to the fact that the process is energy efficient and melting is either absent or localized to a narrow skin. As a result, the materials are not heat affected dramatically, i. e., annealed, oxidized, and residual stresses are deeply reduced compared to many other processes, as are the intermetallic phases that form between dissimilar metals. The disadvantages of MPW are mainly related to the cost and workpiece geometry. MPW is initially more expensive than other types of welding technologies (small machines begin around $100 000), but, once up and running, it has a much lower cost than most other processes. The coils are extremely important and for optimal process performance have to be specially designed and manufactured for each application. In addition, there are high voltage and current levels in the operation of the machine that may present a safety hazard when working on the machine. Coaxial positioning of the parts to be welded is also critical, as is the angle of impact and gap. Efforts are under way to refine the MPW process and extend the process for the joining of noncylindrical components. Nonclosed coils are being developed to allow increasing part accessibility.

Manufacturing Engineering

7.5 Rapid Prototyping and Advanced Manufacturing

733

7.5 Rapid Prototyping and Advanced Manufacturing

Manufacture in a Competitive Market The purpose of every manufacturer’s technological activity is to process materials by means of various

technologies in such a way that as a result of specific processes they become marketable products. The business purpose, however, is to configure those processes in such a way that the income resulting from the sale of the manufactured products, aimed at covering production costs and supporting design of new products and new technologies, is as high as possible. The new concepts usually have an increasing, cyclically changing nature, i. e., a step forward in technological growth happens when existing technologies and manufacturing processes do not assure superiority or at least a technological balance of a manufacturer in the marketplace. The innovative technologies and organisational production aspects are considered to be the most important development factors of present-day production enterprises. This is especially important in long-term perspective, which usually means perfect prosperity of a company, as well as further development of innovative technologies and products. Innovative technologies create the most important indices of competitive production, namely [7.406, 407]:

• • • • • • • •

Cost reduction up to 70% Quality improvement up to 25% Increase in production flexibility up to 89.5% Product innovativeness up to 100% Technology innovativeness up to 70.6% Productivity increase and product line extension up to 64.7% Improvement of external economical indexes effect up to 44.4% Penetration of the international market up to 58.8%

The above data make a sufficient argument for using the newest methods, technologies, and tools in all production types, irrespective of the production scale and the company size. This is all the more important as it is possible to determine a great many variability indices of characteristic features and criteria of manufacturing systems [7.408] (Fig. 7.310). They can be subdivided into several categories: technical, organizational, market-related, cost-related, local, and global. Of course, different criteria may also be formulated for classifying conditions, requirements, and development tendencies related to manufacturing systems. The tendencies of change will be different for different manufacturing areas, company sizes, environments, markets, or product lines.

Part B 7.5

This section presents basic technologies of rapid prototyping and their application in the development and functional verification of market products. Time to market is a very important factor determining the final success. The verification of virtual prototypes, while significant for the project executors, is not always sufficient for evaluation of a new product by future customers. An important argument for creating a physical prototype is the possibility of carrying out complex investigations on a tangible object. In order to accelerate the product development and evaluation, a number of so-called rapid prototyping (RP) technologies have been developed. They are also more generally called time compression technologies (TCT). A characteristic feature of RP technologies is their additivity – a physical object is built by adding material, usually in the form of layers (slices), instead of subtracting, as is the case in traditional manufacturing. An exception, sometimes also classified as an RP technology, is high-speed cutting (HSC) or high-speed machining (HSM). Like virtual prototyping methods, RP technologies require a complete geometric computer model of a 3-D object to be manufactured. Various materials can be used as the construction material, e.g., photopolymers, thermoplastics, plastic films, paper and organic, ceramic or metallic powders. The material applied determines (affects, influences) mechanical and aesthetic properties of created models. The group of TCTs also includes rapid tooling techniques that allow for building a tool to manufacture a short series of a new product (from 5 up to 100 pieces) and reverse engineering methods that allow for digitizing the geometry of an existing object, which is then processed in a CAD environment as (part of) the design of a new product. Parts manufactured with rapid prototyping technologies still need postprocessing with specialized machining technologies for manufacturing on microand nanoscales. These are often called advanced manufacturing technologies. RP technologies are especially important in developing market products since their life cycle is getting shorter and shorter and demand for new products and market competitiveness is still increasing.

Manufacturing Engineering

• •

of the product design. Detail minuteness of the solution – high. A functional prototype permits evaluation of the main functions of the solution in close-to-reality conditions, with limited operational parameters. A technical prototype has all the functionality and aesthetic features of a mass product that allow subjecting it to examination and evaluation within the whole range of operational parameters. It is used for examination and determination of allowed operational parameters. After evaluation by potential users and possible corrections (usually in ergonomic and functional models), it is moved on to series production.

The classification given above is not explicit and, depending on the type of product, features of some models can be synthesized or be absent entirely. They will be understood in different ways in manufacturing processes of cars, home appliances, TV sets, table lamps, or perfume bottles. Typical application areas of these techniques are:

• •

• • • •

Owing to the application of these methods it is possible to significantly reduce the product life cycle as well as reduce the costs and risk of its development and implementation. The possibility of manufacturing objects without any special tools, molds, or dies has undoubtedly become the decisive factor in the increasing interest in these methods to minimize investment risk. The range of materials used in RP technologies is still growing and includes metals, polymers, ceramics, timber, fiber-reinforced materials, and various metal- or polymer-matrix composites. In RP processes some problems occur related to the quality of the obtained objects. Besides the step-

741

wise appearance of inclined surfaces, resulting from laminar object preparation, there are also problems related to material shrinkage during processing (e.g., in stereolithography) and with porosity (SLS). Therefore, efforts are being made to develop materials with lower shrinkage and to formulate suitable strategies of manufacturing processes [7.413, 415, 416, 422–424]. RP Technology Application Areas. RP technologies

are especially useful in these industrial sectors and these fields where it is necessary to create physical models and respond quickly to market demands. The main application areas of the RP techniques are as follows [7.412]:

•

•

•

•

•

Prototype building for: – Verification of design solutions – Analysis and evaluation of design solutions – Examination of flows – Research in wind tunnels – Selection of construction materials Physical model building for: – Searching for design solution ideas – Building design and industrial design – Marketing presentations for customers – Problem solving by the case study technique Manufacture of components for: – Production of tooling and accessories – Production of auxiliary means of production – Marketing research with a trial lot Design and manufacture of tooling for: – Planning of production processes, especially assembly processes – Design and manufacture of prototype tooling, especially for sheet metal forming Design and manufacture of patterns and models for: – Casting technologies, including sand casting and lost-model processes – Vacuum forming – Hydro- and thermoforming – Forming by metal spraying on a pattern – Epoxy techniques and materials

As determined by research in companies using RP technologies, the most important and largest area of RP application is in the manufacture of functional prototypes subject to constructional analysis in working conditions of finished products and their manufacturability analysis. Figure 7.319 shows the shares of application areas of models made by rapid prototyping techniques, obtained on the basis of data acquired in

Part B 7.5

•

Design and ergonomic studies Examination and evaluation of design solutions on the basis of physical models and research methods from the scope of photoelasticity, thermovision, X-ray radiography, flow modeling, etc. Analysis and evaluation of manufacturing processes, especially assembly processes Examination and modeling of flows in plastics forming Marketing examination and evaluation of new products Testing multifunctional models in casting and plastic working Modeling and manufacture of osseous and soft implants in medicine

7.5 Rapid Prototyping and Advanced Manufacturing

744

Part B

Applications in Mechanical Engineering

hardened layer of the photopolymer. When relatively large layers are scanned and hardened, it is necessary to apply an additional liquid layer to ensure constant thickness of the subsequent hardened layer. SL is widely used in building models and prototypes of products and usable objects in many fields such as industrial design, automobile manufacturing, and home appliances, as well as medicine and architecture. To obtain specific properties of models and prototypes, some additional processes are often required that give the object suitable, required features.

Part B 7.5

Solid Ground Curing Technology. The method of direct substrate hardening solid ground curing (SGC) was developed by an Israeli company called Cubital Ltd. and is realized in the form of the SOLIDER system. The principle is similar to that of the SL method, but there are several significant differences [7.428]. In this case the model is also built layer by layer by hardening a photopolymer. However, the UV light source is not a laser but a UV lamp. Moreover, individual model layers are created generally by exposure of a previously prepared mask of the given layer on a glass plate. This mask is made using a technique similar to that used in a laser printer, although a negative image of a model’s layer is created. This means that in the places where the object outline is to be created (exposed), the mask surface is transparent and can transmit UV light, but in other places a nontransparent toner is deposited on the plate. The glass plate, after cleaning, can be repeatedly used for mask making. The pot with the created object moves not only vertically (consecutive model layers) but also horizontally as it is necessary to perform subsequent stages of object creation on individual stations of the SGC machine. When consecutive model layers are created, the nonhardened polymer is collected and free space in the object is filled with wax. This makes it possible for the created model to stiffen and no special supporting elements are required. A cold metal plate is used for wax hardening. Each created model layer is leveled to proper height by milling, which makes it possible to undo operations, i. e., to cancel results of previous actions. Next, a subsequent layer of polymer is applied on a smooth and even surface of the created object. Laminated Object Manufacturing Technology. The

method of laminated object manufacturing (LOM) was developed by the American company HELISYS.

In this method an object is created by cutting out outlines of individual layers of a model with a laser (with power from a few dozen to a few hundreds watts) and sticking consecutive layers of a film moving by means of rollers over the model being built [7.413]. The model is located on a platform that, along with the model creation, is gradually lowered down by a thickness of consecutive model layers. The film is coated underneath with special glue and the cut-out layer is stuck to the previous one by means of a hot roll that melts the glue and presses and levels the surface of the object being created. As the thickness of the film is not exactly constant, a special sensor is used for measurement of the model height. Plastic, ceramic, and metal films can be used. To facilitate removing the excess material from the finished model, especially if it is not prismatic and has complex internal spaces, the laser beam cuts characteristic squares on the film areas not used for the model creation. After pressure welding, the squares make prisms that are easily removed from the model body. This part of the material is waste. However, this material cannot be removed from completely or partially closed internal spaces of the model. This is a disadvantage of the method that can be omitted by subdividing the model into several parts. 3-D Printing Technology. A simple and cheap method of manufacturing conceptual models is 3-D printing (3DP), developed at the Massachusetts Institute of Technology [7.424, 429, 430]. The principle is based on laminar bonding of powdered material with a binder applied by a printing head. A diagram of the 3-D printer operation is shown in Fig. 7.323 and exemplary model in Fig. 7.324. Models manufactured with this type printer are made of powdered starch or powdered plaster. The building process is as follows:

1. The printer applies a powder layer from a container to cover the surface on the molding platform. 2. The binder is overprinted on the prepared substrate to form the first layer of the object cross-section. In overprinted places, the powder is bonded (glued) with the binder. The remaining unbounded powder, in unchanged form, serves to support the physical model. 3. After a layer is completed, the platform with the model is slowly lowered down by a distance equal to the layer thickness.

Manufacturing Engineering

• •

Level of detail: 150 μm Postprocessing: polishing Common characteristics of ceramic parts:

• • •

Accuracy of the produced parts: ±50 μm per 120 mm Level of detail 300 μm Postprocessing: postsintering in the furnace Technological characteristics:

• • • • • •

Fiber laser 50 or 100 W (high absorption of IR light) PM 100: diam. = 100 mm, H = 100 mm PM 250: diam. = 250 mm, H = 300 mm Building in a furnace: Tmax = 900 ◦ C with controlled atm. Building speed: 3–30 cm3 /h Layer thickness: 20–30 μm

Concept Laser. The M3 Linear is a modular sys-

• • • • • •

Materials: tool steel CL50WS I CL60DG, stainless steel CL20ES, titanium Full melting Layer thickness: 20 μm Accuracy: 0.1 mm Build volume: 250 × 250 × 170 mm Speed: 5 cm3 /h

Electron Beam Melting – EBM Technology. Arcam AB

R technology based (Sweden) provides CAD to Metal

751

on the electron beam melting (EBM) process originally developed at Chalmers University [7.441]. It is a powder-based method having a lot in common with selective laser sintering (SLS), but replaces the laser with a scanned 4 kW electron beam that produces fully dense parts. Materials available at present include H13 tool steel, Arcam low alloy steel, titanium alloy (Ti6Al4V), and pure titanium. Arcam low alloy steel is an easy-tomachine material for prototyping applications. Parts are fabricated in a vacuum and at about 1000 ◦ C to limit internal stresses and enhance material properties. The cooling process is also controlled to produce well-defined hardening. As with other processes, the parts require some final machining after fabrication, although the company indicates they feel their finishes might be somewhat better than those available from laser powder forming and other competitive processes. Arcam also says that processing in a vacuum provides a clean environment that improves metal characteristics. The EBM process may ultimately be applicable to a wider range of materials than competitive processes and also has the potential to offer much better energy efficiency. Technical characteristics:

• • • • • •

Materials: steel A6 and H13, Ti6Al4V, Co-Cr Full melting Layer thickness: 50–200 μm Accuracy: 0.2–0.4 mm Build volume: 250 × 250 × 195 mm Speed: 10–60 cm3 /h

Laser Engineering Net Shape – LENS Technology. Laser

engineered net shaping (LENS) technology developed by Sandia National Labs has been commercialized by Optomec [7.442]. This process is similar to other rapid prototyping technologies in its approach to fabricating a solid component by layer additive methods. However, the LENS technology is unique in that fully dense metal components are fabricated directly from raw materials, bypassing initial forming operations such as casting, forging, and rough machining. Parts have been fabricated from stainless steel alloys, nickelbased alloys, tool steel alloys, titanium alloys, and other specialty materials; as well as composite and functionally graded material deposition. Microscopy studies show the LENS parts to be fully dense with no compositional degradation. Mechanical testing reveals outstanding as-fabricated mechanical properties.

Part B 7.5

tem [7.440]. Apart from the additive manufacturing module it offers an erosion processing module and a marking module in one system. Module 1 (laser cusing): the module for producing parts from metallic powders. It allows for building parts layer by layer from many materials (e.g., stainless steel and hot work steel). Metallic powder is melted to produce 100% component density. The exposure strategy allows for producing large-volume parts without deformations. A patented surface postprocessing ensures good surface quality and hardness. Module 2 (3-D erosion module): the module for 3-D material erosion by a laser. It allows for erosion on freeform surfaces. The depth of the erosion process may be individually set by a laser-measuring sensor integrated with the machine software. Module 3 (marking module): the module for creating signs on plastic or metal elements. It allows for laser marking and engraving on a wide variety of materials. Technical characteristics:

7.5 Rapid Prototyping and Advanced Manufacturing

760

Part B

Applications in Mechanical Engineering

Fig. 7.358 View at a single layer of a block

by patients to gradually correct the position of their teeth. The patterns for aligner manufacture are built in stereolithography.

7.5.4 Rapid Tooling Technologies

Part B 7.5

Fig. 7.357 SMI sensor in the three-line scanning process

camera. The acquired image is converted through complicated operations and computer calculations until the final results are obtained [7.455]. Black & White Scanning. Another digitizing method is

used by Align Technology, USA. Since 1997 the company has been manufacturing orthodontic equipment in the system invented by them, Invisalign [7.456]. The manufacture of their teeth aligner starts from an impression of a patient’s jaw, which is then used to make a plaster cast. Several such models are submerged into a block of a thermosetting plastic. The hardened resin/plaster block is placed on a basic digitizing stage. On a device that could be called a scano-milling machine the block is repeatedly milled and then photographed. In each pass its height is reduced by 0.001 in. (Fig. 7.358). A stack of black-and-white images of all layers is transferred to a computer, where, using a program developed by Align, a digital model of the jaw is built in 3-D space. The computer models of patients’ teeth are used by an orthodontist to generate series of aligners to be worn

The pattern models and prototypes obtained with rapid prototyping methods are usually manufactured in small series for marketing and exhibition purposes or for experimental and service research. At this stage of product and manufacturing process development materials (or equivalents) and colors prescribed by the designer are used and the product is given suitable aesthetic features that should fully meet the features of series production. There are several commonly used rapid tooling (RT) technologies. They aim at providing tools (molds, dies) for manufacturing shorter or longer series of products in either specific processes or standard processes common in the production environment. The term rapid tooling covers various techniques of tool manufacturing, including forming inserts of injection molds from plastics, low-temperature melting metal alloys, or metallic powders. Depending on the strength of the applied materials and their durability and application range, the subgroups of rapid soft tools and rapid hard tools can be distinguished among the tools manufactured by RT methods. The latter subgroup is characterized by higher durability and wider application range, and the properties close to those of molds manufactured by traditional machining technologies. The techniques used in the manufacture of tools for mass production are based on highly efficient lost material machining called high-speed cutting (HSC),

Manufacturing Engineering

sponse for display application. However, for higher response speed, reduction of the sheet resistance of ITO layers, as well as the size and cantilevers, must be optimized. A dot-matrix-type device, shown in Fig. 7.384, is fabricated to confirm the function as a display. An 8 × 8 pixel matrix is constructed in 6 × 6 mm square, with a

References

773

pixel size of 500 μm. Using an external voltage driver with a laser incident beam to the glass substrate, the device shows the ability of an individual pixel drive as well as row and column driving. This type of device can display images on transparent media and can be seen from both sides, when every part is made of transparent material.

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7.407 R.F. Scholl: VDI-Zeitschrift 141(9/10) (1999), in German 7.408 E. Chlebus: Computer Technix CAx in Production Engineering (WNT, Warsaw 2000), in Polish 7.409 M. Eigner: Requirements with regard to PDM system architecture and functionality – a vendors report, Proc. Product Data Management based on International Standards (Volkswagen AG, Braunschweig 1999) 7.410 C.-O. Bauer: Produkthaftung-Ansprüche an die Konstruktion haben einen Anteil von 70%, Maschinenmarkt 68 (1984), in German 7.411 E. Westkämper: Manufuture – a vision for 2020, Workshop (Hannover 2004) 7.412 A. Gebhardt: Rapid Prototyping – Werkzeuge für die schnelle Produktentwicklung (Hanser, München 1996), in German 7.413 J.J. Beaman: Additive/Subtractive Manufacturing Research and Development in Europe (World Technology Evaluation Center, Baltimore 2004) 7.414 E. Chlebus: Innovative Rapid Prototyping – Rapid Tooling Technologies in Product Development (Centre for Advanced Manufacturing Technologies, Wroclaw University of Technology 2003) 7.415 W. Liu, L. Li, K. Kochar: A method for assessing geometrical errors in layered manufacturing. Part 1: error interaction and transfer mechanisms, J. Int. Adv. Manuf. Technol. 14, 637–643 (1998) 7.416 W. Liu, L. Li, K. Kochar: A method for assessing geometrical errors in layered manufacturing. Part 2: mathematical modelling and numerical evaluation, J. Int. Adv. Manuf. Technol. 14, 644–650 (1998) 7.417 R. Simmonds: Silikon und Polyurethan im Prototypenbau, Maschinenmarkt 52 (1997), in German 7.418 C.K. Chua, S.M. Chou, T.S. Wong: A study of the state-of-the-art rapid prototyping technologies, Int. J. Adv. Manuf. Technol. 14, 146–152 (1998) 7.419 D.T. Pham, R.S. Gault: A comparison of rapid prototyping technologies, Int. J. Mach. Tools Manuf. 38, 1257–1287 (1998) 7.420 K.E. Oczo´s: Rapid prototyping – meaning, characteristic of methods and applications, Mechanik 10 (1997), in Polish 7.421 K.E. Oczo´s: Progression in additive manufacturing, Mechanik 4 (1999), in Polish 7.422 G. Spur, E. Uhlmann: Rapid Prototyping – Dubbel Taschenbuch für den Maschinenbau, 21st edn. (Springer, Berlin 2005), pp. 94–95, in German 7.423 Wohlers: Wohlers Report 2004: Rapid prototyping, tooling and manufacturing state of the industry, Annual Worldwide Progress Report (Wohlers, Fort Collins 2004) 7.424 Wohlers: Wohlers Report 2006: Rapid prototyping, tooling and manufacturing state of the industry, Annual Worldwide Progress Report (Wohlers, Fort Collins 2006) 7.425 K.E. Oczo´s: Rapid Prototyping and Rapid Tooling – development of methods and techniques of rapid

Manufacturing Engineering

7.426 7.427 7.428 7.429

7.430 7.431 7.432

7.433

7.434

7.435 7.436

7.444 7.445

7.446

7.447

7.448 http://www.aracor.com (2002) 7.449 Cyberware, http://www.cyberware.com/ products/index.html (2001) 7.450 LDI, Laser Design Inc., http://www.laserdesign.com (2001) 7.451 Capture 3D Inc., http://www.capture3d.com/html/ products.html (2001) 7.452 Inspec Inc., http://www.sms-ct.com (2001) 7.453 Materialise NV: Materialise Medical (Materialise NV, Belgium 2002), http://www.materialise.be 7.454 Microscopic Moire Interferometry, http://www.aem. umn.edu/people/faculty/shield/mm.html (2001) 7.455 Photogrammetry, http://www.univie.ac.at/ Luftbildarchiv/intro.htm (2001) 7.456 Align Technology, Inc., http:/www.invisalign.com (2001) 7.457 HEK: Rapid Prototype Tooling (HEK GmbH, Germany 2001) 7.458 http://www.axson.com (2006) 7.459 http://www.ivf.se 7.460 K.W. Goosen, J.A. Walker, S.C. Arney: Silicon modulator based on mechanically-active antireflection layer with 1 Mb/s capability or fiber-in-the-loop applications, IEEE Photon. Technol. Lett. 6(9), 1119–1121 (1994) 7.461 J.B. Sampell: Digital micromirror device and its application to projection displays, J. Vac. Soc. Technol. B 12, 3242–3246 (1994) 7.462 T. Hatsuzawa, T. Oguchi: Application of micromachined SiO2 film for display devices, 10th Int. Conf. Solid-State Sens. Actuators (1999) pp. 804– 807 7.463 T. Oguchi, M. Hayase, T. Hatsuzawa: Driving performance improvement of the interferometric display device (IDD), Optical MEMS 2001 (2001) pp. 107– 108 7.464 T. Hatsuzawa, T. Oguchi, M. Hayase: An electrostaticdriven optical switching structure for display device, Optical MEMS 2001 (2001) pp. 149–150 7.465 T. Oguchi, H. Masanori, T. Hatsuzawa: Electrostatically driven micro-optical switching device based on interference of light and evanescent coupling, Proc. SPIE 4902, 213–220 (2002) 7.466 T. Oguchi, M. Hayase, T. Hatsuzawa: Electrostatically driven display device using evanescent coupling between sheet waveguide and multicantilevers, Optomechatoronic Systems IV, Proc. SPIE 5264, 134–141 (2003)

785

Part B 7

7.437 7.438 7.439 7.440 7.441 7.442 7.443

manufacture of models, prototypes and small-series products, Mechanik 4 (1998), in Polish M. Meindl: Prototypen in Produktentwicklung, Seminarber. IWB 49 (1999), in German http://www.3dsystems.com Cubital Ltd: Cubital Facet List Syntax Guide (Cubital, Raanana ) Z Corporation: Z Corporation family of printers Online in Internet (Z Corporation, Burlington 2004), www.zcorp.com/products/printers.asp J. Kowola: Realizing the potential of 3D Printer, Proc. Euro-URapid 2005 (Leipzig 2005) http://www.stratasys.com C.M. Stotko: E-Manufacturing: Von den Daten zum fertigen Produkt, Proc. Euro-URapid 2005 (Leipzig 2005), in German X. Wu: Direct Laser Fabrication, Proc. Seminar Rapid Product Development (CAMT Wroclaw University of Technology, Wroclaw 2002) M. Schellabear, J. Weilhammer: Direktes MetallLaser-Sintern (DMLS) – Industrielle Anwendung für Rapid Tooling und Manufacturing, Seminarberichte IWB TU Munich Nr. 50, Rapid Manufacturing – Methoden für die reaktionsfähige Produktion (Augsburg 1999), in German http://www.eos.info http://www.fockeleundschwarze.de/ english/fsrd.html http://www.mcp-group.de http://www.trumpf.com http://www.phenix-system.com http://www.cicweb.de, http://www.hig-ag.de http://www.arcam.com http://www.optomec.com Reverse Engineering-Technologies for Reverse Engineering, http://www.myb2o.com/myb2ous/ ReverseEngineering/Tools/Process/ 10618.htm#reverse (2001) Immersion Corporation, http://www.immersion. com (2001) B. Dybala, P. Kolinka: Technologies of reverse engineering in product development, 4th Conf. Prod. Autom. (Wroclaw 2003), in Polish B. Dybala: Methods of modelling and prototyping of anatomical objects, Proc. Euro-URapid 2005 (Leipzig 2005) R. Hermann, M. Hermann: Tomografia Komputerowa (Czerwiec 2001), http://www.zdrowie. med.pl/index.phtml

References

787

Measuring an 8. Measuring and Quality Control

Norge I. Coello Machado, Shuichi Sakamoto, Steffen Wengler, Lutz Wisweh

8.1

8.2

8.3 8.4 8.5

Quality Management............................. 8.1.1 Quality and Quality Management ... 8.1.2 Quality Management Methods ....... 8.1.3 Quality Management Systems ........ 8.1.4 CE Sign ........................................ Manufacturing Measurement Technology 8.2.1 Introduction ................................ 8.2.2 Arrangement in the Manufacturing Process ........ 8.2.3 Specifications on the Drawing........ 8.2.4 Gauging ...................................... 8.2.5 Application of Measuring Devices ... 8.2.6 Coordinate Measurements ............. 8.2.7 Surface Metrology......................... 8.2.8 Form and Position Measuring ........ 8.2.9 Laser Measuring Technology .......... Measuring Uncertainty and Traceability .. Inspection Planning.............................. Further Reading ...................................

787 787 787 793 793 793 793 794 795 797 797 800 807 810 812 816 817 818

Based on physical principles equipment and methods for the registration of measurement values, form- and position deviations and surface characteristics will introduce.

8.1 Quality Management 8.1.1 Quality and Quality Management Nowadays the quality of products, assemblies and services not only includes the fulfilment of functional requirements by maintaining tolerances. It also includes the fulfilment of numerous requirements such as rendered in parts in Fig. 8.1. In this section some fundamentals of quality management will be described from the multitude of requirements. In Sect. 8.2 some aspects of the requirements of manufacturing measurement technology for the qualification of the geometrical quality of products will be shown.

Among the requirements for organizations involved in quality control, the key concepts of quality management (QM) and total quality management (TQM) include planning, monitoring, and improvement of quality, such as the consideration of representatives and departments relevant to quality, as shown in Fig. 8.2.

8.1.2 Quality Management Methods To conform to the requirements of modern quality management, nowadays numerous procedures and methods, with many different applications, are available. Fig-

Part B 8

Considering the incessantly increasing requirements to the quality of products and processes it is necessary to improve a quality-orientated management in all departments of any types of companies and the advantageous application of manufacturing measurement equipment. In addition to diverse technical requirements are also to consider the requirements of national, international and company-specific norms. The companies must not only fulfill the requirements of the quality, but also the requirements of safety, environment and economy. As follows some aspects of the manufacturing measurement technology and quality management and their integration into a manufacturing process will be introduced. Starting with manufacturing geometrical conditions and statements at drawings (nominal state and geometrical limits) the use of measurement equipment and gages to the evaluation of geometric elements will be described. Basic knowledge to measuring standards, uncertainties as well as calibration and measuring instrument inspection will mediates.

790

Part B

Applications in Mechanical Engineering

Arrow diagrams or net plans are important resources for project planning for the investigation of critical paths, which determine the total permanence of a project. In this method the determination of a process sequence is made using series and parallel paths to develop a detailed explanation of the working steps required to achieve the project aim, followed by the assignment of the corresponding process durations. If a lot of information quantities for certain circumstance are available, matrix diagrams are situable for detection of latent structures. By using data evaluation in pairs with the help of matrixes for different characteristics this method enables, for instance, manufacturing and market analysis. Nowadays, in the field of preventive techniques for failure prevention in technological processes, the schematically compounded methods shown in Fig. 8.3 are mostly applied. In current quality management product-related customer wishes are the sources of motivation for development from the designing process through the manufacturing process up to the delivery of the products. With the help of quality function deployment (QFD) the voice of the company can be developed from the voice of the customers. The QFD method systematizes this process under the application of matrixes based on the following four steps:

• • Part B 8.1

• •

Customer wishes in terms of product characteristics Product characteristics in terms of part characteristics Part characteristics in terms of manufacturing regulations Manufacturing regulations in terms of production instructions

Every phase can be described by matrixes in the form of a so-called house of quality. This method offers the possibility to affect the production aim in the conception phase and at the same time to obtain information about the critical product and process characteristics for the fulfilment of the customers expectations. Besides the implementation of marketing information in the product, target conflicts between the individual product characteristics may also become visible. For the detection of potential failure modes during product development, the introduction of new manufacturing methods, and the modification of manufacturing technologies failure mode and effect analysis (FMEA)

is used. FMEA is especially used in the case of cost-intensive and risk-affected products and processes. FMEA has universal application and is not connected with a special field. At the base of a standardized procedure, which can be supported by corresponding blank forms, the main steps of a FMEA can be divided into risk analysis, risk assessment, the determination of measures, and the evaluation of effectiveness. The risk evaluation results from evaluation of the probability of occurrence, its importance (for the customers), and the probability of detection of the corresponding failure before delivery to the customer. The advantages of FMEA above all are decreased numbers of failures in the early phases of product manufacturing, and in product planning. The systematic search for imaginable reasons for a failure, called an unwanted event, is possible with the method of failure tree analysis. This method, which originated from the field of safety engineering, enables an evaluation of fixed correlations by the determination of the quantitative probability of the appearance of failures. For this purpose the function of single components (devices) is described under different conditions using a so-called components tree. A subsequent system analysis aims to describe holistically their organization and the behavior of the technical system. The contribution of the individual components to the protection of the overall function of the system, the evaluation of the consequences of the environmental influences of the overall system, and the description of the reaction of the overall system to failures within the system, of resources, and by faulty operations can be described by a failure tree analysis and be calculated or simulated by various evaluation methods. The methods of statistical research planning have the general aim to adjust the relevant product and process parameters using a systematically procedure in such a way that the quality-relevant characteristics closely approach the ideal value with as few experiments as possible. The weighting of the influencing factors and the quantification of their effect can be solved based on classical statistical research planning using mathematical models (such as factorial research plans); if there are a very large number of influencing factors this can be solved with the help of the empirical procedures developed by Taguchi or Shainin. The Poka Yoke method (from the Japanese: the avoidance of unintentional errors) is dedicated to preventive avoidance of failures in manual manufacturing

Measuring and Quality Control

blocks. The known value of the measurement standard (whose small deviation from the true value is negligible for the purpose of comparing), is called the correct value. The systematic measurement deviations can be calculated from the difference between the measured value of the measurement standard and its correct value. Afterwards one can correct all measuring values by use of the known systematic deviation. The non-measurable or not measured (for instance too expensive) elements of the systematic measuring deviation are combined with random measuring deviations to constitute the measuring uncertainty. So, the measuring uncertainty is a parameter obtained from the measurement. It describes the region around the corrected measuring value where the true value must be found. The complete result of measuring is given as the corrected measuring value plus/minus the measuring uncertainty. In order to guarantee the correctness of measuring results, measuring devices must be affiliated to the national standard of the respective measurement. In Germany for instance, this is the National Physical Technical Institute (PTB), located in Braunschweig, which are responsible for the representation and propagation of physical units. Through the PTB, calibrating laboratories are accredited, so that their measuring

8.4 Inspection Planning

817

devices and measuring standards coincide with the national standards (the units), according to the defined and accepted techniques. These are the laboratories of the German Calibration Service (DKD). All in-company measuring devices, or rather standards, should consistently be traceable back to the national standard of the PTB. In order to verify this, the instruments are calibrated by a DKD laboratory or the PTB themselves. Calibration is defined as the inspection of measuring devices and measurement standards with reference to the accepted national standard. The successful calibration is generally documented through a protocol, the calibration certificate. On the calibration certificate, all of the calibration results, the reference standards, and additional measuring equipment (used during the calibration), the environmental conditions, and the calculated measuring uncertainty are documented. One should use certified instruments, standards, and methods in order to achieve cost-effective, in-company control of inspection instruments. Otherwise, a traceability certificate is not possible. The setting-up and balancing of a measuring instrument, by which known systematic deviations of the measuring result are eliminated, is called adjusting.

8.4 Inspection Planning

•

The type of parameter (measure, form and position tolerance, surface tolerance, etc.)

• •

The drawing view Grid squares (for example, upper left starting clockwise)

in the work plan according to maintenance sequences, in the documentation, delivery instructions, and contractual arrangements, is essential. The definition of the inspection frequency (number of samples, size of sample) occurs on the basis of mathematical statistical facts. The time point in the production process allows company organizational and economical considerations. The late recognition of inadmissible errors can bring about several disadvantages. The definition of inspection methods and inspection equipment are related and thus should each be chosen with the other in mind. The choice of measuring device begins with consideration of the required information content of the measuring result. In this way the aim of the inspection (evaluation of workpiece or process, manufacturing control) and the impact of the measuring instrument itself can be taken into

Part B 8.4

Inspection planning means the planning of quality inspection in the entire production process, from the arrival of raw products until the delivery of the final product. For this, inspection tasks and procedures are specified with inspection feature, inspection location (close to production, measuring room), frequency of inspection, point of time within the production process, inspection methods, inspection equipment, and operators. One should consider both technical and economic aspects. The inspection planner must consider knowledge of the function and application of the piece or the components, safety hazards, the production process, technical documentation (drawings, standards, stipulations), and the inspection equipment. It should be consistently checked that the data is complete, current, and inspected (approved by the operating department). For the choice of inspection procedures, a systematic search in the drawing(s) ordered by

818

Part B

Applications in Mechanical Engineering

account. Geometrical limitations, such as the accessibility of the piece, the geometry of the probing element, the range of measurement (direct measuring, difference measuring) of the instrument, and especially for soft materials, the measuring force, are previously decided. Finalized statements for the usability of a measuring instrument can be made after inspection of the scale division value and the measuring uncertainty. The measuring uncertainty must adhere to the ratio to the inspected tolerance by the relation Tu = 0.1 to 0.2. Alternatively, it is possible to obtain measuring capability coefficients and check the adherence of these characteristics to previously defined limits. Supplemental criteria are, for example, the surfaces available for the measurement, and transfer for processing, protocol and archiving. The required measuring time (capability of the measurement to be automated) in conjunction with the number of pieces to be tested is the essential criteria for the cost effectiveness of the application of a measuring device. Included in the inspection costs are also the equipment costs, equipment observation, calibration, and personnel costs (work time, education).

To guarantee the comparability of the measuring result and low uncertainty of the acquired characteristics the following conditions should be taken into account when specifying measurement methods:

•

• •

•

Explicit guidelines for the measuring procedure including, the required parameters for an appropriate measurement. Specification of the reference basis for the measuring procedure, to the accuracy of the applied measuring instruments and measurement standards, gripping elements employed, and additional measuring equipment. Details of the measuring strategy, for example, the definition of the measurement location on the piece, or the number and arrangement of single measurements as a basis for a good average value. Details of the measuring value collection method for selective inspection and of the further steps of measured value processing, or guidelines for the application of analyzing software (for example, the selection of a compensating method). Legal warranty of adequate qualification of the personnel who conduct the measurement.

The result of inspection planning is the inspection plan.

8.5 Further Reading • Part B 8.5

• • • • • •

T. M. Bosch, M. Lescure: Laser Distance Measurements (Atlantic Books, London 1995) H. Czichos, T. Saito, L. Smith (Eds.): Springer Handbook of Materials Measurement Methods (Springer, Berlin, Heidelberg 2006) E. Dietrich, A. Schulze: Statistical Procedures for Machine and Process Qualification (ASQ Quality Press, Milwaukee 1999) P. F. Dunn: Measurement and Data Analysis for Engineering and Science (McGraw-Hill, Columbus 2004) H. Pham (Ed.): Springer Handbook of Engineering Statistics (Springer, Berlin, Heidelberg 2006) H. J. Hocken, R. J. Hocken: Coordinate Measuring Machines and Systems, 2nd ed. (CRC, Boca Raton 2009) S. Vardeman, J. M. Jobe: Statistical Quality Assurance Methods for Engineers (Wiley, New York 1999)

• • •

•

G. T. Smith: Industrial Metrology: Surfaces and Roundness (Springer, Berlin, Heidelberg 2002) W. N. Sharpe, Jr. (Ed.): Springer Handbook of Experimental Solid Mechanics (Springer, Berlin, Heidelberg 2008) L. Wisweh, M. Sandau. R. Ichimiya, S. Sakamoto: Determination of measuring uncertainty and its use for quality assessment and quality control, Research Report Faculty of Engineering Nr. 47, Niigata University, Japan (1998) N. Zenine, S. Wengler, L. Wisweh: Polygon connections - manufacture and measurement, Proc. VIth International Scientific Conference Coordinate Measuring Technique, Scientific Bulletin of University of Bielsko-Biala. No. 10 Bielsko-Biala (2004)

819

Engineering 9. Engineering Design

Alois Breiing, Frank Engelmann, Timothy Gutowski

The development and design of engineering systems following a methodical approach based on information from the literature [9.1–6] is a useful procedure. The guidelines for design methodology have also been applied to interdisciplinary development projects of this type, using aids such as requirements lists, the functional structure, and morphological boxes, to name just a few. During the design phase of the product development process it is important to comply with the basic design rules: simple, clear, and safe [9.3]. Several examples that clearly show the realization of these three criteria are included in this chapter.

9.1

9.2

Design Theory ...................................... 9.1.1 Product Planning Phase ................ 9.1.2 The Development of Technical Products .................... 9.1.3 Construction Methods ...................

819 819 824 828

Basics .................................................. 842

9.3 Precisely Defining the Task .................... 9.3.1 Task............................................ 9.3.2 Functional Description .................. 9.3.3 Requirements List ........................

843 843 843 844

9.4 Conceptual Design ................................ 845

9.6 Design and Manufacturing for the Environment ............................. 9.6.1 Life Cycle Format for Product Evaluation .................. 9.6.2 Life Cycle Stages for a Product ........ 9.6.3 Product Examples: Automobiles and Computers .......... 9.6.4 Design for the Environment (DFE)........................................... 9.6.5 System-Level Observations ............ 9.7

Failure Mode and Effect Analysis for Capital Goods .................................. 9.7.1 General Innovations for the Application of FMEA ........... 9.7.2 General Rules to Carry Out FMEA ..... 9.7.3 Procedure ................................... 9.7.4 Further Use of FMEA Results ...........

849

849

851 852 853 854 856 859 866 866 867 867 868 869 875

References .................................................. 875

9.1 Design Theory 9.1.1 Product Planning Phase It is possible to structure technical products in individual life stages. These are often the basis for work done by the product manufacturer, but also by the product user. Examples include schedules for the development of a product or maintenance plans.

Figure 9.1 shows essential product life stages of a product in the sequence of production and the application. For examining the structures further, it is possible to subdivide the individual product life phases into steps. In practice, this provides the engineer with a tool, which allows him to categorize his activities accurately.

Part B 9

9.5 Design ................................................. 848 9.5.1 Identify Requirements that Determine the Design and Clarify the Spatial Conditions... 849

9.5.2 Structuring and Rough Design of the Main Functional Elements Determining the Design and Selection of Suitable Designs ... 9.5.3 Detailed Design of the Main and Secondary Functional Elements ..................................... 9.5.4 Evaluation According to the Technical and Economic Criteria and Specification of the Preliminary Overall Design ... 9.5.5 Subsequent Consideration, Error Analysis, and Improvement ...........

Engineering Design

Product Planning Importance. The first two phases of product life, prod-

uct planning and product development, are among the most important tasks in industry. The continuous generation of marketable products is the foundation for the economic success of the company. Because of the inevitable downturn phases for existing products or product groups (Sect. 9.1.1), the systematic planning of new products must take place, something which can also be seen as an innovative product policy [9.4]. Strategies for product planning should not be a barrier for creative companies and their engineers. Rather, these should have a supporting effect as methodological aids.

• • • • • • •

From the world economy (e.g. exchange rates) From the domestic economy (e.g. inflation rate, labour market situation) From legislative and administrative acts (e.g. environmental protection) From the buying market (e.g. suppliers’ market and commodity market) From research (e.g. government-funded research priorities) From technology (e.g. developments in microelectronics or laser technology) as well as From the market

• • • • • •

• • •

Economic areas: domestic market, export markets New factors for the company: current market, new market Market position: market share, strategic free reign of the company, the technical value of its products

• •

From the organization of the company (e.g. product oriented vertical or task oriented horizontal organization) From the staff (e.g. availability of qualified development and manufacturing staff) From financial strength (e.g. investment opportunities) From the size of the company (e.g. in terms of turnover which can be sustained) From the production fleet (e.g. with regard to certain manufacturing technologies) From the product programme (e.g. with regard to components which can be adopted and predevelopments) From expertise (e.g. development, marketing and production experience) as well as From the management (e.g. as project management)

The influences listed are also described as potential of the company. Product Development General Approach. The second phase of product life

is development and construction. This is also often referred to as product development. To further structure this phase of product life, it is usual to break stages down into individual steps. This procedural approach in handling constructive tasks is based on general solution methods and/or working method approaches as well as the general relationships in building technical products. It is not a rigidly prescribed approach, but instead, it is an essential tool for the engineer in product development. The individual working steps are the basis for other activities, e.g. the preparation of schedules or the planning of product development costs. They also help the engineer in finding where he is in the development process. A possible structure can be seen in Fig. 9.3. Despite the variety of product developments, it is possible to work out a sector-independent flowchart, the work steps of which have to be modified to the special conditions in stetting the tasks. The approach begins with clarifying and specifying the task, something which is especially important for new design tasks. The basis for this is the stetting of tasks with individual needs which are developed from product planning tasks. From the wealth of specified requirements, the designer engineer must identify the essential problems to be solved and formulate these in the language of his field of design. The result is a requirements list, which is also known as a specification sheet. It is the

Part B 9.1

As such, the conditions of the market are crucial. A distinction can be made between a buyer’s market and a seller’s market. In the former, the supply is the larger than the demand and in the second the demand is larger. In a seller’s market, production is the bottleneck however on the other hand, in a buyer’s market, products must be designed and developed, which have to be successful in competition with the products of other providers. Further criteria for the identification of markets are:

821

Internal factors come:

Fundamentals. The bases for the planning of prod-

ucts are the relationships in the market, relationships within the environment of the company and within the company itself. These can be defined as external and internal influences on a company, particularly towards its product planning. External influences come:

9.1 Design Theory

Engineering Design

9.1 Design Theory

833

Table 9.2 Points awarded in the utility analysis and VDI guideline 2225 (after [9.3])

Value scale Use-value analysis Pts. Meaning 0 absolutely useless solution 1 2

very inadequate solution weak solution

3 4

tolerable solution adequate solution

5 6

satisfactory solution good solution with few drawbacks

7 8 9 10

good solution very good solution solution exceeding the requirement ideal solution

If several solutions remain, they are obviously preferred. The selection criteria are to be adjusted to the goals of product development and the company. For a more accurate selection, evaluation procedures are used, in particular, VDI guideline 2225 [9.29] and the utility analysis [9.30]. In Table 9.2, a comparison is shown between the two procedures. A detailed approach can be taken from VDI guideline 2225 [9.30]. Design Principles After evaluating the effective structures which have been worked out and/or principle solutions, a structure/solution is usually released for drafting. The design stage in the drafting of a product requires the use of mechanics, the knowledge of strength science as well as knowledge of manufacturing technology, materials technology and other fields. The fine shape is gradually generated from the rough shape:

•

Rough design: spatially and significantly correct, but without details, i. e. preliminary drafts Fine design: all the necessary details are conclusively defined by applying guidelines / regulations, norms, calculations and consider the impact of auxiliary functions

When generating fine shape, it is appropriate to structure the approach in individual work steps. The starting point is the principle solution. Following clarification of the spatial conditions, the designing of the design-determining main functional elements be-

0

unsatisfactory

1

just tolerable

2

adequate

3

good

4

very good (ideal)

gins and following this, the designing of the other main functional bodies. If they are sufficiently specified, the search takes place for solutions to the auxiliary functional elements [9.3]. In this step, these are often bought-in parts. The result of this working step is to define the design of the principle solution, i. e. all the characteristics of geometry, material and condition. The following methods and rules are recommendations, strategies and hints for the designer with which he can successfully work out a structure for a product [9.3]. Basic Design Rules. Basic rules are always valid in-

structions, whose observance helps ensure the success of a solution and whose non-observance leads to major drawbacks. They are derived from general objectives in the construction process. Observance of the basic rules:

• • •

Easy Clear and Safe

leads to the clear fulfilment of the technical function, its economic realization and to safety for humans and the environment. Observance of the basic rule clear helps, to reliably predict the effect and behaviour of structures. Figure 9.20 shows an example of a shaft-hub connection. This is a cross-compression connection. The additional parallel key does not make it any more secure. Sectional weakening results and there are additional notches (lo-

Part B 9.1

•

Guideline VDI 2225 Pts. Meaning

842

Part B

Applications in Mechanical Engineering

In designing parts (pieces) which are convenient to manufacturing processes, the designer has to be aware of the nature of the manufacturing procedures and the specific circumstances of each manufacturing plant (internal or external). Design in accordance with assembly considerations means to reduce, to simplify, to unify and to automate the necessary assembly operations through an appropriate structure, as well as the design of the joints and joining parts [9.3]. In the design measures to simplify the parts production and the assembly, aspects of the testing process and production monitoring are looked at. Design in accordance with norms include the norms which are observed for safety, usage and economic reasons and other technical rules which, as recognized engineering rules, serve the interests of manufacturers and users.

Design in accordance with transportation and packing considerations means taking into account standardized packaging and loading units (containers, pallets) for serial production as well as transportation options for large machinery [9.3]. Design in accordance with recycling considerations means knowing the nature of processing and reclamation procedures and supporting their use through assemblies and component design (shape, joints, materials). At the same time, reclamation-friendly constructive measures (facilitated dismantling and reassembling, cleaning, testing and post-processing or exchange) serve the interests of maintenance compatible design (inspection, servicing, repairs). Figure 9.34 shows recycling possibilities for material products, to which constructive measures must be oriented in order to facilitate recycling [9.35–38].

9.2 Basics

Part B 9.2

The methodical approach to the development and design of technical systems (engineering design) has established itself in virtually all design departments. Teaching specialized knowledge about methodical design is also a fixed component of the curriculum in the teaching of engineering sciences in universities and technical colleges. There are a large number of approaches to design methodology, which are documented the technical literature. For example, Ehrlenspiel [9.1] focuses more on the cost approach to product development. One way of reducing and identifying costs early, according to Ehrlenspiel, is integrated product development. In his method on the other hand, Roth [9.2] divides the design process into many smaller steps and places strong emphasis on the incorporation of design catalogues in the solution process. Pahl et al. [9.3] worked very actively on the German guidelines VDI2221 [9.21] and VDI2222 [9.39] and subdivided the design process into individual activities, to which detailed methods are assigned. Further methods exist for these purposes, for example from Koller [9.6], Gierse [9.40], Hubka [9.41], Bock [9.42] and Rugenstein [9.43]. The essential aspect of each of these is the structuring of the task. This takes place, e.g., by drawing up flow diagrams and using methodical structuring aids, e.g., functional structures, efficacy structures or classification diagrams [9.44].

The methodical approach to the development of a technical system is clarified in this chapter using a practical example from the interdisciplinary field of biomedical engineering, based on the methodical method of Pahl et al. [9.3]. According to Pahl et al., the design process is divided into four stages:

• • • •

Precisely defining the task (problem identification) The concept stage The design Drawing up the final solution (detailed design)

As the example involves an interdisciplinary development project, it is particularly important to draw up only a few, but at the same time all, of the problem or work-related (sub)functions required for adequate structuring of the task and to represent these in a functional structure. It is also necessary to use a generally understood vocabulary. This enables us to ensure that people not yet involved in the process or people who do not have engineering training, e.g., medical experts or biologists can easily obtain an overview. This integration of employees from the individual specialized fields is necessary in order to be able to implement all medical and biological requirements at a high level.

854

Part B

Applications in Mechanical Engineering

Table 9.3 List of environmental concerns and links to manufacturing processes Environmental concerns

Linkage to manufacturing processes

1. Global climate change

Greenhouse gas (GHG) emissions from direct and indirect energy use, landfill gases, etc. Emission of toxins, carcinogens, etc. including use of heavy metals, acids, solvents, coal burning Water usage and discharges, e.g., cooling and cleaning use in particular Electricity and direct fossil fuel usage, e.g., power and heating requirements, reducing agents Land use, water usage, acid deposition, thermal pollution Emissions of chlorofluorocarbons (CFCs), hydrochlorofluorocarbon (HCFCs), halons, nitrous oxides, e.g., cooling requirements, refrigerants, cleaning methods, use of fluorine compounds Land appropriated for mining, growing of biomaterials, manufacturing, waste disposal Materials usage and waste Sulfur and NOx emissions from smelting and fossil fuels, acid leaching and cleaning

2. Human organism damage 3. Water availability and quality 4. Depletion of fossil fuel resources 5. Loss of biodiversity 6. Stratospheric ozone depletion

7. Land use patterns 8. Depletion of non-fossil fuel resources 9. Acid disposition

Part B 9.6

cesses. Often the change in balance takes years to detect and can be influenced by a variety of factors, making isolation and identification of the problems difficult and sometimes controversial. Nevertheless, over time many of these problems have been identified. They include ozone depletion, global warming, acidification, and eutrophication, among others. Corrective action often involves changes in the types and ways we use materials and energy for the production, use, and disposal of products. Table 9.3 lists commonly agreed environmental concerns and aspects of production, consumer use, and disposal that contribute to these concerns. Table 9.3 clearly conveys the message that many of our environmental problems are directly related to materials usage, including energetic materials. In particular, note that several prominent concerns listed in Table 9.3 are directly related to our use of fossil fuels to generate energy. These include: CO2 and NOx emissions from the combustion of all fossil fuels, and SOx and several heavy metals including As, Cd, Cr, and Hg, which are deposited onto land from the combustion of coal [9.48, 49]. In fact, at least four out of nine of the concerns listed above are related to fossil fuel use, including numbers 1, 2, 4, and 9. Because of this overriding importance, we will pay particular attention to tracking energy usage in the life cycle of products.

9.6.1 Life Cycle Format for Product Evaluation A very important aspect of environmental analysis simply involves connecting the dots, in other words,

showing the interconnectivity of human activities, and in particular, material flows. Few people contemplate where resources come from, or where they go after they are used, yet this is essential for life cycle analysis. With a life cycle accounting scheme one can then properly burden each product or activity with its environmental load. This information, in turn, can be used to answer the question, is the utility gained from this product or activity worth the associated environmental load? Although conceptually simple, this task is, in fact, quite complex. The major complexities are: 1. Establishing system boundaries 2. Obtaining accurate data 3. Representing the data with concise descriptors that appropriately assign responsibility 4. Properly valuing the results Our approach will be to represent the product using material flow diagrams that capture the major inputs and outputs. In general, we will not attempt to relate these inputs and outputs to specific levels of environmental harm but only to identify them as environmental loads, known to cause harm, and which are excellent targets for technical improvement. When specific amounts of inputs used or outputs emitted are given, this type of analysis is called a life cycle inventory (LCI). The full life cycle analysis (LCA) includes LCI plus a connection between the loads produced and associated harm caused and often a ranking value among the different types of harm. Some LCA methods use these ranking values to generate a single number result. This can greatly ease decision-making, but requires agreement

Engineering Design

Table 9.5 Typical energy requirements for some common

materials [9.57] Material

Energy cost (MJ/kg)

Made or extracted from

Aluminum Copper Glass Iron Nickel Paper Polyethylene Polystyrene Polyvinylchloride Silicon Steel Titanium Wood

227–342 60–125 18–35 20–25 230–70 25–50 87–115 62–108 85–107 230–235 20–50 900–940 3–7

Bauxite Sulfide ore Sand, etc. Iron ore Ore concentrate Standing timber Crude oil Crude oil Crude oil Silica Iron Ore concentrate Standing timber

Table 9.6 Toxicity ratings for some of the elements [9.49] Toxicity rating

Example elements

High toxicity

Beryllium, arsenic, cadmium, mercury, lead, Lithium, boron, chromium, cobalt, nickel, copper, bismuth Aluminum, silicon, titanium, iron, zinc, bromine, silver, tin, tungsten, gold,

Moderate toxicity Low toxicity

Similarly, primary materials processing can be both materials and energy intensive. For example, the production of 1 kg of aluminum requires on the order of 12 kg of input materials and 290 MJ of energy [9.57]. The energy for this production plus other processing effects, in turn, leads to about 15 kg of CO2 equivalent for every kg of aluminum produced [9.58]. Table 9.5 gives the energy requirements for some materials. Note that aluminum is in the high range of these materials, on the

9.6 Design and Manufacturing for the Environment

order of silicon but substantially less than titanium. The substitution of recycled materials can greatly reduce this energy requirement. Conversely the requirement for ultrahigh purity can greatly increase this requirement. For example, the recycled energy requirement versus virgin material is only about 5% for aluminum and 30% for steel [9.59], while the energy requirements for wafergrade silicon used in the semiconductor industry is about 33 times that of commercial grade [9.60]. Hence, the mere act of selecting materials can in itself define a large part of the environmental footprint for a product. Graedel and Allenby suggest several other criteria to consider when selecting materials, including toxicity and abundance [9.49]. The ratings for some elements are given below in Tables 9.6 and 9.7. Manufacturing Processes As a group, manufacturing processes appear to be quite benign compared to materials extraction and primary processing, as indicated in Fig. 9.54. However, manufacturing processes often set many of the requirements for primary processing outputs. For example, processes with higher scrap rates require more energy in primary processing. Alternatively, processes that can use large quantities of recycled materials will have greatly reduced primary energy needs. This concept can be illustrated more rigorously by writing an equation for the embodied energy content for a hypothetical manufacturing process that uses E m energy per kilogram of product produced. It has become common to discuss the energy “used up” in a process, but by the first law of thermodynamics we know that the energy is not actually lost. Rather, it is made unavailable. A more accurate thermodynamic quantity, exergy can be used up, and is more precisely what we mean in our discussion of energy used. Let the waste fractions be: α to ground, γ to recycle, and β to prompt scrap (recycled within the factory). This process uses a fraction φ of primary material with

Example elements

Infinite supply Bromine, calcium, chlorine, krypton, magnesium, silicon Ample supply Aluminum (gallium), carbon, iron, potassium, sulfur, titanium Adequate supply Lithium, phosphorus Potentially limited supply Cobalta , chromiumb , nickela , lead (arsenic, bismuth), platinumb , zirconium Potentially highly limited supply Silver, gold, copper, mercury, tin, zinc (cadmium) a Supply is adequate, but virtually all from South Africa and Zimbabwe. This geographical distribution makes supplies potentially subject to cartel control. b Maintenance of supplies will require mining seafloor nodules. Note that materials in parentheses are co-mined with the parent material listed in front.

Part B 9.6

Table 9.7 Classes of supply for some of the elements [9.49] Worldwide supply

857

860

Part B

Applications in Mechanical Engineering

Table 9.9 Premanufacturing ratings [9.55] Element designation

Element value & explanation: 1950s automobile

Element value & explanation: 1990s automobile

Materials choice

1, 1

2

Few hazardous materials are used, but most materials are virgin

3

Energy use Solid residue

1, 2 1, 3

2 3

3 3

Liquid residue

1, 4

3

Gas residue

1, 5

2

Virgin material shipping is energy intensive Iron and copper ore mining generate substantial solid residues Resource extraction generates moderate amounts of liquid residues Ore smelting generates significant amounts of gaseous residues.

3 3

Few hazardous materials are used, and much recycled material, Pb in battery in closed recycle loop Virgin material shipping is energy intensive Metal mining generates solid residues Resource extraction generates moderate amounts of liquid residues Ore processing generates moderate amounts of gaseous residues

Table 9.10 Product manufacture ratings [9.55] Element designation

Element value & explanation: 1950s automobile

Element value & explanation: 1990s automobile

Materials choice

2, 1

0

Chlorinated solvents, cyanide

3

Energy use Solid residue

2, 2 2, 3

1 2

3 3

Liquid residue

2, 4

2

3

Some liquid residues from cleaning and painting

Gas residue

2, 5

1

Energy use during manufacture is high Lots of metal scrap and packaging scrap produced Substantial liquid residues from cleaning and painting Volatile hydrocarbons emitted from paint shop

Good materials choices, except for lead solder waste Energy use during manufacture is fairly high Some metal scrap and packaging scrap produced

3

Small amounts of volatile hydrocarbons emitted

Table 9.11 Product delivery ratings [9.55] Element designation

Element value & explanation: 1950s automobile

Element value & explanation: 1990s automobile

Materials choice

3, 1

3

3

Energy use

3, 2

2

Sparse, recyclable materials used during packaging and shipping Over-the-road truck shipping is energy intensive

Solid residue

3, 3

3

3

Liquid residue

3, 4

4

Gas residue

3, 5

2

Small amounts of packaging during shipment could be further minimized Negligible amounts of liquids are generated by packaging and shipping Substantial fluxes of greenhouse gases are produced during shipment.

Part B 9.6

the fuel, etc.) and other greenhouse gases are converted into their CO2 equivalent, the resulting equivalent CO2 emissions over the life time of the vehicle are about 94 metric tons or 9.4 t/year. Other emissions during the use stage are also high, including NOx , volatile organic compounds (VOCs), which contribute to ground-level ozone and smog, and other hazardous materials at lower levels. Other areas of concern are painting and cleaning during manufacturing, leaks and emissions during use and maintenance, and remaining quantities of unrecyclable materials: plastics, glass, foam, rubber, etc. The total energy use by stage, shown in Fig. 9.56, indicates that energy use during material production and manufacturing are also significant [9.66].

3

4 3

Sparse, recyclable materials used during packaging and shipping Long-distance land and sea shipping is energy intensive Small amounts of packaging during shipment could be further minimized Negligible amounts of liquids are generated by packaging and shipping Moderate fluxes of greenhouse gases are produced during shipment

A general assessment of how the environmental performance of the automobile has changed over the years can be found in Graedel, who performed an SLCA to compare a 1950s automobile to one from the 1990s [9.55]. The assumed characteristics of the cars are given in Table 9.8. Their ratings for each of the five impact categories in each of the five life cycle stages are given in Tables 9.9–9.13. The final matrix values are summarized in Tables 9.14, 9.15, and plotted as a target plot in Fig. 9.57. Computers The study of the environmental footprint for computers is an interesting contrast to automobiles. While auto-

Engineering Design

9.6 Design and Manufacturing for the Environment

861

Table 9.12 Product use ratings [9.55] Element designation

Element value & explanation: 1950s automobile

Element value & explanation: 1990s automobile

Materials choice Energy use Solid residue

4,1 4,2 4,3

1 0 1

1 2 3

Liquid residue Gas residue

4,4 4,5

1 0

Petroleum is a resource in limited supply Fossil fuel energy use is very large Significant residues of tires, defective or obsolete parts Fluid systems are very leaky No exhaust gas scrubbing; high emissions

3 2

Petroleum is a resource in limited supply Fossil fuel energy use is large Modest residues of tires, defective or obsolete parts Fluid systems are somewhat dissipative CO2 , lead (in some locales)

Table 9.13 Refurbishment/recycling/disposal ratings [9.55] Element designation

Element value & explanation: 1950s automobile

Element value & explanation: 1990s automobile

Materials choice

5, 1

3

Most materials used are recyclable

3

Energy use

5, 2

2

2

Solid residue Liquid residue Gas residue

5, 3 5, 4 5, 5

2 3 1

Moderate energy use required to disassemble and recycle materials A number of components are difficult to recycle Liquid residues from recycling are minimal Recycling commonly involves open burning of residues

3 3 2

Most materials recyclable; plastics, glass, foam not recycled; sodium azide presents difficulty Moderate energy use required to disassemble and recycle materials Some components are difficult to recycle Liquid residues from recycling are minimal Recycling involves some open burning of residues

Table 9.14 Environmentally responsible product assessment for a generic 1950s automobile [9.55] Environmental stressor Materials choice Energy use Life cycle stage Premanufacture Product manufacture Product delivery Product use Refurbishment, recycling, disposal Total

2 0 3 1 3 9/20

2 1 2 0 2 7/20

Solid residues

Liquid residues

Gaseous residues

Total

3 2 3 1 2 11/20

3 2 4 1 3 13/20

2 1 2 0 1 6/20

12/20 6/20 14/20 3/20 11/20 46/100

Table 9.15 Environmentally responsible product assessment for a generic 1990s automobile [9.55] Environmental stressor Materials choice Energy use Life cycle stage 3 3 3 1 3 13/20

3 2 3 2 2 12/20

mobiles use mostly conventional materials and many standard manufacturing processes, the microchips in computers use much more-specialized materials and rapidly changing process technology. The result is that the complete life cycle of the computer has not been filled in to the extent that the automobile has. This is

Liquid residues

Gaseous residues

Total

3 3 3 2 3 14/20

3 3 4 3 3 16/20

3 3 3 2 2 13/20

15/20 14/20 16/20 10/20 13/20 68/100

clearly illustrated in the important paper by Williams, Ayres, and Heller [9.60], which illustrated that there is far less agreement on the magnitudes of the environmental impacts associated with microchip fabrication. Nevertheless the available data indicate that microelectronics fabrication is very materials and energy

Part B 9.6

Premanufacture Product manufacture Product delivery Product use Refurbishment, recycling, disposal Total

Solid residues

Engineering Design

9.6 Design and Manufacturing for the Environment

863

Table 9.18 Streamlined life cycle analysis: desktop computer display and CPU. Premanufacturing i, j

Environmental stressor

Score

1, 1

Material choice Few recycled materials are used. Many toxic chemicals are used, including Pb in CRT and PWB, Cd in some batteries, Hg in some switches, and brominated flame retardants in plastics. Energy use Extra-high-grade materials for microchip very energy intensive. Other high-energy materials include virgin aluminum, copper, CRT glass. Solid residues Many materials are from virgin ores, creating substantial waste residues. Si wafer chain is only 9% efficient. Liquid residues Some metals from virgin ores can cause acid mine drainage. Gaseous residues Very high energy use and other materials use lead to substantial emissions of toxic, smog-producing, and greenhouse gases into the environment.

0

1, 2

1, 3 1, 4 1, 5

1

1 2 1

Table 9.19 Streamlined life cycle analysis: desktop computer display and CPU. Product manufacture i, j

Environmental stressor

Score

2, 1

Material choice Manufacturing uses restricted and toxic materials (see 1,1) plus cleaning solvents. Energy use Energy use in production is very high for ICs and PWB and moderate to high for conventional materials. If we examine energy use during the manufacture of individual parts of the computer: microchip (0), printed circuit board (1), cathode ray tube (2), LCD (0), other bulk material (3) Solid residues There are large solid residues for chemical processes, such as CVD, PVP and plating, e.g., printed circuit boards yield 12 kg of waste for each kilogram of finished product. Also high performance requirements often result in low yields. Liquid residues Large quantities of waste liquid chemicals, e.g., approximately 500 kg of waste liquid chemicals for each kilogram of product including plating solutions and cleaning fluids. Very high volumes of water are also used. Gaseous residues Manufacturing energy use and processes lead to substantial emissions of toxic, smogproducing, and greenhouse gases into the environment.

1

2, 2

2, 3

2, 4

2, 5

1

1

1

1

Table 9.20 Streamlined life cycle analysis: desktop computer display and CPU. Product packaging and transport Environmental stressor

Score

3, 1

Material choice Several materials, large quantities, minimal recycling activity. Energy use Long distances traveled. Large volumes of materials. Solid residues Waste volumes are large, no arrangements to take back product packaging after use. Liquid residues Little or no liquid residue is generated during packaging, transportation, or installation. Gaseous residues Gaseous emissions are released by transport vehicles.

3

3, 2 3, 3 3, 4 3, 5

tances some products need to travel. The use phase can be very energy intensive. For example, data given by Kawamoto [9.74] and Cole [9.75] sets the residential

2 2 4 2

annual energy use for a desktop computer and monitor at about 380 MJ/year. In a commercial/industrial setting where the computer monitor may be on con-

Part B 9.6

i, j

864

Part B

Applications in Mechanical Engineering

Table 9.21 Streamlined life cycle analysis: desktop computer display and CPU. Product use i, j

Environmental stressor

Score

4, 1

Material choice Power from electrical grid uses 50% coal. Energy use High to very high energy usage. Solid residues Little direct solid residues (excluding printing functions) but power uses coal, resulting in mining residues. Liquid residues Little direct liquid residues (excluding printing function) but coal mining yields liquid residues. Gaseous residues No emissions are directly associated with the use of computers. However, gaseous emissions are associated with energy production for use of computers.

2

4, 2 4, 3 4, 4 4, 5

1 3 3 1

Does not include printing

Table 9.22 Streamlined life cycle analysis: desktop computer display and CPU. Refurbishment/recycling/disposal ratings i, j

Environmental stressor

Score

5, 1

Material choice Product contains significant quantities of lead and brominated flame retardants and may contain mercury and cadmium. Often these are not clearly identifiable or easily removable. Many materials are not recycled. Energy use The product is not designed for energy efficiency in recycling, or for high-level reuse of materials. Also, the transport of recycling is energy intensive because of weight/volume and location of suitable facilities. Solid residues Dissimilar materials are joined together is ways that are difficult to reverse and the product overall is difficult to disassemble. Little recycling. Short life cycle of computers compounds these problems. Liquid residues Product contains no operating liquids and minimal cleaning agents are necessary for reconditioning (not including printing functions). Gaseous residues Roasting of printed wiring boards (PWBs) to recycle metals leads to emissions.

1

5, 2

5, 3

5, 4

5, 5

1

1

3

2

Table 9.23 Streamlined life cycle analysis: desktop computer display and CPU. Environmentally responsible product

assessment for the computer display and CPU

Part B 9.6

Life stage

Materials

Energy

Solid

Liquid

Gaseous

Total

Premanufacture Product manufacture Product delivery Product use Recycling Total

0 1 3 2 1 7/20

1 1 2 1 1 6/20

1 1 2 3 1 8/20

2 1 4 3 3 13/20

1 1 2 1 2 7/20

5/20 5/20 13/20 10/20 8/20 41/100

tinuously, the estimate is 1500 MJ/year. For a 3 year lifetime, this is more than half of the energy used in production. The end-of-life issues are several; there are several materials of concern as mentioned earlier, and the shear volume of retired computer and electronics represents a significant solid waste/recycling challenge. Currently only a very small percentage of computers

are recycled [about 11%, as estimated by the Environmental Protection Agency (EPA)]. Using the materials lists given in Table 9.17 and the information cited in the references reviewed here [9.55, 60, 72–76] we have developed a baseline SCLA for a 1990s desktop computer and CRT display. The results are given in Tables 9.18– 9.23. A target plot is given in Fig. 9.58.

866

Part B

Applications in Mechanical Engineering

Table 9.24 Energy efficiency guidelines [9.49, 78, 79] Action

Reason

Do SLCA/LCI/LCA for product Encourage use of clean renewable energy sources Choose the least harmful source or energy Note for fossil fuels the cleanest is natural gas followed by oil products, and then coal Have subsystems power down when not in use Permit users to turn off systems in part or whole Avoid high-energy materials Avoid high-energy processes Specify best-in-class energy efficiency components Insulate and/or use waste heat

Identify energy usage Reduce harmful by-products and preserve resources Reduce harmful by-products

9.6.4 Design for the Environment (DFE) Design for the environment, like design for manufacturing or design for assembly, is a set of guidelines to help designers meet particular design goals. Often these guidelines are reduced to simple rules that aid understanding. However, behind these rules are observations and models that capture how the product can be expected to perform as the result of certain design decisions. To a certain extent this whole chapter has been aimed at understanding how products and product decisions result in environmental loads. There can be, however, different environmental goals. For example, designing an automobile for lower fuel consumption may lead to using structural composite materials for weight reduction, whereas designing for recyclability would probably lead to the use of metals for the struc-

Reduce energy usage and fossil fuel consumption Reduce energy usage and fossil fuel consumption Reduce energy and preserves resources Reduce energy Reduce energy usage and fossil fuel consumption Reduce losses/increases efficiency

tural components. In this section we outline some of the generally agreed upon guidelines for two important environmental goals: reduced hydrocarbon fuel consumption and increased recyclability. These are summarized in Tables 9.24 and 9.25.

9.6.5 System-Level Observations In this section we have presented an overview of engineering actions to lessen the impact of materials use, manufacturing, and design decisions on the environment. One of the goals of this section has been to identify the connections between a product life cycle and the associated environmental loads. To do this we have frequently normalized the environmentally sensitive parameters such as energy requirements or emissions by some measure of useful output such as the weight of the output, the economic activity, or, in some

Table 9.25 Recyclability guidelines [9.49, 78, 80]

Part B 9.6

Rating

Description or action

Reason or comment

Good Good

Product is reusable/remanufacturable Materials in part are recyclable with a clearly defined technology and infrastructure No toxic materials, or if present, clearly labeled and easy to remove Allow easy removal of materials, avoid adhesives and joining methods which cannot be reversed Material is technically feasible to recycle but infrastructure to support recycling is not available Material is organic – can be used for energy recovery but cannot be recycled Avoid mixtures which cause contamination, and painting and coatings which are difficult to remove Material has no known or very limited technology for recycling

Extends life of product Most metals, some plastics in particular: PET & HDPE

Good Good Less good Less good Avoid Avoid

Avoid Pb, Hg, Cd Facilitates separation and sorting Most thermoplastics, some glass thermoplastics, rubber, wood products e.g., polyvinylchloride (PVC) in PET, Cu in steel, painted plastics Heated glass, fiberglass, thermoset plastics, composite materials

Engineering Design

cases, just by the product itself. This scheme helps assign responsibility and allows us to track progress by enabling comparisons. At the same time, however, by measuring the environmental load too narrowly there is a danger of missing the overall trend. One way of making this point is by writing the environmental impact in terms of several normalized parameters. For example, consider impact = population

wealth impact . person wealth

(9.2)

This is a mathematical identity, known as the IPAT equation, which associates impact I , with three important elements: P for population, A for affluence, and T for technology. Our focus has been on the last term – impact/wealth (or impact/product etc.). Many variations on the IPAT equation are possible, for example A = products/person, T = impact/product, etc. It is the collection of the terms on the right-hand side that give the impact. Hence, a technology improvement could be offset by increases in population and/or wealth/person. This is unfortunate, but appears not to be in the domain of the engineer. If this was all there was to the story, the IPAT equation would be a neat way to subdivide responsibility. The implication is that, if engineers can improve the technology term, then they have done their job. The actual picture unfortunately is much more complicated, as technology improvements do not only improve the environment but also play an important role in stimulating the economy. In fact, relatively recent

9.7 Failure Mode and Effect Analysis for Capital Goods

867

economic growth theories, pioneered by Nobel laureate Robert Solow, now give primary importance to technology change [9.81, 82]. Hence the very act of improving the performance of a product could, and often does, stimulate increased production and consumption of the product. Some versions of this effect are called the rebound effect or Jevon’s paradox, after the 19th century economist who noted that more-efficient production and use of a resource (coal in his case), stimulated more consumption of the resource, not less [9.83]. In a similar vein, one could observe that taken as a whole labor-saving technological progress in developed countries has not led to less employment (but it has led to increased income). The general rule is that people respond to incentives, and all the incentives in a market economy point toward increasing investment and output rather than decreasing employment or resource use [9.82]. If society wants to reduce resource use, or emissions, or toxic waste, etc., it will need to provide the incentives, most likely through policy instruments, to do this. There are many successful examples to illustrate this point. The USA has reduced emissions of lead and sulfur dioxide, it has reduced the energy consumed by refrigerators, and the world has stabilized the levels of ozone in the upper atmosphere through implementation of the 1976 Montreal Protocol. Hence, the engineering actions described in this chapter should be taken in conjunction with a wider incentive and policy system that will preserve the engineering efficiency gains.

9.7 Failure Mode and Effect Analysis for Capital Goods With regard to the rework of the initially developed and applied approach see [9.89, 90].

9.7.1 General Innovations for the Application of FMEA The complexity of many products due to their mechatronic character but also because of the simultaneously applied engineering concepts complicates the distinction between the three traditional types of FMEA: system FMEA, design FMEA, and process FMEA (Fig. 9.59). In addition many FMEA sessions mix all three fields [9.90]. Instead of this distinction a continuous form of FMEA therefore has to be implemented, which

Part B 9.7

Failure mode and effect analysis (FMEA) [9.84, 85] is a method to recognize and eliminate mistakes or causes of faults during the product design process and in particular in the earliest stages. This method was developed in 1963 by the National Aeronautics and Space Agency (NASA) within the Apollo mission to design products without design failures. This is especially important when products cannot be repaired easily, e.g., satellites or spaceships. The method was adopted later by the aviation industry, the automotive industry, in medicine and nuclear technology as well as by the armaments industry [9.85, 86]. Today this method is increasingly used in all fields of the development process of consumer and capital goods [9.84, 87–89].

872

Part B

Applications in Mechanical Engineering

• •

Rare resources No sustainable environment

Possible errors in the development process. Internal functions from a function analysis (hierarchical and/or process functional structure) • External functions from a use analysis • Assembly of the product structure • Assembly/disassembly: – Assembly/disassembly operation – Assembly/disassembly regulations – Utilities (e.g., oil for the removal of bearings) – Assembly/disassembly devices – Control and/or measuring devices (e.g., torque spanner) – Additional means (e.g. hoisting devices) • Components from the product structure and/or parts list • Manufacturing: – Manufacturing processes (e.g., lapping) – Manufacturing operations (for manual manufacturing, e.g., deburring) – Manufacturing regulations – Manufacturing means and devices (e.g., drilling patterns) – Auxiliary manufacturing requirements (e.g., coolant) – Control and measuring devices (e.g., calipers)

•

Part B 9.7

The outer function takes into account the human being in his incompleteness as users during the product life. This must be included into the FMEA. The user is a component of the system; (s)he influences all processes, starting from idea generation, through development and usage until the end of the product life. The user causes failures and errors at all stages. With the integration of the available use analysis (Table 9.28) that covers all stages of a product’s life [9.94] possible sources of error during assembly, maintenance, and repair are also considered (Table 9.27, fourth block). In order to register these potential sources of error systematically the FMEA is expanded by the integration of the use analysis. These entities can be taken from the tabular recording of the man–machine interfaces. Moreover each part, assembly, and product needs the following documentation: Possible errors within the technical documentation. Check the:

• • •

•

•

Manufacturing documents (drawings and lists) Documents for assembly/disassembly (e.g., instruction sheets) Calculation documents, such as: – Load assumptions – Verification of strength – Verification of deformation – Verification of stability (e.g., buckling, bending, stability) Balances such as: – Balance of performance – Balance of weight – Position of the centers of gravity – Balance of the moments of inertia – Balance of temperature – Balance of coolant Documents such as: – Manufacturing documents – Instruction sheets – Instructions for maintenance and service – Spare-part catalogue

Possible errors during market launch. Storage: – Activities – Apparatus (e.g., bearing block) – Racks, halls, stacks (e.g., storage rooms with air conditioning) • Transport: – Activities – Apparatus (e.g., lifting gear) – Means of transportation (e.g., overhead crane) • Mounting: – Activities – Mounting regulations and instructions – Apparatus (e.g., lifting gear) – Measuring and test equipment (e.g., theodolite) • Initial operation: – Activities and tests in accordance with: · Instruction manual (Chapter Initial setup) · Checklist · Users’ handbook · Maintenance instruction

•

Possible errors in the use stage and in decommissioning. • Initial operation: – Activities in accordance with: · Instruction manual (Chapter Initial setup) · Checklist

Engineering Design

9.7 Failure Mode and Effect Analysis for Capital Goods

873

Table 9.28 Use analysis of a nutcracker No.

Subfunction first order

Man–product relationship: needed activities

Man–machine interface

Affiliated requirement

Required functions resp. possible carriers of function

1

Detection (of the object)

Eye – object Sense of touch – object

Noticable design Recognizable design Shiny color

Color Contrast Grade of reflection

2

Transporting/ placing (the object)

Hand – handle Hand – object body Eye – hand – handle

3

Equipment (with a nut) Locating (of the nut)

Nutcracker: Seek Ask for Find Nutcracker: Grasp, lift, carry Put down Slacken Open nutcracker Insert nut Hold nut Press against stop Clamp nut Move leverage Hit against anvil Turn knob Inner function

Little weight, ergonomic handle, handy surfaces, crack protection Stable stand Easy to equip Safely to equip Easy to use Sure hold of nut Limit clamping force Sure force insertion Notice finger/hand span

Lightweight construction Handle – leverage Corrugated surface Platform Trough Stop Trough Clamping claw Vise Handle Leverage

Force amount [N] Distance amount [mm] Limit force/distance Selection of effective functionalities that can be cheaply realized

Leverage Spline Screw Thrust piece Splines Blade Clamping screw Collecting pan, sack Basin Flap Opening Room design Shape of surface Surface roughness

4

Hand – object Hand – nut Finger – nut Hand – nut Eye – finger – nut Hand – leverage Fist – anvil Hand/finger – knob –

5

Produce (opening) force

6

Guide force/ amplify force

7

Nut opens by: · pressure · effect of spline

Inner function

–

8

Remove (result)

Remove cracked nut Remove nut and shell

Finger – crecked nut Hand – cracked nut Eye – finger – cracked nut

Easy to remove Sure to remove

9

Cleaning

Hold nutcracker Shake out crack room Clean crack room

Hand – nutcracker Finger/hand – cleaning device

Easy to handle No unreachable corners Easy to clean surface

•

•

Service: – Activities and test in accordance with: · Instruction manual · Users’ handbook · Service manual and spare-part catalogue · Logistics documents (e.g., global workshop catalogue)

Column 5. Here the status of currently used measures for the prevention of failures and test procedures is entered. These entries are used to reduce the causes of failure in column 4 and to detect possible sources of error.

Part B 9.7

•

· Maintenance history · Document Operating: – Activities in accordance with: · Instruction manual · Users’ handbook Maintenance: – Activities and test in accordance with: · Instruction manual · Users’ handbook · Service documentation · Maintenance history (e.g., exhaust gas document for a motor vehicle)

Engineering Design

9.7.4 Further Use of FMEA Results Within the concept and sketching phases several competing solutions or alternatives are available. In order to identify the best solution a ranking procedure is carried

References

875

out. If the criterion risk is already part of this ranking procedure it is reasonable to use the sum of the RPZ or RPZ∗ values of each solution. The relationship between acceptance, risk, and weighting is shown in Fig. 9.67.

References 9.1

9.2

9.3

9.4 9.5 9.6 9.7

9.8

9.9 9.10 9.11

9.12 9.13

9.15 9.16 9.17

9.18 9.19

9.20 9.21

9.22

9.23 9.24 9.25

9.26

9.27 9.28

9.29

9.30 9.31

9.32 9.33 9.34 9.35

9.36 9.37

W.F. Daenzer: Systems Engineering, 6th edn. (Industrielle Organisation, Zürich 1989) VDI: VDI 2221: Methodik zum Entwickeln und Konstruieren technischer Systeme und Produkte (VDI, Düsseldorf 1993), in German F. Zwicky: Entdecken, Erfinden, Forschen im morphologischen Weltbild, 2nd edn. (Baeschlin, Glarus 1989), in German H. Seeger: Industrie-Designs (Expert, Grafenau 1983), in German H. Hertel: Biologie und Technik (Krausskopf, Mainz 1963), in German P. Kerz: Konstruktionselemente und -prinzipien in Natur und Technik, Konstr. 39, 474–478 (1987), in German P. Kerz: Natürliche und technische Konstruktionen in Sandwichbauweise, Konstr. 40, 41–47 (1988), in German P. Kerz: Zugbeanspruchte Konstruktionen in Natur und Technik, Konstr. 40, 277–284 (1988), in German W. Kroy: Abbau von Kreativitätshemmungen in Organisationen. In: Personal-Management in der industriellen Forschung und Entwicklung (Heymanns, Köln 1984), in German R. Kühnpast: Das System der selbsthelfenden Lösungen in der maschinenbaulichen Konstruktion. Ph.D. Thesis (TH Darmstadt, Darmstadt 1968), in German K.-H. Habig: Verschleiß und Härte von Werkstoffen (Hanser, München 1980), in German VDI: VDI 2242 Blatt 1 und 2: Konstruieren ergonomiegerechter Erzeugnisse (VDI, Düsseldorf 1986), in German I. Klöcker: Produktgestaltung (Springer, Berlin 1981), in German VDI: VDI 2243 Blatt 1: Recyclingorientierte Produktentwicklung (VDI, Düsseldorf 2002), in German H. Meyer: Recyclingorientierte Produktgestaltung (VDI, Düsseldorf 1983), in German M. Pourshirazi: Recycling und Werkstoffsubstitution bei technischen Produkten als Beitrag zur Ressourcenschonung (TU Berlin, Berlin 1987), in German R.-D. Weege: Recyclinggerechtes Konstruieren (VDI, Düsseldorf 1981), in German VDI: VDI 2225 Blatt 1 und 2: Technisch-wirtschaftliches Konstruieren (VDI, Düsseldorf 1998), in German

Part B 9

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K. Ehrlenspiel: Integrierte Produktentwicklung: Denkabläufe, Methodeneinsatz, Zusammenarbeit, 2nd edn. (Hanser, München 2002), in German K. Roth: Konstruieren mit Konstruktionskatalogen: Konstruktionslehre, 3rd edn. (Springer, Berlin, Heidelberg 2001), in German G. Pahl, W. Beitz, J. Feldhusen, K.-H. Grote: Konstruktionslehre, 7th edn. (Springer, Berlin 2007), in German F. Kramer: Innovative Produktpolitik (Springer, Berlin 1988), in German W. Rodenacker: Methodisches Konstruieren, 4th edn. (Springer, Berlin 1991), in German R. Koller: Konstruktionslehre für den Maschinenbau, 4th edn. (Springer, Berlin 1998), in German Dubbel: Taschenbuch für den Maschinenbau, 21st edn. (Springer, Berlin 2004), ed. by K.-H. Grote, J. Feldhusen, in German H. Petra: Systematik, Erweiterung und Einschränkung von Lastausgleichslösungen für Standgetriebe mit zwei Leistungswegen. Ph.D. Thesis (TU München, München 1981), in German DIN: DIN 69910: Wertanalyse (Beuth, Berlin 1987), in German DIN: Sachmerkmale, DIN 4000 – Anwendung in der Praxis (Beuth, Berlin 2006), in German DIN: DIN 4000 (z.Zt. mit Entwürfen 163 Teile): Sachmerkmal-Leisten [für Norm- und Konstruktionsteile] (Beuth, Berlin 2006), in German DIN: CAD-Normteiledatei nach DIN, 3rd edn. (Beuth, Berlin 1984), in German D. Krauser: Methodik zur Merkmalbeschreibung technischer Gegenstände (Beuth, Berlin 1986), in German H. Czichos, M. Hennecke: Hütte – Das Ingenieurwissen, 33rd edn. (Springer, Berlin 2008), in German H. Holliger-Uebersax: Handbuch der allgemeinen Morphologie, 4th edn. (MIZ, Zürich 1980), in German J. Müller: Grundlagen der systematischen Heuristik (Dietz, Berlin 1970), in German H.G. Schmidt: Heuristische Methoden als Hilfen zur Entscheidungsfindung beim Konzipieren technischer Produkte (TU Berlin, Berlin 1980), in German V. Krick: An Introduction to Engineering and Engineering Design, 2nd edn. (Wiley, New York 1969) R.K. Penny: Principles of engineering design, Postgrad. J. 46, 344–349 (1970)

876

Part B

Applications in Mechanical Engineering

9.38

9.39 9.40

9.41

9.42

9.43

9.44

9.45

9.46

9.47

9.48

9.49 9.50 9.51

9.52

Part B 9

9.53

9.54 9.55 9.56

9.57

C. Zangemeister: Nutzwertanalyse in der Systemtechnik, 4th edn. (Wittemann, München 1976), in German VDI: VDI 2222: Methodisches Entwickeln von Lösungsprinzipien (VDI, Düsseldorf 1997), in German F.J. Gierse: Funktionen und Funktionsstrukturen, zentrale Werkzeuge der Wertanalyse, VDI-Berichte, Vol. 849 (VDI, Düsseldorf 1990), in German V. Hubka: Theorie Technischer Systeme: Grundlagen einer wissenschaftlichen Konstruktionslehre, 2nd edn. (Springer, Berlin, Heidelberg 1984), in German F. Hansen: Konstruktionssystematik: Grundlagen für eine allgemeine Konstruktionslehre, 2nd edn. (VEB Verlag Technik, Berlin 1965), in German J. Rugenstein (Ed.): Arbeitsblätter Konstruktionstechnik (Technische Hochschule Magdeburg, Magdeburg 1978/1979), in German F. Engelmann: Produktplanung und Produktentwicklung in kleinen und mittleren Unternehmen (Shaker, Aachen 1999), in German Novespace: Parabolic Flight Campaign with A300 ZERO-G User’s Manual, 5th edn. (Novespace, Paris 1999), www.novespace.com/VEnglish/ Microgravity_a/man_vola/flightUserManual.htm R. Bjärnemo: Evaluation and Decision Techniques in the Enginnering Design Process (Heurista, Zürich 1991) A.F. Osborn: Applied Imagination – Principles and Procedures of Creative Thinking (Scribner, New York 1957) J.O. Nriagu, J.M. Pacyna: Quantitative assessment of worldwide contamination of air, water and soils by trace metals, Nature 333, 134–149 (1988) T.E. Graedel, B.R. Allenby: Design for Environment (Prentice Hall, New York 1998) W. Leontief: Input-Output Economics, 2nd edn. (Oxford Univ. Press, Oxford 1986) C. Hendrickson, A. Horvath, S. Joshi, L. Lave: Economic input-output models for life-cycle assessment, Environ. Sci. Technol. 13(4), 184A–191A (1998) R. Miller, P. Blair: Input-output analysis: Foundations and extensions. In: Environmental InputOutput Analysis (Prentice Hall, New York 1985) pp. 236–260, Chap. 7 S. Joshi: Product environmental life-cycle assessment using input-output techniques, J. Ind. Ecol. 3(2,3), 95–120 (2000) S. Suh, G. Huppes: Methods for life cycle inventory of a product, J. Cleaner Prod. 13, 687–697 (2005) T.E. Graedel: Streamlined Life-Cycle Assessment (Prentice Hall, New York 1998) Environmental Protection Agency: EPA TRI 1998 Data Release Web Page (EPA, Washington 1998), http://www.epa.gov/tri/ V. Smil: Energies – An Illustrated Guide to the Biosphere and Civilization (MIT Press, Cambridge 1999)

9.58

9.59 9.60

9.61

9.62

9.63

9.64

9.65 9.66

9.67

9.68

9.69 9.70 9.71

9.72

9.73

9.74

K.J. Martchek, E.S. Fisher, D. Klocko: Alcoa’s worldwide life cycle information initiative, Proc. Total Life Cycle Conference – Land, Sea and Air Mobility, SAE Int. P-339, 121–125 (1998) P.F. Chapman, F. Roberts: Metals Resources and Energy (Butterworth-Heinemann, London 1983) E. Williams, R. Ayres, H. Heller: The 1.7 kg microchip: Energy and chemical use in the production of semiconductors, Environ. Sci. Technol. 36(24), 5504–5510 (2002) J. Dahmus, T. Gutowski: An environmental analysis of machining. In: ASME Int. Mechanical Engineering Congress, ed. by L. Yao (ASME, New York 2004) S. Dalquist, T. Gutowski: Life cycle analysis of conventional manufacturing techniques: Sand casting. In: ASME Int. Mechanical Engineering Congress, ed. by L. Yao (ASME, New York 2004) J. Sherman, B. Chin, P.D.T. Huibers, R. Garcia-Valls, T.A. Hatton: Solvent replacement for green processing, Environ. Health Persp. 106, 253–271 (1998), Suppl. 1 V.M. Thomas, T.G. Spiro: The U.S. dioxin inventory: Are there missing sources?, Environ. Sci. Technol. 30(2), 82A–85A (1996) A. Grubler: Technology and Global Change (Cambridge Univ. Press, Cambrigde 1998) J.L. Sullivan, R.L. Williams, S. Yester, E. Cobas-Flores, S.T. Chubbs, S.G. Hentges, S.D. Pomper: Life cycle inventory of a generic US family sedan – Overview of results USCAR AMP project. In: SAE International 1998, Total Life Cycle Conference Proc. (Society of Automotive Engineers, Warendale 1998) pp. 1–14, paper 982160 G.A. Keoleian, K. Kar, M.M. Manion, J.W. Bulkley: Industrial Ecology of the Automobile: A Life Cycle Perspective (Society of Automotive Engineers, Warrendale 1997) H. Maclean, L. Lave: A life-cycle model of an automobile, Environ. Sci. Technol. 32(13), 322A–329A (1998) T.E. Graedel, B.R. Allenby: Industrial Ecology and the Automobile (Prentice Hall, New York 1998) J.M. DeCicco, M. Thomas: A method for green rating of automobiles, J. Ind. Ecol. 3(1), 55–75 (1999) M.A. Weiss, J.B. Heywood, E.M. Drake, A. Schafer, F.F. AuYeung: On the Road in 2020, Energy Laboratory Report MIT EL 00-003 (MIT, Cambridge 2000) R. Kuehr, E. Williams (Eds.): Computers and the Environment Understanding and Managing their Impacts (Kluwer Academic, Dordrecht 2004) Microelectronics, Computer Technology Corporation: Life Cycle Assessment of a Computer Workstation, Report HVE-059-094 (MCC, Austin 1994) K. Kawamoto, J. Koomey, B. Nordman, A. Meier: Electricity used by office equipment and network equipment in the U.S. In: Conf. Energy Efficiency in Buildings (EPA, Lawrence

Engineering Design

9.75

9.76

9.77

9.78

9.79

9.80

9.81

9.82

9.83

Berkeley National Laboratory, Berkeley 2000), http://enduse.lbl.gov/projects/Indo/Puba.html D. Cole: Energy consumption and personal computers. In: Computers and the Environment: Understanding and Managing Their Impacts, ed. by R. Kuehr, E. Williams (Kluwer Academic, Dordrecht 2003) pp. 131–159 E. Williams: Environmental impacts in the production of personal computers. In: Computers and the Environment: Understanding and Managing Their Impacts, ed. by R. Kuehr, E. Williams (Kluwer Academic, Dordrecht 2004) pp. 41–72 Environmental Protection Agency: EPA egrid 2004 (EPA, Washington 1998), www.epa.gov/cleanenergy/ egrid/index.htm B. Bras: Environmentally Conscious Design and Manufacture, Lecture Notes ME, Vol. 4171 (Georgia Tech, Atlanta 2004), www.srl.gatech.edu/ K. Otto, K. Wood: Product Design: Techniques in Reverse Engineering and New Product Development (Pearson Education, Upper Saddle River 2001) B. Metzger: Design for Recycling: Influencing the Design Process at a Major Information Technology Company, MS Thesis (MIT, Cambridge 2003) R.M. Solow: Technical change and the aggregate production function, Rev. Econ. Statist. 39, 312–320 (1957) W. Easterly: The Elusive Quest for Growth: Economists’ Adventures and Misadventures in the Tropics (MIT Press, Cambridge 2002) W.S. Jevons: The Coal Question: An Inquiry Concerning the Progress of the Nation, and the Probable

9.84 9.85

9.86 9.87

9.88

9.89

9.90

9.91 9.92 9.93 9.94

9.95

References

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Exhaustion of our Coal-mines, Reprints of Economic Classics (Kelley, Fairfield 1906) DIN: DIN 25448: Ausfalleffekt-Analyse (Beuth, Berlin 1978), in German Procedures for Performing a Failure Mode, Effects and Criticality Analysis (FMECA), MIL Std. 1629A (Military Standard, Washington 1980) P. Conrad, P.E. Hedderich: Navy Proactive Maintenance (US Navy, Washington 2000) N. Berens: Anwendung der FMEA in Entwicklung und Produktion (Verlag Moderne Industrie, Landsberg 1989), in German C.H. Kepner, B.B. Tregoe: Entscheidungen vorbereiten und richtig treffen (Verlag Moderne Industrie, Landsberg 1988), in German M. Schubert: FMEA – Fehlermöglichkeits- und Einflußanalyse (Deutsche Gesellschaft für Qualität, Frankfurt 1993), in German A. Breiing: Die FMEA in sinnvoller Form für Investitionsgüter (Institut für Mechanische Systeme, ETH Zürich 2003), in German A. Breiing: The evaluators influence on the results of evaluation, MCE 2000, Neukirchen (2000) A. Breiing: Who evaluate the evaluators?, Int. Conf. Computer Integrated Manufacturing (Zakopane 2001) A. Breiing, R. Knosala: Bewerten Technischer Systeme (Springer, Berlin, Heidelberg 1997), in German A. Breiing: Vertiefungsvorlesung Produkte-Design (Institut für Mechanische Systeme, ETH Zürich 2000), in German A. Breiing, M. Flemming: Theorie und Methoden des Konstruierens (Springer, Berlin, Heidelberg 1993), in German

Part B 9

879

Piston Machi 10. Piston Machines

Vince Piacenti, Helmut Tschoeke, Jon H. Van Gerpen

10.2 Positive Displacement Pumps ................ 10.2.1 Types and Applications ................. 10.2.2 Basic Design Parameters ............... 10.2.3 Components and Construction of Positive Displacement Pumps.....

893 893 894

10.3 Compressors ......................................... 10.3.1 Cycle Description .......................... 10.3.2 Multi-Staging .............................. 10.3.3 Design Factors .............................

910 911 912 913 913 913 915 916 920 927

879 879 882 884

10.4 Internal Combustion Engines ................. 10.4.1 Basic Engine Types ....................... 10.4.2 Performance Parameters ............... 10.4.3 Air Systems .................................. 10.4.4 Fuel Systems................................ 10.4.5 Ignition Systems .......................... 10.4.6 Mixture Formation and Combustion Processes ............ 10.4.7 Fuels .......................................... 10.4.8 Emissions .................................... 10.4.9 Selected Examples of Combustion Engines .................

891

References .................................................. 944

Piston machines are the most used power and work machines in the mechanical engineering industry. The piston machines are divided in so-called reciprocating and rotary piston machines. With the first one a reciprocating motion is transformed to a rotary motion in the case of the power machine and conversely in the case of the working machine. Today rotary piston machines are almost exclusively used as work machines. Important innovations and intensive researches are practiced particularly for the use of the piston machines as an internal combustion engine. Therefore the mixture formation and the combustion process, with their consequences in terms of emission and fuel-consumption are int the center of attention.

10.1 Foundations of Piston Machines ............ 10.1.1 Definitions .................................. 10.1.2 Ideal and Real Piston Machines ..... 10.1.3 Reciprocating Machines ................ 10.1.4 Selected Elements of Reciprocating Machines.............

901

929 931 933 939

10.1 Foundations of Piston Machines 10.1.1 Definitions

Part B 10

Piston machines employ a moving displacer (also called a piston) to convert a medium’s potential energy into kinetic energy or vice versa, i. e., they use the movement of the displacer to increase the energy content of the medium. This occurs in a working chamber that can be altered by the displacer motion. In piston machines, the moving displacer effects both the charge cycle (filling and draining of the medium) and the work cycle (expansion and compression). The characteristic mode of operation for piston

machines is a self-contained working chamber that varies periodically due the piston’s movement. Piston machines can be classified according to their method of operation, the piston motion and the medium used (Fig. 10.1). When piston machines are classified according to their method of operation then power and work machines are differentiated. A power machine converts a medium’s potential energy into mechanical energy. Power machines include engines (pneumatic engine, hydraulic motor) and thermal machines (steam engines, combustion engines). Work machines on the other hand utilize mechanical energy to increase the energy of the medium being

Piston Machines

In the limiting case of an infinite number of compression stages that include intercooling back to the inlet temperature, the total work required will be equal to that for isothermal compression. Even the division of a compression process into two stages can save considerable work input. A two-stage compression process is depicted in Fig. 10.69. The compression process begins at state 1, which corresponds to the piston at BDC and inlet pressure. The gas is compressed in the first stage to the inter-cooler discharge pressure at state 2. The gas is then discharged at p2 into an intercooler before entering the second compressor stage at state A. In this idealized case, the intercooler is assumed to operate at constant pressure but the volume of gas is decreased due to the drop in temperature to the initial temperature of the gas. Then, the gas is compressed to state B before being discharged at pB . If the pressure increase had been attempted with a single stage of compression, then the process line would pass through states 1, 2, and 3. Since the area enclosed on the p–V diagram is the work needed to accomplish the process, the shaded area is the difference in work between the single stage and two-stage compression processes. Clearly, the two stage compression is more efficient. The optimum pressure for intercooling is generally assumed to correspond to an equal pressure ratio for each stage. This assumes the intercooling is able to reduce the gas temperature to the inlet temperature at each stage. If rs is the pressure ratio for each stage, rt is the overall pressure ratio, and s is the number of stages, then √ (10.68) rs = s rt .

10.4 Internal Combustion Engines

913

10.3.3 Design Factors At the end of the compressor’s discharge stroke, shown in Fig. 10.67b, gas fills the clearance volume at the discharge pressure. This gas expands as the piston moves away from the cylinder head until its pressure drops below the inlet pressure when the intake valve opens. The induction of fresh charge does not begin until this point is reached so the full volume displaced by the piston is not utilized. When the clearance volume is large, then the capacity of the compressor is less. The volumetric efficiency of a compressor can be approximated as  1  Vclearance rpk − 1 − Leakage , (10.69) ηv = 1 − VDispl where the leakage can generally be assumed to be between 0.03 and 0.05. Lower-molecular-weight gases usually have higher leakage. It can be seen from the equation for ηv that an increase in clearance volume directly causes a decrease in volumetric efficiency. Its significance is much greater for high values of the pressure ratio rp . Although compressor designers try to minimize it, the clearance volume cannot be entirely eliminated. Reducing it to less than 4% of the displacement volume is difficult. The amount of clearance volume will affect the capacity of the compressor and its efficiency. Overall compression efficiency is improved when valve flow area is large. However, the desire to minimize the clearance volume conflicts with the desire to maintain large valves. Thus, there is often a tradeoff between volumetric efficiency and compression efficiency, which determines the actual value of the clearance volume.

10.4 Internal Combustion Engines 10.4.1 Basic Engine Types Engines can be categorized in many different ways. The number of cylinders, the type of valve actuation, and whether the engine is turbocharged or naturally aspirated are all possible choices. Some engines are spark-ignited and utilize a homogeneous fuel–air mixture and some are compression-ignited, also called diesel engines, and utilize a heterogeneous fuel–air mixture. Another characteristic is whether the engine uses the two-stroke or four-stroke engine cycle.

Part B 10.4

In an internal combustion engine, the working fluid consists of a fuel–air mixture and the combustion products of this mixture. Although many cycles have been proposed, the traditional two-stroke and four-stroke cycles still dominate current use. Depending on their design and application, internal combustion engines provide excellent portability, power density, and fuel economy. Vehicles that utilize internal combustion engines provide unsurpassed range, drivability, and driver comfort while maintaining low levels of hazardous pollutants.

Piston Machines

is close to the exhaust pressure. As the piston continues its downward motion, it uncovers the intake port so fresh charge can enter the cylinder and repeat the cycle. Because the two-stroke engine needs to complete all four processes in a single revolution, it must start the exhaust process well before the piston has reached bottom dead center. A four-stroke engine can wait until about 140◦ after TDC before starting to open the exhaust valve since the primary criterion is that the period of rapid pressure equalization that occurs when the valve is first opened, called the blowdown, is essentially complete by BDC. A two-stroke engine must start opening the exhaust port at about 90◦ after TDC to provide sufficient time for the blowdown before the intake port opens and the intake process starts. Opening the exhaust valve early so that the cylinder pressure is throttled down to ambient allows no recovery of the energy in those hot gases and is the major reason why two-stroke engines are less efficient than four-stroke engines. In four-stroke engines, almost the entire cylinder contents of burned product gases, called residual gases, is expelled when the piston reaches TDC at the end of the exhaust stroke. Then, as the piston moves away from TDC, it produces a low pressure in the cylinder which draws in a fresh air charge through the intake valve. Four stroke engines are said to be self-scavenging. That is, the piston motion is directly responsible for moving the exhaust gases out of the engine and drawing in fresh air. Two stroke engines are not self-scavenging. Some mechanism other than piston motion is needed to exchange the gases in the cylinder. By opening the exhaust valve early, while the cylinder pressure is still high, most of the residual gases can be expelled. The fresh charge must be forced into the cylinder from a pressurized source, which might be a crankcase that is pressurized by the downward motion of the piston as in single cylinder two-stroke engines used for hand-held power equipment. It might also be from an engine-driven blower as is common in diesel two-stroke engines.

10.4.2 Performance Parameters

915

brake power, as Pb = Tb ω = Tb 2π N ,

(10.70)

where Pb is the brake power, Tb is the brake torque, ω is the rotational speed, usually in radians/unit time, and N is the rotational speed in rev/unit time. The source of power in the engine is the work done on the piston by the expanding combustion gases. The power associated with this piston work is called the indicated power. The difference between the indicated power and the brake power is the power required to overcome friction and to drive the accessories including the water and oil pumps Pi = Pb + Pf ,

(10.71)

where Pi is the indicated power, Pb is the brake power, and Pf is the friction power. Direct calculation of the indicated power requires measurement of the cylinder pressure. The brake power can be calculated from the measured engine torque and speed. The friction power must be calculated from the difference of the indicated and brake power. Generally, small engines run at high rotating speeds and large engines run at low rotating speeds. To allow comparisons between engines of different sizes, it is common to calculate the mean piston speed, which is the average velocity of the piston as the engine makes one revolution MPS =

2S = 2SN , time for one revolution

(10.72)

where S is the stroke, and N is the engine rotating speed. The mean effective pressure (MEP) is a way to normalize the work done by the engine against the size of the engine. It is intended as a measure of engine loading. The MEP is defined as the ratio of the work done by the engine in one cycle to the displacement volume. A four-stroke engine undergoes one cycle in two revolutions (or 4π radians) so the work done is equal to the torque times the angular displacement. When the brake torque is used, the quantity is known as the break mean effective pressure (BMEP) BMEP =

4πTb . Vd

(10.73)

Since work is measured in N m and volume in m3 , the ratio has units of pressure N/m2 . The MEP is sometimes described as the pressure which, if applied as a constant pressure during the expansion stroke, would give the same work as actually produced by the engine.

Part B 10.4

Engine speed and torque are the two most fundamental quantities of engine performance. Both are usually measured quantities with speed given in revolutions per minute (rpm) and torque in Newton-meters (N m). Power is defined as torque times rotational speed. When the torque is measured at the engine flywheel, it is called the brake torque and the power calculated from it is the

10.4 Internal Combustion Engines

916

Part B

Applications in Mechanical Engineering

The mechanical efficiency is a measure of how much of the power produced by the combustion process is delivered to the output shaft. It is defined as the ratio of the brake power to the indicated power Pb Pf = 1− , (10.74) Pi Pi where ηm is the mechanical efficiency, Pb is the brake power, Pi is the indicated power, and Pf is the friction power. The thermal efficiency is defined as the ratio of the power produced by the engine to the rate at which fuel energy is supplied to the engine, as indicated by the lower heating value (LHV). When the brake power is used, the quantity is known as the brake thermal efficiency ηm =

Brake thermal efficiency = ηbt =

Pb . m˙ fuel (LHV) (10.75)

The mechanical and thermal efficiencies are sometimes confused. For a modern engine running at full load, the mechanical efficiency may be 90% or higher. However, the thermal efficiency will generally be 30– 45%. The specific fuel consumption (SFC) is the ratio of the fuel flow rate to the power of the engine. When brake power is used, the quantity is known as the brake specific fuel consumption m˙ fuel . (10.76) Pb The BSFC is similar to an efficiency in that it measures how little fuel may be required to do a certain quantity of work. The lower the BSFC, the more efficient the engine. The volumetric efficiency is a measure of how well air moves through the engine. For a four-stroke engine m˙ actual m˙ actual  , = (10.77) ηv = rpm m˙ ideal ρref Vd 2 BSFC =

Part B 10.4

where ηv is the volumetric efficiency, m ˙ actual is the actual mass flow rate of air (or air–fuel mixture) entering the engine, m ˙ ideal is the ideal mass flow rate of air (or air–fuel mixture), ρref is a reference density, Vd is the rpm displacement volume, and 2 is the number of engine cycles per minute. For spark-ignited engines, the values of m˙ actual and m˙ ideal refer to the fuel–air mixture entering the engine. For diesel engines they refer only to the air entering the engine.

The volumetric efficiency tends to be ambiguous for several reasons: 1. There is uncertainty about where the reference density should be calculated. Some sources suggest using ambient conditions while others suggest using the average intake manifold pressure and temperature. 2. Although it is considered to be an efficiency, there is no reason why the volumetric efficiency cannot be greater than one. If the ambient density is used to compute the volumetric efficiency of a turbocharged engine, the volumetric efficiency may be as high as 2 or 3. Even a naturally aspirated engine with a tuned intake system can have a volumetric efficiency of 1.2 or 1.3. 3. In engines with a large valve overlap period, a significant amount of air can blow through the engine directly from the intake to the exhaust without participating in a combustion process. This air could contribute to a high volumetric efficiency but is not available for combustion.

10.4.3 Air Systems The power produced by all internal combustion engines is limited by their ability to draw air from the atmosphere. Fuel systems can always be designed to provide the amount of fuel appropriate to this air flow. To increase the power produced by an engine of a certain displacement volume, the air flow needs to be increased. This can be done with passive techniques that are incorporated into the engine’s design or through the addition of external devices, such as a supercharger. Natural Aspiration In a naturally aspirated engine, the air flows into the cylinder through the intake manifold and intake ports without the use of an external compressor of blower. At high engine speed this air moves at high velocity. When the piston approaches the end of the intake stroke, the momentum of the air keeps the air moving toward the cylinder and can continue to force air into the cylinder after the piston has started upward on the compression stroke. By properly timing the closing of the intake valve, the amount of air trapped in the cylinder can be increased beyond that which would be predicted based on ambient air density. This phenomenon, called the ram effect, increases with air velocity and therefore with engine speed.

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Part B

Applications in Mechanical Engineering

a)

b)

Part B 10.4

Fig. 10.81a,b Fuel injection control systems

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Part B

Applications in Mechanical Engineering

Common-Rail Systems. This system offers the greatest flexibility in the choice of fuel-injection parameters. Pumping Arrangement. The common-rail (CR) system utilizes a single pump to pressurize the fuel which is delivered to an accumulator rail. One injector per engine cylinder is connected to this rail by means of a highpressure line (Fig. 10.88). Pumping Principle. Fuel is delivered by the lowpressure system to the high-pressure pump, where it is pressurized by the pumping plungers (arranged either radially or inline) and sent from there to the accumulator rail. Since all injectors are connected in parallel to the rail, they are all constantly pressurized and inject only when an electric signal is sent to each injector. Control System. The start of injection (timing) and du-

ration of injection (fueling) is controlled by a solenoid valve (electromagnetic or piezo) on each injector. When the actuating signal is sent to the injector, a coil or piezo stack inside the injector is energized, upsetting the pressure balance (on both sides of the nozzle needle) that was holding the nozzle closed. The needle then lifts and the injector delivers fuel to the engine. When the signal ceases, the pressure above the needle increases, forcing the needle closed and thus ending injection.

Part B 10.4 Fig. 10.88 Common-rail system

In addition, a sensor in the high-pressure circuit monitors the system pressure and sends this information to the electronic control unit (ECU) so that the pressure can be regulated to a value that is optimal for the engine’s operating condition. Low-Pressure System. Regardless of the fuel injection design, all fuel injection systems require a primary fuel pump to deliver the fuel from the fuel tank through the fuel filter to the injection pump. Primary Fuel Pump. The primary fuel pump can be ei-

ther mechanical or electric; the electric pump can be inside the fuel tank, mounted on the engine, or mounted on the vehicle. Fuel Filter. The fuel filter must strain out impurities

in the fuel, as contamination will cause wear, orifice plugging, component sticking, and seizures. The filter medium must be fine enough to trap small particles and the filter size must be large enough to assure adequate service life. Often a preliminary filter is used in addition to the main filter to extend the filter change interval. In addition, filters should have the ability to separate water out of the fuel, as water will cause wear, corrosion, and seizures. Many filters today have water separation, a waterin-fuel indicator, and a heater combined in one unit.

Piston Machines

10.4.5 Ignition Systems This section will cover the principles of ignition and the two main design types. It will explain how the high voltage needed for ignition is generated and the importance of ignition timing. Lastly it will cover spark plug design and function. There are two basic types of ignition system: conventional coil and electronic. The conventional coil design can have one of three types of trigger; the electronic design can either have a distributor or be distributor-less. All designs use essentially the same method for generating high voltage, and all systems use the same design type of spark plug. Principle A gasoline internal combustion engine needs a spark to ignite the compressed air–fuel mixture in the combustion chamber. The spark is a discharge between the two electrodes that protrude into the combustion chamber. The ignition system generates the high voltage (up to 30 000 V) [10.24] needed to create the spark discharge and also initiates the spark to occur at the proper piston position (ignition timing). Ignition System Design Conventional Coil Ignition. This system consists of

an ignition coil, ignition distributor, and spark plugs;

10.4 Internal Combustion Engines

927

see Fig. 10.89. As the coil is similar for all types of systems it is explained under point 3 (high-voltage generation). The distributor rotates in sequence with the engine’s crankshaft and at half of the crankshaft’s speed for fourstroke engines or at crankshaft speed for two-stroke engines. One of three types of triggers is used in the distributor to control the current through the ignition coil:

• •

•

Mechanical breaker points: a mechanical switch that is closed and opened once per firing event by a cam located on the distributor shaft. The number of cam lobes equals the numbers of cylinders. Breaker-triggered transistorized ignition: this design is similar to mechanical breaker points except the primary ignition circuit is controlled by a transistor instead of by the breaker points. Only the control current is switched by the breaker points; this extends the breaker-point life and allows higher primary currents to be controlled. Transistorized ignition with Hall-effect trigger or induction-type pulse generator: the breaker points are totally eliminated and replaced by either a Halleffect sensor or an induction-type pulse generator located in the distributor. The sensor or generator create one signal per cylinder; this signal is used to charge and discharge the coil.

Part B 10.4

Fig. 10.89 Conventional coil ignition

Piston Machines

chiometric. Except for cold starts and brief periods of high power demand, modern vehicles equipped with three-way catalysts and closed loop control of air–fuel ratio operate in a narrow band around stoichiometric. Figure 10.94 shows three different approaches to fuel–air mixture formation in spark-ignited engines. The traditional approach of introducing the fuel with a carburetor into the intake air stream is only used for small engines and is obsolete for larger engines that are subject to emissions controls. Most engines today use port fuel injection, as shown in Fig. 10.94b. This approach provides very uniform air–fuel mixture between cylinders and excellent atomization of the fuel at all speeds. Figure 10.94c shows direct injection of the fuel into the cylinder. Although not yet widely used, this approach allows some degree of charge stratification in the cylinder and fuel economy that approaches the diesel engine.

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fuel-economy penalty on IDI engines. Advances in fuel injection technology have allowed DI engines to operate at equivalent speeds with much better fuel economy. A DI engine with the fuel sprayed directly into a chamber in the cylinder formed by a toroidal recess in the piston is the most common configuration in modern diesel engines. Alternative Combustion Systems A major drawback of both spark ignited and compression ignited engines is their high NOx emissions. Both engines require after-treatment to reduce NOx to acceptable levels. Combustion systems that are homogeneous charge, like spark-ignited engines, but utilize autoignition, like a compression-ignited engine, have been developed. These engines utilize an air–fuel mixture that would ordinarily be quite lean, but by controlling the temperature, it can be made to auto-ignite in a gradual and controlled manner towards the end of the compression stroke. Temperature and air–fuel ratio can be optimized to reduce NOx emissions to very low levels.

10.4.7 Fuels This section will cover the basics of gasoline, diesel, and alternate fuels. It will start with the original of petrochemical fuels and the refining process. The basic composition and key characteristics of gasoline and diesel fuels will then be explained. Lastly an overview of fuel substitutes and alternate fuels will be given, whereby this cannot cover in detail the plethora of newly emerging fuels. Petroleum Refining and Basic Organic Chemistry [10.25] Most conventional fuels are made from petroleum crude oils, consisting primarily of paraffinic, naphthenic, and aromatic hydrocarbons. Raw crude oils have a wide range of densities ranging from as thin as water to as thick as tar. Crude oil is converted into usable products by means of refining; the most important products are gasoline, jet fuel, and diesel fuel. Other valuable products are heating oils, liquefied petroleum gas, lubricating oils and asphalt. To convert crude oil the feedstock is typically distilled. Since the different components of crude oil (e.g., gasoline, diesel) have different boiling points, the lighter components (those with relatively low boiling points, e.g., propane and butane) rise to the top of the distillation column where they are drawn off. The nextheavier components (e.g., gasoline) are drawn off lower

Part B 10.4

Compression Ignition Engines Compression ignition engines, also known as diesel engines, bring only air into the cylinder through the intake valve. The engines rely on compression of the air to produce sufficient temperature that the fuel auto-ignites soon after it is injected near the end of the compression process. In contrast to the homogeneous charge sparkignited engine, the air–fuel mixture in the diesel engine is always heterogeneous. Since there is a distribution of fuel–air ratios ranging from very lean to very rich, there is always some location in the cylinder where conditions are optimum for auto-ignition and the cycle-to-cycle variability for diesel engines is very small. Diesel engines run without throttles so they have the advantage of low pumping losses. Load is controlled by varying the amount of fuel that is injected into the cylinder. At light load and idle, the air–fuel ratio may be 70:1 or higher. At full load, the air–fuel ratio may be as low as 20:1. The stoichiometric ratio of 14.5–14.8 is generally not achieved because of high smoke levels. Diesel engines can be categorized into direct injection (DI) and indirect injection (IDI), although indirect injection designs are now mostly obsolete. The IDI engines utilized a small chamber apart from the main chamber, called a prechamber or turbulence chamber, that was connected to the main chamber by a narrow passageway. Fuel was injected either into the separate chamber, or into the passageway, and the rapid air motion between the two chambers caused by the piston motion, provided excellent fuel–air mixing. This rapid mixing allowed high-speed operation of the engines but heat transfer and throttling losses exacted a severe

10.4 Internal Combustion Engines

932

Part B

Applications in Mechanical Engineering

on the column, then the subsequently heavier components (kerosene and then diesel) are drawn off towards the bottom. The fuels must then be upgraded, usually by hydroprocessing (which uses hydrogen with a catalyst) to remove undesired components. Fuels with higher boiling points are then cracked (broken down) into lower boiling points using very high temperatures and catalysts. Gasoline Basic Composition. Gasoline fuels for spark-ignition engines are hydrocarbon compounds, which sometimes contain oxygenous components to enhance performance.

• • • • • • •

Key Characteristics.

• • • •

• •

Grade: usually stated as regular or premium; an indication of anti-knock property. Octane number: resistance to knock (pre-ignition). Density: weight per unit volume; energy content increases as density increases. Volatility: how easily the fuel vaporizes. The fuel must vaporize quickly for good cold starting but not so quickly as to cause vapor-lock. Volatility is characterized by the fuel’s vapor pressure and/or evaporation points dependant upon temperature. Sulfur content: must be kept low to allow proper operation of the catalytic converter or other aftertreatment device. Additives: may be used to enhance one or more of the properties stated above, or to protect against aging, contamination or corrosion.

Diesel Basic Composition. Diesel fuels for compression-

ignition engines are usually distilled from crude oil. They consist of a large number of different hydrocarbon compounds including n-paraffins, olefins, naphthenes and aromatic compounds. Diesel fuel ignites at ≈ 350 ◦ C, much lower than gasoline, which ignites at ≈ 500 ◦ C. Key Characteristics.

Part B 10.4

• • •

Grade: the standard to which the fuel must conform. Density: weight per unit volume; energy content increases as density increases. Viscosity: resistance to flow; low viscosity leads to leakage losses, while high viscosity may impair injection pump function.

• •

Cetane number: ease with which fuel ignites; combustibility increases as cetane number increases. Cold filter plugging point: the temperature at which the fuel clogs the filter. Flash point: the storage temperature at which flammable vapors are produced. Water content: amount of water in fuel; water causes corrosion and poor lubrication, leading to wear and seizures. Contaminants: foreign particles in fuel; the particles cause erosive and abrasive wear. Lubricity: measure of the fuel’s lubrication properties; low lubricity causes wear and seizures. Sulfur content: amount of sulfur in fuel; sulfur does not harm the fuel injection system but will harm most after-treatment devices. The removal of sulfur by hydrogenation also removes the ionic fuel components that aid lubrication, reducing the lubricity properties of the fuel. Additives are thus needed to restore lubricity to a sufficient level. Oxidation stability: resistance to forming acids. Additives: may be used to enhance one or more of the properties stated above.

Alternate Fuels [10.26] In addition to the standard fuels there are several alternatives to gasoline and diesel. These are often pursued in order to reduce emissions or to reduce consumption of nonrenewable fuels as most alternate fuels are from a renewable source. It should be noted that alternate fuels are not always compatible with the fuel system (some require extensive modifications), and that they may increase one emission component while reducing another. Alternate fuels can be divided basically into two categories: gasoline substitutes/additives and diesel substitutes/additives. Gasoline Substitutes/Additives.

• • • • •

Coal hydrogenation: coal and coke Liquefied petroleum gas (LPG): hydrocarbon mixtures (mostly propane) that are liquid at ambient temperatures under relatively low pressures Liquefied natural gas (LNG): methane that is cooled to < −160 ◦ C and condensed to a liquid by compression Compressed natural gas (CNG): natural gas (mostly methane) compressed to high pressure Hydrogen: produced by electrolysis of water or from natural gas/coal

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Part B

Applications in Mechanical Engineering

high ozone levels. The resolution of this apparent contradiction lies with understanding the role of altitude as explained in Fig. 10.95. In the stratosphere, above 15 000 feet, the concentration of ozone can be very high, approaching 10 000 ppb (parts per billion). This ozone is formed by reactions involving sunlight and oxygen. It filters the ultraviolet solar radiation that causes skin cancer. Some researchers have argued that this ozone is destroyed by reactions with chlorine atoms originating from CFCs. At lower altitudes the natural concentration of ozone is up to 3 orders of magnitude lower than in the stratosphere. This is fortunate since high levels of ozone interfere with plant growth and are a strong irritant. High levels of ozone can be produced at lower elevations by reaction of volatile organic compounds (VOCs), carbon monoxide, oxides of nitrogen (NOx ), and sunlight. This complex set of chemical reactions produces a large number of different chemical compounds, many of which are harmful and irritating to people. Ozone, although only one chemical compound, is widely used as a measure of the overall concentration of the complex chemical mixture, sometimes known as smog. The EPA recently reduced the maximum allowable ozone concentration from 120 ppb averaged over a 1 h period to 80 ppb averaged over an 8 h period. Normal background levels of ozone are typically 20–40 ppb and can exceed 200 ppb during severe smog episodes [10.24]. Ozone is a secondary pollutant. It is not found in significant amounts in the exhaust of engines. However, compounds that are found in engine exhaust contribute to the formation of ozone, such as, VOCs, carbon monoxide, and NOx . Another major source of VOCs is evaporative emissions. Evaporative emissions originate from losses of fuel during refueling as well as when the vehicle undergoes diurnal heating and cooling. These emissions are strongly tied to the Reid vapor pressure of the fuel, which is why it is now closely controlled in areas where air pollution is a problem. Evaporative emissions are only a problem with volatile fuels such as gasoline and its blends with alcohol. Diesel fuel’s vapor pressure is so low that it does not contribute to evaporative emissions.

Part B 10.4

Regulated Pollutants The Environmental Protection Agency (EPA) regulates the tailpipe emissions of both spark-ignition and compression-ignition engines in the United States. Regulated pollutants from spark-ignited engines include carbon monoxide, oxides of nitrogen, and unburned

hydrocarbons. Compression ignited, or diesel, engines must meet requirements for particulates as well as these gaseous species. Carbon monoxide is primarily determined by the engine’s air–fuel ratio. When the engine is operated fuel-rich there is insufficient oxygen to convert all of the carbon to carbon dioxide, so a portion is converted to carbon monoxide. Carbon monoxide is actually an intermediate product in the oxidation of hydrocarbons and is always present in significant amounts during the combustion process. Measured levels in the exhaust are usually higher than would be expected because the oxidation of the carbon monoxide tends to be a slow process that is limited by the rate of the reaction of CO with the OH radical, as shown in the following equation CO + OH → CO2 + H .

(10.82)

The concentration of the OH radical decreases rapidly as the in-cylinder temperature drops during expansion, leaving the CO frozen at an elevated level. An additional mechanism that affects homogeneous charge engines is the partial oxidation of trapped fuel that emerges from crevices or oil films during the expansion process when the temperature is too low to oxidize the fuel completely before the exhaust valve opens. In carbureted engines, rich-burning cylinders resulting from the nonuniform distribution of fuel between cylinders is an important source of carbon monoxide. Carbon monoxide emissions from diesel engines are generally well below regulation limits because diesels always operate with excess air. Oxides of nitrogen (NOx ) consist primarily of nitric oxide (NO) and nitrogen dioxide (NO2 ). Nitric oxide originates through three potential mechanisms that are usually categorized as fuel NOx , prompt NOx , and thermal NOx . Fuel nitrogen can contribute to NOx formation but is usually not important for engines because gasoline and diesel fuel contain small amounts of nitrogen. Prompt NOx is formed by reactions between nitrogen and hydrocarbons during the combustion process. This mechanism also does not seem to be an important source of NOx for engines. The primary source of engine NOx emissions is thermal NOx . This mechanism involves the following three reactions O + N2 → NO + N , N + O2 → NO + O , N + OH → NO + H .

(10.83) (10.84) (10.85)

Since these reactions require significant concentrations of the radicals O, N, and OH, they only occur at

Piston Machines

935

in the SOF are known carcinogens and the small size of the particulates (0.01–0.1 μm) increases the potential for their inhalation and retention in the lungs. For these reasons, the regulatory levels for particulate emissions have been progressively lowered so that after 2007 exhaust filtration technology has been required for most on-highway engines. Measurement Instruments A variety of instrumentation technologies have been developed to quantify the levels of pollutants in engine exhaust gases. Some techniques such as Fourier transform infrared spectral analysis have broad applicability and are widely used for engine development. For emissions certification, specialized instruments are still used that have been developed to measure specific species, and often over limited ranges. Oxides of nitrogen are measured with devices that take advantage of the chemiluminescent reaction that occurs when NO reacts with ozone to form NO2 and oxygen. The photon of light that is emitted by this chemical reaction can be measured and directly related to the concentration of NO. Total NOx can be measured by passing the exhaust gas through a catalyst that converts the NO2 into NO before the gas is exposed to ozone. Carbon monoxide and carbon dioxide are most commonly measured with nondispersive infrared (NDIR) absorption instruments that measure the amount of light of a specific wavelength that is absorbed by the exhaust gas. The wavelengths and path lengths for the light are chosen to provide the best sensitivity for the gas of interest. This technique requires that water vapor, a broad-band absorber of infrared radiation, be removed before the measurement can be performed. The water is usually removed by cooling the gas to condense the water or passing the gas stream through a chemical desiccant. Unburned hydrocarbons are measured using a flame ionization detector. These devices contain a small hydrogen flame located between two electrically charged plates. A small amount of the exhaust stream is fed into the hydrogen flame and the hydrocarbon-based carbon atoms produce flame ionization that can be measured as an electric current between the charged plates. The particle filters and all connecting lines must be heated to prevent condensation of the hydrocarbon vapors before they enter the flame. The heated flame ionization detector (HFID) measures the number of carbon atoms associated with hydrocarbons in the exhaust and thus requires an assumption to be made regarding the chemical composition of the hydrocarbons. Measurements

Part B 10.4

high temperatures. The reactions also require significant time to equilibrate so most of the NO formation occurs in the post-flame gases. Virtually all NOx control strategies, such as timing retard and exhaust gas recirculation (EGR) focus on reducing the temperature of the post flame gases. Unburned hydrocarbon emissions from sparkignited engines generally originate from fuel that is trapped in crevices, oil films, or deposits and is thus protected from combustion during the main combustion event. This sequestered fuel is released when the pressure drops during the expansion process but the temperature may be too low for complete combustion. Some of the fuel may burn to carbon monoxide but a significant portion will remain unburned or only partially burned and this will be released in the engine exhaust. Some of the products of partial combustion, such as olefins and aldehydes, are highly reactive and are strong contributors to photochemical smog reactions. Occasional misfiring cycles can also be a significant source of unburned hydrocarbon (UHC) from spark-ignited engines. UHC from diesel engines generally originate from fuel that has been overmixed with air so that the mixture is too lean to burn under the conditions in the cylinder. These conditions are most likely to be encountered at idle and light loads. Regulated emissions from compression-ignited, or diesel, engines include the CO, NOx , and UHC described for spark ignition (SI) engines, but also include particulates. Particulates from diesel engines are operationally defined as whatever collects on a filter when the exhaust is cooled to 52 ◦ C after the filter has had a chance to equilibrate in a temperature and humidity controlled environment. The primary constituent is carbonaceous matter, usually referred to as soot, that originates from high temperature pyrolysis reactions in the fuel-rich regions of the cylinder. The carbonaceous particles provide sites for the condensation and adsorption of high molecular weight hydrocarbons as the combustion products cool and this portion of the particulate is often referred to as the soluble organic fraction (SOF) or the volatile organic fraction (VOF). These high molecular weight hydrocarbons may originate from the fuel but are more frequently associated with the lubricating oil. Particulate may also contain sulfates resulting from the reaction of fuel-based sulfur to sulfur trioxide and then to a variety of sulfate compounds which may be observed as small droplets of sulfuric acid. Finally, the particulate may include inorganic compounds resulting from engine wear and lubricant additives. Many of the compounds identified

10.4 Internal Combustion Engines

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Part B

Applications in Mechanical Engineering

performed on gasoline-fueled engines often assume the hydrocarbon has the same structure as hexane. Assuming the unburned hydrocarbons have the same chemical structure as the fuel is also a common assumption for both gasoline and diesel engines. Particulates are measured by filtering a portion of the exhaust gas and then weighing the increase in mass of the filter. The temperature of the filter is carefully controlled because if it is too low an excessive amount of the unburned hydrocarbon vapors may condense on the filter. The techniques used to capture a representative sample of the exhaust gas and allow the determination of the amount of particulate during a transient test cycle are described in the following section.

Part B 10.4

Test Cycles Emissions from passenger cars and other light-duty vehicles are measured while the vehicle is operated on a chassis dynamometer. The chassis dynamometer connects the drive wheels of the vehicle to a load absorber through a set of rollers. The device allows the vehicle to be operated in a controlled laboratory but with an accurate simulation of actual in-use driving conditions. Flywheels and dissipative absorbers are used to simulate vehicle inertia and air resistance so the vehicle can be operated over transient driving cycles. Test cycles that involve following a vehicle speed versus time curve that models different driving conditions are used for emissions certification. Trained drivers can follow these curves very exactly although most installations now use computerized throttle controllers. The wide variety of transmission, drive line, and engine combinations used in heavy-duty applications precludes the emissions certification of vehicles. Heavy duty emissions testing focuses on testing the engine itself while it is outside the vehicle connected to a computer-controlled load absorber. The engine is operated over a 20 min cycle where both the engine speed and torque are specified on a second-by-second basis. The 20 min test cycle consists of four 5-min segments that model different types of city and highway driving. Exhaust emissions for both chassis dynamometer and engine dynamometer test systems involve injecting some or all of the exhaust gas stream into a dilution tunnel to lower the temperature of the exhaust gas and to simulate the particulate agglomeration processes that occur when the exhaust enters the atmosphere. These systems are equipped with flow control systems so that a constant volumetric flow rate is maintained for the sum of the engine exhaust and the dilution air. A sample of the diluted exhaust gas is filtered and the weight

of the particulate is measured. In the case of chassis dynamometers, the pollutant is expressed as g/mile and for the engine dynamometer it is expressed as g/horsepower-hour or g/kW h. The denominator of the engine dynamometer term is the total amount of work performed by the engine during the test cycle. Gaseous emissions are also sampled from the dilution tunnel. They may be collected in special chemically inert bags to obtain an integrated total for the cycle, or measured second by second to investigate the effect of different parts of the test cycle on a pollutant of interest. Both chassis and engine dynamometer testing are conducted under carefully controlled laboratory conditions. There have been some claims that this testing is not representative of emissions from in-use vehicles and attempts have been made to characterize in-use emissions using chassis dynamometers to test vehicles chosen at random from traffic flows. This experience has shown that significant numbers of vehicles have improperly operating emission control systems and actual emission levels are higher than would be expected from emission certification data. Measurements have been attempted using light absorption techniques from passing traffic but results have been mixed. Variability in measurement points, vehicle types, weather effects, etc. mean that extremely large numbers of measurements are required. SI Engine Emissions Characteristics The primary pollutants of regulatory concern for spark-ignited engines are carbon monoxide, oxides of nitrogen, and unburned hydrocarbons. The levels of these pollutants in the engine exhaust depend strongly on the engine’s operating conditions such as spark timing, load, speed, and air–fuel ratio. While the engine speed and load are controlled by the operator (for a manual transmission), the timing and air–fuel ratio are set by the engine’s electronic control module (ECM) to keep the levels of the exhaust pollutants within the range allowed by emissions regulations while ensuring adequate vehicle performance. Under cold starting and high-power-demand conditions the air–fuel ratio is calibrated to be fuel-rich. However, under all other operating conditions, the ECM maintains the air–fuel ratio close to the chemically correct, or stoichiometric, ratio. The impact of timing, speed and most other operating parameters on carbon monoxide is secondary to the air–fuel ratio. There may be some effect on CO as these parameters are varied but this is most likely due to changes in air–fuel ratio or in causing the engine to operate at non-optimum conditions for oxidation of the CO.

Piston Machines

tor nozzle holes and lower intake air temperatures tend to move the NOx –particulate tradeoff to more favorable operating points where both pollutants are reduced. Exhaust gas recirculation can be problematic with diesel engines because the intake manifold pressure is frequently at a higher pressure than the exhaust manifold. Some systems direct the exhaust from upstream of the turbine to upstream of the compressor, which forces the exhaust gas to pass through the compressor. Other approaches use throttling to lower the pressure of the air entering the compressor so that exhaust can be drawn in from an ambient pressure source after the turbine. Most diesel engines are equipped with turbochargers that allow demands for increased power to be met while still maintaining the air–fuel ratio at values that ensure low emissions. To meet NOx emission standards, highly-rated engines use heat exchangers known as intercoolers or aftercoolers to reduce the temperature of the compressed air from the turbocharger compressor. Using ambient air as the exchange fluid for the intercoolers is the norm for most applications. Further improvements in engine air supply can be obtained from the use of variable geometry turbocharging. These turbochargers are equipped with variable area turbine nozzles so the exhaust velocity entering the turbine can be optimally matched to the engine’s speed and load. This provides greater intake air boost pressures over a wider range of operating conditions. Diesel engines cannot use the three-way catalyst technology that is used for spark-ignited engines because diesel engines always operate with excess air and it is difficult to reduce NOx under lean conditions. Recent developments in catalyst technology have produced lean NOx catalysts but their low efficiency has limited their acceptance. Catalytic systems that absorb the NOx and then periodically release it as harmless gases when the engine is momentarily operated rich have been more successful and may be used in the near future.

10.4.9 Selected Examples of Combustion Engines

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based on the 3.0 l inline-six 530d. The engine’s rated output is 200 kW and thus increased by 25% over its predecessor. Just like the power, the maximum torque was raised to 560 N m. The engine weight was increased by 14 kg, while specific consumption at maximum output was reduced by 7 g/kW h to 233 g/kW h compared to engines years older. Crankcase and Transmission. The crankcase cast from

pearlitic gray cast iron (GG25+) is based on the deep skirt concept already proven in preceding models. The side panels of the crankcase (crankcase skirts) are very deep. A special head design of the skirt area achieves more stiffness. The viscous damper first used in the 530d is used again in the 535d too. The damping effect is generated by varying shear forces in a highly viscose fluid in a narrow gap between the housing and swivel flywheel rim. Mixture Formation and Combustion. The proven con-

cept of BMW direct injection engines has also been adopted in this generation of engine. A central perpendicular injection nozzle and two intake and two exhaust ducts per cylinder are located on the cylinder head. One of the two intake ports is a swirl duct and the other a tangential duct. The two exhaust ducts are still combined in the cylinder head. To reduce raw emissions, combustion has been concentrated in the outer zones of the piston combustion bowl. Moreover, the engine’s compression ratio has been reduced from 17 : 1 (530d) to 16.5 : 1 by further optimizing the piston combustion bowl geometry. Injection System. The injection system of the 535d is based on the second generation common rail system already used in the 530d with a maximum injection pressure of 1600 bar. The flow was elevated in the 530d by 20%. This injection system supports up to five injections with minimal injection intervals between injections per combustion cycle. The induction-side high-pressure pump’s volume control generates maximum pressure as required. A micro-blind hole injection nozzle with six spray holes is used. Fuel consumption in the New European Driving Cycle (NEDC) test cycle is 8 l/100 km. Exhaust System. The particle filter is an integral part

of the exhaust system of the Euro-4 package. A secondgeneration filter with catalytically coated SiC substrate is used. With a 4.5 l volumetric capacity, the particle filter has a considerably longer service life than the first generation filter. Two exhaust temperature sensors and

Part B 10.4

Compression Ignition Engine with Twin Turbo Technology (BMW 535d) The world’s first use of twin turbo technology for car diesel engines sets this engine apart from comparable engines. Along with increasing the specific power to 67 kW/l, most notably the speed range has been expanded to approximately 5000 min−1 . With a bore of 84 mm and a stroke of 90 mm, the engine design is

10.4 Internal Combustion Engines

Piston Machines

The crankcase has an open deck (an open water jacket in the direction of the cylinder head) and deep skirt design (side panels far below the crankcase). Along with the advantage of simpler manufacturing, the open deck variant reduces cylinder barrel deformation when the cylinder head is bolted together. In order to withstand the high mean pressures of 21.7 bar in every operating situation, the material used is GJL (lamellar graphite cast iron), thus achieving a very low weight of 29 kg. Transmission. Above all, great importance was at-

tached to the engine acoustics. As opposed to the 1.4 l 66 kW, a steel crankshaft with 23% more stiffness was used for the TSI. This improves engine sound quality. Calculation and development tools make it possible to develop a piston for use in a supercharged engine with a specific power of 90 kW/l. This light metal piston’s combustion chamber bowl has a pronounce edge to control the flow. In order to provide the piston suffi-

941

cient operational stability, oil ducts bolted into the main oil gallery inject with approximately 2 bar against the hot outlet side of the piston. Finally, the piston pin diameter was enlarged because of the considerably higher ignition pressure. Injection. The TSI engine is being used for the first

time with a multiple hole, high-pressure injection valve with six fuel outlet bores. The nearly unlimited arrangement of the injection valve’s spray makes it possible to form the fuel injection spray. Among other things, this not only optimally homogenizes the mixture but also prevents wetting of the intake valve when there is early injection. This reduces the hydrocarbons (HC) emissions. The TSI injection pressure raised to 150 bar is generated by an adapted high-pressure pump. Compared to the FSI, its significant features include a longer cam stroke, the use of a roller tappet and the forged aluminum housing, all of which made it pos-

Part B 10.4

Fig. 10.101 VW 1.4l TSI

10.4 Internal Combustion Engines

Piston Machines

The transmission is also designed to have a long service life. Not only the crankshaft optimized for weight and stiffness but also the forged fracture-split connection rods contribute to this. These measures lead to considerably long running times so that an overhaul is only expected after an average of 350 000 miles. Induction System and Cylinder Head. To enable an

optimal turbocharge cycle, the Cummins 600 turbo diesel is equipped with four valves per cylinder. The redesigned intercooler as well as the turbocharger’s enlarged compressor wheel and housing achieve an optimal air flow during the induction phase. Reinforced inconel exhaust valves and cobalt stellite exhaust valve seats are used to increase the engine’s service life. Injection and Combustion. The 600 turbo diesel engine

employs a Bosch high-pressure common-rail injection system. This system enables pilot injection before main injection. Thus the ignition delay time of the subsequent main injection is reduced considerably and combustion runs more gently, ultimately producing less combustion noise. The injector is arranged centrally between the four valves and supports the target values for high efficiency and low emissions.

10.4 Internal Combustion Engines

943

Modern V8 Gasoline Engine with Variable Valve Timing This engine is descended from the modular V8 and V10 engine family (MOD for short), developed by Ford in 1991. The engines are variably designed in terms of their cylinder heads (two-, three- or four-valve cylinder heads) and their use (trucks and cars). In conjunction with the six speed automatic transmission, electronically controlled throttle, variable valve timing and other state of the art engine technologies, it was possible to develop an engine that satisfies the requirement for greater power while simultaneously reducing gasoline consumption. This engine is currently used in the Ford Explorer and a slightly modified version is used in the Ford Mustang. Basic engine. The basic engine is a 4.6 l unit. The eight

cylinders arranged in a V shape have a bore of 90.2 mm and a stroke of 90 mm. This engine also has a cylinder angle of 90◦ often used for V8 engines (compensation for higher-order inertial forces and moments). Depending on its vehicle use, the cylinder block is made of aluminum (Ford Mustang) or cast iron (Ford Explorer). Cylinder Head, Induction Pipe and Exhaust Manifold.

In contrast to the central crankcase, the cylinder head in the Ford Explorer as well as the Mustang is made of

Exhaust System and Turbocharger. An in-cylinder

Fig. 10.104 Ford 4.6l single overhead camshaft (SOHC) 90◦ V8-

engine (illustration courtesy of the Ford Motor Company)

Part B 10.4

solution and an oxidation catalyst reduce particulate and nitrogen oxide emissions considerably. A newly engineered piston combustion bowl likewise reduces pollutants. Its compliance with the 2004 emission standards makes it possible to dispense with an external EGR line, which would add over 50 components to the engine’s configuration and consequently make it more prone to failure. An expensive soot filter can be dispensed with for the same reasons. A turbocharger with electronically controlled waste gate is integrated to further reduce emissions and reach the maximum power of 325 HP. To spare the brake system when driving downhill, the Cummins 600 turbo diesel engine is equipped with an additional exhaust valve. It is closed as required and reduces the exhaust gas mass flow coming from the cylinder. This increases the in-cylinder pressure as a result of which the piston works against a stronger back pressure during the compression phase and crankshaft rotation is delayed.

944

Part B

Applications in Mechanical Engineering

aluminum. The three valve cylinder head is lighter and smaller than the four valve variant. The new cylinder head enables a higher compression ratio of 9.8 : 1 when 87 octane fuel is used. The large dual intake ports create a direct path to the intake valves for enhanced flow behavior at high rpm. At low rpm and engine loads, a processor-controlled charge motion control valve (CMCV) in the induction line closes shortly behind the injection nozzle. This considerably increases the flow velocity in the induction tract as well as the in-cylinder flow resulting in a more ignitable and faster combustible mixture. Consequently, in conjunction with the variable valve timing, an optimal charge motion characteristic can be achieved in the induction tract. As a result, fuel consumption drops by 10% compared to the predecessor model. In addition, the flow conditions in the longitudinally optimized intake manifold could be noticeably improved and a discharge of combusted gases from the cylinder accelerated. Due to their mass inertia, extremely light intake and outlet valves make high engine speeds possible and simultaneously reduce fuel consumption through their enhanced frictional properties. To minimize valve gear noise, the cam covers were made of magnesium. Ignition System. The three-valve technology allowed

arranging the spark plugs centrally in the cylinder head. This results in three advantages:

•

The central position to the cylinder produces a symmetrical flame with complete fuel combustion. Since the proportion of uncombusted fuel is negligible, the engine can generate more power while simultaneously reducing emissions (uncombusted hydrocarbons).

• •

The narrow and more-oblong design of the spark plugs make it possible to enlarge the valve diameters. This results in better engine performance and lower fuel consumption. A new powertrain control module (PCM) controls the ignitions more precisely, which ultimately manifests itself in higher efficiency.

Variable Camshaft Timing (VCT). After two- and four-

valve engines in the modular engine family have been put in the widest variety of vehicles, a 24 valve cylinder head in the V8 variable valve timing is being implemented for the first time in 2005. A single overhead camshaft per cylinder bank and low profile roller-finger followers with low friction activate the intake and exhaust valves. The powertrain control module electromagnetically changes the oil flow for the hydraulic cam timing mechanism, which enables the camshaft to rotate opposite the drive sprockets. The mechanism can switch between fully advanced and fully retarded timing in only a few milliseconds. VCT achieves an angular camshaft control of 50◦ CA. The dual-equal camshaft timing developed by Ford changes the intake and exhaust valve timing simultaneously. This system provides decisive advantages over fixed timing in the engine’s complete speed range. Short seat timing at low speeds causes the cylinder pressure to drop less strongly as a result of which a high torque is generated. The slight valve overlap also reduces emissions. The seat timing increases at high speeds. The greater charge mass in the cylinder also increases engine performance. This synchronous control of the timing enables constructing the cylinder head less complexly and with less weight than fully variable systems in which the intake valve is controlled separately from the exhaust valve.

References 10.1 10.2

Part B 10

10.3

10.4

K.-H. Küttner: Kolbenmaschinen, 6th edn. (Teubner, Stuttgart 1993), in German H.T. Wagner, K.J. Fischer, J.D. von Frommann: Strömungs- und Kolbenmaschinen, 3rd edn. (Vieweg, Wiesbaden 1990), in German H. Tschöke: Vorlesungsskript Grundlagen Kolbenmaschinen (Otto-von-Guericke-Universität, Magdeburg 2004), in German K.-H. Grote, J. Feldhusen (Eds.): Dubbel Taschenbuch für den Maschinenbau, 21st edn. (Springer, Heidelberg 2005), in German

10.5

10.6 10.7

10.8 10.9

V. Küntscher: Kraftfahrzeugmotoren – Auslegung und Konstruktion, 3rd edn. (Technik, Berlin 1995), in German H. Grohe: Otto- und Dieselmotoren, 10th edn. (Vogel, Würzburg 1992), in German R. van Basshuysen, F. Schäfer: Lexikon Motortechnik – Der Verbrennungsmotor von A–Z, 1st edn. (Vieweg, Wiesbaden 2004), in German KWW Crane GmbH: DEPA-Druckluft-Membranpumpen (CPFT, Düsseldorf 2005), in German Ponndorf Gerätetechnik GmbH: Hose Pumps (Ponndorf, Kassel 2005)

Piston Machines

10.10 10.11 10.12

10.13 10.14

10.15 10.16 10.17 10.18 10.19

G. Vetter: Pumpen (Vulkan, Essen 1992), in German Alpha Laval Bran Lübbe GmbH: Diaphragm Metering Pumps (Bran Lübbe, Norderstedt 2005) W. Hinze: Kolbenpumpen und –verdichter, Bildsammlung zur Vorlesung (Technische Hochschule Magdeburg, Institut für Kolbenmaschine und Maschinenlaboratorium (IKM), Magdeburg 1990), in German R. Prager: Technisches Handbuch Pumpen, 7th edn. (Technik, Berlin 1987), in German LEWA Herbert Ott GmbH: ecofolow – Die innovativen Dosierpumpen (LEWA, Leonberg 2005), in German Eckerle Industrie Elektronik GmbH: Internal Gear Pumps (Eckerle, Malsch 2006) R. Neumaier: Rotierende Vedrängerpumpen (Lederle Hermetic, Gundelfingen 1991), in German Kräutler GmbH: Screw Pumps Series M (Kräutler, Lustenau 2006) Netzsch-Mohno GmbH: Nemo® -Pumpen (Netzsch, Waldkraigburg 2006), in German R. Bosch GmbH: Mechanisches Benzineinspritzsystem mit Lambda-Regelung K-Jetronic (Krebs GmbH, Stuttgart 1981), in German

10.20 10.21 10.22 10.23 10.24 10.25

10.26

10.27

10.28

References

945

Johnson Pumpen GmbH: Impeller Pumps (Johnson Pumpen, Löhne 2006) M. Urich, B. Fisher: Holley Carburetors and Manifolds (HP, New York 1987) R. Bosch GmbH: Gasoline Engine Management Basics and Components (Bosch, Stuttgart 2001) R. Bosch GmbH: Diesel-Engine Management, 3rd edn. (Bosch, Stuttgart 2004) R. Bosch GmbH: Ignition Systems for Gasoline Engines (Bosch, Stuttgart 2003) R. Bosch GmbH: Automotive Handbook, 6th edn. (Society of Automotive Engineers, Warrendale 2004) A Student’s Guide to Alternate Fuel Vehicles (California Energy Commission, Sacramento 2006) (http://www.energyquest.ca.gov/transportation/ index.html) National Research Council: Rethinking the Ozone Problem in Urban and Regional Air Pollution (National Academy, Washington 1991) J.T. Kummer: Catalysts for automobile emissions control, Prog. Energ. Combust. Sci. 6, 177–199 (1980)

Part B 10

947

Ajay Mathur

This chapter is intended to present an overview of Pressure Vessels/Heat Exchangers and covers basic design concepts, Loadings & testing requirements relevant to these equipment. Design criteria, fabrication, testing & certification requirement of various Standards/Codes adopted in different countries are discussed on a comparitive basis to bring out similarities of features. In order to complete the overview, a brief discussion is provided on commonly used Materials of construction and their welding practises along with updates on the on-going developments in this area. The author is a Mechanical engineering graduatefrom M.S University-Baroda (India) & has over 20 years experience in design and fabrication of Pressure Vessels, exchangers, Skid mounted plants and Fired Heater modules for Refinery, petrochemical Nuclear & chemical plants in India & abroad.

11.1

Pressure Vessel – General Design Concepts 11.1.1 Thin-Shell Pressure Vessel ............. 11.1.2 Thick-Walled Pressure Vessel ......... 11.1.3 Heads ......................................... 11.1.4 Conical Heads .............................. 11.1.5 Nozzles ....................................... 11.1.6 Flanges ....................................... 11.1.7 Loadings .....................................

947 947 949 950 950 950 950 951

11.1.8 External Local Loads ..................... 951 11.1.9 Fatigue Analysis ........................... 951 11.2 Design of Tall Towers ............................ 11.2.1 Combination of Design Loads......... 11.2.2 Wind-Induced Deflection .............. 11.2.3 Wind-Induced Vibrations ..............

952 952 952 952

11.3 Testing Requirement ............................ 953 11.3.1 Nondestructive Testing (NDT).......... 953 11.3.2 Destructive Testing of Welds .......... 953 11.4 Design Codes for Pressure Vessels ........... 11.4.1 ASME Boiler and Pressure Vessel Code ........................................... 11.4.2 PED Directive and Harmonized Standard EN 13445 ........................ 11.4.3 PD 5500 ...................................... 11.4.4 AD Merkblätter .............................

954 954 954 956 958

11.5 Heat Exchangers................................... 958 11.6 Material of Construction ........................ 11.6.1 Carbon Steel ................................ 11.6.2 Low-Alloy Steel ............................ 11.6.3 NACE standards ............................ 11.6.4 Comparative Standards for Steel..... 11.6.5 Stainless Steel.............................. 11.6.6 Ferritic and Martensitic Steels ........ 11.6.7 Copper and Nickel Base Alloys ........

959 959 960 960 960 960 964 964

References .................................................. 966

11.1 Pressure Vessel – General Design Concepts Pressure vessels are closed structures, commonly in the form of spheres, cylinders, cones, ellipsoids, toroids and/or their combinations and which contain liquid or gases under pressure. There are various other requirements such as end closures, openings for inlet/outlet pipes, internal/external attachments for support and other accessories.

11.1.1 Thin-Shell Pressure Vessel When the thickness of the vessel is less than about one tenth of its mean radius, the vessel is called a thin-walled vessel and the associated stresses resulting from the contained pressure stress are called membrane stresses. The membrane stresses are assumed to be uni-

Part B 11

Pressure Ves 11. Pressure Vessels and Heat Exchangers

950

Part B

PARTMARK

Part B 11.1

under internal pressure. The prestresses so created help to neutralize the stress peaks in the existing stress distribution, making the material stress almost uniformly throughout the thickness, as shown in Fig. 11.3. This also considerably reduces the required wall thickness. Prestressing is carried out by the following methods:

• • •

shrink-fitting outer layers over the core, inner layer(s) wire/coil wrapping autofrettage

A detailed introduction to the basic theory of membrane stress and its application to commonly encountered elements of pressures vessels is presented in [11.1]. However, a brief discussion on other vessels components such as heads, nozzles and flanges is covered below.

11.1.3 Heads There are three general categories of heads (also called dished ends): Hemispherical: These dished ends are analyzed as the thin-walled spherical shells discussed earlier. Ellipsoidal: Ellipsoidal heads are developed by the rotation of a semi-ellipse and have a 2:1 ratio of major R to minor axis h. These heads are the most frequently used end closures in vessel design, particularly for internal pressures greater than 10 bars and also for bottom heads of tall, slender columns. Torispherical: Torispherical heads have a meridian formed of two circular arcs, a knuckle section with radius r, and a spherical crown segment with a crown radius of L. The maximum crown radius equals the inside diameter, which gives the same maximum membrane stress in the crown region as in the cylindrical region. The minimum knuckle radius is 6% of the crown radius, although a 10% knuckle is the most commonly used.

11.1.4 Conical Heads A conical head is generated by the rotation of a straight line intersecting the axis of rotation at an angle, α, which is the half-apex angle of the formed cone.

The formulae for computing the thickness of different types of heads under both internal and external pressure are provided in Table 11.1. There is a failure phenomenon in the knuckle region due to tangential stress under compression, which can occur through elastic buckling (circumferential wrinkles) at a stress much lower than the yield strength or through plastic buckling. A reliable analysis for predicting buckling failure has been introduced in the harmonized pressure vessel standard EN 13445, which will be discussed later.

11.1.5 Nozzles Nozzles or openings are provided in pressure vessels to satisfy certain process requirements such as inlet or outlet connections, manholes, hand holes, vents and drains etc. These may be located on the shell or head according to the functional requirement and could be circular, elliptical or rectangular in shape. The basic construction of a nozzle connection consists of essentially short pieces of pipes welded to the vessel wall at an opening made in the wall. The other side would normally be a flanged end suitable for connection to the corresponding piping or to bolt on the blind cover (as in the case of a manhole). The complete nozzle may also be formed by rolling or forging to the required shape. In addition to weakening of the vessel wall, the nozzle opening also causes discontinuity in the wall and creates stress concentration at the edges of the opening. This is compensated by providing reinforcement pads around the nozzle necks, which are suitably attached to the vessel wall. Rules are provided in every pressure vessel code to calculate the reinforcement requirement for all nozzles. At times, additional thickness is provided at the base of the nozzle wall itself; such nozzles are called self-reinforced nozzles.

11.1.6 Flanges Tall columns are usually constructed in detachable sections for ease of fabrication, transportation, erection, assembly, and internal maintenance. Like the nozzles and the piping system, these sections (or heads) must be provided with end flanges with an arrangement for easy bolting and dismantling as required. A flanged joint therefore consists of a pair of flange; each is attached to one of the components to be joined and is held securely in place by a series of bolt or studs. A gasket is interposed between the two adjoining flange face. The joint must have structural integrity with (zero) min-

Pressure Vessels and Heat Exchangers

1. to ensure a positive contact pressure at the gasket flange interface to prevent leakage in service. The gasket must be able to withstand the required sealing force, 2. the gasket sealing force is to be provided by bolt tightening without overstressing, 3. to ensure the structural integrity of flange sections and minimize flange deflections.

11.1.7 Loadings Loadings or forces are the causes of stress in pressure vessels. It is important to identify areas where and when these forces are applied to pressure vessels. The stresses produced by these loads, which could be general or local are additive and define the overall state of stress in the vessel or its component. The combined stresses are then compared to the allowable stress defined by the pressure vessel code. An outline of the various categories and types of loadings is summarized in Tables 11.2, 3, respectively.

11.1.8 External Local Loads Stresses caused by external local loads at the points of attachment to the vessel must be assessed to keep these

stresses within the prescribed limits. These loads are usually significant at nozzles, the vessel support region, at brackets, lifting lugs, and saddle supports for horizontal vessels. Since the contact area of the attachment is relatively small compared to the vessel area, a simplified form of the interface force distribution between the vessel and the support is assumed. The analysis is based on elastic stress analysis and stress categorization is used to compare the resultant stresses. This approach is used in annexure G of the PD 5500 code and in the Welding Research Council (WRC) bulletins WRC 107 and 297 used while in the design of the ASME code. In 1991 the WRC published another bulletin, WRC 368, for the evaluation of shell and nozzle stresses due to internal pressure. The analytical solution for evaluating localized stresses in the shell wall above the saddle supports for a horizontal vessel is based on the method developed by Zick and published in 1951. The method used in the harmonized standard EN 13445-3 (clause 16) for evaluating nozzle loads is based on limit load analysis. This standard provides separate rules for calculating line loads for lifting eyes, supporting brackets, and saddle supports.

11.1.9 Fatigue Analysis Vessels undergoing cyclic service and repeated loading may fail in fatigue due to progressive fracture of localized regions. The behavior of metals under fatigue conditions varies significantly from the normal stress–strain relationship. Damage accumulates dur-

Table 11.2 Categories of loadings

General loads

Local loads

General loads are applied more or less continuously across a vessel section

Local loads are due to reactions from supports, internals, attached piping and equipment such as mixers, platforms etc.

Examples

Examples

• Pressure loads – internal or external pressure (design, operating, hydrotest and hydrostatic head of liquid) • Moment loads – due to wind, seismic, erection and transportation • Compressive/tensile loads – due to dead weight, installed equipment, ladder, platform, insulation, piping and vessel contents • Thermal loads – skirt head attachment

• Radial load – inwards or outwards • Shear load – longitudinal or circumferential • Torsional load • Tangential load • Moment load – longitudinal or circumferential • Thermal loads

951

Part B 11.1

imum leakage during service. Several configurations of flanges in various construction materials and a large variety of gaskets are available; the selection is mainly dependent upon the service requirements. The main consideration for the design of a flanged joint are:

11.1 Pressure Vessel – General Design Concepts

952

Part B

PARTMARK

Part B 11.2

ing each cycle of loading and develops at localized regions of high stress until subsequent repetitions finally result in visible cracks, which grow, join, and spread. Localized stresses at abrupt changes in sections such as at the head junction or a nozzle opening, misalignment, defects during fabrication, and thermal gradients are probable causes for fatigue failure. Special attention should be paid to manufacturing tolerances, nonde-

structive testing, and in-service inspection of vessels designed for fatigue. All pressure vessel codes have established specific criteria for determining when a vessel must be designed for fatigue. Each code has adopted a methodology for carrying out fatigue analysis based on the use of fatigue curves obtained from test specimens. The fatigue design rules of some of the pressure vessel codes are discussed later.

11.2 Design of Tall Towers 11.2.1 Combination of Design Loads The shell thickness of tall columns as computed based on internal or external pressure is not usually sufficient to withstand the combined stresses produced by the operating pressure plus weight, and wind or seismic loads. Combined stresses in the longitudinal direction σL due to pressure P, dead weight W and applied moment M, with W and M taken at the elevation under consideration, are calculated as follows: 1. On the windward side       W PD 4M − + , (11.3) σL = 4d π Dd π D2 d   (PD/4) + (4M/π D2 ) − (W/π D) d= . allowable stress (11.4)

2. On the leeward side       PD 4M W − . − σL = 4d π Dd π D2 d

•

National building code (NBC) British standard (BS) 6399

• • • •

Code for Seismic Loads ASCE-7 UBC/NBC International building code (IBC) 2000 Response spectrum data

Tall cylindrical vessels are normally designed to be self-supporting; they are supported on cylindrical or conical skirts with base rings resting on concrete foundations, firmly fixed to the foundations by anchor bolts. Detailed analytical methods for computing the thickness of the skirt components and sizing of the anchor bolts can be found in [11.2, 3], which also provide procedures for other types of supports such as lugs, legs, and rings due to wind and seismic loads.

11.2.2 Wind-Induced Deflection (11.5)

For the design of a particular vessel, the value of the moment derived from either the wind or seismic loads is used in these expressions. This is due to the assumption that the wind and seismic loads are not expected to occur simultaneously and therefore the higher moment of the two is considered to be governing. These loads are based on site-specific data, which is obtained from one of the following national standards as applicable to the installation site.

•

• •

Code for Wind Loads American Society of Civil Engineers (ASCE) 7, formerly American National Standards Institute (ANSI) A58.1 Uniform building code (UBC)

A sustained wind pressure will cause tall columns to deflect with the wind. Most engineering specifications limit the deflection to 150 mm per 30 m of column height. The vessel is assumed to be a cantilever beam firmly fixed to the concrete pedestal and individual deflections induced by wind load and moments are calculated for each varying section of the vessel using the deflection formula for cantilever beams. The total deflection is then calculated using the method of superposition.

11.2.3 Wind-Induced Vibrations Wind-induced vibrations can be caused by vortex shedding, the magnitude of which is dependent on wind velocity and vessel diameter. Vortex shedding results in severe oscillations, excessive deflections, structural damage and even failure. When the natural frequency

Pressure Vessels and Heat Exchangers

11.3 Testing Requirement

Steady loads

Non-Steady loads

These loads are long term and continuous

These loads are short term and variable

Examples

Examples

• Internal/external pressure • Dead weight • Vessel contents • Loading due to attached piping and equipment • Loading to and from vessel supports • Thermal loads • Wind loads

• Shop and field hydrotest • Earthquake • Erection • Transportation • Upset, emergency • Thermal loads • Startup, shutdown

of a column or stack coincides with the frequency of vortex shedding, the amplitude of vibrations is greatly magnified. After a vessel has been designed statically, it is necessary to determine if the vessel needs to be

investigated dynamically for vibrations. Detailed methods for determination the need for dynamic analysis and a method for carrying out this dynamic analysis are provided in [11.3].

11.3 Testing Requirement 11.3.1 Nondestructive Testing (NDT) NDT of the raw material, components, and finished vessel is important from the safety point of view. The most widely used methods of examination for plates, forgings, castings and welds are briefly described below. Radiographic examination is done either by X-rays or gamma rays. The former has greater penetrating power, but the later is more portable. Single-wall or double-wall techniques are used for tubular components. Penetrameters, or image quality indicators, check the sensitivity of a radiographic technique to ensure that any defect will be visible. Ultrasonic techniques use vibrations with a frequency between 0.5 and 20 MHz transmitted to the metal by a transducer. The instrument sends out a series of pulses, which are seen on a cathode ray screen after being reflected from the other end of the member. Reflections either from a crack or inclusion in the metal (or weld) can be detected on the screen; based on the magnitude and position of the signal, the location of the flaw can be ascertained. Liquid penetrant examination involves wetting the surface with a colored fluid that penetrates open cracks. After wiping out excess fluid, the surface is coated with a developer fluid, which reveals the liquid that has penetrated the cracks. Another system uses

a penetrant that becomes florescent under ultraviolet light. Magnetic particle examination, which can only be used on magnetic material, is carried out by passing magnetic flux with the help of a probe through the part to be tested. Fine magnetic particles, which are dusted over the surface, tend to concentrate at the edge of the crack. To pick up all the cracks, the area is probed in two directions.

11.3.2 Destructive Testing of Welds In contrast to the NDT methods, which are essentially predictive techniques, the mechanical integrity of welds is checked by testing sample test plates called production test coupons. The coupons are welded along with the actual vessel joint (usually a longitudinal seam) and thus are representative of the actual welding techniques employed for the vessel. The following tests are normally carried out on the test piece: 1. Tensile testing, which includes transverse tensile and all-weld tensile tests 2. Bend test – transverse bend/side bending 3. Macro-etching, hardness, impact testing 4. Intergranular corrosion test (IGC) for austenitic stainless-steel material/welds 5. Ferrite checking

Part B 11.3

Table 11.3 Types of loadings

953

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Part B

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Part B 11.4

11.4 Design Codes for Pressure Vessels In modern competitive industry, new process plants are being set up rapidly and existing units are continually revamped, modernized and refurbished for the chemical, petrochemical, pharmaceutical, energy, refinery, and nuclear industries all over the globe. A variety of equipment is needed for the storage, handling and processing of hydrocarbons and chemicals in these processing plants. Unfired pressure vessels such as storage tanks, Horton spheres, mounded bullets, reactors, autoclaves, distillation/fractionating columns, and heat exchangers are some of the basic components of any such process plant. Various codes specifying the requirements for the design, material, fabrication, inspection, and testing of pressure vessels have been written and adopted as national standards in various countries. Most the international pressure vessels have been developed with a higher degree of technical similarity between them. Core area such as vessel class, design criteria and requirements for independent inspection and certification are based on similar (but not identical) guiding principles. A compilation of websites of various organizations, associations, technical standards, and current European Union (EU) legislation relating to pressure equipment sector is presented in [11.4]. The subsequent subsections present a brief discussion of the key features of some of the international pressure vessel codes.

11.4.1 ASME Boiler and Pressure Vessel Code The ASME boiler and pressure vessel code, section VIII, published by the American Society of Mechanical Engineers, also known as ASME International, is a widely accepted code in the USA and 80 other countries in the world. The code is written by voluntary engineering talent and is constantly upgraded by the corresponding committee members to include the latest developments in material and design methodology. ASME section VIII is written against a well-defined theoretical background and is divided into three subdivisions: 1, 2 and 3. The important design rules of both the codes are summarized in the respective appendices of each code. The contents of the three divisions are organized to cover specific pressure ranges, as illustrated in Table 11.4. As can be seen from the code comparison table, division 2 permits higher working stresses at the expense

of stringent material testing and more-careful quality control. In addition to detailed design rules division 2 provides for discontinuities, fatigue, and other stress analysis considerations, which are based on maximum shear stress theory. Division 2 also contains rules for vessels with layered construction (multiwalled vessels) Fatigue Analysis Clause AD-160 of division 2 provides several methods for exempting fatigue evaluations. If the cyclic operation does not meet all the conditions of AD-160 a fatigue evaluation method as per appendix 5 or 6 is added. The stress ranges are first determined for the specified cyclic operation and then, using fatigue curves presented in appendix 5, the associated number of allowable cycles and Miner’s rule are used to determine the life fraction and cumulative damage. Fatigue curves up to 370 ◦ C for carbon/low-alloy steel and 430 ◦ C for austenitic stainless steel are provided in the code. Division 3, which is a comparatively recent publication, provides a state-of-the art code and is intended for high-pressure applications where fatigue and fracture dominate.

11.4.2 PED Directive and Harmonized Standard EN 13445 The early phase of development of design codes and associated legislation in the pressure equipment sector was done predominantly at the national level. In view of the substantial economic potential of this sector, a need was felt in the European community to introduce a uniform and harmonized regulatory framework within the EU. The objective of the common legislation mechanism promulgated through directives was to minimize, if not eliminate, trade barriers between EU member states for pressure equipment, at the same time meeting essential safety requirements stipulated by the new directives. Of the several European directives enforced since 1987, the Pressure Equipment Directive (PED) (97/23/EC) and the Simple Pressure Vessel (SPV) Directive (87/404/EEC) are the two principal instruments for the pressure equipment sector. The approach of the directives includes the identification of the product, prescription of the essential safety requirements (ESRs) to be met by technical standards, demonstration of conformity and CE marking. Technical standards adopted by the European Committee for Standardiza-

Pressure Vessels and Heat Exchangers

11.4 Design Codes for Pressure Vessels

Section VIII division I

Section VIII division II

Section VIII division III

EN 13445 part 3

First publication

< 1940

1968

1997

2002

Units adopted

ˇrF and ksi

Pressure limits

Upto 3000 psig

No limits, usually + 600 psig

No limits, usually from 10 000 psig

Design factor Tensile strength

3.5

3.0

Yield strength

1.5

1.5

Average stress for 1% creep in 100 000 h Allowable stress calculated by Testing groups

1.0

1.0

Committee and provided grades and products NDE requirement dependent on weld efficiency factor 1.3 × design pressure

in Tables in section II C for individual

Designer

Stringent NDE requirement

Classified from I to IV in decreasing extent of NDT

Hydrostatic test

◦C

1.25 × design pressure

Yield based with reduction factor for yield to tensile ratio less than 0.7

NDE requirement is even more stringent than Division 2 1.25 × design pressure

and N/mm2

For gas-ps up to 3000 bar and/or ps∗ V up to 3000 bar L For liquid-ps up to 1000 bar and/or ps∗ V up to 10 000 bar L Ferritic/normalized steel – 2.4 Austenitic steel – 3 Ferritic/normalized steel – 1.5 Austenitic steel – 1.5 or 1.2 (depending on rupture elongation) Guidelines for design in creep range are under development

Greater of 1.43 × allowable pressure and 1.25 × temperature-adjusted pressure

Table 11.5 EN 13445:2002 Unfired pressure vessels – a quick reference Reference

Title

Contents/special features

EN 13445-1:2002

General

Scope, extent of testing with respect to weld joint coefficient, material grouping, etc.

EN 13445-2:2002

Materials

Materials listed include steels with sufficient ductility, cast iron and aluminium. Permitted or tabulated design stress are not provided. List of normative annexures are provided which include technical, inspection and delivery condition. Material listed in CE harmonized product standard can be used for that product. Material listed in CE harmonized material standard, if appropriate to the product. European approval of material (EAM) required for materials not listed in the harmonized standards. Particular material appraisal (PMA) required for material not listed in the harmonized standards or approved via EAM.

EN 13445-3:2002

Design

See Table 11.6 listing features for individual components.

EN 13445-4:2002

Fabrication

Provides weld designs, tolerances, production testing, post-weld heat treatment and repair requirements.

EN 13445-5:2002

Inspection and testing

Specifies nondestructive testing, pressure testing, marking and documentation requirement for noncyclic operation and special provisions for cyclic operations.

EN 13445-6:2002 CR 13445-7:2002

Requirement for design and fabrication of pressure vessels and pressure parts constructed of spheroidal graphite cast iron. Supporting standard for guidance on the use of the conformity procedures.

prEN 13445-8

Additional requirement for pressure vessels of aluminium and aluminium alloys.

Part B 11.4

Table 11.4 Comparison of various divisions of ASME codes vis-à-vis EN13445

955

956

Part B

PARTMARK

Part B 11.4

Table 11.6 A quick summary of EN 13445 part 3 Type of analysis

Component

Special features

Design by formulae for non-cyclic loading (used in clauses 7 to 16) (full pressure cycles less than 500 cycles)

Dished ends

Additional formulae for knuckle and knuckle buckling

Cones and conical ends Opening in shells Opening in flat ends Flanges

Based on limit analysis Pressure area method Replacement of section modulus Modified Taylor forge method, alternate method also provided based on limit load analysis carrying out detailed assessment of flange–bolt–gasket system, useful for joints where bolt loads are monitored Linked to testing group I/II/III/IV In addition to traditional method, new method using limit analysis approach in which edge loads and restraints are addressed, is provided Allowable tube loads are calculated Covers both thin- and thick-walled bellows Rules are based on Expansion Joint Manufacturer’s Association (EJMA) standards Covers both unreinforced and reinforced vessels where outside stiffeners are attached Local loads are assessed by comparison with allowable loads calculated based on limit load analysis Fatigue strength calculated using fatigue curves, which are more conservative than those used in detailed fatigue analysis for the unwelded region Table is provided for selecting stress factor for various design configurations Correction factors depending upon temperature, thickness, mean stress and surface finish are applied on fatigue curves Cumulative damage calculated as per Miner’s rule Guidance provided on bending stress calculations due to misalignment of weld and recommendation given for weld-toe grinding New route based on Eurocode (for steel structure), which overcomes the shortcomings of the familiar stress categorization method, addresses failure modes directly by way of design checks under the influence of actions (all imposed thermo-mechanical quantities including pressure, thermal and environmental) using partial safety factor depending on nature of single action or combination of actions Based on categorization of stresses into primary, secondary and peak stress and comparing the same with specified limits, Stress classification table is provided for given component and its location depending upon the source load to help list and allocate stress category

Weld joint efficiency Tubesheets

Bellows

Rectangular vessels Non-pressure local loads Design by formulae for cyclic loading (used in clauses 17 and 18) (full pressure cycles exceeding 500 cycles)

Simplified fatigue analysis (clause 17)

Design by analysis (covered by annexes B and C)

Direct route (annex B)

Detailed fatigue analysis (clause 18)

Stress categorization route (annex C)

tion (CEN/CENELEC), which provide means for the user to comply with the ESRs of the PED, are called harmonized standards. EN 13445:2002 Unfired Pressure Vessel is a major harmonized product standard within the CEN pressure equipment portfolio. The standard utilizes expertise and best practices from across the European member states as well other internationally accepted standards. The adoption of the first issue of this standard, published in 2002, was preceded by discussions between experts who took nearly 10 years to achieve a major technical convergence. The various sections of EN 13445 along with a brief description of the respective contents are tabulated in

Table 11.5, while Table 11.6 summarizes the essential features of the design rules for various pressure vessel components, as covered in part 3 of EN 13445. An excellent presentation of the background to the rules of EN 13445 part 3 is available [11.5].

11.4.3 PD 5500 PD 5500:2000, the specification for unfired fusion welded pressure vessels, is a recent replacement for BS 5500:1997. It was issued under the status of a published document (PD) in anticipation of simultaneous release of the harmonized standard EN 13445 for pressure equipment in Europe.

Pressure Vessels and Heat Exchangers

11.4 Design Codes for Pressure Vessels

Information

ASME section VIII division 1 Part Summary

PD 5500 Section Summary

AD Merkblätter Section Summary

Responsibilities

UG-99

1.4

Druckbehälter VO

Certification

UG-115 to 120

Responsibilities listed for manufacturer and authorized inspector (AI) Manufacturer to have certificate of authorization to construct ASME stamped vessel

Construction categories

–

–

3.4

Joint types

UW-3

5.6.4

Weld joint details Welder’s approval

UW-12, UW-13, UW-16 UW-28, 29, 48

Permissible materials

UG-4, UG-10

Defines A, B, C, D category with different NDT requirements; UW12 gives joint efficiencies Shows typical weld joints for guidance and are not mandatory Weld procedure specification (WPS), procedure qualification record (PQR) and welder’s qualification are required UG-4 refers to materials specified in ASME section II

2.1.2

This sections references British standard materials

Material identification

UG-94

4.1.2

NDT techniques

Assembly tolerance

UW-51 to 53, UW-11, UW-42 UG-80, UW-33

Material for all pressure parts is marked and certified for traceability NDT techniques are detailed in ASME section V

4.2.3

Pressure testing

UG-99, UW-50

Tolerances for circularity and alignment are specified Test pressures are specified along with other requirements of testing

Positive material identification is required for all pressure parts Ultrasonic testing (UT) and radiographic testing (RT) testing both are acceptable Tolerances for circularity and alignment are specified Test pressures are specified along with other requirements of testing

Heat treatment

UCS-56

1.4

E.1(1)– E.1(6) 5.2, 5.3

5.6.4

5.8.1

Though PD 5500 does not currently have formal status as a harmonized standard and compliance with its technical requirement does not qualify presumption of conformity to PED, it does include information showing how its technical content would comply with the ESR of the directive.

Responsibilities for code compliance is on manufacturer Code compliance is documented by use of form X issued by manufacturer and counter signed by AI Three categories with different material and NDT requirement are defined Defines A and B welded joints, with different NDT requirements

Shows typical weld joints for guidance and are not mandatory WPS, PQR and welder’s qualification are required

Druckbehälter VO

Authorized inspector to issue final vessel certification Authorized inspector to issue final vessel certification

HP 0

Four testing groups I, II, III and IV are defined

HP 2/1

WPS, PQR and welder’s qualification are required

W0 to W13 for metallic and N series for non-metallic material

W0 to W13 cover all types of alloyed/unalloyed steel, castings, forgings, clad steel bolts and nuts but do not include gaskets

HP 5/3

DIN standards are referenced for all NDT techniques

HP 8/2, HP 30

HP 7/1 to HP 7/4

Fatigue Analysis Annexure C of the code presents criteria for exemption from fatigue analysis. A simplified fatigue analysis using design curves can be done using conservative estimates of the stress range due to pressure changes and thermal gradients. By using appropriate an design curve

Part B 11.4

Table 11.7 Summary of the salient features of ASME, PD 5500 and the AD code

957

958

Part B

PARTMARK

Part B 11.5

to obtain allowable cycles and satisfying a cumulative damage rule, a simplified analysis can be done. A detailed analysis is required if the specified criterion is not satisfied. Detailed methods for determining stresses due to pressure, thermal gradient, and piping loads based on using stress concentration factors are provided in annexure G. Based on the individual stresses thus obtained, the maximum principal stress range for each individual cycle is determined and fatigue evaluation is done as per annexure C. The fatigue curves are limited to 350 ◦ C for ferritic steel and 430 ◦ C for austenitic stainless steels.

11.4.4 AD Merkblätter Arbeitgemeinschaft Druckbehälter (AD) Merkblätter regulations are a set of generally accepted rules of technology regarding pressure vessels and contain safety

requirement for equipment, design, manufacture and testing, and materials. These regulations are compiled by seven trade associations of Germany, who together form the AD. The AD associations represent a balanced combination of material and pressure vessel manufacturer’s, operators, employer’s liability insurance, and technical inspectorates. To a large extent the AD Merkblätter code is based on Deutsches Institut für Normung (DIN) standards and is continuously amended in keeping with technical progress. The associations has published a regulation called AD 2000 conforming to the safety requirement and other stipulations as laid down in the PED, which has been made compulsory in Europe from May 2002 onwards. A quick summary showing the key technical points of PD 5500 in comparison with the ASME section and AD Merkblätter code are shown in Table 11.7.

11.5 Heat Exchangers Heat exchangers are devices that transfer heat from a hot to a cold fluid. They are used extensively in processing plants and are given specific names when they serve a special purpose, for example superheaters, condensers, evaporators etc. In a surface-type exchanger, the two process fluids are separated by a physical barrier and the heat is transferred from the warm/hot fluid through the barrier to the cold fluid. Shell-and-tube and

plate exchangers are the most commonly used types of surface exchangers. The construction of shell-and-tube exchangers is broadly divided into the shell side and tube side (also called the channel section). Several small-diameter tubes (on the tube side) are attached to larger pressure vessels (known as the shell side), or parts thereof, called tube sheets. The tubes are distributed within the tube

Table 11.8 Design rules for tube sheets as per different codes TEMA

ASME section VIII division 1

EN 13445-3

Reference section

Section 1999 edition

Appendix AA-1 edition 2001 and UHX-12 edition 2002 (mandatory)

Clause 13 D-2002 (based on Code francais de construction des Appareils a Pression (CODAP)/unifired pressure vessel (UPV) rules)

Assumptions

Perforated tubesheet and unperforated rim not accounted for; the effect of tube sheet attachment with shell/channel not considered 0.45 ≤ η ≤ 0.60

Refined and rational analytical treatment is used after taking into account actual geometry (based on model proposed by F. Osweiller in 2000)

Safety factor Allowable stress

2.6

1.5 Stress classification of division 2 appendix 4

Remarks

TEMA approach leads to lower thickness than ASME due to higher ligament efficiency and high safety factor

Higher thickness obtained in ASME rules than UPV/CODAP due to lower allowable stress

U tube tubesheet

Ligament efficiency

0.25 ≤ μ ≤ 0.35 2.0 Based on primary and secondary stress as per appendix C

Pressure Vessels and Heat Exchangers

11.6 Material of Construction

Fixed/floating tubesheet Reference section Assumption

Remarks

Stiffening effect of tube bundle and weakening effect of tube holes are assumed to counterbalance each other, coefficient F is not dependent on the stiffness ratio X of the axial tube bundle rigidity to the bending rigidity of the tube sheet TEMA does not provide the same design margin for all cases, leading to over-thickness for higher X and under-thickness for lower X

Appendix AA-2 edition 1992

Clause 13 E-2002 (based on CODAP/UPV rules)

Coefficient F is dependent on the stiffness ratio X

Coefficient F is dependent on the stiffness ratio X; the value of F is higher than ASME since tubes are assumed to be uniformly distributed over the whole tube sheet

sheet in a certain pattern, the three most common of which are the triangular, square and rotated triangular, and square. Designs for the joint between the tube and tube sheet vary widely and are chosen to be compatible with the severity of the service conditions. The joint may be expanded, welded, or a combination of both. There are various constructional details of welded joints, the choice of which is based upon service and environment.

Various configurations and designs of shell-andtube exchangers are covered extensively by the Tubular Exchanger Manufacturers’ Association (TEMA). The principle of mechanical design for most of the components of the heat exchanger is identical to the design of a pressure vessel. However, the design of the tube sheet is typically different because of its constructional geometry. The tube sheet design rules have been rationalized in recent years by various pressure vessel codes, which are summarized in the Table 11.8.

11.6 Material of Construction 11.6.1 Carbon Steel Steel is an iron alloyed with carbon at a level of 0.05–2.0%. In addition it contains smaller proportions of phosphorus, sulphur, silicon, aluminum, and manganese. These steels are known as plain carbon steels, which are classified as mild-, medium- and high-carbon steels according to the percentage of carbon. Mild steel has 0.05–0.3% carbon by weight, medium-carbon steel has a carbon content of 0.3– 0.6% and high-carbon steel has more than 0.5%, up to a maximum of 2%, carbon content. Mild steels are the most versatile materials for the construction of pressure vessel due to their good ductility and relative ease of forming, rolling, forging, fabrication, and welding. They are also most suited and economic for applications where the rate of corrosion is low. During the manufacture of these steels, silicon and/or aluminum are added to react with dissolved oxygen in the molten metal alloy to form a slag of Al2 O3 /SiO2 , which floats

to the top and is removed; the resultant steel is called killed steel. A fully killed steel usually contains less than 150 ppm oxygen and at least 0.10% silicon. Besides being cleaner due to the formation of fewer oxides and inclusions, fully killed steels are much easier to weld due to a lower tendency to outgas during welding. Welding Mild-steel electrodes are grouped into those with rutile-type flux covering and those with low hydrogen flux covering. Rutile-covered electrodes are used for general fabrication involving thinner sections, lower tensile strength, and in applications where there is no requirement for impact properties. For all other applications, where strength, impact properties, and weld quality are essential, low-hydrogen-type electrodes are employed. The flux covering eliminates sources of potential hydrogen and thus minimizes the chances of clod cracking.

Part B 11.6

Table 11.8 (cont.)

959

960

Part B

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Part B 11.6

11.6.2 Low-Alloy Steel

11.6.3 NACE standards

Low-alloy steel contains additions of the elements Ni, Cr, Si, Mo, and Mn in amounts totaling less than 5%. The added elements improve mechanical properties, heat treatment response and /or corrosion resistance. The weld ability of low-alloy steels is also good; however since these steels are hardenable by heat treatment, they do require careful attention to welding procedure including pre- and post-weld heat treatment (PWHT) for stress relief, which is discussed later. The workhorse alloys for pressure vessels, exchanger and heater tubes, and piping for elevated temperature service, usually greater than 250 ◦ C, contain 0.5%–9.0% chromium plus molybdenum. With the increasing chromium content, resistance to hightemperature hydrogen attack, and resistance to sulfidation and oxidation increases.

The National Association of Corrosion Engineers (NACE) is a worldwide technical organization that studies various aspects of corrosion in refineries, chemical plants and other industrial systems. NACE standard MR0175, entitled Sulfide corrosion cracking resistant metallic material for oilfield equipment, is widely used for applications in sour gas and oil environments. NACE compliance is recommended in systems where there is a likelihood of sulfide cracking due to the presence of a measurable amount of H2 S. Since the susceptibility of carbon, low-alloy and austenitic stainless steel to sulfide corrosion is directly related to strength and hardness level, it these standards recommend that the hardness of the aforementioned plate material should be restricted to 22 HRC (200 BHN). The cold working of these steels during forming/rolling shall be less than 5%. Post-weld heat treatment is to be carried out for carbon steels in the case of greater cold working. A few duplex stainless and some nickel-based alloys are also acceptable according to the NACE criteria, subject to a maximum hardness level of 28 and 35 HRC, respectively.

Developments There has been an increasing trend towards improved toughness properties and temper embrittlement resistance by restricting levels of impurity elements at the ladle. To minimize the temper embrittlement of low-alloy steel, the phosphorous content is restricted to 0.010% or lower, while the combined phosphorous–tin content is limited to 0.010%. The effects of the tramp elements have been addressed by the Bruscato factors X and J, as defined by the following equations:

(10P + 4Sn + 5Sb + As) 100 (all elements in ppm) ,

X=

J = (Si + Mn)(P + Sn) × 104

(elements in %) .

For this reason PWHT is a must for all creepresisting Cr–Mo-type alloy steels. PWHT also stabilizes and softens the microstructure at the heat-affected zone (HAZ) of the weld. If the base metal is quenched and tempered, higher PWHT temperatures can be specified for improved resistance to creep embrittlement. Fabrication In view of the criticality of preheating, post-heating, and PWHT, it is prudent to employ specialized heattreatment techniques using electrical resistance pads or induction coils,especially for thick piping sections.

Welding All weld procedures must be qualified to meet the same hardness levels standards as specified for the corresponding parent material.

11.6.4 Comparative Standards for Steel The discussion for carbon steel material and the discussion to follow for other construction materials are generally based on the generic composition of materials without referring to any code of construction. It is difficult to furnish equivalence of any grade of material from one code to another; at best steels grades can be compared based on the closest matching technical requirements. Tables 11.9, 10 list some of the comparable standards for flat and tubular products commonly used in fabrication of pressure vessel.

11.6.5 Stainless Steel Alloys of iron and carbon with over 12% chromium, which resist rusting under most atmospheric conditions, are called stainless steels. The alloys become more corrosion resistant as the chromium level increases. As more nickel is added, several phases are possible and the alloy may undergo transformation depending on the

Pressure Vessels and Heat Exchangers

11.6 Material of Construction

Harmonized European standard Description

Standard

General requirement

EN 10028-1

Non-alloy and alloy steel with elevatedtemperature properties

EN 10028-2

ASTM

DIN

BS 1501

Grade SA 20 DIN 17155 P235GH

SA 283 Gr C/

HI

P265GH

SA 516 Gr 55 SA 516 Gr 60

H II

P295GH P355GH 16Mo3 13CrMo4-5 10CrMo9-10

SA 516 Gr 65 SA 414 Gr G SA 204 Gr B SA 387 Gr 12 SA 387 Gr 22

17Mn4 19Mn6 15Mo3 13CrMo4 4 10CrMo9 10

161 Gr 360/ 164 Gr 360 161 Gr 400/ 164 Gr 400 224 Gr 490 1503-243 B 620 Gr 27 620 Gr 31

DIN 17102 Weldable fine-grain, normalized

EN 10028-3

P275N P275NH P275NL1 P275NL2 P355N P355NH P355NL1 P355NL2 P460N P460NH P460NL1 P460NL2

SA 516 Gr 60 SA 662 Gr A SA 537 CL 1 SA 662 Gr C SA 737 Gr B

StE 285

224 Gr 400

WStE 285 TStE 285 EStE 285 StE 355 WStE 355 TStE 355 EStE 355 StE 460 WStE 460 TStE 460 EStE 460

224 Gr 430

224 Gr 490 224 Gr 490 224 Gr 490

DIN 17280 Nickel steel with temperature properties

alloy low-

EN 10028-4

11MnNi5-3 12Ni14 X12Ni5 (12Ni19) X8Ni9 NT X8Ni9 QT

13MnNi6 SA 203 Gr D,E,F SA 645 SA 353 SA 553

Weldable fine-grain, thermomechanically rolled

EN 10028-5

Weldable fine grain, quenched and tempered Stainless steel

EN 10028-6

P690Q / QH QL1/QL2

SA 517, SA 533, SA724

EN 10028-7

Various gardes (refer to Table 11.10)

SA 240

10Ni14 12Ni19

P355M / ML1/ML2 P420M / ML1/ML2 P460M / ML1/ML2

Note: Common legend for Tables 11.9, 10 is shown under Table 11.10

DIN 17440 DIN 17441

BS 1449-2 and BS 1501-3

Part B 11.6

Table 11.9 Comparative chart for material standards of flat products (plates) for pressurized use

961

962

Part B

Part B 11.6

PARTMARK

Table 11.10 Comparative chart for material standards of tubular products for pressurized use Harmonized European standard Description Standard Grade

ASTM

Non-alloy EN 10216-1 for general use

P195

SA 53 Gr A/SA 106 Gr A

P235 P265

SA 53 Gr B/SA 106 Gr B

Unalloyed EN 10216-2 and alloyed for elevated temperature

P195GH

P235GH P265GH

16Mo3

10CrMo5-5 13CrMo4-5 10CrMo9-10 X11CrMo5 X11CrMo9-1 X10CrMoVNb9-1 Unalloyed EN 10216-3 and alloyed, fine grain

Unalloyed EN 10216-4 and alloyed, low temperature

DIN

BS 3059-1 Gr 320 DIN 1629 St 37 DIN 1629 St 44 DIN 17175

BS 3601 Gr 360 BS 3601 Gr 430 BS 3059-2 BS 3602 Carbon/ C−Mn alloy

St 35.8 St 45.8

360 440

SA 179 – Cold-drawn tubes for exchanger SA 192 – Boiler tubes SA 210 Gr A1 – Boiler/ superheater tube SA 210 Gr C Tube Pipe SA 209 T1 SA 335 P1 SA 213 T2 SA 335 P2 SA 213 T11 SA 213 T12 SA 213 T21 SA 213 T22 SA 213 T5 SA 213 T9 SA 213 T91

SA 335 P11 SA 335 P12 SA 335 P21 SA 335 P22 SA 335 P5 SA 335 P9 SA 335 P91

360 430

BS 3606 Exchanger tube Gr 320

400 440

17Mn4 15Mo3

243

10CrMo9 10 12CrMo195 X10CrMoVNb91 DIN 17179 WStE/TStE 285

P355N/NH P355NL1/NL2 P460N/NH P460NL1/NL2 ASTM 333

ASTM 334

EStE/StE 355 WStE/TStE 355 EStE/StE 460 WStE/TStE 460 DIN 17173

Gr 1

Gr 1

TTSt35 N

243 BS 3604 (ferritic) 621 620

13CrMo44

P275NL1/NL2

P215 NL

BS

620-470 91

622 625 620-470

621 620 622 625

BS 3603 carbon/alloy

P265 NL Gr 6 Gr 6 430 LT 12Ni14 Gr 3 Gr 3 10Ni14 530 LT 12Ni14+ QT Gr 3 Gr 3 10Ni14 530 LT X10Ni9 Gr 8 Gr 8 X8Ni9 509 LT X10Ni9 + QT Gr 8 Gr 8 X8Ni9 509 LT Legend for steel grade to EN series G – Other characteristics follows, N – Normalized condition, H – Elevated temperature property required, M – Thermo mechanically rolled, QT – Quench and tempered, L1 – Low temperature property, impact testing at −50 ◦ C, L2 – Special low temperature property, impact testing at −50 ◦ C, enhanced requirement

Pressure Vessels and Heat Exchangers

Developments Newer grades of stainless steel have been developed to overcome the limitations of low 0.2% proof stress, sensitivity to stress and pitting corrosion especially in chloride media, inadequate corrosion in reducing media, and preferential attack on the ferrite phase in strong oxidizing media. Nitrogen alloyed steel such as AISI 304LN and 316LN have been developed with the addition of 0.2% nitrogen, resulting in improved proof stress by about 15%. Nitrogen alloyed steel finds wide application in the transportation and storage industries. For reactors, strippers, and condensers in urea service steels with higher chromium and nickel contents with nil ferrite have been developed. Modified compositions of AISI 310 steel such as SANDVIK 2RE69 and Assab 725 LN have been developed for strong oxidizing conditions in fertilizer plants. For elevated-temperature applications in furnaces, and hydrocarbon and steam reformers, where higher

creep strength is also necessary, casting alloys such as HK-40 and IN657 have been developed. Duplex stainless steels were developed to combine the attractive properties of ferritic and austenitic stainless steels. In simple terms, the ferrite could be said to provide mechanical strength and stress corrosion resistance, while the austenite provides ductility and the two combine to produce a fine-grained, twophase microstructure with high strength and good corrosion resistance. Of the many alloying elements Cr and Mo enhance the formation of ferrite, while Ni and N stabilize the austenite. Resistance to pitting and crevice corrosion in chloride environments is increased, expressed by the pitting resistance equivalent PREN = %Cr + 3.3 × %Mo + 16 × %N. This number is used to rank materials according to their expected resistance to pitting corrosion. A 23% Cr Mo-free grade would have a PREN value of about 25. Regular Mo-alloyed duplex grades have a PREN value of 30–36. Steels having a PREN value higher than 40 are normally defined as super-duplex stainless steels. Welding Duplex stainless-steel welds with matching composition filler material show high ferrite levels, which has low toughness and poor ductility. Therefore all welding consumables for duplex materials are over-alloyed with nickel, which allows more austenite to form so that the ferrite level in welds is lowered and the welds have good ductility and corrosion resistance. It is recommended to achieve a ferrite content of approximately 22–70%; equivalent to 30–100 FN (ferrite number). In addition to the ferrite count, a corrosion test in ferric chloride is also carried out as per ASTM G48, which gives a good assessment of the corrosion resistance of the weld metal. As per this test, the critical pitting temperature (CPT) is specified at 22 ◦ C for duplex and 35 ◦ C for super-duplex steel. Preheating of duplex material is not required except where heavy loads on high-ferrite-containing welds may cause cracking. Post-welding solution annealing is required only in cases where the resultant weldment has deteriorated due to detrimental phase transformation and/or has high ferrite levels. Root passes of nitrogen-alloyed stainless steel are welded with higher-alloyed filler, to compensate for the influence of nitrogen. Urea-grade stainless steels and steels in hightemperature applications are welded with matching composition electrodes enriched with 4–5% manganese to counteract the tendency for microfissuring.

963

Part B 11.6

actual content of Cr–Ni–Fe and C. Gamma or austenitic stainless steel is an iron alloy containing at least 18% Cr and 8% Ni with carbon up to 0.10%. The austenitic structure provides a combination of excellent corrosion resistance, oxidation, and sulfidation resistance with high creep resistance, toughness and strength at temperatures up to 550 ◦ C. The 18Cr–8Ni stainless alloys form a series known as the American Iron and Steel Institute (AISI) type 300 series, with varying amounts of carbon, molybdenum, and titanium added. The 18–8 series have good formability besides being readily weldable without stress relief; however they can be hardened by cold working. These steels are susceptible to grain-boundary chromium carbide precipitation, known as sensitization, when subjected to a temperature range of 535–800 ◦ C. To prevent sensitization, low-carbon grades (C < 0.03%) and stabilized grades with added columbium or titanium are used. The traditional grades of stainless steel that are extensively used in the fabrication of chemical plant and equipment are AISI 304 type and the 2% molybdenumbearing 316 types along with their low-carbon versions 304L and 316L or the stabilized grades 321 (with Ti) or 347 (with Cb) where intercrystalline corrosion is to be avoided. Higher-alloyed grades such as AISI 309 and 310 have a higher chromium content that makes them suitable for high-temperature applications such as furnace liners, preheaters and column trays.

11.6 Material of Construction

964

Part B

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Part B 11.6

11.6.6 Ferritic and Martensitic Steels Ferritic steels are chromium–iron stainless steel with little or no nickel and form a body centric structure unlike the face-centered austenitic steel. When ferritic steels are modified by heat treatment, they become hardened and form martensitic steels. Martensitic steels derive their excellent hardness from the high levels of carbon added to their alloy. The most commonly used martensitic steel is ASTM type 410 stainless steel used for column tray and tower lining in crude service for refinery applications. The increased carbon level in 410 steel results in a much harder martensitic cutlery steel or tool steel type 420. By increasing the percentage of chromium, transformation hardening is suppressed, as in ASTM types 430 and 446, which are essentially ferritic. These steels are resistant to chloride stress corrosion cracking; however they are subject to ductile–brittle temperature embrittlement, thereby restricting their mechanical properties. The limiting values for X and J factor are usually specified for welding consumables, although it would be preferable also to restrict these for the base material. A step-cooling simulation treatment is performed on higher-thickness quench and tempered plates to determine susceptibility to embrittlement phenomenon in terms of meeting the specified shift in the 40 ft − lb charpy V-notch (CVN) transition temperature. Welding With increasing base and weld material strength and hardenability, hydrogen diffusibility in the weldment is kept below 5 ml/100 g of deposited weld metal. The flux covering of all electrodes is of the low-hydrogen type and employs binders that give high resistance to moisture absorption. Prior to use, they are dried or baked at the manufacturer’s recommended temperature. Although there are several theories for determining the optimum preheat temperature, the common industrial practice is to use carbon equivalent as guidance to select the temperature, as shown here

CE < 0.4 < 0.55 < 0.70 < 0.8 < 0.9

Temperature ◦ C 50 100 150 200 250

Maintaining the preheat after welding (also called post-heating) for a specified period (generally 300– 350 ◦ C for 30 min) in some cases (say for pipe thicknesses greater than 12 mm with a chromium content of 2–7%) also helps to reduce hydrogen levels, thereby preventing cold cracks and stress corrosion cracking. Martensitic steels can be welded but caution needs to be exercised as they will produce a very hard and brittle zone adjacent to the weld. Cracking in this zone can occur (particularly in thicker sections) and therefore preheating and PWHT is recommended. Though ferritic steels are less prone to cracking due to their lower strength and non-hardenability, the weldment suffers from excessive grain growth, sensitization and a lack of ductility. Due to the excessive grain growth problem, only thin-gauge sheets are generally used. Filler material can be of either a similar composition, or alternatively an austenitic grade can be used to help weld toughness and increase ductility. Table 11.11 lists some of the comparable standards for stainless-steel grades commonly used in the fabrication of pressure vessel. Developments Since the ferritic grades do not possess good welding properties, hybrid utility ferritics such as 3CR12 with controlled martensite (dual phase steel) have been developed to overcome these welding difficulties. Using new steel-refining techniques, along with the addition of titanium or niobium, it has been possible to develop extremely corrosion-resistant grades such as superferritic stainless steel.

11.6.7 Copper and Nickel Base Alloys Brass Brasses are commercially produced with varying percentages of copper and zinc to provide a range of properties depending on the end-use requirements. Admiralty brass, which is widely used for tubes in water-cooled condensers for low water speeds, is an alloy brass containing 71% Cu, 28% Zn, and 1% Sn. To prevent dezincification, small amounts of arsenic, phosphorous or antimony are added. At high water speeds and when seawater contains air bubbles, aluminum brass containing 2% Al is more suitable due to the formation of a protective film. For tube plates in condensers and exchangers, it is usual practice to use high-zinc brasses, hot-rolled Muntz metal (60% Cu, 40% Zn) or Naval brass (60% Cu, 39% Zn,

Pressure Vessels and Heat Exchangers

11.6 Material of Construction

Structure

Austenitic

Martenstitic

Ferritic

Precipitationhardening steel

Hardenability

Hardenable by cold work

Hardenable by heat treatment

Nonhardenable

Agehardenable

ASTM 240 Grade

UNS No.

EN 10028-7 Grade

Number

Analysis built up from basic type

304

S 30400

X5CrNi18-10

1.4301

304L 308

S 30403 S 30800

X2CrNi18-10 X2CrNiMo8-14-3

1.4303 1.4432

309 310

S 30900 S 31000

X2CrNiCuWN25-7-4 X5CrNi25-21

1.4501 1.4335

316

S 31600

X5CrNiMo17-11-2

1.4401

316L 316N

S 31603 S 31603

X5CrNiMo17-12-2 X2CrNiMoN17-11-2

1.4404 1.4406

321

S 32100

X6CrNiTi18-10

1.4541

347

S 34700

X6CrNiNb18-10

1.4550

410

S 41000

X12Cr13

1.4006

Cr 18% + Ni 8% basic type 304 with low carbon Higher Cr and Ni for more corrosion and scaling resistance Still higher Cr and Ni Highest Cr and Ni (Cr 25% + Ni 20%) Mo added for corrosion resistance 316 with low carbon 316 with nitrogen added for low-temp. service Ti added to avoid carbide precipitation Cb added to avoid carbide precipitation Cr 12% basic type

420

S 42000

X46Cr13

1.4034

431

S 43100

X4CrNiMo16-5-1

1.4418

405

S 40500

X6CrAl13

1.4402

430 442

S 43000 S 44200

X6Cr17

1.4016

446

S 44600

17-7 PH

S 17700

X7CrNiAl17-7

1.4568

14-8MoPH

S 13800

X8CrNiMoAl15-7-2

1.4532

and 1% Sn) to take advantage of higher tensile strength, although the two-phase structure of these alloys cannot be satisfactorily inhibited against dezincification. Bronze Bronze is a tin alloy of copper with other elements such as aluminum added for additional properties. Because of the hardening effect of tin, hot-rolled bronze plates have greater strength than brass plates and therefore can be used for tube plates and channel material for exchangers.

Higher C, cutlery application Higher Cr and Ni added for improved ductility Al added to Cr 12% to prevent hardening Cr 17% basic type Higher Cr to resist oxidation and sulfidation at higher temperature

Cu–Ni Alloys Alloys of copper and nickel have historically been used in saltwater condensers as they show better resistance to saltwater than brasses. Increasing nickel content was found to be beneficial and 30% Ni alloy was adopted as the standard for naval vessels. The addition of iron and Mn was found to improve resistance to impingement attack. These alloys are used as tubes for heat exchangers, saltwater pipelines, and hydraulic lines as well as for several applications in marine and offshore

Part B 11.6

Table 11.11 Comparative chart for various stainless-steel grades

965

966

Part B

PARTMARK

Part B 11

platform services. Cupronickel tubes are superior to brass in terms of better resistance to dezincification for applications involving higher metal temperature of water-cooled exchangers. They are also excellent materials for tube plates and, because of their good formability and weldability, they can be used in sheet form for the fabrication of heat-exchanger shells and water boxes. Monel, a nickel-copper alloy (67% Ni, 30% Cu) has good resistance to saltwater, and to hydrochloric and hydrofluoric acid under nonoxidizing conditions. Therefore they are excellent material for cladding and trays in towers handling acid vapors. Other Nickel-based alloys are classified as: 1. Chromium bearing as in Inconel 600, and Hastelloy C-22 and C-276; 2. Containing chromium and molybdenum such as Inconel 625, Hastelloy B, Incoly 825; 3. Precipitation hardening alloys such as Monel K500, and Inconel 817. These alloys show excellent resistance to pitting, stress corrosion cracking in chloride environments and retain strength at elevated temperatures. Therefore they are excellent candidates for exchanger tubes, heat-transfer plates for plate heat exchangers (PHE), and pressure coils for steam/hydrocarbon reformers, naphtha-cracking furnaces etc. in the petrochemical and fertilizer industries.

Welding Gas tungsten arc (GTAW), gas metal arc (GMAW), and shielded metal arc (SMAW) processes are most commonly used for welding brasses and bronze. Whereas thin gauges are welded with GTAW using zinc-free fillers, heavier gauges are joined by a GMAW/SMAW process using zinc-free silicon bronze or aluminum bronze fillers/electrodes. Zinc-free fillers are prescribed since the evolution of zinc fumes makes the weld porous and affects visual observation of the welding process; moreover zinc fumes are extremely hazardous to health. Argon and helium, either individually or in combination, are used for shielding in the case of the GTAW/GMAW process. Welding consumables for welding of all Cu–Nibased alloys are available with compositions matching the specific parent material with the generous addition of manganese and/or niobium, which are added intentionally to give resistance to hot cracking and to raise hot strength. Most of these consumables are often used for dissimilar metal welding between the nickel base and most steels or between other ferrous and nonferrous alloys. Carbon and silicon are controlled to low levels to minimize detrimental precipitates in the weld metal and HAZ for electrodes with specifications matching with some of the high-molybdenum alloys such as Hastelloy C276 and Hastelloy B.

References 11.1 11.2 11.3

J.F. Harvey: Theory and Design of Pressure Vessels (Van Nostrand Reinhold, Amsterdam 1985) D.R. Moss: Pressure Vessel Design Manual (Gulf, Houston 1987) H.H. Bednar: Pressure Vessel Design Handbook (Van Nostrand Reinhold, Amsterdam 1986)

11.4

11.5

C. Matthews: Engineer’s Guide to Pressure Equipment – The Pocket Reference (Professional Engineering, Suffolk 2001) G. Baylac, D. Koplewicz (Eds.): EN 13445 Unfired Pressure Vessels – Background to the Rules in Part 3 Design (UNM, Paris 2002), (Issue 2 download from www.unm.fr)

967

Turbomachin 12. Turbomachinery

The following chapter consists of two sections. Section 12.1 presents a concise treatment of the theory of turbomchinery stages including the energy transfer in absolute and relative systems. Contrary to the traditional approach that treats turbine and compressor stages of axial, radial or mixed configurations differently, these components are treated from a unifying point of view. Section 12.2 is dedicated to steady and unsteady performance of gas turbine engines, where the components are treated as generic modules. Thus, any arbitrary power generation or aircraft gas turbine engine with single or multiple shafts can be composed of these modules. Several examples show, how different gas turbine configurations can be constructed and dynamically simulated. Finally, a section about the new generation gas turbines shows, how the efficiency of gas turbines can be improved far beyond the existing level. This chapter is based on [12.1], where the reader finds detailed explanation of relevant aerodynamic aspects of turbomachines, their component losses and efficiencies, and the design and off-design performance calculations.

12.1 Theory of Turbomachinery Stages........... 967 12.1.1 Energy Transfer in Turbomachinery Stages ............ 967 12.1.2 Energy Transfer in Relative Systems 968

12.1.3 General Treatment of Turbine and Compressor Stages ................ 12.1.4 Dimensionless Stage Parameters ... 12.1.5 Relation Between Degree of Reaction and Blade Height for a Normal Stage Using Simple Radial Equilibrium ............ 12.1.6 Effect of Degree of Reaction on the Stage Configuration ........... 12.1.7 Effect of the Stage Load Coefficient on Stage Power ........................... 12.1.8 Unified Description of a Turbomachinery Stage ........... 12.1.9 Special Cases .............................. 12.1.10 Increase of Stage Load Coefficient: Discussion ..................................

969 972

973 975 975 976 979 979

12.2 Gas Turbine Engines: Design and Dynamic Performance .......... 981 12.2.1 Gas Turbine Processes, Steady Design Operation ........................ 981 12.2.2 Nonlinear Gas Turbine Dynamic Simulation ................................. 989 12.2.3 Engine Components, Modular Concept, and Module Identification 990 12.2.4 Levels of Gas Turbine Engine Simulations, Cross Coupling .......... 992 12.2.5 Nonlinear Dynamic Simulation Case Studies ............................... 996 12.2.6 New Generation Gas Turbines, Detailed Efficiency Calculation ...... 1007 References .................................................. 1009

12.1 Theory of Turbomachinery Stages 12.1.1 Energy Transfer in Turbomachinery Stages Energy transfer in turbomachinery is established by means of a number of stages. A turbomachinery stage

consists of a row of fixed, guide vanes called stator blades, and a row of rotating blades termed the rotor. To elevate the total pressure of a working fluid, compressor stages that partially convert the mechanical energy into potential energy are used. According to the law of conservation of energy, this energy increase requires

Part B 12

Meinhard T. Schobeiri

Turbomachinery

Since for the stage type under consideration, V1 = V3 and U2 = U3 , (12.16) can be simplified as r=

W32 − W22 2 W3 − W22 + V22 − V32

.

(12.17)

This result can also be obtained by decomposing the Euler equation of motion [12.1, Chap. 3, Eq. (3.46)] for inviscid flows into its three components in a cylindrical coordinate system. The Euler equation is expressed as 1 V · ∇V = − ∇ p . ρ

V2 = e1 (Wu2 + U2 ) + e2 Wm2 ,

V32

= (Wu3 + U3 )

2

2 + Wm3

,

The assumptions needed to arrive at (12.23) are (12.18)

∂Vr ∂Vr  0 , axial symmetric: =0, ∂R ∂ϕ With these assumptions, (12.24) yields

1 Wu3 − Wu2 . 2 U

(12.21)

12.1.5 Relation Between Degree of Reaction and Blade Height for a Normal Stage Using Simple Radial Equilibrium In axial flow compressors or turbines, the working fluid has a rotational and translational motion. The rotating fluid is subjected to centrifugal forces that must be balanced by the pressure gradient in order to maintain the radial equilibrium. Consider an infinitesimal sector of an annulus with unit depth containing the fluid element which is rotating with tangential velocity Vu . The centrifugal force acting on the element is shown in Fig. 12.8. Since the fluid element is in radial equilibrium, the centrifugal force is obtained from dF = dm

Vu2

(12.22)

R with dm = ρ R dR dφ. The centrifugal force is kept in balance by the pressure forces dρ d p Vu2 =p . dR dρ R

V2 1 ∂p = u . ρ ∂R R

(12.20)

Rearranging (12.20) yields the final relationship for the particular stage we introduced above r=

∂Vr 0. ∂z (12.26)

(12.19)

Using (12.18) and (12.19), (12.17) gives 2 − W2 Wu3 W32 − W22 u2 = . r= 2U(Wu2 + Wu3 ) 2U(Wu2 + Wu3 )

∂Vr ∂Vr ∂Vr Vu2 1 ∂p + Vu + Vz − =− . ∂R R∂ϕ ∂z R ρ ∂R (12.25)

since U2 = U3 = U , V22 − V32 = W22 − W32 + 2UWu2 + 2UWu3 .

(12.24)

In the radial direction Vr

2 V22 = (Wu2 + U2 )2 + Wm2 , V3 = e1 (Wu3 + U3 ) + e2 Wm3 ,

(12.23)

973

(12.27)

Equation (12.27) is identical with (12.23). Calculation of a static pressure gradient requires additional information from the total pressure relation. For this purpose, we apply the Bernoulli equation neglecting the gravitational term 1  1 2 . (12.28) P = p + ρV 2 = p + ρ Vu2 + Vax 2 2 Using (12.28), the change in radial direction is dVu dVax d p0 dp (12.29) = + ρVu + ρVax . dR dR dR dR If the stagnation or total pressure P = p0 = const and Vax = const, (12.29) yields dVu dp + ρVu =0, dR dR

or

dVu dp = −ρVu . dR dR (12.30)

Equating (12.30) and (12.23) results in Vu

dVu Vu2 + =0 dR R

(12.31)

or dVu dR + =0. Vu R

(12.32)

The integration of (12.32) leads to Vu R = const. This type of flow is called free vortex flow and fulfills the requirement to be potential flow, ∇ × V = 0. We use

Part B 12.1

The velocity vectors and the corresponding kinetic energies are determined from the stage velocity diagram in connection with the angle and direction convention as follows

12.1 Theory of Turbomachinery Stages

Turbomachinery

the compressor or turbine designer. Equations (12.50– 12.53) can be expressed in terms of the flow angles α2 , α3 , β2 , and β3 , which lead to a set of four nonlinear equations μ2 φ2 (1 − ν2 ) cot2 α2 + 2μν φ λ cot α2 − λ2

Vm2 /Vm3 = 1. The flow angles are calculated from   1 λ −r +1 , cot α2 = φ 2   1 λ cot α3 = (12.57) − −r +1 . φ 2 The stage load coefficient is calculated from

φ2 (1 − ν2 ) cot2 α3 + 2φ λ cot α3 + λ2

λ = φ(cot α2 − cot β3 ) − 1 for ν = 1 and μ = 1 .

− 2(1 − r)λν2 + (μ2 − 1)φ2 ν2 = 0 ,

(12.58)

(1 − ν2 )(μ φ cot β2 + ν)2 + 2ν λ(φ μ cot β2 + ν) − λ2 − 2(1 − r)λ + (μ2 − 1)φ2 = 0 , (1 − ν )(φ cot β3 + 1) + 2λ(φ cot β3 + 1) + λ 2

2

− 2(1 − r)λν2 + (μ2 − 1)φ2 ν2 = 0 .

2

(12.54)

12.1.9 Special Cases Equations (12.50–12.54) are equally valid for axial, radial, and mixed flow turbine and compressor stages. Special stages with corresponding dimensionless parameters are described as special cases as listed below. Case 1: Constant Mean Diameter In this special case, the diameter remains constant, leading to the circumferential velocity ratio of ν = U2 /U3 = 1. The meridional velocity ratio is μ = Vm2 /Vm3 = 1. The flow angles expressed in terms of other dimensionless parameters are   1 λ φ2 2 + (1 − r) − (μ − 1) , cot α2 = φμ 2 2λ   1 φ λ − − (1 − r) − (μ2 − 1) , cot α3 = φ 2 2λ   1 λ φ2 2 cot β2 = + (1 − r) − (μ − 1) − 1 , μφ 2 2λ   1 φ λ − + (1 − r) − (μ2 − 1) − 1 . cot β3 = φ 2 2λ (12.55)

The stage load coefficient is calculated from λ = φ(μ cot α2 − cot β3 ) − 1

for ν = 1 and μ = 1 . (12.56)

Case 2: Constant Mean Diameter and Meridional Velocity Ratio In this special case, the circumferential and meridional velocities are equal, leading to ν = U2 /U3 = 1 , μ =

979

The generalized stage load coefficient for different μ, νcases can be summarized as λ = φ[μν cot α2 − cot β3 ] − 1 λ = φ[μ cot α2 − cot β3 ] − 1 λ = φ[ν cot α2 − cot β3 ] − 1 λ = φ[cot α2 − cot β3 ] − 1

for ν = 1 and μ = 1 , for ν = 1 and μ = 1 , for ν = 1 and μ = 1 , for ν = 1 and μ = 1 . (12.59)

12.1.10 Increase of Stage Load Coefficient: Discussion Following the discussion in Sect. 12.1.3 regarding the increase of the specific stage mechanical energy and the subsequent discussion in Sect. 12.1.8, we proceed with (12.53), where the stage load parameter λ is expressed in terms of μ and ν and the blade angle α2 and β3 as λ = φ(μν cot α2 − cot β3 ) − 1 .

(12.60)

The effect of flow deflection on the stage load coefficient of axial flow turbines was already discussed in Sect. 12.1.8. As we saw, turbine blades can be designed with stage load coefficients λ as high as 3 or more. In turbine blades with high λ and Reynolds numbers Re = Vexit c/ν > 150 000, the governing strong negative pressure gradient prevents major separation from occurring in the flow. However, if the same type of blade operates at lower Reynolds numbers, flow separation that results in a noticeable increase of profile losses may occur. For high-pressure turbines (HPT), the strong favorable pressure gradient within the blade channels prevents major separation from occurring in the flow. However, low-pressure turbine (LPT) blades, particularly those of aircraft gas turbine engines that operate at low Reynolds numbers (cruise conditions up to Re = 120 000), are subjected to laminar flow separation and turbulent reattachment. While axial turbine blades can be designed with relatively high positive λ,

Part B 12.1

− 2(1 − r)λ + (μ2 − 1)φ2 = 0 ,

12.1 Theory of Turbomachinery Stages

Turbomachinery

ward lean, however, reduces the flow deflection Θ and ΔVu . As a result, the stage load coefficient λ is reduced. For the comparison, the radial exit case with β3 = 90◦ is plotted. In calculating the stage load coefficient λ, the influence of the radius ratio ν = R2 /R3 = U2 /U3 on the stage load coefficient becomes clear.

12.2 Gas Turbine Engines: Design and Dynamic Performance A gas turbine engine is a system that consists of several turbomachinery components and auxiliary subsystems. Air enters the compressor component, which is driven by a turbine component that is placed on the same shaft. Air exits the compressor at a higher pressure and enters the combustion chamber, where the chemical energy of the fuel is converted into thermal energy, producing combustion gas at a temperature that corresponds to the turbine inlet design temperature. The combustion gas expands in the following turbine component, where its total energy is partially converted into shaft work and exit kinetic energy. For power generation gas turbines, the shaft work is the major portion of the above energy forms. It covers the total work required by the compressor component, the bearing frictions, several auxiliary subsystems, and the generator. In aircraft gas turbines, a major portion of the total energy goes toward generation of high exit kinetic energy, which is essential for thrust generation. Gas turbines are designed for particular applications that determine their design configurations. For power generation purposes, the gas turbine usually has a single spool. A spool combines a compressor and a turbine that are connected together via a shaft. Figure 12.17 exhibits a single-spool power generation gas turbine, where a 14-stage compressor shares the same shaft with a three-stage turbine. While in power generation gas turbine design the power-to-weight ratio does not play an important role, the thrust-to-weight ratio is a primary parameter in designing an aircraft gas turbine. High-performance aircraft gas turbine engines generally have twin-spool or multispool arrangements. The spools are usually rotating at different angular velocities and are connected with each other aerodynamically via air or combustion gas. Figure 12.18 exhibits a typical high-performance twin-spool aircraft gas turbine with a ducted front fan as the main thrust generator. Gas turbine engines with power capacities less than 20 MW might have a split

shaft configuration that consists of a gas generation spool and a power shaft. While the turbine of the gas generation spool provides the shaft work necessary to drive the compressor, the power shaft produces the net power. In addition to the above design configurations, a variety of engine derivatives can be constructed using a core engine as shown in Fig. 12.19.

12.2.1 Gas Turbine Processes, Steady Design Operation Starting with the single-spool power generation gas turbine that consists of a multistage compressor, a combustion chamber, and a turbine, the h–s diagram is shown in Fig. 12.20a. The compression process from 1 to 2 is accomplished by the compressor with a polytropic efficiency ηpol that can be accurately calculated using the rowby-row or stage-by-stage methods discussed in [12.6]. The combustion process from 2 to 3 is associated with certain total pressure loss coefficient ζcomb , thus it is not considered isobaric. The expansion process from 3 to 4 causes an entropy increase that is determined by the turbine efficiency. Figure 12.20b shows the h–s diagram for a twin-spool aircraft engine. In contrast to the single-spool engine, the compression process is accomplished by two compressors that are operating at two different angular velocities. Air enters the low-pressure (LP) compressor driven by the LP turbine and is compressed from 1 to 2. Further compression from 2 to 3 occurs in the high-pressure compressor (HP compressor) driven by the HP turbine. After addition of fuel in the combustion chamber, the fist expansion occurs in the HP turbine, whose power exactly matches the sum of the HP compressor power and the power required to compensate bearing frictions. The second expansion in the LP turbine matches the power by the LP compressor, bearing friction, and the auxiliary subsystems. In off-design operation, there is always a dynamic

981

Part B 12.2

impellers have the same diameter ratio ν and the same rotational speed ω. The λ-behavior of these impellers is shown in Fig. 12.16, where the relative exit flow angle is varied in the range of β3 = 80◦ − 105◦ . As shown, forward lean results in higher deflection Θ, larger ΔVu , and thus higher negative λ, which is associated with a higher profile loss. Back-

12.2 Gas Turbine Engines: Design and Dynamic Performance

Turbomachinery

(12.75)

Equation (12.75) in dimensionless form yields  T2 1  mc πc − 1 , = 1+ T1 ηc  T4 T3 T3

= − ηT 1 − (πc )−m T . (12.76) T1 T1 T1 Introducing the temperature ratio θ = T3 /T1 , the temperature ratio T4 /T1 (12.76) becomes   

T4 = θ 1 − 1 − (πc )−m T ηT . (12.77) T1 To determine the temperature ratio T5 /T1 , we rearrange (12.74) to obtain   T4 T2 T2 T5 + = ηR − . (12.78) T1 T1 T1 T1 Using (12.76) and (12.77), (12.78) can be rearranged to  

  T5 = ηR θ 1 − 1 − (πc )−m T T − 1 T1    1  mc 1  mc π −1 +1+ π −1 . − ηc c ηc c

From (12.80) special cases are obtained. Setting ηR = 0 gives the thermal efficiency of a gas turbine without recuperator. The ideal case the of Brayton cycle is obtained by setting all loss coefficients equal to zero, all efficiencies equal to unity, and c¯ PC = c¯ PCC = cPT = const. Equation (12.80) properly reflects the effects of individual parameters on the thermal efficiency and can be used for preliminary parameter studies. As an example, Fig. 12.8 shows the effect of pressure ratio, the turbine inlet temperature, and the component efficiency on thermal efficiency for two different cases. As Fig. 12.24 shows, for each turbine inlet temperature, there is one optimum pressure ratio. For temperature ratios up to θ = 3.5 pronounced efficiency maxima are visible within a limited π-range. When approaching higher inlet temperature, however, this range widens significantly. For a gas turbine without recuperator, the thermal efficiency (the solid curves in Fig. 12.24) shows that, for θ = 4.0, increasing the pressure ratio above 15 does not yield a noticeable efficiency increase. However, this requires the compressor to have one or two more stages. The temperature ratio θ = 4.0 corresponds to a turbine inlet temperature of T3 = 1200 K at a compressor inlet temperature of T1 = 300 K. The dashed curves in Fig. 12.24 indicate that tangibly higher thermal efficiencies at a substantially lower pressure ratio can be achieved by utilizing recuperators. This is particularly advantageous for small gas turbines (so called microturbines) with power ranging from 50 to 200 kW. The required low maximum pressure ratio can easily be achieved by a single-stage centrifugal compressor. Comparing cases 1 and 2 in Fig. 12.24 shows that thermal efficiency reduces if low-efficiency components are applied.

(12.79)

Introducing (12.79) and the definition θ = T3 /T1 into (12.73), the thermal efficiency equation for a gas turbine with a recuperator is written as  

ηth = c¯ PT ηT θ 1 − (πc )−m T (1 + β)   m  1 c − c¯ Pc πc − 1 η c  × c¯ PCC θ(1 + β − ηR )    1  mc πc − 1 (1 − ηR ) − 1+ ηc 

  −1 + θηR ηT 1 − (πc )−m T . (12.80)

Improvement of Gas Turbine Thermal Efficiency The above parameter study indicates that, for a conventional gas turbine with a near-optimum pressure ratio with or without a recuperator, the turbine inlet temperature is the parameter that determines the level of thermal efficiency. For small-size gas turbines, the recuperator is an inherent component of the gas turbine. For large power generation gas turbines, however, this is not a practical option. Using a recuperator in a large gas turbine requires a significantly lower pressure ratio, which results in a large-volume recuperator and turbine. As a result, in order to improve the thermal efficiency of conventional gas turbines, increasing the turbine inlet temperature seems to be the only option left. Considering this fact, in the past three decades,

987

Part B 12.2

The turbine inlet temperature T3 and the environmental temperature T1 , and thus their ratio T3 /T1 , is considered as a known parameter. This parameter can also be used for parametric studies. Therefore it is desirable to express the ratio T5 /T1 in terms of T3 /T1 . We find this ratio by utilizing the recuperator effectiveness ηR h5 − h2 T5 − T2 ηR =  . (12.74) h4 − h2 T4 − T2 From the compressor and turbine energy balance in (12.61) we find 1  1 , T2 = T1 + (T2s − T1 ) = T1 + T1 πcm c − 1 ηc ηc

 T4 = T3 − (T3 − T4s )ηT = T3 − T3 1 − (πc )−m T ηt .

12.2 Gas Turbine Engines: Design and Dynamic Performance

996

Part B

Applications in Mechanical Engineering

Part B 12.2

compressor stages and simultaneously calculates the blade temperatures. For the combustion chamber, primary air, secondary combustion gas, and metal temperature are calculated. Dynamic calculations are performed throughout the simulation, whereas the modules are coupled by plena. Each module is described by differential and algebraic equations. The details of information delivered by this level and degree of complexity is demonstrated by the following example. The first two stages of a four-stage turbine component of a highperformance gas turbine engine must be cooled. For the first four turbine rows we use the diabatic expansion process that requires three differential equations for describing the primary flow, three differential equations for describing the cooling flow, and one differential equation for describing the blade temperature. This leads from two cooled turbine stages to 28 differential equations. The generic structure allows to cross-couple levels 1 to 3. For example, we wish to simulate a gas turbine engine with a global compressor performance map, but need to obtain detailed information about turbine blade temperature, which is necessary to calculate the relative expansion between the blades and the casing, then we may use the diabatic calculation method. In this case, we cross-couple the first- and third-level simulation.

12.2.5 Nonlinear Dynamic Simulation Case Studies Three case studies dealing with three completely different gas turbine systems are presented. Table 12.1 shows the matrix of the cases where the engine types and transient-type simulations are listed. These studies demonstrate the capability of the generic structured method discussed in [12.6] to simulate complex systems

dynamically and with high accuracy. The case studies presented in this chapter are related to real-world engine simulation and are intended to provide the reader with an insight into nonlinear engine dynamic simulation. The selected cases ranging from zero-spool, single-shaft power generation to three-spool four-shaft thrust and power generation gas turbine engines provide detailed information about the engine behavior during design and off-design dynamic operation. For each engine configuration the simulation provides aerothermodynamic details of each individual component and its interaction with the other system components. Since the presentation of the complete simulation results of the three cases listed in Table 12.1 would exceed the scope of this chapter, only a few selected plots will be displayed and discussed for each case. Case Study 1: Compressed Air Energy Storage Gas Turbine The subject of this case study is a zero-spool, singleshaft compressed air energy storage (CAES) gas turbine [12.1], which is utilized to cover peak electric energy efficiently demand during the day. Continuous increases of fuel costs have motivated the power generation industry to invest in technologies that result in fuel saving. Successful introduction of combined cycle gas turbines (CCGT) has drastically improved the thermal efficiency of steam power plants, which is equivalent to a significant fuel saving. Further saving is achieved by using the excess electrical energy available during the period of low electric energy demand (6–8 h during the night) to compress air into a large storage system. During periods of peak demand, the compressed air is injected into the combustion chambers and mixed with the fuel. After the ignition process is completed, the high-pressure high-temperature gas expands in the turbine, generating electric energy for about 2–4 h. In contrast to a CCGT, the period of operation of a CAES

Table 12.1 Simulation case studies

Tests

Gas turbine type

Transient type

Case 1

CAES: Compressed air energy storage power generation gas turbine engine, zero-spool, single shaft, two turbines, two combustion chambers. Single-spool, single-shaft, power generation gas turbine engine, BBCGT9. Three-pool, four-shaft, thrust and power generation core engine.

Generator and turbine shut down.

Case 2 Case 3

Adverse load changes. Operation with fuel schedule.

1010

Part B

Applications in Mechanical Engineering

12.7

12.8

M.T. Schobeiri: The ultra-high efficiency gas turbine engine with stator internal combustion, UHEGT Patent 1389-TEES-99 (1999) M.T. Schobeiri, S. Attia: Advances in nonlinear dynamic engine simulation technology, ASME 96GT-392, Int. Gas Turbine Aero-Engine Congress Exposition (Birmingham 1996)

12.9

M.T. Schobeiri, M. Abouelkheir, C. Lippke: GETRAN: A generic, modularly structured computer code for simulation of dynamic behavior of aeroand power generation gas turbine engines, ASME Trans. J. Gas Turbine Power 1, 483–494 (1994)

Part B 12

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Gritt Ahrens, Torsten Dellmann, Stefan Gies, Markus Hecht, Hamid Hefazi, Rolf Henke, Stefan Pischinger, Roger Schaufele, Oliver Tegel 13.1 Overview.............................................. 1012 13.1.1 Road Transport – Vehicle Technology and Development ...... 1015 13.1.2 Aerospace – Technology and Development ...................... 1019 13.1.3 Rail Transport – Rail Technology and Development ...................... 1022 13.2 Automotive Engineering ....................... 1026 13.2.1 Overview ................................... 1026 13.2.2 Automotive Technology ............... 1032 13.2.3 Car Development Processes.......... 1049 13.2.4 Methods for Car Development ...... 1055 13.3 Railway Systems – Railway Engineering.. 1070 13.3.1 General Interactions of Modules of a Railway System with Surrounding Conditions ....... 1070 13.3.2 Track ........................................ 1076 13.3.3 Running Gears ........................... 1086 13.3.4 Superstructures .......................... 1091 13.3.5 Vehicles .................................... 1092 13.3.6 Coupling Systems ....................... 1092 13.3.7 Safety ....................................... 1093 13.3.8 Air Conditioning ......................... 1095 13.4 Aerospace Engineering.......................... 1096 13.4.1 Aerospace Industry ..................... 1096 13.4.2 Aircraft ..................................... 1096 13.4.3 Spacecraft ................................. 1098 13.4.4 Definitions ................................ 1098 13.4.5 Flight Performance Equations ...... 1108 13.4.6 Airplane Aerodynamic Characteristics ........................... 1109 13.4.7 Airplane General Arrangements ... 1114 13.4.8 Weights .................................... 1121 13.4.9 Aircraft Performance................... 1122 13.4.10 Stability and Control ................... 1131 13.4.11 Loads........................................ 1137 13.4.12 Airplane Structure ...................... 1140 13.4.13 Airplane Maintenance Checks ...... 1144 References .................................................. 1144 For general reading on automotive engineering, refer also to [13.1–5].

Part B 13

Transportation is derived from two Latin words trans and porta meaning in between and carrying, respectively. Transportation is seen as one of the basic human needs and has a significant impact on a country’s economy; productivity usually correlates well with the amount of transportation of goods and people. Transportation takes place on the ground, sea, and in the air and can be subdivided into the areas automotive, railway, naval, and aerospace. The respective engineering disciplines have gained increasing importance in the past as they face severe challenges for the future arising from: (i) increased transportation demand and customer needs, (ii) shortage of energy and rising fuel prices, and (iii) more stringent legislative requirements regarding for example pollutant and noise emissions and safety issues. Section 13.2 provides an overview of aspects of automotive engineering. It starts with a historical view of how cars have evolved over time until today. Section 13.2.2 covers automotive technology, first describing the different car types and the fundamental requirements for car development. The technological areas and corresponding components relevant to cars are then briefly explained according to their major functions, the requirements they have to fulfill, and the challenges for further development in the future. The car development process, with emphasis on the early phase where the car concept is defined and verified, is described in Sect. 13.2.3. Finally, some methods used in car development and cross-functional aspects to be covered in order to manage the car development process and meet the goals of a car development project are depicted. At the end of the Chapter, a list of references is provided which will enable the interested reader to obtain detailed information about the technological aspects of modern cars and their development.

Transport Systems

Fig. 13.19 Blended wing body (source: DLR)

aircraft in all the different flight regimes, in each of which the aircraft control behavior is different. Afterwards in a first attempt, this technology was introduced into the Airbus A310, until it finally became mature in the Airbus A320, which made its maiden flight in 1987. Flow control technology or artificial instability are other examples of technology development, and manufacturing technologies such as friction steer welding or laser beam welding, advanced bonding or surface coating have been developed in the past and are part of the production process today. Following the complete vehicle assembly, the vehicle will be operated in a larger system. Aircraft navigate with the help of air-traffic control, they are linked to other traffic in the air, and on the ground, especially in the vicinity of airports, they need to be loaded and unloaded and are part of a so-called intermodality concept that links personal and public transport on the ground with air or sea transport. Challenges in Aeronautical Engineering Looking at aeronautics’ history, it can be structured into three blocks. From its beginning until the end of World War II, physical understanding was the dominating driver. This began with daring pilots in fantastic flying machines, permanently hunting for records in range, speed, and altitude. As the next phase, coinciding with the introduction of jet engines, commercial aeronautics emerged. Many different configurations have been studied, such as vertical take-off and landing (VTOL) aircraft such as the Dornier Do 31, supersonic transport in the shape of Concorde, and flying wings such as the Northrop YB-49. This led to the third phase, which is based on today’s configuration of a commercial transport aircraft, all looking very much the same regardless of the manufacturing company. This configuration has reached a high level of maturity, so after all the expensive configuration studies, finally civil transport aircraft design and manufacture pays off. However, with the success of commercial transport, three other issues have emerged. Firstly, airports are increasingly operating at their capacity limits, so it is questionable whether there is any chance to increase air traffic, even if there is a demand for it. Secondly, linked to this, environmental aspects play a leading role. Even though the contribution of aeronautics to global emissions may be small, i. e., at about 2% today, it is debated very intensely. Thirdly, and still linked to growth, safety issues are of increasing importance. Today’s reliability rate of 10−9 failures per flight hour for critical components will not be sufficient if the number of aircraft

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Part B 13.1

step is the certification process, which ends with entry into service (EIS). The whole development process as outlined above is almost the same for any aircraft manufacturer, and can be seen as a series of milestones as shown in Fig. 13.18. At present, the market analysis may last for 2 years, the predevelopment for some 3 years, the development and manufacture for about 5 years, and the certification for another year. Just before the committed start of a programme, technology development may take place, with technology feasibility or prematurity as a first step, and technology application studies as the final step. Overall, the time between the first thought about a new aircraft and the EIS is approximately 10–15 years. For example, first thoughts on the Airbus A380 were published in 1989; at that time it was called the megaliner, ultra-high-capacity aircraft (UHCA). Later it became the very large commercial transport (VLCT, as a common Airbus–Boeing feasibility study. The committed programme start occurred in 2000, and finally the A380 was introduced into airline service in 2007, corresponding to a total of 18years. Of course, all manufacturers try to speed up this process. For the given and already highly optimized standard aircraft configuration, i. e., fuselage, wing, engines, and tailplane as for today’s aircraft, further optimization is possible mainly by improving the design chain, including supplier management. However, for a completely new design, such as a blended wing body (BWB) (Fig. 13.19) or an oblique flying wing (OFW), the exhaustive time scale as described above is likely to remain. Apart from monodisciplinary technologies such as a new material, a new actuator or a specific aerodynamic vortex generator, integrated technologies make their way into the product, too; for example, the fly-bywire technology was a must for the European supersonic transport aircraft Concorde in the 1960s. Without it, it would not have been possible for the pilots to fly this

13.1 Overview

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Part B 13.2

absorb some of the energy. Another important function of a coupling is data transmission. Conventional couplings just transmit the pneumatic signal and energy of the brake’s main air pipe. For passenger cars there is also an electric coupling that links the cars’ energy supply and various types of signal cables. In Europe the manually operated screw coupling is standard, offering the possibility to combine all cars without limitation. The advantage of standardization compensates for the disadvantage that the coupling cannot be automated. Automatic couplings in Europe are only fitted to multiple-unit trains in passenger service which have to be coupled solely with other units of similar type. In the USA and in the states of the former USSR automatic couplings are also used for conventional passenger and freight trains.

Shunting of freight trains is – because of the screwcoupling among others – very complicated and requires special shunting yards of huge dimensions. Due to shunting the average speed of a freight car in Germany is below 8 km/h despite the maximum speed of freight trains being 100 km/h loaded and 120 km/h empty. Within this introduction the significance of today’s transportation has been outlined, whereas increasing demand for commercial and recreational freight and passenger travel will enhance the importance of transportation as a highly interdisciplinary field. Transportation and its dependencies offers researchers multiple opportunities to optimize various aspects, i. e., cost, time, safety, and reliability. In this chapter however, the engineering involved in automotive, railway and aerospace will be described in more detail.

13.2 Automotive Engineering The development of cars differs from the development of other technical products. In this chapter it will be explained why this is the case from a general point of view. Furthermore it will be stated how the topic of automotive engineering is imparted. In principle, a car is a technical product such as a toaster, a refrigerator or a computer. All of these products are things used in everyday life.

13.2.1 Overview Today every technical device is subject to innovation, development, and production, which are the basics of engineering in general. However, there are differences between cars and their development compared with other technical products, which will now be described. First of all, a car is a highly complex product which has developed tremendously since the times it simply had to transport its load from one point to another. Today, the passenger and their satisfaction are the focus. The passenger is not only kept safe, dry, and warm but also entertained, informed, and even comforted in their seat. The function of transport seems to have become secondary. Still its realization has gained complexity too (Sect. 13.2.2). Buying a car is normally a highly individual process. Thousands of models of hundreds of brands are available. After having decided for a certain brand and a specific model again there are thousands of possibilities to configure one’s individual car (at least for premium European car brands).

Furthermore, a car is a mass product. Every year, millions of cars are produced and sold in countries all over the world. Characteristics of mass products are: (a) a high number of produced units per year, and (b) there is no direct customer for the development (i.e., there is only a customer for an individual car) but the company itself. Moreover, cars are durable products. About 20 years go by from the first idea to the recycling of cars, and some of the cars remaining at this point even start a second career as classics after this long period of time. In order to achieve this level of durability the development team has to have a look for the future: which features will be demanded 3–5 years later? How much is the customer willing/able to pay for the specific feature? Are the development departments of other OEMs working on similar features and what will the specifics of those be? Will there be regulations that might prohibit the use of this feature? Due to its complexity, required quality, and resulting high development and production costs the car is quite an expensive product. Because of the sum of these characteristics – that the car is an expensive, highly complex, and highly individualized mass product – a lot of jobs depend on the automotive industry, not only in many industrial countries. In Germany, for example, one-seventh of all jobs are directly or indirectly dependent on the car industry [13.12]. As a consequence, the automotive industry has a huge influence on society.

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everyone could buy a car. A pioneer in this field was Henry Ford. He developed a simple car that was cheap to produce and cheap to run – the Ford Model-T (the so called Tin Lizzy, Fig. 13.28). To achieve this goal, Ford used ideas which are still current: he lowered the producing costs with the introduction of new production methods (e.g., the assembly line), he simplified every component of the car (reaching two goals: greater reliability and lower production costs), and he restricted the variety of options available to choose from. Good Styling Wakes Desirability. After World War I

Part B 13.2

Fig. 13.28 1912 Ford Model-T roadster (copyright 1995– 1999 The Henry Ford Organization, Photo: P.833.38916)

shock absorber also demonstrated their reliability in car races. However, improving the chassis and body was only one way to win races; increasing the engine power was another. In the late 1890s and early 1900s the classic approaches for increasing the power of an engine were found: increasing the engine displacement, increasing the compression (which led to the development of higher-quality fuel types), improving the carburetor, including more valves into the cylinder head, locating camshafts above the cylinder head [overhead camshaft (OHC) engines], and so on. Increasing the motor power led to the development of better braking systems for all four wheels which was no natural thing first and optimized suspensions. Cars for Everyone: the Ford Model-T as an Example. At this stage, cars were still not affordable for most

people. Hence, one of the next main goals in car development was to find a way to build cars cheaper so that

(WWI), developing more reliable cars was not enough. Increasingly, the customer wanted to have an individual car to stand out from other motorists. This development was accelerated by cars such as the Tin Lizzy; if everyone had the same car, the demand for more individuality and outlining became increasingly important. Although there was still only one type of carriage – the frame body – emphasis was placed on a number of different body styles: phaetons (Fig. 13.29), tourers, town cars (Fig. 13.30), several styles of convertibles, convertible sedans, Pullman bodies with an extended number of seats, limousines with short and long wheelbase, roadsters, coupés, sedans, etc. The only limit for this kind of technology was the solvency of the customer. Of course, only very rich people had the means to choose whatever they want from this range, and order a car at an OEM-independent coach builder such as Gläser in Dresden, Castagna or Farina (later Pininfarina) in Italy, Park Ward in England or Saoutchik in France (Fig. 13.31). In the years following World War II (WWII) cars were optimized in three development dimensions: reliability, affordability, and eye-catching styling. WWII

Fig. 13.29 Mercedes 28-95 PS Phaeton (courtesy of Daim-

Fig. 13.30 1933 Mercedes-Benz 290 Cabriolet C (courtesy

lerChrysler)

of DaimlerChrysler)

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stopped car development throughout the world from about 1941 onwards; car companies changed into defense companies producing tanks, military trucks, jeeps, and even airplanes.

a)

a)

b)

Fig. 13.32a,b Two Mercedes-Benz 170 V; (a) 1936 Convertible A, (b) 1946 light truck (courtesy of Daimler-

Chrysler)

b)

Fig. 13.31a,b Mercedes-Benz Type 630 Modell K, body by Castagna (a) and Mercedes-Benz Type 630 Modell K, body by Farina, (b) both 1926 (courtesy of DaimlerChrysler)

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The pontoon-type body was built upon unit body cars, provided more space than the old-fashioned body types, and was much lighter than older designs. On the other hand, this body type strongly restricted the degrees of freedom with respect to individuality of body shaping because of the lack of a separate frame. Though the idea of the pontoon style and unit body soon showed their superiority, it took almost 10 years

Fig. 13.33 1947 Kaiser-Frazer

Part B 13.2

A New Start. After WWII many of the old European OEMs were not able to rise again. Some of them had lost their coach supplier (such as Adler) and were not able to produce. Others had lost their complete production plants as war reparations to the Soviet Union (Auto Union and BMW). Some OEMs had to reestablish themselves (such as DKW and BMW) in Western Germany. All of the cars produced at this time were mainly the same as those produced before WWII. Car development was thrown back years; the first goal mentioned in this paragraph, technical reliability, became once again the most important. In those days, it was not important to have a good-looking car, but one which was able to fulfill its function to transport people and goods (Fig. 13.32). As times improved, good design and affordability again became important development goals. A new body style was introduced by Kaiser-Frazer in 1946, the so-called pontoon-type body (Fig. 13.33).

13.2 Automotive Engineering

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a)

Part B 13.2

b) Fig. 13.35 1959 Cadillac Convertible (source: http://www. classic-cadillac.com, Classic Cadillac Community, Timmendorfer Strand)

Fig. 13.34 (a) Mercedes-Benz 170 S-V, (b) Mercedes-Benz 180 Pontoon (both 1953) (courtesy of DaimlerChrysler)

until the last companies switched their vehicle range. Mercedes-Benz, for example, even as late as 1955 sold a modern and an old-fashioned car in the same class (Fig. 13.34).

Transportation. Almost immediately all car companies optimized their current car types to pass the government security tests. Research was set up to develop safer cars. Research was expensive and so was changing current cars to pass new tests. This almost marked the end for many car companies that could not afford this kind of development or had car types in their programs that were not adaptable to the new rules. One class of cars was especially affected by this: the convertibles. The largest market for cars, the US market, stopped buying convertibles because they were considered unsafe (especially in the case of a rollover). As a result almost every OEM that served this market took convertibles out of their program. The casualty of this develop-

Styling Dominates Technical Issues. In the subsequent years the number of car body styles decreased, but styling exploded. Some companies, mainly those in the USA and their subsidiaries (such as Ford Germany and Opel) brought out new cars every year. The only new thing about these cars was the styling; technical issues were mainly the same – except that almost every car had large tail fins on the rear. The high point of this development was the 1959 Cadillac Convertible (Fig. 13.35). The Need for Safety Changes Car Development. In the mid 1960s, after the release of a book about car safety (Unsafe at any speed by Ralph Nader, Pocket Books, New York 1966), the US government took measures to make cars safer: cars had to pass standardized crash tests, which were tightened every 2–3 years. Every car company selling cars in the USA had to pass these tests in order to obtain the approval of the US Department of

Fig. 13.36 1976 MG Midget with US security bumpers

(source: http://en.wikipedia.org/wiki/Image:1976.mg. midget.arp.jpg)

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a)

13.2 Automotive Engineering

1031

b)

Fig. 13.37 (a) 1978 Mercedes-Benz S-Class, (b) 1979 Mercedes-Benz S-Class (courtesy of DaimlerChrysler)

Reliable, Affordable, Good Looking, Safe – and Fuel Saving? In 1973 there was an oil crisis. The oil-

exporting nations reduced the amount of oil produced to a minimum and as a consequence the prices of oil and fuel rose tremendously. People could not afford to run their cars in the way they were used to. Now everyone tried to save oil and fuel. In Germany, for example, four car-free Sundays were installed in the autumn of 1973. This naturally also affected the car industry. Several measures were taken by the automobile industry to develop cars that were more economical.

Fig. 13.38 Exhaust system without (left) and with (right) catalytic converter (courtesy of DaimlerChrysler)

However, now there was a conflict of targets in car development: cars had to be safe, but safety meant that cars became heavier, which resulted in higher fuel consumption. Hence, new ways of developing and producing cars had to be found to solve this conflict. It was not sufficient to concentrate on one development target; for the first time in car history the car had to be looked upon as a unit. One of the first measures to achieve both security and light weight was to use new materials such as highstrength low-alloy (HSLA) steel and new plastics. The dramatic changes in this area can be seen when compar-

Fig. 13.39 Mazda MX-5 Miata (copyright: Mazda)

Part B 13.2

ment was mainly the British car industry: almost every British OEM had convertibles in their program, including the MGB, the MG Midget (Fig. 13.36), the Jaguar E-Type, the Austin–Healey Sprite, and the Triumph TRseries. All these cars ceased to exist because of these security regulations or were unaesthetically adapted due to the addition of security bumpers and plastic adaptations.

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Applications in Mechanical Engineering

ing the 1978 Mercedes-Benz S-Class and its successor (Fig. 13.37). Plastics replaced chromium-plated metal, engines made out of aluminum replaced those made out of grey cast iron, and aerodynamics was improved. The carburetor was increasingly replaced by the fuel injection, because an injection system controlled by microcomputer was able to reduce fuel consumption in a way that an analog carburetor could never achieve. However, there was another reason why the carburetor fell out of favor. Do Cars Damage the Environment? A phenomenon un-

Part B 13.2

known until that time was experienced from the early 1980s: the dying of forests caused by acid rain, which itself was the consequence of industrial waste gases as well as car exhausts. Measures had to be taken to reduce air pollution. This trend influenced car development: the catalytic converter for cars with gasoline engines, which had been in use since the mid 1970s in the US, was now used in Europe as well (Fig. 13.38). The diesel engine was developed for direct injection and common rail technology and, in combination with exhaust-gas turbocharging, a former lame duck named diesel found its way into sports cars, luxury cars, and even convertibles. Mass Individualization as a New Trend. In the late 1980s the common car changed due to a change in society in the industrial nations: the demand for more individual products. Throughout the 1980s there were several studies for new, small fun cars, but the first one

to make it into serial production was the Mazda MX-5 (Miata) in 1989 (Fig. 13.39). Because of the success of this car, other OEMs also created cars for this market: the Porsche Boxster, the Fiat Barchetta, the Mercedes SLK, and BMW Z3 are some examples of this new style. Another trend which emerged in the 1980s was vans. As they became wealthier, societies in the industrialized nations had more leisure time that was now used for hobbies. For a lot of those hobbies bulky accessories were needed and these hobbies were carried out anywhere but at home – as a consequence cars had to provide more space. The first such vans introduced were the Chrysler Voyager and the Renault Espace in 1984. A classic among these vans is the Volkswagen Microbus. This mass individualization led to an exploding OEM product range and a trend called crossover, meaning that several car types are crossed. The sports utility vehicle (SUV), for example, is a crossing between a station wagon and an all-terrain vehicle. What Are the Trends for the Future? Technology is heading towards saving even more fuel. Today new petroleum reservoirs are still being discovered, but it is predictable that one day there will be not enough reserves to run millions of cars let alone other uses. Steps towards saving fuel include, for example, more widespread use of the diesel engine because it needs less fuel than a gasoline-driven car. Hybrid cars are also an alternative to conventional cars (Sect. 13.2.2). Other technologies under investigation include engines driven by fuel cells, hydrogen, and vegetable oil. Electronic features for enhancing driving safety, accident avoidance systems, and infotainment systems will probably play an even more important role than today in fulfilling customer demands. The variety of options and the frequency of replacement of model line versions might be reduced since there is no real return on invest any more.

13.2.2 Automotive Technology

Fig. 13.40 Mercedes-Benz F 500 Mind – a look into automobile future (courtesy of Mercedes Car Group)

Automotive technology consists of separate areas, which in general have their organizational counterparts in the departmental structure of the automotive company in terms of functional departments and model lines. In this section, an overview of car types and the general targets for car development (and thereby automotive technologies) is given. Then, the technological

Transport Systems

areas are briefly described with the demands which have to be taken into account by each and the major functions to be realized.

Targets for Car Development Customer Demands. Customer demands are the most

crucial targets for car development. Methods for the translation of customer demands to technical requirements are described in the literature, namely the house of quality [13.13]. When clustering the demands that customers and society place on cars one can identify various target conflicts. What is needed is cars that are:

• • • • • • • • • •

Safe Emotional Comfortable High quality Highly reliable Low emission Low noise Highly recyclable Have decent driving performance and load capacity Low cost, both in acquisition and utilization

A rough overview of the major design requirements in different market segments is shown in Table 13.2.

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Regulations. Regulations from legislation, car associa-

tions, and consumer groups are a major influence on car development and the final products themselves. In different countries, different regulations have to be taken into account to:

• •

Be able to introduce a car model (line) into this specific domestic market at all Be able to fulfill the consumer expectations, especially concerning car safety and fuel economy

The European Union has published far more than 50 regulations concerning active and passive car safety (prevention of accidents, reduction of consequences of accidents, car emissions, etc.). Causes for the definition of regulations are manyfold: from the protection of the domestic markets and domestic car manufacturers to protection of people, the environment, and the traffic. Table 13.3 shows as an example the relevant standards concerning safety published by the National Highway and Traffic Security Association (NHTSA), an operating unit of the Department of Transport (DoT) of the US government. Technical Requirements – Specific Example: Climate Stress. Technical requirements for car de-

velopment are derived from a number of external and internal influences on the car and its operation. Here, as an example area, climate parameters to be taken into account when designing a car, are described. A car and its components are exposed to a multitude of external factors in terms of climate stress. The strength of these factors depends on the planned operating area of a car and has to be taken into account when designing a car:

• • • •

Temperature: the maximum and minimum operating temperature and the temperature levels where the car and its components are kept (e.g., during transport). Humidity: from extremely dry conditions (e.g., the Mojave Desert) to tropical conditions – the most stressful environment is a humid, hot climate. Water: rain, car wash (with different kinds of washing equipment). Sand and dust: a challenge for the layout of sealings (e.g., keeping the passenger compartment free of dust, and taking care that the air convection compo-

Part B 13.2

Car Types Car types can be classified into one-box, two-box, and three-box concepts. Cars designed as one-box concepts are perceived as one single volume (one box) and are to be found mainly in the area of vans but also in small cars such as the MCC Smart and Mercedes A-class. Their major advantage is very good space economy, while these cars are comparatively high and thus have disadvantages in terms of aerodynamics and vehicle dynamics due to the high center of mass. Two-box concepts divide the car into two different volumes, the front volume usually used for the engine bay, and the second volume for passenger compartment and/or loading space. Two-box concepts are used for SUVs, station wagons, and cars in the compact class such as the Volkswagen (VW) Golf. Finally, the three-box concept is the classic division of the car body into three volumes, separating the engine bay from the passenger compartment and the trunk. This concept is used for limousines, classic coupés, convertibles, and roadsters.

13.2 Automotive Engineering

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Applications in Mechanical Engineering

Table 13.2 Design requirements in different market segments [13.14]

Part B 13.2

Mini car

Small car

Family car

Luxury car

Performance sedan

Sports car/coupé

Rallye or track car

Versatile accommodation Small frontal area Small engine

Versatile accommodation Small frontal area Small engine

Versatile accommodation

Distinctive style

Fast appearance

Sleek styling

Priority to function

Low Cd and reasonable area Choice of engines with diesel option

Low Cd

Low Cd

Low Cd

Good performance

Good performance

Good performance

Wide choice of engines, optional diesel, possibly with turbo Smooth performance

Large engine with fuel injection and/or turbo Fun to drive

Large engine with fuel injection and/or turbo Fun to drive

Ground effect and low Cd Maximum power output

Maximum fuel economy Low cost

Good fuel economy

Good fuel economy

Good fuel economy for class

Good fuel economy for class

Performance first

Low cost

Low cost

Ride secondary Easy to service and repair Minimum mass Maximum package for size

Adequate ride Easy to service and repair Minimum mass Maximum package for size

Good ride

Value for money Good ride

Value for money Good handling

Cost secondary Good handling

Controlled mass Maximum package for size

Good powerto-mass ratio Reasonable luggage room

Good powerto-mass ratio Reasonable luggage room

Some noise acceptable 4 seats FWD

Reasonable noise 4 seats FWD

Very quiet interior 5 seats FWD or RWD

Quiet at high speed 2+2 FWD or RWD

Quiet at high speed 2+2 RWD

• • •

Easy to service and repair Minimum mass Maximum package for size

Low noise 5 seats FWD or RWD

nents in the cooling system do not become covered with dust. Sun: especially for lower parts in the cockpit, high temperatures up to 80 ◦ C and above lead to thermal stress and aging. Corrosion: especially for operation on salted winter roads and in coastal climates. Chemical fluids: engine oil and fuel can come into contact with certain areas of the car.

•

Quick response, ultimate handling Performance first Cost no object Maximum road holding Fast repairs at p.t.o. service stops Low mass To carry long-range fuel tank and large-section spare tire Noise not important 2 seats only RWD

Air pressure: extreme operating conditions in highaltitude areas have to be taken into account when designing seals and membranes.

Body Targets for body design can be divided into two different classes: targets relevant from the point of view of the end customer and those relevant for internal optimized production [13.15].

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Table 13.3 Prescriptions of the federal motor vehicle safety

standards (FMVSS) (relevant extract) [13.16]

Standard Title No. 101 102 103

109 110 111 113 114 116 117 118 119 120 121 124 125 129 135 138 139 201 202 203 204 205 206

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Table 13.3 (cont.)

Standard Title No. 207 208 209 210 212 213 214 216 219 223 224 225 301 302 303 304 305 401 403 500

Seating systems Occupant crash protection Seatbelt assemblies Seatbelt assembly anchorages Windshield mounting Child restraint systems Side impact protection Roof crush resistance Windshield zone intrusion Rear impact guards Rear impact protection Child restraint anchorage systems Fuel system integrity Flammability of interior materials Fuel system integrity of compressed natural gas vehicles Compressed natural gas fuel container integrity Electric-powered vehicles Interior trunk release Platform lift systems for motor vehicles Low-speed vehicles

Targets relevant for customers are:

• • • • • • • • • •

Appealing design Maximum safety Minimal fuel consumption High comfort High level of functionality High quality and long life time Attractive/acceptable price Low maintenance cost Low noise emissions Usable every day Targets relevant for production are:

• • • • •

Easy assembly Utilization of existing production machinery Small number of different parts Easy to manufacture High, constant process quality

Part B 13.2

104 105 106 108

Controls and displays Transmission shift lever sequence, starter interlock, and transmission braking effect Windshield defrosting and defogging systems Windshield wiping and washing systems Hydraulic and electric brake systems Brake hoses Lamps, reflective devices, and associated equipment New pneumatic bias ply and certain specialty tires Tire selection and rims Rear view mirrors Hood latch system Theft protection Motor vehicle brake fluids Retreated pneumatic tires Power-operated window, partition, and roof panel systems New pneumatic tires for vehicles other than passenger cars Tire selection and rims Air brake systems Accelerator control systems Warning devices New nonpneumatic tires for passenger cars Light vehicle brake systems Tire pressure monitoring systems New pneumatic radial tires for light vehicles Occupant protection in interior impact Head restraints Impact protection for the driver from the steering control system Steering control rearward displacement Glazing materials Door locks and door retention components

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Part B 13.2

Fig. 13.41 Visualization of the load paths in the car body

(courtesy of Mercedes Car Group)

Fig. 13.42 Car body of a limousine (courtesy of Mercedes Car

Group)

• • •

Carryover of part and platform strategies Optimized utilization of material Low production cost

The basic layout of the body is influenced by the basic load cases of a car: bending case, torsion case, combined bending and torsion, lateral loading, and fore and aft loading [13.17]. These load cases lead to stresses in the vehicle body structure. Theses stresses must under the worst load conditions be kept at acceptable limits. The torsional and bending stiffness of the vehicle structure is a main influence on the NVH performance of the car, the tightness of sealings, and high-speed performance, especially of convertibles [13.18–20]. There are various basic concepts for the layout of body types. The ladder frame, historically the first and

most flexible way to build car bodies, had its disadvantages especially in terms of weight. Thus, today in most cases the car body is an integral structure with sheetsteel parts spot-welded together (Figs. 13.42, 13.43), providing structural and other functions. Since integral structures – also due to their flexibility in terms of design and utilization of different materials (Fig. 13.40) – are very complex, traditional mechanical analysis cannot be used to predict their behavior in the layout phase, but rather finite element (FE) analysis must be used to determine the optimal shape and material usage. This is also true for crash simulations of the body (Fig. 13.41). The exterior of the body is defined by three major influences: styling, aerodynamics, and packaging. Together with the body design itself, these are the tightest simultaneously running constraints in the early phase of car development. Because weight reduction while optimizing stability and crash performance is a challenge which cannot be met by using conventional steel bodies, lightweight design, e.g., using aluminum or tailored blanks, is used to optimize weight, stiffness, and crash performance while trying to limit the production cost. Since sheet-metal stamping of body shell parts for the car assembly process is partly outsourced, in the car body development process, modules are defined which are delivered by suppliers preassembled and then connected as a whole to other body parts. A typical example is the front bumper, where often, besides the body sheet metal parts, electrical components such as the front lights and the ventilation device as well as crash deformation elements made from plastic material are integrated into one module that is delivered just in time and just in sequence to the production line of the car manufacturer. Car body properties are the significant parameters used to describe the behavior and performance of the car body. Tolerances in the design process as well as in the assembly process contribute a lot to the body quality and the perception of car quality by the customer. Too large or too inhomogeneous joints between two body sheet metals deliver a sense of low quality in engineering and styling. Chassis Overview. Targets for chassis design from the point of

view of the end customer are related to the class of vehicles (buses, trucks, SUV, convertible, etc). The most fundamental differences among the requirements for different classes of vehicles are between passenger and

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commercial vehicles [13.14]. For passenger vehicles, the major concerns are:

• • •

Ride comfort Good handling characteristics (depending on the style of driving) Provision of these features over a wide range of different driving scenarios and scenarios

For commercial vehicles, the driving force is economical operation. Thus, design is usually based on a fully loaded vehicle being the most economic way to transport goods from point A to point B, and long time of operation. The major concerns here are: Low cost Reliability of operation

Between these two different classes of vehicles with completely different demands in terms of function and performance are the requirements for buses, building a compromise between these classes. The function of the chassis is to isolate the passengers and/or load from shocks and vibration caused by the roughness of the driving surface. Two basic components are used to cover this function:

• •

Springs, providing flexibility Dampers, absorbing energy

Figures 13.44–13.46 show different car axles. The basic components of the chassis are shown in Fig. 13.47 as a design principle. The driving characteristics of a car are dependent on a number of chassis and car concepts and layouts. The concepts differ in terms of the position of the engine inside the car (front engine, mid engine, rear engine) and the type of wheel drive (front-wheel drive, rear-wheel drive, and four-wheel drive). Most of the disadvantages of the car concepts described briefly in Table 13.4 are reduced nowadays through the application of electronic driving support systems. For further reading on automotive chassis in general, refer to [13.21–30].

Fig. 13.43 Car body of a sports utility vehicle (courtesy of Dr. Ing.

h.c. F. Porsche AG)

•

Hold the car stationary when on the flat or a gradient [13.31]

These functionalities have to be provided:

• • • • •

On slippery, wet, and dry roads On rough and smooth roads On split friction surfaces During straight-line braking or when braking on a curve With dry and wet brakes

Brakes. Brakes are among the most important components in a car. They have to operate under any circumstance, and under every operating condition have to provide the functionalities to:

• •

Decelerate the car in a controlled and repeatable fashion and, when appropriate, cause the car to stop Permit the car to maintain a constant speed when traveling downhill

Fig. 13.44 Car axle of a sports utility vehicle (courtesy of Mercedes

Car Group)

Part B 13.2

• •

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Applications in Mechanical Engineering

• • •

Lower emissions of carbon dioxide and carbon monoxide Diesel fuel is easier to manufacture High reliability and long service life

Disadvantages are:

• • • •

Higher output of nitrogen-oxides emissions and soot particles Higher weight Lower engine speed Less smooth engine running, and less impulsive reaction to driver signals

Part B 13.2

Future diesel engines will have to meet the following demands:

• • • • • • •

Good environmental properties (e.g., use of particle filters) Further reduction of fuel consumption (e.g., increased injection pressure) Reduction of production cost (e.g., use less expensive material or simpler engine concepts) Longer lifetime Even greater reliability Greater comfort (reduction of vibration, smooth torque development over engine speed) Reduction of noise emission

achieve these targets. Today, a certain percentage of all cars sold in the market of California have to meet the restrictions of ZEV/ULEV, otherwise the automotive manufacturer has to pay penalties. One contribution to ULEV are cars with hybrid drives (Fig. 13.54). These drives consist of a minimum of two different energy conversion units and use two different energy storage methods for means of vehicle propulsion. The main potential benefits of the hybrid drive are:

• • •

Reduction of fuel consumption Reduction of emissions Reduction of noise

There are three different concepts for hybrid drives: parallel, serial, and mixed. Serial hybrids use electrical energy for wheel drive, and the energy stored in the battery is recharged from

Besides the combustion engine (p.t.o. or diesel), which is by far the most commonly used propulsion unit in today’s cars, there are a lot of different engine types which are used very rarely or in research prototype cars, e.g.:

• • •

The electrical motor, powered by battery, fuel cell or by a generator operated by a combustion engine (Figs. 13.51–13.53) The Stirling engine, which has very low emissions and is characterized by a smooth and continuous torque output even at low engine speed The gas turbine, which is characterized by low vibrations and low emissions

Fig. 13.49 Conduction of airstream for cooling of brakes

(courtesy of Dr. Ing. h.c. F. Porsche AG)

For further information on automotive engines in general, refer to [13.37–46]. Low-Emission Engine Concepts. The rising number

of cars, especially in urban areas such as Los Angeles, CA, has led to the definition of regulations aiming at reduction of air pollution and fuel consumption. Zero-emission vehicles (ZEV), today only effectively realizable using electrical motors or fuel cells, and ultralow-emission vehicles (ULEV), are required to

Fig. 13.50 Brake test on a testing machine (courtesy of Mercedes Car Group)

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Part B 13.2

Fig. 13.51 Twelve-cylinder combustion engine (courtesy of Mercedes Car Group)

Fig. 13.52 Six-cylinder combustion engine (courtesy of Dr. Ing. h.c. F. Porsche AG)

Fig. 13.53 Eight-cylinder combustion engine, turbocharged (courtesy of Dr. Ing. h.c. F. Porsche AG)

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Generator Hybrid transmission

Battery

Gasoline engine

Electric motor

Power split device

Fig. 13.54 Schematic view of a hybrid drive concept (courtesy of Toyota Motor Corp.)

Part B 13.2

Reduction gear

time to time by a generator powered by a combustion engine. In parallel hybrids, the wheels are driven both by electrical motors or a combustion engine alternatively or even simultaneously. Mixed hybrids are a combination of parallel and serial power flow, and many versions are available. The major components of hybrid drives are the combustion engine, the battery, the gearbox, and the electrical engines, which have to be harmonized for integration into the final concept. For further information about low-emission concepts, refer to [13.47–53]. Transmissions. The function of the transmission is

to adjust the engine speed and torque according to the needs of the current driving situation. Two basic concepts are implemented in today’s cars: manual (Fig. 13.56) and automatic transmissions (Figs. 13.55, 13.57). Manual transmissions offer in most cases better efficiency compared with automatic transmissions, which in turn provide greater comfort and, depending on the experience of the driver, even optimize the utilization of the engine speed and torque in different driving situations. Clutches. The clutch is placed between the engine and the transmission in cars with manual gearboxes, providing: Fig. 13.55 Seven-gear automatic transmission (courtesy of Mercedes Car Group)

• • • •

Adaptation of engine speed during approach Separation of engine and transmission when shifting gears Safety for transmission and other components during overload conditions Damping vibrations

In cars with automatic transmission, the hydraulic unit of the automatic transmission provides these functionalities. For further information about transmissions and clutches, refer to [13.54–57]. Interior When designing the interior of a car, the man–machine interaction is the core issue. The interior has to be adapted to the driver and the passengers as far as possible. Ergonomics of the controls and information Fig. 13.56 Manual transmission (courtesy of Mercedes Car Group)

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instruments presented to the driver and the passengers is a major influence in order to be able to drive safely and without being stressed. Methods and tools used for ergonomic development are described in Sect. 13.2.4. Besides the components and their placement inside the car, another important aspect of positive feeling inside the car is the interior climate [13.58]. Separately adjustable air conditioning for driver and passengers, not producing any noticeable draft, heated seats and steering wheels, as well as an air scarf for convertibles are elements which cover the needs for a pleasant interior climate in modern cars (Fig. 13.58).

Fig. 13.57 Automatic transmission in the context of a four-wheel

drive (courtesy of Dr. Ing. h.c. F. Porsche AG)

when planning to use leather on a surface, and the manufacturing process of placing tiny pieces of wood on the gear stick has to be taken into account when designing the standard design variant. When introducing a new, additional interior material, extensive tests (head impact, airbag functionality, etc.) have to be carried

Fig. 13.58 Climate control in a luxury car (courtesy of Mercedes Car Group)

Part B 13.2

Interior Materials. Individualization of luxury cars plays an important role in sales. To be able to configure a car in such a way that no-one else owns a similar one is often a very important feature for customers of these kinds of cars. Thus, providing a choice of different interior materials (aluminum, carbon, different types of wood, different types of leather, alcantara, etc. [13.59]) from which the customer can choose when configuring the car is a characteristic of luxury cars. In order to be able to provide this multitude of materials, the design of the interior components has to take account of the fact that different materials could be applied as the outer shell. Sharp edges and small radii should be avoided

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13.2 Automotive Engineering

Fig. 13.62 Packaging of components in a sports car (courtesy of Dr. Ing. h.c. F. Porsche AG)

Due to their physical working principle, sensors can be divided into various categories (Table 13.5). Besides sensors, actuators are another important group of elements in an electronically operating system. Actuators range from starting generators, supplementary drives to different actuators in the surrounding of the engine (crankshaft actuation, electromechanical gear shifting), those used for implementation of safety features (tightening seat belts, electrical brakes, electrically actuated rollover safety in convertibles), for comfort functions (powered windshields, powered sunroof, memory-based electric seat readjustment), for

information functions (CD player, navigation system), and to provide active light management depending on the external brightness, to mention only a few. With the large number of electric and electronic components in a car, electrical energy consumption becomes a critical issue. Even during standstill, most modern cars need a certain voltage to be in a standby position for remote opening systems and for theftprotection devices. Since especially in cold outside temperatures, the driver and the passengers demand a large number of electrically supported functions (defrosting, seat heating, etc.) the management of these

Part B 13.2

Fig. 13.61 Integration of engine and power-train components into the car concept (courtesy of Mercedes Car Group)

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Fig. 13.65 Crash simulation and hardware crash (courtesy of Mercedes Car Group)

Part B 13.2 Fig. 13.66 Crash simulation and hardware crash of a convertible (courtesy of Mercedes Car Group)

into a basic design with main dimensions and definition of the placement of the most important components in the car (Figs. 13.60–13.63). The result of packaging is a compliant arrangement of components in terms of space and functional dependencies. The major influences on the defined car concept resulting in the car packaging are [13.15]:

• • • • • • • •

Technical data Primary competitors Range of use (leisure, city, off-road, sports, etc.) Body versions Safety concepts including crash structures Seating capacity and ergonomic requirements for seats Trunk volume Engine and power train concepts

One of the results of packaging is the dimensional concept of a car where all main measures of the car are defined. For further information about packaging and ergonomic aspects in automotive engineering refer to [13.70–72].

Automotive Safety As well as dealing with crash safety, automotive safety is a broad area covering many aspects. Figure 13.64 gives an overview over the whole field of automotive safety. Active and passive safety are prime selling arguments. The responsibility for the health of the driver, the passengers, and other traffic participants is also taken very seriously by automotive manufacturers. Active safety is the area of measures aiming at avoiding an accident. Passive safety is the area of measures minimizing the consequences of an accident when it happens. Besides technological provisions in the car concerning safety, the factor most strongly influencing the probability of an accident and its consequences is the driver: careful, defensive driving is the best precaution. Various coefficients describe the criticality of body stresses induced by an accident, and regulations demand that test data are below a certain level for each of these. These coefficients include the head protection criterion (HPC), the thorax compression criterion (TCC), and the tibia compression force criterion (TCFC).

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Table 13.6 Dummy types defined in Federal Motor Ve-

hicle Safety Standard 572: Antropomorphic Test Devices (http://www.nhtsa.gov), NHTSA, Washington USA

FMVSS 572 Subpart B FMVSS 572 Subpart C FMVSS 572 Subpart D FMVSS 572 Subpart E FMVSS 572 Subpart F

FMVSS 572 Subpart N FMVSS 572 Subpart O

FMVSS 572 Subpart P

FMVSS 572 Subpart R

Designing the car to meet these regulatory demands impacts on the car structure, the materials used, and the shape and location of interior components, and safety measures such as airbags and their deployment algorithms have to be adapted. For the verification and validation of the crash performance of a car, crash simulation and hardware crashes are used (Figs. 13.65 and 13.66). For the tests, various dummies are used. Table 13.6 shows the different dummy types used in today’s crash tests. For further information about automotive safety refer to [13.73–76].

13.2.3 Car Development Processes Overview The development of cars is – like every other product development – a company-specific process. Many in-

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fluences such as the size and level of globalization of the company, its product portfolio, the number of produced cars, and the proportion of outsourcing during the product generation process affect the characteristic of the specific development process. Generally, the development of cars consists of three main elements:

• • •

The strategic phase The car development project The adaptation phase

The following picture gives an overview of the car development process (CDP). Like any other product development process, car development starts from the global point of view and the rough concept. During the strategic phase the car is planned, one could say, from above. Aspects considered at this stage come from the environment, the market, and the company itself and lead to the strategic specification of the car. Aspects that influence strategic decisions are, for example, social trends such as increasing awareness of environment or the increasing necessity for safety, the need to substitute technologies as a consequence of improvements or to provide replacing technologies as a political move (e.g., the fuel cell as an alternative drive mechanism), the product portfolio of competitors, rationalization of the companies own workflow, and new functions to be implemented in order to make the product more attractive such as active light illumination or headway distance control. The variety of aspects influencing the strategic definition of the car is huge but there are just as many approved methods to support this phase of economical and political decisions. The methods are general and there are many good summaries on this topic in the literature [13.77]. The main specifications which have to be defined during the strategic phase of a car are summarized in Fig. 13.67. One important boundary condition for the development of a car is the definition of the product family. For this step the needs and trends of the market have to be analyzed, the product portfolio of the competitors compared with the company’s own portfolio, and the profitability of the possibilities calculated. By defining the key performance indicators the characteristics of a car are determined which are decided by the customer target group which will be reached. Besides the factors price, design and general affection for the brand have a big influence to. Examples are the horse power to be supplied, the noise and

Part B 13.2

FMVSS 572 Subpart I FMVSS 572 Subpart J FMVSS 572 Subpart K FMVSS 572 Subpart L FMVSS 572 Subpart M

50th percentile male Three-year-old child Six-month-old infant Hybrid III test dummy Side impact dummy 50th percentile male Six-year-old child Nine-month-old child Newborn infant Free motion headform Side impact hybrid dummy 50th percentile male Six-year-old child test dummy, beta version Hybrid III 5th percentile female test dummy, alpha version Hybrid III three-year-old child crash test dummy, alpha version CRABI 12-month-old infant crash test dummy, alpha version

13.2 Automotive Engineering

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• • • •

Sample delivery of parts produced with series tools are positively approved. Logistics processes are defined and verified; ability to handle the logistics according to the planned production volume is proved. Marketing concept (advertising strategy) is defined. The dealer organization is informed about the product and its maintenance.

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Depending on the product life cycle and competitors’ product developments, facelift projects are established in order to upgrade a car which has been in the marketplace for a certain time with additional features, better performance, and adapted styling. After another period of time, the next generation of car development starts.

13.2.4 Methods for Car Development

Activities After Start of Production After the start of production, the car development project is finished. At this point two major activities are still ongoing:

• •

Development of further options to be offered to the customers at a later point of time Support of series production

Further options are usually planned with the car development project in total. The production schedule of these options is integrated into the overall production scenario of how many cars will be sold at which time in what markets. Support of series production is an ongoing activity which is usually not planned together with the car development project but is rather a support function which is continuously improved. Here:

As with the development of most technical artifacts, car development makes use of various methods for defining and verifying form, function, and performance. The methods used can be categorized into:

• •

Virtual methods Hardware methods

Virtual methods operate on a product description, usually contained in a computer-based product definition. Computer-aided tools are used to generate and verify the current state of the product definition (Fig. 13.73). Hardware methods make use of real parts, components, assemblies or products (in car development projects, usually prototypes and pre-series cars). On testing machines, on special driving courses, or out on the street, the product or parts of it are tested for function, performance, and durability (Fig. 13.73). Virtual and hardware methods usually go hand in hand when a car is being developed (Fig. 13.74). Generally, with virtual methods a large number of design alternatives can be generated and/or evaluated in a comparatively short amount of time, whereas hardware methods cover more aspects of the real behavior of the product, since not all aspects of product behavior are modeled in the virtual methods. In the following some of the most important methods for car development will be highlighted and it will be explained how they are used in the development process.

Changes of parts are made in order to optimize production processes in terms of cost and reliability. Design changes according to feedback from the customers and dealers are implemented. Design is optimized in order to reduce material cost.

Methods for Product Layout and Conceptual Development In the early phase of a car development project, styling, package, the body-in-white structure, and aero- and thermodynamics are the key factors which have to be harmonized in order to generate a suitable overall car concept.

Depending on the type of change of the part design, effects have to be taken into account up to spare parts provision, thus each change is evaluated in detail in terms of overall cost and benefit.

Styling Virtual. Computer-aided styling (CAS) tools allow

• • •

the definition and manipulation of two-dimensional

Part B 13.2

Series development is done in even closer cooperation with the suppliers than concept development, since sourcing for all parts is defined during series development, whereas during concept development often only strategic suppliers are directly integrated in the car development process. With the start of series development at the latest, the project team structure is defined and fully operational. The teams consist of members of design, production, sales, purchasing and quality and are responsible for the development of the assigned components within the given limits of cost, time, quality, functionality, and performance.

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Table 13.7 Strengths and weaknesses of various methods and tools for ergonomics development [13.71]

Part B 13.2

Method/tool

Strengths

Weaknesses

Design recommendations and checklists

• •

Quick Easy to use

•

Anthropometry and biomechanics

• • •

Quick Good for novel designs Useful for asessing the influence of age, sex, race, etc. upon design

• • •

• • •

• 3-D human modelling CAD systems

Mock-ups and fitting trials

Owner questionnaires and interviews

• • • • • • • • • • • •

User- and task-specific predictions, quick and accurate for geometric issues such as fit, reach, and vision Enables effective communication at an early stage Compromises can be objectively explored Control selection of users and their tasks Study comfort and performance over time Sound basis for identifying good and poor designs using both objective and subjective methods Essential for novel designs Compromises can be investigated Design problems are quickly identified Valuable information direct from the user population Small details may be detected which the casual observer may have overlooked User involvement

• •

• • •

Can be time consuming and expensive Can be difficult to obtain representative subjects May not be a very realistic simulation of task or environment

• • •

User may take poor design for granted Opinions can be strongly biased Cannot be used for novel designs until after production Biased sample – does not include those people who chose not to use the existing equipment Biased sample – low response rate from postal questionnaires, who returns them? No detailed assessment of body size, performance or comfort Can be time consuming Require production and/or prototype vehicles to test Can be difficult to obtain representative subjects

• • •

User trials and road trials

• • • •

Control selection of users and their tasks Study comfort and performance over time Sound basis for identifying good and poor designs using both objective and subjective methods Allows comparative testing

Packaging and Ergonomics Virtual. Packaging in the early phase of a car devel-

opment process means defining prescriptions for space

Relevance to specific users, tasks or vehicle type may be dubious May have little scientific validity No account taken of compromises Either too specific (i. e., should be 457.2 mm) or too general (i. e., should be comfortable) May be a lack of data relevant to user or task Data may be out of date Data often relate to standardized postures, not necessarily working postures Design may become too academic, mistakes being hard to identify Expensive to set up (hardware, software, training), but very cost effective thereafter Does not assess personal preferences, psychological space, fatigue, task performance

• • •

utilization by the different technical departments. Also, the main space features of a car such as the size of the trunk are defined here. Space prescription is usu-

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Both have their virtual counterparts, which are used earlier in the process.

Part B 13.2

Fig. 13.80 DMU of components in the engine bay of

a sports utility vehicle (courtesy of Dr. Ing. h.c. F. Porsche AG)

right-hand drive, automatic and manual transmission, different engines, and different customer-specific equipment), packaging has to define the most critical (in terms of space) car configurations, and will track the fitting of parts with respect to each other on the basis of these configurations. Based on experience, a trade-off is made between complete coverage of all car variants that are potentially critical and the expense of this level of coverage. In order to be able to generate a DMU automatically, the designer has to assign his 3-D CAD model to a node in the bill of materials, and has to position it in each relevant car configuration. Positioning can be done either in absolute coordinates (relative to the vehicle null point) or in relative coordinates describing the position relative to another part on which it is, for example, mounted. Part collisions can be checked on demand (when the designer wants to verify his part design in his specific geometrical surrounding), or on a regular basis as a complete geometrical car check. Conflicts between two parts are documented, and a recommended action is communicated by packaging to the two part owners. Hardware. Most automotive companies use hardware to

verify the space allocation of parts and the ergonomic suitability of the position of interior components. The engine bay, which contains flexible parts (cables, tubes) that cannot be appropriately modeled in CAD systems today, is one example. The seat box is another example, where hardware verification is used in order to check the ergonomic position of every element in the future seat.

Body Structure The main physical structure of a car is the body-in-white structure (BiW structure). With the layout of this structure, the basic performance features of a car are determined, too. To a certain extent, the BiW structure accounts for the weight of a car, the bending and torsion stiffness, and its crash behavior. If changes in the layout of the BiW structure are necessary later in the process due to conflicts in space management or unsatisfactory crash performance, these changes result in heavy additional cost, since changing this structure leads to necessary changes in all other sections of the car connected with the BiW structure and in the highly automated manufacturing lines in the factory which are planned, ordered, and built early in the process, too. Thus, methods for a thorough layout of this structure according to the goals defined for the car to be developed are used. Virtual. Since body-in-white structures are developed

in the early phases of car development, when no hardware is yet available, the focus of methods for layout of the BiW structure is on virtual methods. For the layout of a structure, generative algorithms can be used. One set of algorithms widely applied in the automotive industry is implemented in the package SFE CONCEPT. According to the definition of load cases, material coefficients, and major geometrical boundary conditions such as free space for the passenger compartment and trunk, the algorithm identifies at which points of space material is needed in order to fulfill the demands for smooth load flow and minimum deflection of the beams of the BiW structure. The result of this algorithm is a space structure of voxels which then can be used for a first layout of the structure in the CAD system. The result of this structure is then taken for finite element analysis to prove that the performance criteria are still met after the structure has been designed in such a way that it can also be manufactured. Modal analysis of the BiW structure will show which frequencies will lead to resonance reactions, resulting in noise and discomfort for the passengers, and which therefore have to be avoided when guiding the load path into the BiW structure. Depending on the car family the BiW structure is intended to cover, precautions for reinforcements in the structure have to be taken into account. An example is the need for reinforcement when the BiW structure of a coupé is intended for use in a convertible, since bend-

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ing and torsion stiffness will decrease in this case due to the missing roof, in order to give the coupé additional stability.

Aero/Thermodynamics The basic aero- and thermodynamic behavior of a car is determined by the layout of the exterior, the main air channels inside the car, and the position of the engine and other power-train components. Thus, this behavior has to be checked early in the process, when the styling process is not yet finished, in order to allow for necessary design changes to be made due to flaws in the aerodynamic performance [13.83–85]. Virtual For prediction of the aero- and thermodynamic

behavior of a car, computational fluid dynamic (CFD) methods are used. With the help of these methods, the air flow around and inside a car can be visualized, a key performance indicator of a car – the cw coefficient which contributes to the fuel consumption, especially at high speeds – can be determined, and air flow can be analyzed. Minimum air mass flows are defined, for example, for the cooling needs of the engine through the the radiator, and of the brakes. The normal force to the road consists of the weight of the car and of the force generated by the air flow, the down force. The down force is also being calculated in the early phase, as it is critical for driving stability at high speeds. Changes in the exterior car shape and additional aerodynamic spoiler can affect the down force. Hardware In order to analyze the airflow around and

inside a car, flow analysis models can be used. Early in

Fig. 13.81 Test with sports utility vehicle to verify perfor-

mance in dry and dusty environment (courtesy of Dr. Ing. h.c. F. Porsche AG)

the process, scaled models can be used to evaluate exterior airflow and provide criteria to decide on a styling alternative that is more suitable in terms of aerodynamic performance. Later in the process, 1 : 1 scale models can be used for analyzing both exterior and interior airflow. The hardware-based approach is losing favor against the use of virtual simulations. Methods for Series Development With the concept confirmed, the series phase starts. Increasingly virtual methods are substituting and being complemented by hardware methods. A huge number of different development and testing methods are used in series development to ensure that

Fig. 13.82 Test with sports utility vehicle to verify performance in cold and snow environment (courtesy of Dr. Ing. h.c. F. Porsche AG)

Part B 13.2

Hardware. To ensure that the results of the calculation are correct, one of the first BiW structures to be manufactured as a prototype structure is often used for the verification of bending and torsion stiffness on testing machines. Since these tests are also quite inexpensive and the correct layout of the BiW structure is fundamental, this approach is reasonable. The first prototype with the new BiW structure, in most cases built shortly before the end of the concept phase, is used for first driving tests and, most important for the verification of the structure, in case of accidents. Due to the highly dynamic processes and its high dependency on dynamic material properties, the results of the simulation of a crash are still uncertain, which is why hardware verification is still needed before series development can start.

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Fig. 13.83 Test with sports utility vehicle to verify performance in wet environment (courtesy of Dr. Ing. h.c. F. Porsche AG)

tions such as door opening, and heating and cooling of the passenger cell are analyzed, as well as engine startup performance under extreme conditions. An extension of the climate chamber is the climate wind tunnel, in which different wind flow can additionally be generated with the car standing still or using its engine to turn the wheels on rollers mounted to the floor. Climate simulation on the test track is usually combined with analysis of the behavior of the car and especially its cooling system at high speeds. To simulate the car being parked in a garage with a hot engine, after these tests the car can be put into a closed chamber to simulate this extreme operating condition. Climate simulation is also done in extensive tests in different climate zones in the world such as Northern Canada and Death Valley. Here, it is important to minimize the effort in transporting the test cars between the different test locations while maximizing the difference in climatic conditions, in order to minimize cost and time lost during transportation. Snow, sand, different road conditions, and stop-and-go traffic in metropolitan areas are also covered during these tests. Chassis Tuning. For tuning of the chassis system dif-

Fig. 13.84 Test with sports utility vehicle to verify performance under extreme road conditions (courtesy of Dr. Ing. h.c. F. Porsche AG)

ferent driving situations are simulated by test drivers. Additional adaptations in terms of springs, dampers and, most important, electronic stability systems are derived. In order to cover all combinations in which a car can be driven by a customer, the variants of tire size and type, usage of winter chains, and the different engine, chassis, and body types have to be taken into consideration. Therefore, with the large number of car variants that a customer can order, the effort required to tune the chassis can increase greatly. Table 13.9 shows a sample combination matrix for chassis tuning tests.

the components developed will meet functional, performance, and quality targets. Each automotive company has its own particular approach in terms of which methods are used for what kind of evaluation at which point in time. Figures 13.81–13.84 give an overview of different tests to be performed in the development of a sports utility vehicle. Using three example methods, a general insight into the methods for series development is provided below. Climate Simulation. A climate chamber (Fig. 13.85)

is used to simulate extreme climate conditions. Heat and cold are simulated, together with different levels of humidity and sunlight incidence. Different kinds of behavior are analyzed in the climate chamber: car func-

Fig. 13.85 Car test in climate chamber (courtesy of Mer-

cedes Car Group)

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Table 13.9 Sample combination matrix for chassis tuning tests

Tire size Tire type Winter chain Engine type Chassis type Car body type

18 Summer Without 3400 ccm Normal Small

19 Winter With 4500 ccm Comfort Wide

Hardware-in-the-Loop. Hardware-in-the-loop (HIL) is an approach to test certain hardware components in their future operating environment, when this environment is not already available, i. e., when other interoperating components are not available yet. In this case, the other components as well as the environmental conditions are simulated by a computer program in real time, and the simulation parameters are input to the component to be tested. HIL is used for mechanical, electronic, and electromechanical components. The HIL approach is used to decouple the behavior of components such as controllers in an interconnected network (for example, the CAN bus). With clearly defined interfaces between the components and the definition of the communication bus structure, the HIL method is similar to the methods used in software engineering for some time already. An example of the utilization of HIL is the testing of controllers for active body control in a test-bed with simulated signals from sensors and actuators before the controller is put into the networked car environment in a prototype. Tests of a component can be reproduced, and thus also critical conditions in terms of operating behavior can be reproduced and used as test criteria for approving the release of the component. With the decoupling approach of HIL, product development time can be reduced, since it is not necessary

Off-road

4500 ccm turbo Sport

Adaptive

to wait for the last component in a network to be available in hardware. Also, due to the modular structure of the network of components, the complex interaction of components can be controlled. Cross-Functional Methods Product Structure and Bill of Materials. The car is log-

ically and/or functionally structured. The power train, the doors, and the cockpit might be high-level elements of this structure which are substructured further. The leaves of the structure tree represent the parts or components. The part or components describing data is matched via PDM software and transformations that describe the position of the specific part or component are added. The functionality of the PDM software enables the digital generation of assemblies or the entire car. For this purpose the product structure will be interpreted, and the geometrical description of the parts and components can be loaded and positioned element by element using the attached transformations. This functionality is the basis for all kind of simulations (Fig. 13.86). The product structure again is the basis for the BOM (Fig. 13.87). In the bill of materials the leaves of the structure of the car are focused upon. The geometrical description itself is neglected; its existence and the level of quality are of importance and, hence, represented. Instead, further information is added which enables the configuration of the car. The BOM describes the contents of the accessory packages to be offered, the specifics of the American, European or Japanese versions, the colors that will be available, the options that can be chosen, and the dependencies that exist between these configurations. The BOM, and the system in which it is handled, form the basis for all logistical activities. Material and supplier parts are ordered using the BOM for prototypes as well as the final, customer-specific car. The plants in which the cars will be assembled can be planned with respect to capacities, required tools, robots etc. and manufacturing costs can be calculated since the part-

Part B 13.2

Besides tuning of the chassis, it also has to be verified that there is enough space between the tire (all potentially usable tires) and the fender liner under all driving conditions. For this purpose, early in the process wheel covers are generated as boundary faces for the movement of the tire under every condition in the CAD system, on the basis of which the fender liner is designed. The correct sizing of the fender liner is then verified in hardware tests later on. Most critical in terms of space needed are large tire sizes with a sporty chassis layout and the usage of winter chains.

20 All season

1070

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Applications in Mechanical Engineering

motive companies usually can no longer afford to have due to the extreme specialization required for the different technologies. Therefore, the integration of these suppliers of the car development project from the very start is of vital importance. Examples of technologies and components developed by suppliers are headlamps and electromechanical components such as antilock braking systems. When integrating suppliers into car development, one has to consider:

Part B 13.3

• • •

The product substance Its extent in terms of engineering service The interaction between the supplier and the OEM

Depending on this, the following aspects have to be agreed upon in contracts with the supplier:

•

The kind of data exchange (mail, direct access to systems from the outside or by resident engineers)

• • • •

The kind, form, and contents of the results to be delivered by the supplier The kinds of simulations and tests to prove the suitability of the concept and its application in the context of the car Delivery of prototype parts, if applicable and necessary Delivery of parts for series production, if the supplier will also source the component for series supply

In order to integrate development partners successfully there has to be a trade-off between open transfer of information and retaining specific expertise in the OEM and the relevant supplier. Nonengineering Support of Car Development. Dur-

ing car development, the engineering departments are supported by various nonengineering functions in the company. Table 13.12 briefly describes the most important functions.

13.3 Railway Systems – Railway Engineering 13.3.1 General Interactions of Modules of a Railway System with Surrounding Conditions Railways have many technical and economical interfaces to the surrounding world, as indicated in Fig. 13.95. The aims of the railway are usually provided externally, from policy and economics regarding market, finances, and environment. These aims are transformed into strategies be the management of a railway company, defined by instructions to several subareas such as marketing, which define the product in terms of timetable and comfort. The timetable provides lots of information; it defines the locations to be connected and the distances to be overcome. By defining the times of departure and arrival, the travel speed is fixed. Also the frequency of operation of trains is defined. The railway operation must be able to fulfill this requirements by providing adequate, educated staff in trains and at fixed locations. Energy to move the trains must be provided at the right locations. Communication must be enabled over one or even several lines with many trains. If the schedule fails, disturbance management must be able to restore the system to proper

operation as soon as possible, whether failure is caused by exterior or interior reasons. Infrastructure such as the tracks, perhaps catenary, the design speed of the track and its gage, the structural gage, the axle loads, stations for passengers and/or loading/unloading facilities for goods must all fit the demands. Information technologies for passengers are also gaining in importance. The type of vehicles chosen must be adequate for the required operation, for instance, locomotives, coaches or diesel multiple units (DMUs). The vehicles must fit the infrastructure and the operation in terms of speed, axle load, etc.. Maintenance must provide reliable system elements by avoiding failures because of the effects of wear. Maintenance is increasingly being outsourced today. If all of the elements shown in the boxes on the diagonal in Fig. 13.95 are provided by one company it is called an integrated railway otherwise it is known as a segmented railway. The interaction of the elements produces results in terms of earnings, and the quality of the process (for example, punctuality). Because of high cost pressures the aim for a economically sound railway system is to run as fast

1096

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Applications in Mechanical Engineering

13.4 Aerospace Engineering Aerospace engineering is a branch of engineering that deals with the design, construction, and operation of aerospace vehicles.

13.4.1 Aerospace Industry

Part B 13.4

The aerospace industry is a collection of organizations involved in research, design, construction, test, and operation of aerospace vehicles. In the USA, the aerospace industry consists of 20 prime contractors, 10 major airlines, a large government-supported research agency, and thousands of smaller companies that supply special components to these prime contractors. The total employment in the industry varies somewhat with changing business conditions, but in recent years has averaged about 2.5 million people, of whom approximately 75 000 are employed as engineers. The aerospace industries in developed countries such as Russia, Japan, and the European countries are not quite as large as that of the USA in terms of number of employees, but are similar in nearly every respect. Aerospace industries are growing rapidly in populous countries such as China and India. Aerospace Industry Product Classifications The products of the aerospace industry are many and varied, meeting a number of mission requirements. The broadest product classifications are related to the customer purchasing the product, giving rise to the classification into civil and military products [13.96]. More specific product classifications are derived from the type of aerospace vehicle and the particular use to which it is put. The section is organized in this manner.

13.4.2 Aircraft The term aircraft is an all-inclusive term for any form of craft designed for navigation in the air. In the years since the first actual man-carrying flight in a hot-air balloon in the late 1700s, there have been a number of types of aircraft that have provided the means for aerial navigation. A brief recap includes the hot-air balloon ascension of de Rozier and d’Arlandes in 1783, the hydrogen balloon flight of J. A. C. Charles and M. N. Robert in 1783, and the successful steam-engine-powered airship (balloon) of Giffard in 1852. The German Otto Lilienthal developed a man-carrying glider that made over 2000 glides before suffering a fatal crash in 1896. As has been well documented, it was the Wright broth-

ers, Orville and Wilbur, who made the first controlled powered flights of an airplane in 1903. Progress in aircraft design was slow in the first few years after the Wright flights, but by the start of World War I (WWI), many flying machines of various types and configurations had been successfully built and flown. During WWI, military requirements gave rise to the development of numerous types of aircraft with very specialized capabilities, which were produced in their thousands. Following the war, the use of aircraft for the transportation of passengers came into widespread use, with the establishment of airline companies and air routes, first between major European cities, but later in America and other parts of world as well. In the period between World War I and World War II, specialized aircraft were used to set nonstop distance records between continents, while other specialized aircraft set records for speed and altitude. World War II saw the introduction of new technology in aircraft design with the advent of practical helicopters, jet engines, rocket propulsion systems, and guided missiles. Following World War II, there was significant growth in private, recreational flying, expansion of the international commercial air transportation system, as well as continuing development of experimental aircraft that flew higher, faster, and farther than previous aircraft. With the creation of the National Aeronautics and Space Administration (NASA) in 1958, a variety of unique aircraft and spacecraft have been designed to meet very specific mission objectives laid down by that Agency. In recent years, there has been increasing military interest in unmanned combat air vehicles (UCAVs). Aircraft Types The two major categories of aircraft types are lighter than air (LTA) and heavier than air (HTA). A lighter than air craft is one that rises aloft by making use of Archimedes’ principle, that is, by displacing a weight of air that is greater than the weight of the craft itself, and so creating a buoyant force. A heavier-than-air aircraft is one that rises aloft due to Bernoulli’s principle acting on the aircraft’s lifting surfaces, creating suctions on the upper surface and pressures on the lower surface relative to the ambient air pressure [13.97–127]. The design and operation of civil aircraft in the USA is subject to numerous regulations promulgated by the Federal Aviation Administration (FAA) of the Department of Transportation. Table 13.15 presents a summary of the various types of FAA regulations.

Transport Systems

13.4 Aerospace Engineering

1097

Table 13.15 Summary of Federal Aviation Regulatory (FAR) categories

FAR part

Certification procedures for products and parts Airworthiness standards, normal, utility, acrobatic, and commuters Airworthiness standards, transport category airplanes Airworthiness standards, normal category rotorcraft Airworthiness standards, transport category rotorcraft Airworthiness standards, manned free balloons Airworthiness standards, aircraft engines Airworthiness standards, propellers Noise standards, aircraft type and airworthiness standards Airworthiness directives Maintenance, preventive maintenance, rebuilding, and alteration Identification and registration marking Aircraft registration General operating and flight rules Special air-traffic rules and airport traffic patterns IFR (instrument flight rules) altitudes Standard instrument approach procedures Ultralight vehicles Certification and operation, domestic, flag, and supplemental air carriers, and commercial operators of large aircraft Certification and operation, aiplanes having seating capacity of 20 or more passengers, or a maximum payload capacity of 6,000 pounds or more Certification and operation of scheduled air carrier helicopters Air taxi operators and commercial operators Agricultural aircraft operations

21 23 25 27 29 31 33 35 36 39 43 45 47 91 93 95 97 103 121

Lighter-Than-Air Aircraft. One can distinguish be-

tween the following types of LTA aircraft:

•

•

•

Hot-air balloon, which consist of a large envelope made of lightweight fabric to contain the hot air, a burner located below the envelope, usually fueled by kerosene, to heat ambient air, causing it to rise into the envelope. A basket hung underneath the burner is provided for the pilot and passengers. Light-gas balloon, which is similar in arrangement to a hot-air balloon, but without the burner. The buoyant force is generated by the use of light gasses such as helium in the envelope, which displace the relatively heavier ambient air. Blimp or nonrigid airship, which is basically a large gas balloon whose streamlined shape is maintained

•

125 127 135 139

by internal gas pressure. In addition to the gas envelope, the blimp has a car attached to the lower part of the envelope for the crew and passengers, engines and propellers to develop forward speed, and fins with hinged aft portions for control. Rigid airship, a lighter-than-air aircraft with a rigid frame to maintain its shape and provide a volume for the internal placement of light gasbags. The rigid airship also has a car attached to the lower part of the rigid frame for the crew and passengers, engines, propellers, and tail fins similar to the blimp. Rigid airships reached the peak of their development in the mid 1930s, but several spectacular accidents curtailed further development.

Heavier-Than-Air Craft. HTA aircraft can be divided

into three main categories.

Part B 13.4

Regulatory category

1098

Part B

Applications in Mechanical Engineering

Part B 13.4

A glider is an aircraft that flies without an engine. The simplest form of a glider is the hang glider, which consists of a wing, a control frame, and a pilot harness. The pilot is zipped into the harness and literally hangs beneath the wing, with his hands on the control bar of the control frame. The wing has an aluminum frame that supports the wing fabric, and internal battens to provide a proper shape to the fabric. Hang gliders are usually launched from a very steep hill or a cliff that affords sufficient altitude for gliding flight. Simple utility gliders which have rigid structural elements similar to an airplane are used primarily for training. These gliders are launched into the air by being towed by a power winch, an automobile, or an airplane. Extremely refined sailplanes, usually made of very lightweight materials and featuring very long thin wings, take advantage of rising air currents, and can soar for a long time and cover distances of hundred of miles in a single flight. A variation of the sailplane is the motorglider, basically a sailplane with a small motor and propeller, which is used for take-off and climb to soaring altitude, whereupon the motor is shut off, and is then retracted along with the propeller to revert to the sailplane configuration. An airplane is an air vehicle that incorporates a propulsion system and fixed wings, and is supported by aerodynamic forces acting on the wings. Airplane propulsion systems may be a piston engine driving a propeller, a turbojet engine, or a rocket engine, depending on the required mission. Airplanes range in form from small general aviation aircraft, usually privately owned, with one or two engines, to larger commercially operated air transport aircraft that can carry from 20 to upwards of 500 passengers and can fly distances from 500 to over 8000 miles nonstop. In addition to these civil aircraft types, there a number of military aircraft types designed for different missions, such as fighter, attack, bomber, reconnaissance, transport, and trainer. A very small class of airplanes, known as experimental research aircraft, usually powered by rocket engines, has been built to obtain flight test data at extremely high speeds and altitudes. The ultimate development in this area is the US Space Shuttle, which is a rocket-powered spacecraft for most of its mission, and an unpowered glider for the approach and landing phase of the flight. A helicopter is an aircraft that is supported by aerodynamic forces generated by long thin blades rotating about a vertical axis. The rotor blades are driven by the helicopter’s propulsion system, usually a piston or gas turbine engine. Helicopters range in

size from small, two-seat personal utility models to large transport types that can carry up to 40 people. Large heavy-lift helicopters are often used in specialized hauling and construction tasks, where their ability to remain airborne over a fixed spot for extended periods of time is unique. Helicopters have also been used in several military applications such as air–sea rescue, medical evacuation, as battlefield gunships, and for special-operations troop transport. Recent developments in helicopter technology have led to hybrid helicopter craft called the tilt rotor. In this machine, there are two rotors to provide the vertical forces required for take-off and landing, but as the name implies, these rotors may be tilted to varying degrees until they are aligned in the direction of flight, acting like the propellers on a conventional airplane. The tilt rotor has small wings to provide the aerodynamic lift required during cruise flight, during which the rotors are used to provide forward thrust.

13.4.3 Spacecraft Spacecraft fall into two major categories, unmanned, with no humans aboard, and manned, with humans aboard. Examples of unmanned spacecraft include civil communication satellites, military reconnaissance satellites, and scientific probes that gather information on our solar system. Examples of unmanned spacecraft include the Echostar and Eutelsat civil communication satellites, the Aquila and Cosmos military reconnaissance satellites, and the Hubble Space Telescope and Mars Global Surveyor scientific probes. Examples of manned spacecraft include the Vostok, Soyuz, Mir, Mercury, Gemini, Apollo, and Space Shuttle vehicles.

13.4.4 Definitions The following are some important definitions related to a good understanding of aerospace engineering. Units Although there has been a policy in the USA in recent years to convert to the international system (SI) of units, the US aerospace industry continues to use English units in its work. This publication will use English units as primary, since most American engineers are familiar with this terminology. A list of conversion factors between SI and English units is given in Table 13.16.

Transport Systems

13.4 Aerospace Engineering

1099

Table 13.16 Conversion factors between SI and English units Conversion factors 1.00 kg = 0.06853 slug 1.00 slug = 14.592 kg At the surface of the Earth, an object with a mass of 1.00 kg weighs 9.8 N or 2.205 lb, and an object with a mass of 1.00 slug weighs 32.17 lb or 143.1 N Length 1.00 m = 3.2808 ft 1.00 ft = 0.3048 m = 30.48 cm Force 1.00 N = 0.2248 lb 1.00 lb = 4.4482 N ◦ Ra = ◦ F + 460 Temperature 1.00 K = 1.8 ◦ Ra 1.0 ◦ Ra = 0.5556 K K = ◦ C + 273 Pressure 1.00 N/m2 = 1.4504 × 10−4 lb/in2 = 2.0886 × 10−2 lb/ft2 1.00 lb/in2 = 6.8947 × 103 N/m2 1.00 lb/ft2 = 47.88 N/m2 Velocity 1.00 m/s = 3.2808 ft/s = 2.2369 mi/h 1.00 ft/s = 0.6818 mi/h = 0.3048 m/s Density 1.00 kg/m3 = 1.9404 × 10−3 slug/ft3 1.00 slug/ft3 = 515.36 kg m3 lb s kg = 20.886 × 102 2 Viscosity 1.00 ms ft lb s kg 1.00 2 = 47.879 ft ms J BTU ft lbf Nm = 1.00 = 2.3928 = 5.9895 Specific heat 1.00 kg K kg K lbm ◦ Ra slug ◦ Ra Nm J ft lb 1.00 = 1.6728 × 10−1 = 1.6728 × 10−1 slug ◦ Ra kg K kg K Frequently used equivalents Mass

γ Gas constant R (air) Specific heat cp (air) Gravitational constant at sea level g0 Radius of the Earth r0

Flight Speed Terminology One of the key performance parameters for an airplane is its maximum level-flight speed. For a variety of

1.4 (air) 287.05 N m/(kg K) = 1718 ft lb/(slug ◦ Ra) 1004.7 N m/(kg K) (J/(kg K)) = 6006 ft lb/(slug ◦ Ra) 9.8 m/s2 = 32.17 ft/s2 6.378 × 106 m = 20.92 × 106 ft

technical and economic reasons, various airplanes are designed to operate at speeds most appropriate to their design missions. Modern airplanes operate at speeds

Part B 13.4

1 bhp 550 ft lb/s = 33 000 ft lb/min 1 knot (kn) (i. e., nautical mile per hour) 1.152 statute mile per hour 1 knot (kn) (nautical mile per hour) 1.69 ft/s 1 statute mile per hour 0.868 knot (nautical miles per hour) 1 statute mile per hour 1.467 ft/s 1 ft/s 0.682 statute mile per hour 1 ft/s 0.592 knot (nautical miles per hour) 1 kilometer 0.621 statute mile 1 kilometer 0.539 nautical mile 1 statute mile 1.609 kilometer 1 nautical mile 1.854 kilometer 1 radian 57.3 degrees Note that the preceeding values are equivalents. The conversion factors are the reciprocals. Frequently used constants

Transport Systems

13.4 Aerospace Engineering

1101

Table 13.17 Characteristics of the US standard atmosphere Kinematic viscosity (ft2 /s)

q/M2

Sonic velocity

(slug/cu ft)

Density ratio (σ )

(lb/ft2 )

Altitude

Temperature

Pressure

Density

(ft)

(◦ F)

(◦ Ra)

(psf)

(kn)

59.0

518.7

2116.2

0.0023769

1.0000

0.0001572

1481.0

1116.4

661.5

1000

55.4

515.1

2040.9

0.0023081

0.9710

0.0001610

1429.0

1112.6

659.2

2000

51.9

511.6

1967.7

0.0022409

0.9427

0.0001650

1377.0

1108.7

656.9

3000

48.3

508.0

1896.7

0.0021752

0.9151

0.0001691

1328.0

1104.9

654.6

4000

44.7

504.4

1827.7

0.0021110

0.8881

0.0001732

1279.0

1101.0

652.3

5000

41.2

500.9

1760.9

0.0020482

0.8616

0.0001776

1233.0

1097.1

650.0

6000

37.6

497.3

1696.0

0.0019869

0.8358

0.0001820

1187.0

1093.2

647.7

7000

34.0

493.7

1633.1

0.0019270

0.8106

0.0001866

1143.0

1089.3

645.4

8000

30.5

490.2

1572.1

0.0018685

0.7860

0.0001914

1100.0

1085.3

643.0

9000

26.9

486.6

1512.9

0.0018113

0.7619

0.0001963

1059.0

1081.4

640.7

10 000

23.3

483.0

1455.6

0.0017556

0.7385

0.0002013

1019.0

1077.4

638.3

11 000

19.8

479.5

1400.0

0.0017011

0.7155

0.0002066

979.8

1073.4

636.0

12 000

16.2

475.9

1346.2

0.0016480

0.6932

0.0002120

942.1

1069.4

633.4

13 000

12.6

472.4

1294.1

0.0015961

0.6713

0.0002175

905.6

1065.4

631.4

14 000

9.1

468.8

1243.6

0.0015455

0.6500

0.0002233

870.2

1061.4

628.8

15 000

5.5

465.2

1194.8

0.0014962

0.6292

0.0002293

836.0

1057.4

626.4

16 000

1.9

461.7

1147.5

0.0014480

0.6089

0.0002354

802.9

1053.3

624.0

17 000

−1.6

458.1

1101.7

0.0014011

0.5892

0.0002418

770.8

1049.2

621.6

18 000

−5.2

454.6

1057.5

0.0013553

0.5699

0.0002484

739.8

1045.1

619.2

19 000

−8.8

451.0

1014.7

0.0013107

0.5511

0.0002553

709.8

1041.0

616.7

20 000

−12.3

447.4

973.3

0.0012673

0.5328

0.0002623

680.8

1036.9

614.3

21 000

−15.9

443.9

933.3

0.0012249

0.5150

0.0002697

652.7

1032.8

611.9

22 000

−19.5

440.3

894.6

0.0011836

0.4976

0.0002772

625.6

1028.6

609.4

23 000

−23.0

436.8

857.2

0.0011435

0.4806

0.0002851

599.4

1024.5

606.9

24 000

−26.6

433.2

821.2

0.0011043

0.4642

0.0002932

574.1

1020.3

604.4

25 000

−30.2

429.6

786.3

0.0010663

0.4481

0.0003017

549.7

1016.1

601.9

26 000

−33.7

426.1

752.7

0.0010292

0.4325

0.0003104

526.2

1011.9

599.4

27 000

−37.3

422.5

720.3

0.0009931

0.4173

0.0003195

503.4

1007.7

596.9

28 000

−40.9

419.0

689.0

0.0009580

0.4025

0.0003289

481.5

1003.4

594.4

29 000

−44.3

415.4

658.8

0.0009239

0.3881

0.0003387

460.3

999.1

591.9

30 000

−48.0

411.9

629.7

0.0008907

0.3741

0.0003488

439.9

994.8

589.3

31 000

−51.6

408.3

601.6

0.0008584

0.3605

0.0003594

420.3

990.5

586.8

32 000

−55.1

404.8

574.6

0.0008270

0.3473

0.0003703

401.3

986.2

584.2

33 000

−58.7

401.2

548.5

0.0007966

0.3345

0.0003817

383.1

981.9

581.6

34 000

−62.3

397.6

523.5

0.0007670

0.3220

0.0003935

365.5

977.5

579.0

35 000

−65.8

394.1

499.3

0.0007382

0.3099

0.0004058

348.6

973.1

576.4

36 000

−69.4

390.5

476.1

0.0007103

0.2981

0.0004185

332.3

968.8

573.8

37 000

−69.7

390.0

453.9

0.0006780

0.2843

0.0004379

330.9

968.1

573.6

38 000

−69.7

390.0

432.6

0.0006463

0.2710

0.0004594

316.7

968.1

573.6

39 000

−69.7

390.0

412.4

0.0006161

0.2583

0.0004820

301.8

968.1

573.6

40 000

−69.7

390.0

393.1

0.0005873

0.2462

0.0005056

287.7

968.1

573.6

41 000

−69.7

390.0

374.6

0.0005598

0.2346

0.0005304

274.2

968.1

573.6

Part B 13.4

(ft/s)

0

1102

Part B

Applications in Mechanical Engineering

Table 13.17 (cont.)

Part B 13.4

Kinematic viscosity (ft2 /s)

q/M2

Sonic velocity

(slug/cu ft)

Density ratio (σ )

(lb/ft2 )

(ft/s)

(kn)

0.0005336 0.0005087 0.0004849 0.0004623 0.0004407 0.0004201 0.0004004 0.0003818 0.0003639 0.0003469 0.0003307 0.0003153 0.0003006 0.0002865 0.0002731 0.0002604 0.0002482 0.0002366 0.0002256 0.0002151 0.0002050 0.0001955 0.0001834 0.0001777 0.0001376 0.0001077

0.2236 0.2131 0.2031 0.1936 0.1845 0.1758 0.1676 0.1597 0.1522 0.1451 0.1383 0.1318 0.1256 0.1197 0.1141 0.1087 0.1036 0.0988 0.0841 0.0897 0.0855 0.0815 0.0777 0.0740 0.0579 0.0453

0.0005564 0.0005837 0.0006123 0.0006423 0.0006738 0.0007068 0.0007415 0.0007778 0.0008159 0.0008559 0.0008978 0.0009418 0.0009879 0.0010360 0.0010871 0.0011403 0.0011961 0.0012547 0.0013161 0.0013805 0.0014481 0.0015189 0.0015932 0.0016712 0.0021219 0.0026938

261.3 249.0 237.4 226.2 215.6 205.5 195.8 186.7 177.9 169.5 161.6 154.0 146.8 139.9 133.3 127.1 121.1 115.4 110.0 104.8 99.9 95.2 90.8 86.5 82.4 64.9

968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 968.1 971.0 974.4

573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 573.6 575.3 577.3

Altitude

Temperature

Pressure

Density

(ft)

(◦ F)

(◦ Ra)

(psf)

42 000 43 000 44 000 45 000 46 000 47 000 48 000 49 000 50 000 51 000 52 000 53 000 54 000 55 000 56 000 57 000 58 000 59 000 60 000 61 000 62 000 63 000 64 000 65 000 70 000 75 000

−69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −69.7 −67.3 −64.6

390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 390.0 392.4 395.1

357.2 340.5 324.6 309.4 295.0 281.2 268.1 255.5 243.6 232.2 221.4 211.0 201.2 191.8 182.8 174.3 166.2 158.4 151.0 144.0 137.3 130.9 124.8 118.9 92.7 73.0

sure. Aircraft altimeters are pressure gages calibrated to read pressure altitude. Also important is the density altitude, the geometric altitude on a standard day for which the density is equal to the ambient air density. Pressure altitude, density altitude, and temperature are related through the equation of state p = ρRT. It should be noted that another standard atmosphere has been defined by the International Civil Aviation Organization (ICAO). The ICAO standard atmosphere and the US standard atmosphere are identical up to 65 617 ft. Beyond 65 617 ft the ICAO standard atmosphere maintains a constant temperature up to 82 300 ft, while the US standard atmosphere reflects an increasing temperature with a constant gradient to beyond 100 000 ft. Axis Systems The airplane design process, with respect to achieving performance objectives of altitude, speed, range, pay-

load, and take-off and landing distance requires analysis of the airplane in motion. The Newtonian laws of motion state that the summation of all external forces in any direction must equal the time rate of change of momentum, and that the summation of all of the moments of the external forces must equal the time rate of change of moment of momentum, all measured with respect to axes fixed in space. If the motion of the airplane is described relative to axes fixed in space, the mathematics becomes extremely unwieldy, as the moments and products of inertia vary from instant to instant. To overcome this difficulty, use is made of moving or Eulerian axes that coincide in some particular manner from instant to instant with a definite set of axes fixed with respect to the airplane. The most common choice is to select a set of mutually perpendicular axes defined within the airplane as shown in Fig. 13.153, with their origin at the airplane center of gravity (c.g.). The airplane’s motion

1120

Part B

Applications in Mechanical Engineering

Part B 13.4

and wheel, or control stick, rudder pedals, instrument panel, glare shield, plus a variety of levers, knobs, and switches to operate various aircraft systems. Specific requirements for pilot field of view and downward vision from the defined pilot design eye position are contained in the federal air regulations (FARs) and the military specifications (Mil Specs). The constant-section passenger compartment for larger airplanes is usually pressurized, and circular or near-circular in cross section, because of the structural weight efficiency of this shape for pressure vessels. For larger-capacity longrange jet transports, two aisles are provided for greater passenger mobility, and for ease of entry and exit from multiple adjacent seats. These larger circular cross sections provide significant space below the passenger deck to carry large amounts of revenue cargo, either in special containers or stacked on flat pallets. A typical cross section for a twin-aisle transport is shown in Fig. 13.186. The length of the passenger compartment must be sufficient to accommodate the required number of passengers, allow for galley space, lavatories, coat rooms, plus passenger entrance doors, and emergency exits. There are specific requirements in the FARs for emergency exits to be used in survivable accidents. The aft fuselage or afterbody is influenced by conflicting requirements of aerodynamic performance and structural weight. The afterbody should be long enough to avoid severe curvature and separation drag, while being as short as possible to avoid limiting the airplane pitch attitude on the ground during normal take-offs, as well as avoiding excessive weight from a long afterbody. Empennage Geometry For conventional aft-tail configurations, the horizontal and vertical tail arrangement, called the empennage, is the major element in providing both static aerodynamic stability in pitch and yaw, as well as providing aerodynamic control moments in pitch and yaw. For unconventional configurations such as flying wings or forward horizontal tail canards, static aerodynamic stability and control are provided by other means. The aft horizontal tail is the major contributor to static aerodynamic stability in pitch. This is quite logical, since static longitudinal stability involves the generation of aerodynamic restoring moments which are dependent on an aerodynamic force from the horizontal tail (proportional to the horizontal tail area) and a moment arm (proportional to the distance from the airplane center of gravity to the horizontal tail m.a.c.).

The horizontal tail also provides the aerodynamic control moments to allow the pilot to achieve equilibrium in pitch at any desired lift coefficient, allowing the control of airspeed in steady unaccelerated flight, and the curvature of the flight path in accelerated flight. Longitudinal control is usually provided through the hinged, moveable, aft portion of the horizontal tail called the elevator, although some designs move the entire horizontal tail about a fixed pivot point. This arrangement is called an all-moveable horizontal, or a stabilator. Landing Gear Most modern airplanes use a tricycle landing gear configuration that is one with two main wheels aft of the c.g. and one forward. Except for small airplanes with low cruise speed, landing gears are usually retracted for climb and cruise flight. The landing gear wheels and tires must be adequate to handle a variety of taxi, take-off, and landing loads prescribed by the FARs, as well as spreading the reaction loads from the gear sufficiently so as not to overstress the runway pavement. The landing gear also has to house the brakes. Propulsion Systems Propulsion systems for modern airplanes are of one of the following types:

• • • • •

Piston engine-propeller Turbine engine-propeller Turbojet engine Turbofan engine Turbofan engine with afterburner

Small personal utility or acrobatic airplanes are usually powered by piston engine-propeller combinations, while larger personal utility and smaller commuter airplanes are usually powered by turboprop propulsion. Business jets and larger jet transports are powered by turbofans. High-performance military airplanes are usually powered by low-bypass turbofans equipped with afterburners. The key parameter for the propulsion system is the specific fuel consumption c, i. e., the amount of fuel burned per hour, per unit of output of the propulsion system. For piston engines and turboprops, it is expressed as c=

lb . bhp/h

For turbojets and turbofans, it is expressed as c=

lb . lb/h

1122

Part B

Applications in Mechanical Engineering

Table 13.23 Airplane weight definitions

Part B 13.4

Weight

Symbol

Definition

Manufacturer’s weight empty Operating weight empty

MWE OWE

Maximum zero-fuel weight

MZFW

Maximun landing weight

MLW

Airplane weight at the end of the manufacturing process. Airplane weight ready for operation. Includes flight crew, cabin crew, food, galley service items, potable water, cargo containers and pallets, life vests, life rafts, emergency transmitter, lavatory fluids, and unusable fuel. Airplane weight with maximum design payload on board, but no fuel. Design payload includes all passengers and their baggage, plus the maximun design cargo weight. Airplane weight defined as the maximum for which the airplane meets all of the structural design requirements for landing. It is usually somewhat higher than the MZFW. Airplane weight defined as the maximum for which the airplane meets all of the structural design and performance requirements for takeoff. Includes the maximum design payloads plus the fuel required to fly the design mission plus the required reserve fuel.

Maximum weight

take-off

gross

MTOGW

empty weight. This process, usually conducted by aircraft weight engineers, initially involves much reliance on empirical data from actual aircraft, correlated with appropriate physical parameters. This data is assembled into a group weight statement, a list of weights of the major elements that make up the MWE. Examples are shown in Table 13.24. As the design work progresses, the group weights are updated as various parts of the aircraft are specifically defined. Major effort is required to ensure that the initial target weight for the entire aircraft is not exceeded during the design and manufacturing phase of the project. Balance Diagram and C.G. Limits The airplane balance diagram is used to ensure that the airplane center of gravity (c.g.) is in the proper location for all of the probable loading conditions considering OWE c.g. location, fuel loading and usage, passenger loading, and cargo loading. The OWE c.g. is usually set by designers based on experience for a specific airplane design. Then the extreme excursions of the c.g. due to the most probable adverse loading conditions that move the c.g. forward and aft are examined by calculation to establish forward and aft limits for c.g. travel. The results of these calculations are plotted on a chart of airplane gross weight versus c.g. location so that appropriate c.g. limits can be established. Stability and control and structural design criteria must be met at these c.g. limits.

13.4.9 Aircraft Performance Aircraft performance is the part of the subject of flight mechanics that deals with parameters such as speed, rate of climb, range, fuel consumption, and runway length requirements. Level-Flight Performance The simplest performance condition is steady levelflight cruise, when all forces are in equilibrium as the aircraft moves at a constant speed and altitude. From Fig. 13.162, equilibrium requires that

ρ lift L = weight W = CL V 2 S , 2 W CL = (ρV 2 /2)S and ρ thrust T = drag D = CD V 2 S 2

subsonic flight .

For any given weight, CL may be found and substituted into the induced drag term. ΔCDC , the empirical compressibility drag coefficient, is dependent on CL and the Mach number. Several fundamental airplane characteristics can be derived from the drag equation. One major objective of airplane design is to minimize the drag for any required lift. At any altitude and speed, the ratio of drag to lift depends only on the ratio of CD to CL . At low Mach

Transport Systems

13.4 Aerospace Engineering

1123

Table 13.24 Summary of group weight statements. Transport airlines in lb Weight elements

Furnishings Air conditioning Antiicing system Load and handling Empty weight (less dry engine) Dry engine MEW MTOGW

737-200

727-100

727-200

707-320

DC-1010

L-10111

DC-1030

747-100

11 391

11 164

17 682

18 529

28 647

34 909

36 247

48 990

47 401

57 748

88 741

2790

2777

4148

4142

6004

4952

4930

13 657

8570

14 454

11 958

11 118

11 920

17 589

22 415

22 299

22 246

23 704

44 790

49 432

46 522

68 452

4182

4038

7244

7948

11 216

11 682

11 449

18 581

19 923

25 085

32 220

1462

1515

2226

2225

3176

4644

6648

8493

8916

9328

10 830

2190

1721

3052

3022

5306

9410

7840

7673

8279

13 503

9605

1434

2325

2836

2984

2139

2035

2098

5120

5068

5188

6886

817

855

0

849

0

0

0

1589

1202

1592

1797

575

518

723

827

550

1002

916

1349

1016

1645

1486

753

835

1054

1147

1557

2250

1744

4150

4401

4346

5067

1715

2156

2988

2844

3944

2414

2752

5366

5490

5293

5305

1108

1100

1844

1896

1815

1870

2058

2827

2801

3186

4134

8594

9119

11 962

14 702

16 875

15 884

15 340

38 072

32 829

33 114

48 007

1110

1084

1526

1802

1602

2388

2296

2386

3344

2527

3634

474

113

639

666

626

794

673

416

296

555

413

15

19

55

54

62

62

228

57

–

–

DC-855

DC-862

–

49 770

51 240

75 528

86 017

105 756

116 535

118 749

203 521

198 968

224 148

297 867

6160

6212

9322

9678

19 420

16 936

17 316

23 229

30 046

25 587

35 700

55 930

57 452

84 850

95 695

125 176

133 471

136 065

226 750

229 014

249 735

333 567

108 000

104 000

161 000

175 000

312 000

325 000

335 000

430 000

430 000

565 000

775 000

numbers, ΔCDC = 0 and CD = CDp +

CL2 . πAR e

For minimum drag, CD /CL is a minimum. Now CDp CD CL = + . CL CL πAR e

At the value of CL for which CD /CL is a minimum, d(CD /CL )/ dCL = 0. Then CDp d(CD /CL ) 1 =− 2 + =0. dCL πAR e CL And for L/D = maximum, CDp =

CL2 . πAR e

Part B 13.4

Wing group Tail group Body group Landing gear Nacelle group Propulsion group Flight controls Auxiliary power Instruments Hydraulic system Electrical system Avionics

DC-930

1124

Part B

Applications in Mechanical Engineering

Thus, for minimum drag, the lift coefficient is the value for which drag due to lift is equal to parasite drag. For this condition  CL(L/D)max = CDp πAR e . The value of L/D is L CL CL , = = D CD CDp + CL2 /(πAR e) for L/D = maximum  CL = CDp πAR e

Therefore CL2 mp = 3πCDp AR e , and CLmp =

CDimp =

Part B 13.4

CL2 . πAR e

Thus,

  CDp πAR e L = D max 2CDp To obtain this minimum drag in flight, we must fly at the speed corresponding to the CL given above. This speed is designated as V(L/D)max . Then  2W . V(L/D)max = CDp πAR eρS Propeller-driven airplanes achieve their best range at the lift coefficient and corresponding speed for (L/D)max . It is customary to study the performance of propeller-driven airplanes in terms of power, since they operate with engines that produce power rather than thrust. Thrust horsepower required for level flight is drag times distance covered per unit time, so CL2 ρ 3 ρ V S. 550 thpreq = DV = CDp V 3 S + 2 πAR e 2 √ Then V = 2W/CL ρS and we obtain 

 1/2 CL 2W 3 CDr 1 thpreq = + . 3/2 550 ρS πAR e C L

The constant 550 is carried to keep the units in horsepower and the other units in the corresponding English system units. The minimum power will be obtained when the term in parenthesis is a minimum. Taking the derivative of that term with respect to CL , equating it to zero, and defining CLmp as the lift coefficient for minimum power required leads to 1 1 3 CDr + =0. − 5/2 2C 2 πAR eC 1/2 Lmp

Lmp

3πCDp AR e =



3CL(L/D)max .

Substituting in the induced drag coefficient portion of the equation gives

and CDp =



3πCDp AR e πAR e

= 3CDp .

At the minimum-power condition, the induced drag coefficient is three times as large as the parasite drag coefficient. This contrasts with the minimum drag condition, for which they are equal. Since, for a given total lift, the speed varies inversely as the square root of the lift coefficient, the speed for minimum power is lower than the speed for minimum drag by the ratio 1/(3)1/4 = 0.76. Taking the inverse, the minimum drag speed is 1.32 times the minimum-power speed. Climb and Descent Performance Figure 13.162 illustrates the force on an airplane in steady-state constant-speed climb. The thrust is shown acting parallel to the flight path direction. In general, this is not quite true, but in conventional aircraft the effects of an inclination of the thrust vector are small enough to be neglected. Equating forces perpendicular and parallel to the flight path

L = W cos γ , T = D + W sin γ . Then sin γ =

T D T D T−D = − = − , W W W W L

γ is the flight path angle or angle of climb. We may assume that γ is sufficiently small so that cos γ is approximately equal to 1.0. Then L = W. rate of climb RC = V sin γ =

V (T − D) W

For propeller-driven aircraft, it is convenient to use power rather than thrust and drag. If RC is to be determined in feet per minute, the usual units, then with V

1128

Part B

Applications in Mechanical Engineering

take-off weight limit, it is necessary to trade payload for fuel if greater range is desired. Operating on the fuel capacity limit line requires large reductions in payload to achieve small increases in range, due to modest improvements in cruise efficiency achieved by reductions in cruise weight. The key points on the payload range curve are calculated using the Breguet range equation for jet aircraft  Range (n. miles) =

V c



 L Wi . ln D Wf

Part B 13.4

For a specific design, on a particular cruise operation, V , C, and L/D are usually taken as constants, Winitial and Wfinal are derived from known weights, i. e., OEW, payload, reserve fuel, maximum take-off weight, maximum fuel capacity. From this equation, it can be seen that maximum range is achieved by cruising at a point where the quantity VL/D is a maximum. Some key ideas about payload range curves are as follows:

• • • • •

Weight-limited payload = MZFW − OWE. Space-limited payload is slightly lower. Passengers + bags range is usually set by MTOGW. Greater passengers + bags range can be achieved by increasing MTOGW (allows more fuel to be carried). If passenger + bags range is limited by maximum fuel capacity, greater range can be achieved only through increased fuel capacity.

Endurance The endurance problem is similar to the range problem except that we are trying to determine how long the aircraft will fly rather than how far it will fly. The quantity analogous to specific range is specific endurance, the hours flown per unit quantity of fuel. In the usual units, specific endurance is measured in hours per pound of fuel. To maximize endurance, fuel flow per unit time must be minimized. Since the specific fuel consumption is nearly constant, the drag must be minimized for jet aircraft, while thrust horsepower must be as small as possible for propeller-driven aircraft. The endurance te for turbojet or turbofan aircraft is

wi te =

wi h/lb fuel dW =

wf

wf

1 dW Dc

wi = wf wi

= wf

1 dW [W/(L/D)]c 1 L dW 1L Wi . = ln cD W c D Wf

Again, c and L/D are assumed to be constant throughout the flight, or taken as average values. Note the similarity between this equation and the jet range equation. Endurance is simply range divided by speed. For the greatest endurance, the aircraft should obviously fly at the speed for minimum drag. This, of course, assumes that c is a constant with speed, a good assumption for jets but not quite true for turbofans. In addition, at very low engine thrust levels, c tends to increase as the thrust is decreased. This may also influence the speed for best endurance. For propeller-driven aircraft, endurance is  wi wi  1 η 550 dW = dW te = thp c/η c DV × 1.69 wf wi

=

wf

325 wf

η L 1 dW , c DV W

where V is in knots and c is in pounds of fuel per brake horsepower per hour. We cannot assume that L/DV is a constant. L/DV is the ratio of lift to thrust power required, and we have shown that thpreq is a nonlinear function of weight. At any given lift coefficient, power required varies with W 3/2 . However, it has been shown that, if V is expressed as 2W/CLσρs S, t e is given by     η  C 3/2 σ S  W 1/2 i L t e (h) = 37.9 −1 . c C D Wi Wf Here we see that, for best endurance, a propeller-driven airplane should be flown at the flight condition for 3/2 maximum CL√ /CD . It is a maximum when the lift coefficient is 3 times the value for maximum lift-todrag ratio. Since low speed as well as a particular lift coefficient is desirable for minimum power required, best endurance occurs at a high density (i. e., low altitude). Therefore, propeller aircraft endurance is best at low altitudes. Take-Off Performance The take-off performance problem is basically an acceleration to the required speed plus a transition to climb

Transport Systems

13.4 Aerospace Engineering

these requirements and procedures are described in the federal air regulations (FAR) part 23 and part 25 Airworthiness Standards, Airplanes. For military aircraft, these requirements and procedures are described in MIL-A-8660, Airplane Strength and Rigidity, General Specification For and MIL-A-8661, Airplane Strength and Rigidity, Flight Loads. The requirements are, in most cases, nearly identical in both the civil and military documents. The information that follows will be based on FAR 23 and 25, with information from MIL-A-8660 and MIL-A-8661 added where significant differences exist:

(W/g)V 2 (13.5) . R For a level-flight turn, the weight W must be equal to the vertical component of lift L cos φ. Substituting in (13.5), we obtain

•

L sin φ =

[(L cos φ)/g]V 2 , L sin φ = R 2 V . tan φ = gR

(13.6)

Equation (13.6) specifies the angle of bank required for any speed and radius of turn. Conversely, the radius of turn is given by V2 . R= g tan φ Also, since for a level-flight turn W = L cos φ , it follows that the lift for such a turn must be given by L = W/ cos φ and L 1 = =n. W cos φ As we shall see later, the quantity n = L/W is an important parameter defined as the load factor.

13.4.11 Loads Aircraft structures must be designed to withstand the most serious of the infinite number of possible combinations of external loads that may act on it in flight and when landing. Experience, accumulated over many years of design, analysis, and research, has led to the formulation of a very rational set of procedures that determine the design loads and define the airspeeds for which the design loads are imposed. For civil aircraft,

•

Flight conditions (FAR 25.331–25.459): – Maneuver load generated by intentional pilot application of controls – Gust load generated by sudden change in angle of attack due to encountering a gust Landing conditions (FAR 25.473–25.511): – Level landing – Tail-down landing – One-wheel landing – Side load conditions – Braked roll conditions – Yawing conditions

Air Loads Flight Load Factor. An important concept in the analy-

sis of air loads imposed under various flight conditions is the flight load factor n, which is defined as follows n=

aerodynamic force ⊥ longitudinal axis . aircraft weight

For an aircraft in steady, level flight, the aerodynamic force perpendicular to the longitudinal axis is given by the lift, which is equal to the weight. Since the weight is due to the force of gravity, the aircraft is said to be in 1 g flight. If the lift is four times the weight, the aircraft is subjected to 4 g’s. In a simpler form, n=

lift . weight

V –n Diagrams. The analysis of the critical design air loads for an aircraft employs a chart known as the V –n diagram. These charts show flight load factors as a function of equivalent airspeed and represent the maximum load factors expected in service, based on the requirements of the applicable specifications. These load factors are called limit load factors. The airplane structure must withstand these loads without damage.

Part B 13.4

longitudinal stability. If the longitudinal control input is made fairly rapidly, the speed will not have time to reduce to the speed required for equilibrium, and the lift will exceed the weight. With lift greater than weight, the airplane will experience a vertical acceleration. The maneuver just described is called an abrupt pull-up and may be the start of more complicated maneuvers. For a level-flight turn, referring to Fig. 13.208, the horizontal component of the lift vector accelerates the airplane laterally and curves the flight path. In a turn of radius R, the lateral force L sin φ, where φ is the angle of bank, must balance the centrifugal force on the airplane. Thus

1137

1144

Part B

Applications in Mechanical Engineering

Table 13.30 Summary of typical maintenance checks for transport airplanes A-Check B-Check C-Check D-Check

B 737

B 747

A 300

A 320

Time required

Man-hour

350 h 5.5 months 15 months 22000 h 25000 loading 108 months

650 h 1800 h 18 months 31000 h 72 months –

350 h 1000 h 18 months 25000 h 12500 loading 108 months

350 h – 15 months – – 102 months

Overnight One day A few days ≈ 6 weeks

20–130 200–1000 600–1400 50000

Part B 13

increase in composites and titanium, and a significant reduction in the use of aluminum. An even more startling change in structural materials distribution has taken place in military aircraft design. Figure 13.217 shows the distribution of structural materials in the McDonnell Douglas F-18 of 1978 and the Lockheed Martin F-22 of 2003. The most startling difference in the materials use between these two aircraft is the large reduction in the use of aluminum alloy and steel in the F-22 and the large increase in the use of titanium and composites. In addition to the introduction of newer, nontraditional materials, several new processes for producing parts from these new materials have been introduced, which reduce the number of parts required and also reduce the amount of labor required to produce each part. Examples of these new processes are resin trans-

fer molding (RTM) for producing composite parts, and hot isostatic pressing (HIP) for producing large highquality castings.

13.4.13 Airplane Maintenance Checks As noted earlier, in order to insure safe operations, especially for commercial transport aircraft, regular formal maintenance checks are made of the airplanes systems and structure. These checks range from the very simple preflight check of the aircraft conducted by the flight crew prior to each flight, to the extensive, detailed maintenance inspection checks conducted by technical specialists at major maintenance facilities. A summary of the various types of maintenance checks that are conducted by the airline operators is presented in Table 13.30.

References 13.1 13.2 13.3 13.4 13.5 13.6 13.7 13.8

13.9

13.10

J.Y. Wong: Theory of Ground Vehicles (Society of Automotive Engineers, Warrendale 1993) H. Heisler: Advanced Vehicle Technology (Butterworth-Heinemann, Oxford 1989) D. Hoyle: Automotive Quality Systems Handbook (Butterworth-Heinemann, Oxford 2000) C. Clarke: Automotive Production Systems and Standardization (Springer, Berlin Heidelberg 2005) D. Gruden (Ed.): Traffic and Environment (Springer, Berlin Heidelberg 2003) IEA: Energy Balance of OECD Countries 2005 (IEA, Paris 2005) IEA: Energy Balance of Non-OECD Countries 2005 (IEA, Paris 2005) Energy Information Administration (EIA): International Energy Annual 2004 (EIA, Washington 2006), http://www.eia.doe.gov IFEU: UmweltMobilCheck, Wissenschaftlicher Grundlagenbericht (IFEU – Institut für Energie und Umweltforschung, Heidelberg 2006), in German Lufthansa: Balance – Das Wichtigste zum Thema Nachhaltigkeit bei Lufthansa (Lufthansa, Frankfurt 2007), in German

13.11

13.12

13.13 13.14

13.15

13.16 13.17

13.18

E. Pasanen: Ajonopeudet ja jalankulkijan turvallisuus [Driving Speeds and Pedestrian Safety] (Helsinki University of Technology, Espoo 1991), in Finish K. Eichner: Auto Jahresbericht 2004 (Verband der Automobilindustrie e.V. (VDA), Frankfurt 2004), http://www.vda.de/de/service/jahresbericht/files/ VDA2004.pdf, in German D. Clausing: Total Quality Development (ASME, New York 1994) D. Bastow, G. Howard, J.P. Whitehead: Car Suspension and Handling (Society of Automotive Engineers, Warrendale 2004) H.-H. Braess, U. Seiffert (Eds.): Vieweg Handbuch der Kraftfahrzeugtechnik (Vieweg, Wiesbaden 2003), in German http://www.nhtsa.gov J. Happian-Smith (Ed.): An Introduction to Modern Vehicle Design (Butterworth-Heinemann, Oxford 2002) L.L. Beranek: Noise and Vibration Control (McGrawHill, New York 1971)

Transport Systems

13.19 13.20

13.21 13.22 13.23

13.24

13.26 13.27 13.28 13.29

13.30

13.31

13.32

13.33 13.34 13.35 13.36

13.37 13.38 13.39 13.40

13.41 13.42

13.43

13.44 13.45

13.46

13.47

13.48

13.49 13.50

13.51

13.52 13.53

13.54

13.55

13.56

13.57

13.58 13.59 13.60 13.61 13.62

C.F. Taylor: The Internal Combustion Engine in Theory and Practice (MIT Press, Boston 1985) W.W. Pulkrabek: Engineering Fundamentals of the Internal Combustion Engine (Prentice Hall, Englewood-Cliffs 2003) R. Stone: Introduction to Internal Combustion Engines (Society of Automotive Engineers, Warrendale 1999) H. Heisler: Advanced Engine Technology (Society of Automotive Engineers, Warrendale 1995) F. Zhao, D.L. Harrington, M.-C. Lai: Automotive Gasoline Direct-Injection Engines (Society of Automotive Engineers, Warrendale 2002) L. Guzzella, C.H. Onder: Introduction to Modeling and Control of Internal Combustion Engine Systems (Springer, Berlin Heidelberg 2004) SAE: Advanced Hybrid Vehicle Powertrain Technology, SAE 2002 World Congress, Detroit, Michigan (Society of Automotive Engineers, Warrendale 2002) G. Killmann: Toyota Prius – Development and market experiences, VDI Bericht 1459 (VDI, Düsseldorf 1999) P. Eastwood: Critical Topics in Exhaust Gas Aftertreatment (Taylor & Francis, London 2001) G. Mom: The Electrical Vehicle: Technology and Expectations in the Automobile Age (Johns Hopkins Univ. Press, Baltimore 2004) R. Johansson, A. Rantzer (Eds.): Nonlinear and Hybrid Systems in Automotive Control (Springer, Berlin Heidelberg 2003) R.L. Evans: Automotive Engine Alternatives (Springer, Berlin Heidelberg 1987) J.T. Pukrushpan, A.G. Stefanopoulou, H. Peng: Control of Fuel Cell Power Systems (Springer, Berlin Heidelberg 2004) N.D. Vaughan, D. Simner: Automotive Transmissions and Drivelines (Butterworth-Heinemann, Oxford 2002) P.G. Gott: Changing Gears: The Development of the Automotive Transmission (Society of Automotive Engineers, Warrendale 1991) G. Lechner, H. Naunheimer: Automotive Transmissions: Fundamentals, Selection, Design, and Application (Springer, Berlin Heidelberg 1999) T. Birch, C. Rockwood: Automatic Transmissions and Transaxles (Prentice Hall, Englewood-Cliffs 2001) T. Birch: Automotive Heating and Air Conditioning (Prentice Hall, Englewood-Cliffs 2002) W. Fung, M. Hardcastle: Textiles in Automotive Engineering (CRC, Boca Raton 2001) H. Wallentowitz, C. Amsel (Eds.): 42 V-PowerNets (Springer, Berlin Heidelberg 2003) U. Seiffert, L. Wech: Automotive Safety Handbook (Society of Automotive Engineers, Warrendale 2003) E. Chowanietz: Automobile Electronics (Newnes, Burlington 1995)

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A.D. Dimaragonas, S. Haddad: Vibration for Engineers (Prentice Hall, Englewood-Cliffs 1992) B. Hall: Noise vibration and harshness. In: An Introduction to Modern Vehicle Design, ed. by J. Happian-Smith (Butterworth-Heinemann, Oxford 2002) T.D. Gillespie: Fundamentals of Vehicle Dynamics (Society of Automotive Engineers, Warrendale 1992) J. Reimpell, H. Stoll, J.W. Betzler: The Automotive Chassis (Butterworth-Heinemann, Oxford 2001) W.F. Milliken, D.L. Milliken: Race Car Vehicle Dynamics (Society of Automotive Engineers, Warrendale 1995) W.F. Milliken, D.L. Milliken: Chassis Design: Principles and Analysis (Society of Automotive Engineers, Warrendale 2002) H.B. Pacejka: Tyre and Vehicle Dynamics (Butterworth-Heinemann, Oxford 2002) C. Campbell: Automobile Suspensions (Chapman Hall, London 1981) J.R. Ellis: Vehicle Handling Dynamics (Mechanical Engineering Ltd., London 1994) J.C. Dixon: Tires, Suspension and Handling (Society of Automotive Engineers, Warrendale 1996) ISO: ISO 8855: Road Vehicles – Vehicle Dynamics and Road-Holding Ability – Vocabulary (International Organization for Standardization, Geneva 1991) J.D. Halderman, D.C. Mitchell: Automotive Steering, Suspension, and Alignment (Prentice Hall, Englewood-Cliffs 2003) P.C. Brooks, D.C. Barton: Braking Systems. In: An Introduction to Modern Vehicle Design, ed. by J. Happian-Smith (Butterworth-Heinemann, Oxford 2002) D. Neudeck, R. Martin, N. Renzow: Porsche brake development: from the race track to the road. In: Advanced Brake Technology, ed. by B.J. Breuer (Society of Automotive Engineers, Warrendale 2003) T.P. Newcomb, R.T. Spurr: Braking of Road Vehicles (Chapmann & Hall, London 1996) R. Limpert: Brake Design and Safety (Society of Automotive Engineers, Warrendale 1992) W.C. Orthwein: Clutches and Brakes: Design and Selection (Marcel Dekker, New York 2004) U. Stoll: SBC – The Electro-Hydraulic Brake System from Mercedes-Benz. In: Advanced Brake Technology, ed. by B. Breuer, U. Dausend (Society of Automotive Engineers, Warrendale 2003) J.B. Heywood: Internal Combustion Engine Fundamentals (McGraw-Hill, New York 1988) F. Schleder: Stirlingmotoren (Vogel, Würzburg 2002), in German K. Mollenhauer: Handbuch Dieselmotoren (Springer, Berlin Heidelberg 1997), in German C.R. Ferguson, A.T. Kirkpatrick: Internal Combustion Engines: Applied Thermosciences (Wiley, Hoboken 2001)

References

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Part B

Applications in Mechanical Engineering

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13.73 13.74 13.75

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13.77 13.78

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R.K. Jurgen (Ed.): Automotive Electronics Handbook (McGraw-Hill, New York 1995) C.O. Nwagboso (Ed.): Automotive Sensory Systems (Chapman Hall, Boca Raton 1993) U. Kiencke, L. Nielsen: Automotive Control Systems: For Engine, Driveline and Vehicle (Springer, Berlin Heidelberg 2000) J.F. Keshaw, J.D. Halderman: Automotive Electrical and Electronic Systems (Prentice Hall, EnglewoodCliffs 2004) J. Marek, H.-P. Trah, Y. Suzuki, I. Yokomori (Eds.): Sensors for Automotive Technology (Wiley, Hoboken 2003) J. Valldorf, W. Gessner (Eds.): Advanced Microsystems for Automotive Applications 2005 (Springer, Berlin Heidelberg 2005) T. Rybak, M. Steffka: Automotive Electromagnetic Compatibility (EMC) (Springer, Berlin Heidelberg 2004) B. Peacock, W. Karwowski (Eds.): Automotive Ergonomics (Taylor & Francis, London 1993) J.M. Porter, C.S. Porter: Occupant accommodation: an ergonomics approach. In: An Introduction to Modern Vehicle Design, ed. by J. Happian-Smith (Butterworth-Heinemann, Oxford 2002) M. Blomè, T. Dukic, L. Hanson, D. Högberg: Simulation of Human-Vehicle Interaction in Vehicle Design at Saab Automobile: Present and Future. In: Recent Developments in Automotive Safety Technology, ed. by D. Holt (Society of Automotive Engineers, Warrendale 2004) pp. 621–627 M. Huang: Vehicle Crash Mechanics (CRC, Boca Raton 2002) N. Jones: Structural Impact (Cambridge Univ. Press, Cambridge 1997) J.A.C. Ambrosio, M.F.O.S. Pereira, F.P. da Silva (Eds.): Crashworthiness of Transportation Systems: Structural Impact and Occupant Protection (Springer, Berlin Heidelberg 1997) F.J. Stützler, C. Chou, J. Le, P. Chen: Development of CAE-Based Crash Sensing Algorithm and System Calibration. In: Recent Developments in Automotive Safety Technology, ed. by D. Holt (Society of Automotive Engineers, Warrendale 2004) pp. 327– 337 G. Pahl, W. Beitz: Engineering Design (Springer, Berlin Heidelberg 1997) L. Sage: Winning the Innovation Race: Lessons from the Automotive Industry’s Best Companies (Wiley, Hoboken 2001) M. Maurer, C. Stiller (Eds.): Fahrerassistenzsysteme mit maschineller Wahrnehmung (Springer, Berlin Heidelberg 2005), in German G. Döllner, C. Gümbel, O. Tegel: Prozesse und Bausteine des CAx-Datenmanagements in der Digitalen Produktentwicklung, 6. Automobiltechnische Konferenz ’Virtual Product Creation 2002’ (Berlin 2002), in German

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13.88

13.89 13.90 13.91

13.92

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13.95

13.96

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C.E. Armi: American Car Design Now: Inside the Studios of America’s Top Car Designers (Rizzoli, New York 2004) A. Parnow: Nutzen und Einsatz von RAMSIS bei DaimlerChrysler, RAMSIS User Conference (Kaiserslautern 2004), in German M.B. Abbott, D.R. Basco: Computational Fluid Dynamics (Longman, Harlow 1989) R.H. Barnard: Road Vehicle Aerodynamic Design (MechAero, St. Albans 2001) W.H. Hucho (Ed.): Aerodynamics of Road Vehicles from Fluid Mechanics to Vehicle Engineering (Society of Automotive Engineers, Warrendale 1998) U. Weidmann: Grundlagen zur Berechnung der Fahrgastwechselzeiten, Vol. 106 (IVT, Zürich 1995), in German K. Endmann: Bewährung des Y-Stahlschwellenoberbaus, EI–Eisenbahningenieur 10, 25–30 (2000), in German A. van Wilcken, F. Fleischer, H. Lieschke: Herstellung Feste Fahrbahn Rheda, Type Walter-Heilit with bibloc sleeper used for Köln-Rhein/Main, with 300 km/h regular train speed, Eisenbahntechn. Rundsch. 51, 172–182 (2002), in German C. Esveld: Modern Railway Track, 2nd edn. (MRTProductions, Zaltbommel 2001) K. Popp, W. Schiehlen: Fahrzeugdynamik (Teubner, Stuttgart 1993), in German Arbeitsgemeinschaft Rheine-Freren: Rad/SchieneVersuchs- und Demonstrationsfahrzeug Definitionsphase R/S-VD (Ergebnisbericht der Arbeitsgruppe Lauftechnik, Minden 1980), in German M. Hecht: New freight bogie is an important contribution for growth of rail-freight, Eur. Railw. Rev. 4, 61–64 (2002) K.H. Grothe, J. Feldhusen, H. Dubbel: Taschenbuch für den Maschinenbau, 21st edn. (Springer, Berlin Heidelberg 2005) pp. Q50–Q87, in German M. Löber, S. Schneider, N. Sifri, P. Trosch: Innovative crashfähige Kastenstruktur der TRAXXLokomotiven, Elektr. Bahn. 102(H8/9), 334–344 (2004), in German J. Pachl: Systemtechnik des Schienenverkehrs, Bahnbetrieb planen, steuern und sichern, 4th edn. (Teubner, Stuttgart 2004), in German P. Argüelles, J. Lumsden, M. Bischoff: European Aeronautics: A Vision for 2020 (Office for Official Publications of the European Communities, Luxembourg 2001) D.P. Raymer: Aircraft Design: A Conceptual Approach (American Institute of Aeronautics and Astronautics, Reston 2006) D. Küchemann: The Aerodynamic Design of Aircraft (Pergamon, Oxford 1978) Greener by Design: http://www.greenerbydesign. org.uk/home/index.php, accessed 18 Oct 2007

Transport Systems

13.114 C.D. Perkins, R.E. Hage: Airplane Performance Stability and Control (Wiley, New York 1949) 13.115 N.S. Currey: Aircraft Landing Gear Design: Principles and Practices (AIAA, Washington 1988) 13.116 J. Roskam: Airplane Design, Part IV; Layout Design of the Landing Gear and Systems (Roskam Aviation and Engineering Corporation, Ottawa 1989) 13.117 R.S. Shevell, I. Kroo: Introduction to Aircraft Design Synthesis and Analysis, Course Notes (Stanford University, Palo AIto 1981) 13.118 Anonymous: The Aircraft Gas Turbine Engine and its Operation (United Technologies Corporation, East Hartford 1988) 13.119 Anonymous: The Jet Engine (Rolls Royce pic, Derby 1986) 13.120 A.P. Fraas: Aircraft Power Plants (McGraw-Hill, New York 1943) 13.121 USAF Stability and Control Datcom: Air Force Flight Dynamics Laboratory (Wright-Patterson Air Force Base, Dayton 1975) 13.122 Anonymous: Brief Methods of Estimating Airplane Performance, Report No. SM-13515 (Douglas Aircraft Co., Santa Monica 1949) 13.123 Anonymous: DC-9-30 Performance Handbook (Douglas Aircraft Co., Long Beach 1969) 13.124 H.H. Cherry, A.B. Croshere Jr.: An Approach to the Analytical Design of Aircraft, SAE Quart. Trans. 2(1), 12–18 (1948) 13.125 K.H. Grote (ed.): Dubbel Taschenbuch für den Maschinenbau, 21st edn. (Springer Verlag, Berlin Heidelberg 2002), in German 13.126 D.J. Peery, J.J. Azar: Aircraft Structures (McGrawHill, New York 1982) 13.127 R.S. Shevell: Fundamentals of Flight (Prentice Hall, Englewood Cliffs 1989)

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13.100 C.B. Millikan: Aerodynamics of the Airplane (Wiley, New York 1941) 13.101 A.M. Kuethe, J.D. Schetzer: Foundations of Aerodynamics (Wiley, New York 1950) 13.102 H.W. Liepmann, A.E. Puckett: Aerodynamics of a Compressible Fluid (Wiley, New York 1947) 13.103 L.M. Nicolai: Fundamentals of Aircraft Design (METS, San Jose 1984) 13.104 J.M. Swihart: Design Choice and Marketing of Commercial Jet Airplanes (Boeing Commercial Airplane Company, Chicago 1978) 13.105 R.D. Schaufele: The Elements of Aircraft Preliminary Design (Aries Publications, Santa Ana 2000) 13.106 Federal Aviation Administration: Code of Federal Regulations, Title 14, Aeronautics and Space (Office of the Federal Register: Federal Aviation Administration, Washington 1997) 13.107 L.K. Loftin Jr: Subsonic Aircraft: Evolution and the Matching of Size to Performance (NASA Reference Publication 1060, Arlington 1980) 13.108 D.P. Raymer: Aircraft Design: A Conceptual Approach (AIAA, Washington 1989) 13.109 J. Roskam: Airplane Design: Part I, Preliminary Sizing of Airplanes (Roskam Aviation and Engineering, Ottawa 1989) 13.110 I.H. Abbott, A.E. Von Doenhoff: Theory of Wing Sections (Dover, New York 1959) 13.111 R.D. Schaufele, A.W. Ebeling: Aerodynamic Design of the DC-9 Wiing and High Lift System, SAE Paper No. 67-0846 (Aeronautics and Space Engineering Meeting, Los Angeles 1967) 13.112 Anonymous: The DC-9 Handbook (Douglas Aircraft Co., Long Beach 1991) 13.113 Anonymous: The DC-10 Handbook (Douglas Aircraft Co., Long Beach 1986)

References

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Construction 14. Construction Machinery

Eugeniusz Budny, Mirosław Chłosta, Henning Jürgen Meyer, Mirosław J. Skibniewski

14.1 Basics .................................................. 1150 14.1.1 Role of Machines in Construction Work Execution..... 1150 14.1.2 Development of Construction Machinery – Historical Outline ...... 1150 14.1.3 Classification of Construction Machinery ............ 1154 14.2 Earthmoving, Road Construction, and Farming Equipment ....................... 1155 14.2.1 Soil Science and Driving Mechanics 1155 14.2.2 Tyres.......................................... 1157 14.2.3 Earthmoving Machinery ............... 1160 14.2.4 Road Construction Machinery........ 1164 14.2.5 Farming Equipment..................... 1169

14.3 Machinery for Concrete Works ................ 1175 14.3.1 Concrete Mixing Plants................. 1175 14.3.2 Concrete Mixers........................... 1179 14.3.3 Truck Concrete Mixers .................. 1181 14.3.4 Concrete Pumps .......................... 1182 14.3.5 Concrete Spraying Machines ......... 1185 14.3.6 Internal Vibrators for Concrete ...... 1186 14.3.7 Vibrating Beams.......................... 1187 14.3.8 Floating Machines for Concrete ..... 1189 14.3.9 Equipment for Vacuum Treatment of Concrete ................................. 1190 14.4 Site Lifts .............................................. 1191 14.4.1 Material and Equipment Lifts........ 1191 14.4.2 Material and Equipment Lifts with Access to Personnel .............. 1197 14.5 Access Machinery and Equipment........... 1200 14.5.1 Static Scaffolds............................ 1200 14.5.2 Elevating Work Platforms ............. 1204 14.5.3 Hanging Scaffolds ....................... 1210 14.6 Cranes ................................................. 1213 14.6.1 Mobile Cranes ............................. 1213 14.6.2 Small Capacity Portable Cranes, Gantries, and Winches ................. 1216 14.6.3 Tower Cranes .............................. 1219 14.7 Equipment for Finishing Work ............... 1228 14.7.1 Equipment for Roofwork .............. 1228 14.7.2 Equipment for Plaster Work .......... 1229 14.7.3 Equipment for Facing Work .......... 1234 14.7.4 Floor Work.................................. 1235 14.7.5 Equipment for Painting Work........ 1237 14.8 Automation and Robotics in Construction..................................... 1238 14.8.1 Automation of Earthwork ............. 1240 14.8.2 Automation of Concrete Work ....... 1244 14.8.3 Automation of Masonry Work........ 1249 14.8.4 Automation of Cranes .................. 1250 14.8.5 Automation of Materials Handling and Elements Mounting by Mini-Cranes and Lightweight Manipulators ...... 1251

Part B 14

In this chapter the most common classes of machinery found on construction sites will be presented. For the purpose of this chapter the authors focus on construction machinery and equipment applications in the building and public utility sectors of the construction industry. The classes of machinery and equipment for earth, concreting, assembly, and finishing works described in this chapter are used not only in these two construction industries, but also in road, bridge, and railway building; pile, tunnel, and water foundation; the opening of mines; the building of natural gas and petroleum pipelines; sewerage systems; cooling towers for the power industry; and other industrial building structures. One should note that specialized equipment ensuring the efficiency, high quality, and safety of work during the realization of structures is used in almost all these kinds of construction. Even a brief description of this equipment would require a separate publication. For example, in road building alone 63 types of machines (see the draft International Standard ISO/FDIS 22242) are used. In the final part of this chapter the state of automation and robotization of construction machinery is presented.

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14.8.6 Automation of Construction Welding Work ....... 1252 14.8.7 Automation of Finishing Work ...... 1252 14.8.8 Automated Building Construction Systems for Highand Medium-Rise Buildings ......... 1256

14.8.9 Automation and Robotics in Road Work, Tunneling, Demolition Work, Assessing the Technical Condition of Buildings, and Service-Maintenance Activities ..... 1259 References .................................................. 1264

14.1 Basics 14.1.1 Role of Machines in Construction Work Execution

Part B 14.1

Construction work is to a large extent hard and labor intensive and often poses a health hazard. This is due to the fact that building production involves handling large masses of materials and that some of the materials, such as lime, paints, industrial chemical products, and asbestos, are detrimental to human health. In addition, most construction works are carried out in the open. The mechanization of construction started with hard physical work and labor-consuming effort, such as earth works and the horizontal and vertical transport of materials, only later embracing finishing works. Construction work mechanization is inseparably linked with the technologies used in construction and so one can distinguish work mechanization by the different branches of construction (e.g., housing, public utility building, civil engineering, industrial building, and power facility building) or by particular kinds of work, e.g., earth work, assembly, and finishing work. The transition from craft methods to a more economically effective form of industrial building, using a wide range of prefabricated units, gave an impetus to the development of more efficient machines for the assembly of such units as well as machinery and equipment for concrete works. The mechanization of construction is a worldwide phenomenon and determines the development of this industry. Through construction mechanization one can achieve the following goals:

• • • •

Speed up the rate of work in comparison with manual methods and so shorten the construction cycle. Reduce labor consumption, increase production capacity, and reduce work costs. Make work in construction less arduous and so more attractive. Improve work safety (construction is the most hazardous field of human activity).

Particularly rapid advances in construction mechanization were made after World War II in response to the urgent need to increase construction production capacity to provide the population with housing and improve standard of living. This was done by developing the construction machine building industry and new technologies consisting of the assembly of building structures from prefabricated units. Construction mechanization covered the following kinds of work: earth work, vertical and horizontal materials transport, materials handling, assembly, and finishing work (including external and internal plastering, painting, terrazzo and wooden floor sanding, and element fixing). Mechanization is the primary factor contributing to an increase in productivity and it should be economically worthwhile, which is achieved through the intensive use of modern machines in good working order. Definitions Construction machine: a device whose function is to increase or replace human or animal physical force in carrying out construction processes. In the field of construction machinery one can distinguish two general classes of machines: technological machines (for processing raw materials and/or semifinished products) and transport machines (for changing the location of building elements and materials). Construction work technology: a method for carrying out construction work. Mechanization of construction: activities covering the application of machines, equipment, and mechanized tools to carry out manufacturing processes in construction.

14.1.2 Development of Construction Machinery – Historical Outline The available historical data indicate that cranes form the oldest class of construction machines invented by humans. Cranes were known in Greece as early as the

Construction Machinery

14.2 Earthmoving, Road Construction, and Farming Equipment

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14.2 Earthmoving, Road Construction, and Farming Equipment

• • • • •

The machine must be connected to an energy source. Energy is needed for running the device or the drive. The machine can move actively (automotive) or passively (pulled). It must be equipped with a (wheel or chain) chassis to supply the tools with energy. It must be possible to integrate all components of the machinery system (drive, sensors, actors, etc.) into the vehicle.

Another important feature of earthmoving, construction, and agricultural machinery is the fact that they are designed to fulfil specialized working functions and to be part of complex processes in the area of construction or agriculture.

•

concrete must be regarded as soil, representing artificial, manmade hard soils (rocks) that provide a good driving surface. Soil is the main resource for plant production and, indirectly, for animal production, thus serving man’s demands. Regarding its important role, soil cannot be replaced by any other resource. Soil fertility is mainly dependent on the activity of soil bacteria, fungi, algae, and other microbes. Mobile working machines, especially agricultural machines, are closely linked to this resource, as they are utilized for plant and animal production. The same is true for forestry machines and municipal machines. Earthmoving machines, which are also mobile working machines, also work mainly on soil.

A more detailed description of soil follows, in terms of both its physical and biological features. Soil consists of various components:

• • •

Solids Liquids (water) Gas (air)

This distribution of solid, air, and water can be represented as a three-phase system. Soils are classified depending on their aim and application. So, in the area of earthmoving, for rock production, the decisive criteria are different from those in the area of agriculture, which concentrates on soil fertility. An example of agricultural soil classification is the World Soil Classification initialized by the Food and Agriculture Organization (FAO) [14.6]. Rock may be classified according to the ISO standard 14689-1 entitled Geo-technical Investigation and Testing – Identification and Classification of Rock [14.7]. Apart from these international classification systems there are various national ones [14.8].

14.2.1 Soil Science and Driving Mechanics Soil Composition Regarding mobile working machines, the soil is of special importance in two regards:

•

Mobile working machines move on the soil. Every vehicle requires ground to move on. Depending on the type of chassis used, the drive force must be introduced into the ground in some form, which means that the soil has to take up the driving power; otherwise the wheels or chains would spin. In a broader sense, even roads made of asphalt or

Chassis Types The chassis can be regarded as an interface between the mobile working machine and the ground; two main groups can be distinguished (Fig. 14.5):

• •

Wheel chassis Tracklaying or crawler chassis

In addition to these two groups, there are specialpurpose chassis types such as walking chassis to move machines, e.g., in open-cast mining. The driving resistance can be calculated by multiplying the force due to

Part B 14.2

It is decisive for human action to use tools, devices, and machines. For a long time man has been making use of machines for construction and agriculture. The huge buildings of antiquity could never have appeared without the application of construction machinery. However, agricultural machinery – especially those according to the EU machinery directive [14.4] – did not emerge until the 18th and 19th century, with the UK and the USA being the first to make use of them [14.5]. A particular problem to be addressed for agricultural machinery was the necessity to be mobile, and today it is still mobility which is one of the most important functions of earthmoving, road construction, and agricultural machines. This is the feature which distinguishes them from stationary machines such as machine tools. Therefore, they are summarized as mobile working machines. Due to their requirement for mobility, the following issues are important for this kind of machine and their construction:

Construction Machinery

•

• •

•

Tampers: The tamper is the first compaction device; it is a tamper bar driven by an excenter shaft. The throw is determined by the excenter radius and can be gradually adjusted. Depending on the material, the throw is about 2–7 mm. Another influencing factor is the drive speed, which ranges from 600 to 2400 rpm. Double tampers: Another possibility is to use a double tamper, which is driven by an excenter. Vibration stimulator: The majority of screeds make use of the vibration principle in order to compact the layers. Usually, a vibration stimulator is mounted on the blade of the screed, being driven mechanically with an adjustable frequency. Pressure bars: Pressure bars are similar to tampers. They are driven by pressure impulses which are transmitted into the layer by the bar, thus effecting compaction.

To meet the required geometrical dimension of the road to be constructed, use is made of leveling systems. Graders, dozers, slip-form pavers, and milling machines are also used, designed to fulfil the following tasks [14.21, 24]:

Driver’s stand Motor station Hopper Extendable screed

Auger for material transport

Wheel chassis

Fig. 14.22 Road pavers

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Part B 14.2

sitive to soil unevenness, facilitating more even road construction. In order to meet the requirements of an even layer density and of very even roads, it is necessary to have a regular work process without interruptions. This is only possible with an automotive material reservoir to transport the material from the trucks to the paver in a regulated way [14.23]. In many cases, factors associated with the construction, e.g., too small construction sites, why the paver must work without such a feeder. For this reason, the traction drive as well as all drives for material transport have to be controllable. The command variable of the individual control cycles is the amount of material. In order to measure the amounts of material in the corresponding transport areas, either mechanical material sensors or ultrasound distance sensors are used, with the measured values being processed by digital steering systems. Compacting the asphalt layer is necessary to ensure its stability. Immediate compaction is carried out by the paver’s screed. The following rollers are then used to obtain the final density. The following compaction elements are in use:

14.2 Earthmoving, Road Construction, and Farming Equipment

Construction Machinery

Operation Elements It is only in combination with work devices that a tractor becomes a working machine. These devices may be attached, hitched, or mounted to the tractor. For rear device attachment, a three-bar linkage combined with a power lift has proved to be useful for the following reasons:

• • • •

Statically defined rigid connection between tractor and device Adjustable device due to the power lift The three-bar linkage can be adjusted to different devices by control devices The possibility of lateral mobility restriction or height and lateral mobility restriction

lifting control only works with traction force control. If the speed difference exceeds this limit, the traction force is changed by working depth modification so as to reduce the working depth and the slip. Another function of the electronic lifting control is active vibration removal, which involves balancing of the device’s vibrations when passing on roads by means of automatic hydraulic steering in the opposite direction. This helps to improve driving comfort and steering conditions when driving with heavy devices attached to the tractor. The force-measuring bolts of the lower links serve to measure the force signal of the lifted device. The dynamic part emerged by vibrations is used as an actual value for lifting device control. In a restricted control area, for damping the lifting device is lifted or lowered slightly together with the attached device. Control System and Electronics The task of electronics is to control a tractor’s components [14.32]:

• • • • • • •

Motor Engine Hydraulics Gears Devices Data collection and storage Diagnosis

Modern tractors mainly use microcontrollers [14.26] (Fig. 14.31), equipped with CAN interfaces for communication. This yields new possibilities of diagnosis and overall optimization of the tractor’s system. Due to the fact that tractors are applied with very different devices attached, which also using electronic control systems, it is important to make them communicate by a uniform interface, e.g., according to the ISO 11783 standard [14.33].

14.3 Machinery for Concrete Works 14.3.1 Concrete Mixing Plants Since they must be well suited to their intended use and to construction needs, concrete mixing plants form a class of machinery with highly diverse designs. The diversity of concrete mixing plants’ design features is connected with their capacity (10–250 m3 /h), their compatibility with the means of receiving the produced concrete mix, the production process control automa-

1175

tion, the need for printing certificates for the sold concrete mix, the required assembly area, and the climatic conditions in which they are operated. Concrete mixing plants can be classified as follows [14.34]:

•

Concrete mixing plants (equipped with a mixer) producing ready-made concrete mix and concrete mix batching plants for proportioning and feeding

Part B 14.3

The three-bar linkage consists of two lower links and one upper link. The three-bar linkage’s individual part dimensions are standardized into four categories (I–IV) for different power classes [14.31]. For a long time, rear hitches have been equipped with a control device that automatically lifts and lowers the power lift depending on a control value. By means of this power lift control, the driver is relieved of a task and working efficiency is increased by reducing the slip between the tyre and the soil as well as by raising the drive force. Possible control values are the device position relative to the tractor (position control), the traction force acting between the tractor and the device (traction force control), the device position related to the soil (depth control), and a mixture of traction force and position control (mixed control). When using slip control, the actual driving speed is measured by a radar sensor. The theoretical speed is defined by a wheel-speed sensor. The electronics determines the speed difference and the slip. If the speed difference is smaller than a fixed limit, the electronic

14.3 Machinery for Concrete Works

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Applications in Mechanical Engineering

Part B 14.3

For these machines the width of the floated strip in one pass ranges from 1700 to 2400 mm. The floating machine’s control system consists of push-buttons, two joysticks for controlling the running direction, and two knobs for setting the angles of inclination of the blades. The operator controls the floating machine while sitting in a centrally situated seat whose symmetry axis coincides with the machine’s lateral axis. There are also tandem systems in which the symmetry axis of the operator’s seat coincides with the machine’s longitudinal axis. In two-disk floating machines two floating system designs are used. In one of them the floating blades’ outline circles may overlap while in the other there is a gap between the outline circles. The former design makes it possible to cover the whole floating width but no solid floating disks can be used. In the latter design floating disks can be used but the pass path needs to be corrected. Depending on the floating width, machines of this type usually weigh 300–450 kg and the engine’s maximum power rating is 24 kW. In the latest designs the mechanical systems are replaced by hydraulic systems, which ensure the smooth operation of the machine. In two-disk floating machines the angle of inclination of the blades is adjusted by flexible-connector-type control systems. The control of the floating machine’s running direction is based on the principle of differentiation of the friction forces acting in the particular

quadrants of the outline circles, by changing the inclination of the blade ring. This principle applies to both oneand two-disk floating machines. Control is effected by means of the cranks, for each blade ring independently. In order to ensure operational safety, safety cutout switches, usually in the form of a pedal pressed during operation by the operator’s foot, are used in two-disk floating machines. If the operator falls out of the seat, the floating machine is automatically stopped.

14.3.9 Equipment for Vacuum Treatment of Concrete Vacuum treatment is used to make high-quality concrete bases and floors. Its advantages include:

• • • • •

Rapid increase in concrete strength in the initial period after placing concrete mix and applying the vacuum process A 15% increase in the final strength and the resulting cement savings Improved concrete features such as frost resistance, compression strength, imperviousness to water, and reduction in shrinkage deformation and floor dusting Reduction in the harmful effect of low temperatures on the curing of fresh concrete Quick execution of works

Floating

Vacuum treatment

Levelling of top surface using vibrating beam Spreading of concrete mix and compaction by means of immersion vibrator

Fig. 14.56 Execution of concrete base with vacuum treatment use

Construction Machinery

•

14.4 Site Lifts

1191

Ease of spreading of the concrete mix because of its semiliquid consistency

The use of vacuum processing of concrete is especially advantageous at low ambient temperatures (down to −5 ◦ C) since the removal of excessive water and air bubbles to a large extent eliminates destructive processes. The execution of concrete bases by the vacuum process can be divided into four operations (Fig. 14.56):

• • • •

Roughly, the rate of vacuum treatment is 2 min/cm of base thickness. This means that a 10 cm thick base is treated for about 20 min. Floating is started when a boot impression in the concrete is about 3 mm deep. The floating equipment includes immersion vibrators, vibrating beams, guideways with supports, expansion-joint inserts, vacuum unit with a suction mat, and floating machines. The vacuum unit’s main assembly (Fig. 14.57) is a vacuum pump with a driving motor. The pump usually has a sealing water-ring. The vacuum unit also includes: a vacuum tank, functioning as a settling tank for the

Fig. 14.57 Concrete vacuum treatment unit and suction

mat

sucked in impurities, connected to an atmospheric tank from which the air and water that has been sucked in is carried off, a wheeled frame, and an electric system. The development of vacuum units is directed towards reducing the mass and size of the vacuum unit and improving the mat. The currently used vacuum units made by leading manufacturers enable one-time sucking off of a concrete base 60 m2 in area with a 4 kW driving motor and a machine mass of about 90 kg. The releaent pressure range for vacuum treatment of concrete is 75–95% vacuum (0.75–0.95 kg/cm2 negative pressure). Great advances have been made in the design of the suction mat. Older mat designs consisted of three layers, in the form of a filter cloth, a plastic flow mesh, and a tight cover, laid in turn on the vacuumed concrete mix. Current mats are manufactured as one integrated cover performing all three functions, i. e., ensuring the filtration and flow of the sucked off water and air and providing tight covering.

14.4 Site Lifts 14.4.1 Material and Equipment Lifts Construction material lifts are intended for the vertical transport of building materials during the erection of new buildings and repairs. They may also be employed for the assembly of scaffolds and other construction site protection structures. A classification of material and equipment lifts according to different criteria is shown in Table 14.1. The most common type on construction sites are mast lifts with a cable or rack-and-pinion hoisting gear. Depending on the lifting height the lifts can be operated free-standing or anchored. The maximum lifting

height of free-standing lifts depends on the stability of the supporting structure. The maximum lifting height of an unanchored lift does not usually exceed 12 m. Mast Material and Equipment Lifts with Cable Hoisting Gear The lifting capacity of lifts with a cable hoisting gear usually is below 600 kg. Examples of lifts with a cable carriage hoisting drive are shown in Figs. 14.58, 14.60 and Table 14.2. A lift with a capacity of 200 kg (Fig. 14.58) is made up of the following structural units:

Part B 14.4

Spreading of concrete and compaction by an immersion vibrator Compaction and leveling of the concrete mix’s top surface by means of a vibrating beam pulled on guideways Covering with a suction mat and vacuum treatment Floating of the surfaces by means of rough and finishing floating machines

Construction Machinery

Table 14.5 Specifications of selected shaft material and

equipment lifts Parameters Lifting capacity (kg) Lifting height (m) Lifting speed (m/min) Platform’s dimensions (m) Electric motor – Supply voltage and frequency (V/Hz) – Motor’s power (kW) Total mass of 15 m- and 70 m-high lift, respectively (kg)

500– 1500 15– 70 18– 33 2 × 1 × 1.5 230– 400/50 7 – 10 2300–10 000

• • • • •

• • • • • • •

A shaft An upper beam Guides A bottom cable pulley The platform’s upper beam A platform A winch (typical lifting winches with an electric or diesel drive can be used)

The shaft has a spatial truss structure. The load-bearing platform is made of steel sections. The cable is guided by the bottom and top cable pulleys. The end of the cable is fixed to the upper beam (Fig. 14.65). There is also a shaft lift design in which the shaft is made of only flat frames anchored to the building’s wall. Shaft lifts are equipped with similar safety devices as other material lifts. Material lifts are equipped with the following safety devices:

• • •

A gripping device which stops the platform as it descends whenever it exceeds the maximum allowable rate of descent. Protection against disengagement of the drive wheel from the mast’s rack. As standard, sliding guides are used. They keep the load platform on the mast even if the roller guides fail. An emergency lowering system used in the case of a prolonged power failure. Some lifts are equipped

• • •

1197

with emergency lowering systems with speed selfstabilization – the speed stabilizes below the speed at which the gripping device is actuated. The upper and lower limit switches, automatically stopping the platform at the mast’s highest and lowest levels. Switches and locks for stop doors or barriers, preventing their accidental opening when the platform is outside the stop zone or in motion. Stops to ensure that the platform will be brought to a stop if the limit switches fail. An induction sensor that monitors mast presence during mast assembly. A sound system signalling the start of a platform ride. Protection against electric shock. Overload protection of the electric motors. Switches actuated when the working platform skews in two-mast lifts.

The operation of the cable-driven material lifts described above typically consists of the control of the movement of the carriage by pushing buttons on the control panel at the lower station. It is also possible to switch to control from the platform during assembly and maintenance of the lift.

14.4.2 Material and Equipment Lifts with Access to Personnel Material and equipment lifts with access to personnel are intended for the vertical transport of persons and materials during construction/assembly works and repairs of mainly high-rise buildings in housing and industrial construction. Their design is usually similar to that of material and equipment lifts with a rack-andpinion hoisting gear. A person and material lift consists of a cabin with a rack-and-pinion drive, moving on a mast secured at the bottom to the lift’s base and anchored to the building’s wall, and transport stages (stops) between which transport takes place. The mast has a segmental structure and can be extended by adding mast sections. It is anchored by means of a system of tubes, which makes it possible to adjust the mast’s position relative to the building’s wall. The lift can have two cabins, each with its own drive system, whereby the transport of persons and materials can be doubled. The lift’s cabins move on a common mast independently of each other. Examples of person

Part B 14.4

Shaft Material and Equipment Lifts Shaft material and equipment lifts (Fig. 14.65) are used for the vertical transport during the construction of medium- and high-rise building structures. A shaft lift consists of the following main parts (Fig. 14.65 and Table 14.5):

14.4 Site Lifts

1200

Part B

Applications in Mechanical Engineering

14.5 Access Machinery and Equipment 14.5.1 Static Scaffolds

Part B 14.5

A scaffold is a temporary (usually bar) structure erected to provide safe access during construction, repair, maintenance, and demolition of all kinds building structures. Scaffolds can be classified according to the different criteria specified in Table 14.7, and the main criteria for classifying scaffolds and the related terminology are described below. One of the major criteria is the division of scaffolds with regard to their design and assembly method. Particularly important is the division into tube–coupler scaffolds and system scaffolds. Tube–coupler scaffolds (Fig. 14.68) are constructed from steel tubes and couplers, and the stagings are made from boards or balks. In this type of scaffolds, the dimensions of the structural grid are not rigidly imposed by the dimensions of the components, e.g., by the length of the tubes. Workers assembling a tube–coupler scaf-

fold according to a blueprint ascertain the positions of all the elements which determine the dimensions of the structural grid and the verticality of the uprights. The basic components of the tube–coupler scaffold are shown in Fig. 14.68. In tube–coupler scaffolds, such elements as standards, transons, and bracings are joined eccentrically by right-angle or swivel couplers, as illustrated in Fig. 14.69. A characteristic feature of scaffolds made of prefabricated elements (system scaffolds) is that their dimensions (or some of their dimensions) are determined by the dimensions of their components. All frame and modular scaffold systems belong to this class. A general view of system scaffold constructions is shown in Fig. 14.70. Modular scaffolds and frame scaffolds are shown on the left and right, respectively. In the frame scaffold, the vertical structure is made up of prefabricated flat frames. The frame consists of two uprights permanently connected by transverse el-

Table 14.7 Classification of scaffolds No.

Classification criterion

Name of scaffold

1

Intended use

2

Design and assembly method

3

External load-bearing mode

4

Protection of scaffold against overturning

5

Transferability

6

Operating mode

7

Material from which scaffold load-bearing elements are made

8

Technical–organizational and formal-legal aspects

Working scaffold Protective scaffolds Load-bearing scaffolds Tube–coupler (bricklayer’s) scaffolds Ladder scaffolds Scaffold made of prefabricated elements Modular (system scaffold) Frame Standing scaffolds Suspended scaffolds Trestle scaffolds Outrigger scaffolds Cantilever scaffolds Anchored facade scaffolds Scaffolds secured to base by guy-ropes Free-standing scaffolds Immobile (stationary) scaffolds Mobile (portable) scaffolds Scaffolds used for short periods, e.g., during working shift Permanent scaffolds used for prolonged periods without dismantling Wooden scaffolds Aluminum scaffolds Steel scaffolds Scaffolds in typical version Individually designed scaffolds

Construction Machinery

14.5 Access Machinery and Equipment

1203

Table 14.8 Specifications of typical portable single-mast climbing platforms Parameters Platform’s length/lifting capacity (m/kg)

4.2/1300 7.4/1000 10.5/700

4.2/2000 7.4/1700 10.5/1400 12.5/1200

4.2/2700 7.3/2300 10.5/1900 13.7/1500 16.9/1000

6 6 11.5

20 15 25

15 15 25

18– 20 13– 15 25

100

200

200

200

6 1.0 15 6 1800 1508/48 400 V/50 Hz 3 kW, 16 A

12.5 0.3 50 6 3500 1256/82 400 V/50 Hz 3 kW, 16 A

12.5 1.4 60 6 4000 1256/82 400 V/50 Hz 3 kW, 16 A

12.5 2.5 65 6 4000 1256/82 2 × 400 V/50 Hz 3 kW, 16 A

A scaffold in a typical version means an assembly version of the scaffold which covers the most frequent applications of the scaffold structure. It is assumed that the manufacturer has provided a proof of the scaffold’s static strength and neither its user nor the company assembling it has to provide such a proof in order to certify the scaffold fit for use on the construction site. Also in the case when the assembly version has been realized in accordance with a generally recognized assembly standard the proof does not have to be provided. The generally recognized assembly standard may be defined in assembly norms or instructions issued by the manufacturer of the given type of scaffold. Scaffolds in a typical version are anchored, facade, working scaffolds with a height of up to 24 m and access working towers erected to a height of 8 m outdoors and to a height of 12 m indoors. Typically, a useful load of 2 kN/m2 , sometimes 0.75, 1.5, 3, 4.5, and 6 kN/m2 , is assumed for stagings. Examples of scaffolds in their typical versions are shown in Fig. 14.72. Each scaffold that is not in a typical version should be individually designed and its statics tested. The range of the structural analysis depends on the complexity of a given scaffold structure. Examples of atypical scaffolds are shown in Figs. 14.73–14.77.

Competent construction design companies, usually connected with equipment manufacturers, should be entrusted with the design of atypical scaffolds. When selecting scaffolds the user should take into account the following:

• •

The construction site’s location (a wind load zone, power lines, traffic routes, etc.) The kind of terrain and the lay of the land on which the scaffold is to be founded

Standard Nogging functioning as ledger or crossbar

Coupling head

Vertical bracing

Fig. 14.71 Modular scaffold joint

Part B 14.5

Maximum platform elevation without anchoring – Protractible beams protracted on both sides (m) – Protractible beams protracted on one side of mast (m) Maximum platform elevation with one mast anchoring point located at top (m) Maximum platform elevation with anchoring along entire length of mast (m) Spacing between anchors (m) Max. length of platform’s protractible part (m) Max. loading of struts (kN) Lifting speed (m/min) Transport mass (kg) Mast section: length/weight (mm/kg) Electric specifications of platform lifting gear

4.1/1300 7.1/800 10.1/500

Construction Machinery

Stationary Sectional Hanging Scaffolds This group includes: straight, angular, and arched hanging scaffolds, which are intended for housing and industrial construction applications, mainly facade works. Similarly to the case of the two-person scaffolds described above, the platform is suspended by steel cables from booms laid on the roof and secured with a ballast or anchored in the roof. The scaffold consists of 3–4.5 m long 1.5 m wide segments adding up to a desired length. A schematic of the sectional hanging scaffold is shown in Fig. 14.84. Thanks to the platform’s sectional design, hanging scaffolds of different shapes (angular and arched) can be formed, as shown in Fig. 14.85. The vertical motion of the scaffolds is effected by an electric motor, cardan shafts, and winches.

14.6 Cranes

The possible ways of anchoring the booms are shown in Fig. 14.86, and the specifications of sectional hanging scaffolds are listed in Table 14.14. Mobile Hanging Scaffolds Mobile hanging scaffolds can be moved horizontally on an industrial car without disassembling and reassembling the booms from which they are suspended. A typical mobile hanging scaffold design is shown in Fig. 14.87. The vertically moving work platform is suspended by steel cables from booms mounted in a swinging mode on an industrial car. Drives for traveling on a track laid on the roof of a building and for hoisting the platform are installed on the industrial car. The scaffold can be steered from both the platform and the roof. Scaffolds of this type usually have a hoisting capacity of about 300 kg and are capable of an elevation of 100 m.

Mobile cranes are intended for lifting and lowering loads and transferring them in the horizontal plane [14.23, 32]. Mobile cranes find wide application in the assembly of steel and reinforced concrete structures, repairs and materials handling. Their advantage is their mobility, high traveling speed, and quick setup on a construction site. As regards their undercarriage, mobile cranes are divided into:

• • •

Truck cranes Terrain-wheeled cranes Crawler cranes

Mobile cranes are typically truck-mounted. Cranes with a maximum lifting capacity of up to 20 t are usually mounted on mass-produced truck chassis, whereas high-capacity cranes are mounted on special undercarriages. The latter may have all their wheels driven and turnable, making them highly manoeuvrable and able to move over rough terrain. Modern hydraulically driven cranes have replaced cranes with mechanical and pneumatic steering. A modern truck crane with electrohydraulic drives and steering is shown in Fig. 14.88. The crane’s base is a frame which, depending on the crane’s design and hoisting capacity (maximum

20 t), may constitute a separate subassembly mounted on a typical truck chassis or be an integral part of a special truck chassis (high-capacity cranes). Mobile cranes are usually driven by internal-combustion engines, although some terrain-wheeled cranes and their working tools are driven by hybrid combustion–electric drives. In high-capacity cranes usually two driving motors are used: one for driving the vehicle and the other (situated in the slewing body) for driving the working tools. The crane’s frame incorporates four struts, with hydraulic lifts attached to their ends, extended by two hydraulic servos. For work the struts are protracted horizontally and then the whole crane is jacked up by the hydraulic lifts to such a height that the road wheels do not touch the ground. Some cranes can operate on their road wheels. The slewing body with the operator’s cabin is connected with the chassis frame through a crown bearing. All the working fittings are mounted on the crane body. The jib consists of a stationary section and two to six protractible sections. The jib’s sections are usually protracted synchronously. The winch is mounted at the origin of the telescopic jib’s stationary section. A significant number of cranes are equipped with an auxiliary jib which in its working mode can be attached to the telescopic jib’s head in order to increase the crane’s radius. In the traveling mode the auxiliary jib is attached to the side of the permanent telescopic jib. A counterweight is mounted at the rear of the slewing body.

Part B 14.6

14.6 Cranes 14.6.1 Mobile Cranes

1213

1214

Part B

Applications in Mechanical Engineering

The principal working gears and systems of telescopic-jib cranes are:

All cranes are equipped with the following safety devices:

•

•

•

• •

Part B 14.6

A jib-protracting gear driven by two reversible hydraulic cylinders. As a rule, the jib’s members are protracted synchronously. A crane radius changer driven by a reversible hydraulic cylinder. In high-capacity cranes sometimes two hydraulic cylinders are used for this purpose. The crane radius changer typically allows one to set the jib at an angle of 0–75◦ . A slewing gear driven by a hydraulic engine, a planetary gear, and a crown bearing with outer meshing. The slewing gear is equipped with an automatically controlled multiple disk brake. A lifting gear consisting of cable drum winch, a cable, pulleys, and a pulley block. The cable drum is driven by a hydraulic engine and a planetary gear. As a rule, the winch’s pull force is much weaker than the crane’s maximum lifting capacity. Hence it is necessary to use multistrand blocks to reduce the forces in the cable.

All the working gears and the gear that extends the struts are hydraulically driven. In truck-mounted low-capacity cranes equipped with one internal-combustion engine, the hydraulic oil tank and the hydraulic pumps are mounted in the crane’s undercarriage. Hydraulic oil is fed into the body’s working circuits through a hydraulic rotary joint. In cranes with two internal-combustion engines, the hydraulic pumps of the crane’s working circuits are driven by the engine mounted in the slewing body. The following working motions of the crane are controlled:

• • • • •

Body slewing Change of jib length Inclination of jib Lowering and raising of the hook Traversing gear motions (for terrain crawler cranes and some wheeled cranes in which traveling with a load suspended from the hook is allowable)

These working motions are typically controlled from the operator’s cabin. A system of control levers, which can limit the linking of the particular working motions, ensures proper control of the latter. The recommended systems and directions of motion of the control levers are shown in Fig. 14.89.

• •

•

• •

A load limiter – usually a microprocessor unit signalling that the hook block is reaching the rated load and disabling the crane’s working motions when the rated load is exceeded. A signal indicating that the hook block is approaching the rated load is activated at 0.9–1.0 of the nominal load: an orange indicator light comes on in the control panel in the operator’s cabin and an audible warning is produced. Overload is signalled by a red indicator light and disabling of the working motions, except for downward motion of the lifting gear. The signalling system is activated and motions are disabled when the crane block load is in the range of 1.0–1.1 of the rated load. The load limiter should be calibrated for a given hoisting capacity characteristic. Each load limiter should be equipped with an interlock for disabling the limiter in an emergency: A block upper position limit switch – disengages the winch’s drive when the block finds itself at a certain distance from the jib’s head. Slewing gear limit switches – are used in cranes that cannot turnaround completely, e.g., an allowed rotation angle of 270◦ . These protect the crane against the situation in which the slewing column and the jib reach an out-of-specification position relative to the chassis. Cable unwinding limit switch – protects against complete unwinding of the cable from the winch drum. The limiter is actuated when there are only a few coils of cable left on the drum. Emergency jib retracting and lowering system – enables the retracting and lowering of the jib to a safe position in the case of a failure of the hydraulic system. Hydraulic system protections – enables the automatic return of the piston rods of the struts’, the radius changer’s, and the lifting gear’s cylinders.

The basic parameters characterizing the operating properties of mobile cranes are:

• • •

Hoisting capacity Radius Hoisting height

The values of these parameters are usually presented in the form of diagrams representing hoisting

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Part B

Applications in Mechanical Engineering

A sample hoisting capacity–radius characteristic of a crane with a luffing boom is shown in Fig. 14.107. Quick-Assembling (Self-Erecting) Cranes. Quickassembling cranes form a separate class of tower cranes. Their characteristic feature is that they can be quickly assembled on a setup site. They do not require any other truck crane to be assembled, provided that the construction site has been properly prepared. The access road should be prepared such that the tractor towing the crane can reach the setup site and the latter should be practically at the same level as the access road. The setup site should be large enough for the vehicle with the ballasts to drive up close enough and for the crane to self-ballast (by means of its small auxiliary crane) and

unfold. The crane is set up through the unfolding of the articulated mast and jib segments by its own drive units. During assembly the parts are connected by articulation but, once positioned, they are successively immobilized, forming a fixed load-bearing structure. The way in which self-assembling cranes are erected is illustrated in Fig. 14.108b, which shows four stages of assembly. Once the crane is properly set up, the jib’s tip section is raised slightly. Then, using the crane’s driving gears, its tower is put in a vertical position. Finally, the jib is completely unfolded. Quick-erecting cranes are equipped with a trolley jib. They have a slewing tower which is secured to the base through a rim bearing. An exemplary hoisting capacity–radius characteristic of a quick-erecting crane is shown in Fig. 14.109.

14.7 Equipment for Finishing Work Part B 14.7

The aim of finishing work is to invest a structure with the design features and external and internal appearance. Finishing work includes:

• • • • •

Roofing Outdoor (elevation) and indoor plastering Facing work Flooring Painting

The development of equipment for finishing work has been associated with the mechanization of the most labor-intensive and arduous activities. The first machines for finishing work were mortar pumps, followed by wood floor scrapers, parquet sanders, and mineral floor grinders. Later mechanical painting was introduced. Finishing work is carried out mainly on the construction site but efforts are made to move it to backup facilities and transport ready-made elements to the site in order to increase work effectiveness. The range of finishing work is very wide in terms of both execution techniques and materials. The most commonly used equipment for finishing work is presented below.

14.7.1 Equipment for Roofwork From the materials point of view the roofing used today can be divided into:

•

Tar paper roofing mainly made from thermoweldable membrane

• • • •

Ceramic and stoneware tile roofing Bituminous shingle roofing Metal (zinc- and acrylic-coated steel sheet, rustproof sheet, zinc sheet, titanium–zinc sheet, copper sheet, and other) roofing Polyvinyl chloride (PVC) panel and ethylene propylene diene monomer (EPDM) membrane roofing

Most roofwork is done using hand tools. For making thermoweldable membrane roofing devices equipped with liquefied petroleum gas (LPG) burners are used. There are two methods of making insulating coatings from thermoweldable membrane: 1. By means of a roofing machine and 2. Using only a set of burners A roofing machine consists of the following units: a tar paper spreader, a battery of burners, a flexible gas hose, and an LPG cylinder. The burners’ flames melt the layer of pitch on the tar paper and at the same time heat up the base. Under these conditions the tar paper is pressed against the base by a roller made of segments to ensure that the tar paper is pressed down along the entire width of the roll. On contact with the base the pitch cools quickly, forming a layer that bonds the tar paper to the base. The set of burners includes a six-burner battery as well as a double burner and a single burner. The sixburner battery is secured to a steel frame equipped with two wheels. The single burner and the double burner are

Construction Machinery

University in London, and the former Bristol Polytechnic), and Spain (the Carlos III University in Leganés, Madrid). As a result of the development of automation and robotics in construction in the last three decades this domain, integrating the achievements of robot technology, information technologies (IT), and design for construction (DfC), has acquired the status of a scientific discipline. Twenty years ago the International Association for Automation and Robotics in Construction (IAARC) was formed. This association organizes annual International Symposia on Automation and Robotics in Construction (ISARC). The 21st ISARC was held in Jeju (South Korea) in September 2004, and the 22nd ISARC took place in Ferrara, Italy in September 2005. Papers published in the symposium proceedings represent the latest achievements in this field. In automated construction equipment two kinds of devices can be distinguished: teleoperation manipulators, referred to as construction manipulators, and construction robots. Construction manipulators are remote-controlled by the operator while construction robots are autonomous computer-controlled devices. The robot’s software allows it to perform variable tasks within its application range. In the development of automated equipment, four stages corresponding to the particular generations of this equipment can be distinguished [14.45]. The first generation, which can be called automated construction devices, was developed by outfitting existing construction equipment with electronic sensors and digital control. The principles underlying the development of the first-generation robots are still used in the automation of many types of construction machines. Expensive construction machines are equipped with sensors and computer control. The latter includes a dataprocessing unit and feedback control. Such adaptations are used in excavators, cranes, pile-driving equipment, transport to the horizontal transport of output, and in concrete mix transport and placement. The second generation is associated with the application of manipulators to such construction works as laying reinforcement, building walls out of building blocks, floating concrete surfaces, and laying tiles. Manipulators are newly designed devices but still controlled by operators. The third generation includes autonomous robots with no operator involved in their control. They need an operator only to prepare them for work and sporadically during work. They find application in many kinds

1239

Part B 14.8

inspection, demolition work, underwater work, work in radioactive environments, earthwork on slopes, and work at heights. In many cases, it is for safety reasons that robots must be employed. A survey has shown that about 300 devices are currently available in the robot and automated equipment market. The rapid development of robotics for construction applications in Japan began in earnest in the 1980s. Its direct cause was the shortage of labor in construction. Japan’s business community turned to the government for permission to import workers from abroad. Because of the government’s refusal, construction companies were forced to invest in research and development of robotics for automation in the execution of construction work. Another motivation was the difficulty with conventional performance of tasks that were deemed hazardous or arduous for human workers to perform. Waseda University’s Systems Science Institute in Tokyo pioneered Japanese concepts of implementing industrial robotics on construction sites. Leading engineering construction firms such as Shimizu, Obayashi, Kajima, Taisei, Fujita, and others produced their own construction robot prototypes for various applications on construction job sites. These applications included single-purpose construction robotics as well as entire robotic systems for the performance of high-rise building construction. In the USA the Robotics and Field Sensing Committee of the American Society of Civil Engineers engaged in coordinating research in automation and robotics for construction. The centers of active in this field included Carnegie Mellon University (Pittsburgh, PA), the University of Texas at Austin, Purdue University (West Lafayette, IN), the University of Southern California (Los Angeles), and North Carolina State University (Raleigh). Carnegie Mellon was a US pioneer in these developments, having started independent research and development of construction robotics in the early 1980s, shortly after the early developments of construction robotic concepts in Japan. Also in the 1980s, construction automation and robotics concepts were researched in the former Soviet Union. These included systems and hardware developments at the Moscow Civil Engineering Institute and at the Central Laboratory for Construction and Heavy Manipulators [14.41–44]. Subsequent or parallel developments took place in France (Centre Scientifique et Technique du Batiment), Germany (the Fraunhofer Institute for Production Automation, Technical University of Karlsruhe, and the Technical University of Munich), the United Kingdom (Lancaster University, City

14.8 Automation and Robotics in Construction

1240

Part B

Applications in Mechanical Engineering

Part B 14.8

of construction work such as trenching, masonry work on construction sites, and in precast concrete plants for wall elements production, the assembly of steel structures, the transport of materials to the place where they are to be built in, the spraying of fireproofing insulation onto steel structures, and painting. Moreover, they are used for testing building structures and elements, e.g., sewers, the adhesion of tiles to tall buildings’ elevations, and testing the quality of welded joints in steel structures. Fourth-generation robots are designed for specific structures, taking into account the materials to be used. They are employed in automated building construction systems (ABCS). These robots are designed to be an integral part of a new construction methods which are adapted to the use of construction robots, known as design for robotic construction (DfRC). All four generations of automated construction equipment are used in construction, and transition from one to another has been evolutionary. A major feature of this process is that the role of the operator is reduced, or completely replaced, by computer control. Automated construction equipment used for particular kinds of construction work is described below.

14.8.1 Automation of Earthwork Because of its significant share in the total building production, automation of earthworks deserves special attention [14.46]. However, some factors in earthwork make its robotization difficult, including:

• • • • •

Variable forces of the ground-working tool interaction, due to the variability of the physical parameters of soil and material nonhomogeneity Variable height of the terrain Occurrence of buried objects such as electric cables, pipelines, etc. The possibility that machines working close to the edge of excavation edges may overturn The potential hazard to workers who find themselves within the machine’s range of operation

For these reasons, remote-controlled machines and machines with a robot control system effecting the working tool motions controlled by computer-driven programs are usually employed in earthwork automation instead of true robots. Such machines are used in work environments with radioactive and chemical contamination, in pile driving,

underground work, tunneling, deep point-excavation, diaphragm excavation, and pneumatic caisson work. The automation of earthmoving machines is proceeding in three directions:

• • •

Use of remote control in machines Adaptation of machine control systems for automated execution of specific kinds of work Development of autonomous robots

The first direction (remote control of earthmoving machines) is the most common commercially available solution. On the basis of a three-dimensional image the operator controls the operation of machines and the loading of the excavated material. Remote control can be combined with a semirobotic control system when quality workmanship is required. The second direction (adaptation of the machine’s control system to make its fittings perform a specific task) includes, for example, the steering of the excavator bucket so that it moves along a predetermined trajectory [14.47–50], the control of the dozer blade to ensure that a smooth, leveled surface is obtained, and the control of drilling attachment mounted on an excavator diaphragm wall excavation. The third direction is the development of autonomous third-generation robots for earthwork. The robot’s design should be adapted to adverse service conditions and hazards. Example Applications The research and development work on the automation of earthmoving machinery is primarily concentrated on single-bucket excavators and then dozers and loaders. Many manufacturers offer machines operated by remote control. Extensive research aimed at developing robotic components and adapting the robots to practical service conditions is being conducted by various corporate laboratories throughout the world, including, e.g., the research and development units of the Caterpillar Corporation and Komatsu. This research covers modeling of excavators as robotic manipulators [14.51], cognitive force control of excavators [14.52], soil mechanics with regard to ground-working tool interaction, kinematic and dynamic analysis of mechanisms, sensors enabling the determination of the position of mechanisms in a chosen location and in an absolute reference system, bucket trajectory optimization (leading to improved output and fuel economy) [14.47–50], and sensors detecting the presence of people within the machine’s work range

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• •

The amount of crown. The uniform distribution of temperature on the screed.

Another machine is a hot in-place recycling machine intended for laying reclaimed asphalt pavements (RAP), which:

• • •

Mills the pavement undergoing renovation, heated up by a preceding machine Prepares new asphalt mixture, which includes: reclaimed asphalt, fresh asphalt mixture delivered from an asphalt mixing plant, and chemical additives Lays a new layer of asphalt mixture

Part B 14.8

The hot in-place recycling machine consists of two separate, self-propelled units loosely connected by a conveyor. The set’s front unit is composed of a feeder of fresh asphalt mixture delivered from an asphalt plant, a milling subunit, and a subunit for spraying additives. The rear unit consists of a reclaimed-asphalt pavement feeding and weighing subunit, a fresh-asphalt mixture batching unit, a mixer, and a subunit for laying new pavement. The two units move independently towards the destination, but operate in tandem. The machine’s automation covers: distance maintenance, the harmonization of the two units’ driving speeds, the preparation of asphalt mixture, and feeding the mixture to the screed and laying it. An example of a high level of automation is a road milling machine equipped with an automatic cutter control system (ACCS). With ACCS the machine can work in two modes:

• •

Contour-following mode, in which a constant cutting depth relative to the road surface is maintained Longitudinal and transverse contouring mode, in which the cutting depth is progressively adjusted to the required lateral differential

The cutting depth can be accurately adjusted to compensate for longitudinal and transverse unevenness in the pavement. The cutting depth data for the road section to be milled are entered into the onboard computer, which automatically controls the position of the working tool in the selected operating mode. Automation of Tunneling Work The automation of tunneling is essential because of the hazard to people and the difficult working con-

ditions, which are similar to those in underground mining. The main aim of automation is to eliminate the presence of workers in the danger zone where they could be exposed to headwall landslides and inrushes of underground water in a confined space. Tunnel construction owes its rapid development to automation. The construction of municipal transport tunnels in urban areas, mini-tunnels for utilities (particularly for sewage pipes), and mountain tunnels for intercity transport is a major factor in the economic development of cities and regions. The general trends in the automation of tunneling work are presented below. Extensive information on tunneling machines and equipment can be found in [14.53]. The automation of shield tunneling covers the following operations:

•

• • • • • • •

The automatic transport and assembly of prefabricated tunnel lining units, for which several systems of automatic lining transport and assembly have been developed for the different kinds of lining joints used The control of shield advance along a programmed route The complex automation of: tunneling, tunnel heading stability and shield advance control, output transport, lining assembly, and filling the space behind the lining with cement Shotcreting the lining’s top layer reinforcement. Fabrication of reinforcement for the monolithic tunnel lining layer. Screeding of the top layer of the tunnel’s invert. Transport and assembly of prefabricated concrete slabs for the tunnel’s railway subgrade. Diagnosis of tunneling shield defects.

Most automation solutions are found in the areas of automatic transport and assembly of tunnel lining components and control of shield advance along a fixed route. The automation in the construction of mountain tunnels covers the following aspects:

•

Tunnel boring – when the start button is pushed the boring machine bores the ground in the tunnel’s face, maintaining the tunnel’s design cross section and following the fixed route with a high degree of accuracy. The available machine designs are capable of boring tunnels in hard and semi-hard rock without using explosives.

Construction Machinery

14.3

14.4

14.5

14.6

14.7

14.8

14.10

14.11

14.12

14.13 14.14

14.15 14.16

14.17

14.18

14.19

14.20 14.21

14.22

14.23

14.24

14.25

14.26 14.27 14.28

14.29

14.30

14.31

14.32

14.33 14.34

14.35

14.36

14.37

Hamm AG: Oszillation (Hamm AG, Tirschenreuth 2004), in German D. Lemser: Maschinen für den Straßenbau. In: Der Elsner - Handbuch für Straßen- und Verkehrswesen, ed. by E. Knoll (Elsner, Berlin 2003), in German Bomag AG: Grundlagen der Boden- und Asphaltverdichtung. Bomag Anwendungstechnik (Bomag AG, Boppard 2002), in German M. Buschmann, R. Grundl, H.J. Meyer: Belagfertiger mit leistungsstarker und anpassungsfähiger Technik, Tiefbau 112(12), 772–778 (2000), in German H.J. Meyer: Anwendung von geodätischen Positionsmesssystemen in Straßenbaumaschinen, Baumaschinentechnik 2003, Vol. 23 (Forschungsvereinigung Bau- und Baustoffmaschinen, Dresden 2003), in German Wirtgen GmbH: Slipform paver SP 500 Vario – Technical specification (Wirtgen GmbH, Windhagen 2004) S. Velske: Straßenbautechnik (Werner-Verlag, Düsseldorf 1993), in German Wirtgen GmbH: Cold Recycling Manual, 2nd edn. (Wirtgen GmbH, Windhagen 2004) C.F. Goering: Engine and Tractor Power, 3rd edn. (American Society Agricultural Engineers, Michigan 1992) H. Göhlich, M. Hauck, C. von Holst: 2.5 Ride dynamics – Ride safety – Driver’s place. In: Jahrbuch Agrartechnik – Yearbook Agricultural Engineering, Vol. 11, ed. by H.J. Matthies, F. Meier (Landwirtschaftsverlag, Münster 1999) pp. 61–69 K.T. Renius, M. Brenninger: Jahrbuch Agrartechnik – Yearbook Agricultural Engineering 2.2, Tractor engines and transmission, Vol. 9 (Landwirtschaftsverlag, Münster 1997) pp. 57–61 ISO: ISO 730-1:1994: Agricultural Wheeled Tractors. Rear-Mounted Three-Point Linkage. Part 1: Categories 1, 2, 3, and 4 (ISO, Geneva 2003) H. Auernhammer: Elektronik in Traktoren und Maschinen: Einsatzgebiete, Funktion, Entwicklungstendenzen. Vol. 2 (BLV, München 1991), in German ISO: ISO 11783:2000: Traktors an Machinery for Agriculture and Forestry (ISO, Geneva 2002) ISO: ISO 11375:1998: Building Construction Machinery and Equipment. Terms and Definitions (ISO, Geneva 1998) ISO: ISO 18650-1:2004: Building Construction Machinery and Equipment. Concrete Mixers. Part 1: Terminology and Commercial Specifications (ISO, Geneva 2004) ISO: ISO 11573-1:2006: Building Construction Machinery and Equipment. Concrete pumps. Part 1: Terminology and Commercial Specification (ISO, Geneva 1998) ISO: ISO 21592:2006: Building Construction Machinery and Equipment. Concrete Spraying Machines.

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14.9

ISO: Technical Report ISO/TR 12603:1996: Building Construction Machinery and Equipment – Classification (ISO, Geneva 1996) Richtlinie 98/37/EG des Europaeischen Parlaments und des Rates, 22. Juni 1998 zur Angleichung der Rechts- und Verwaltungsvorschriften der Mitgliedstaaten für Maschinen (1998) ABLI.EG vom 23.07.1998. Nr. 207. p. 1, in German F. Meier, K. Herrmann, K. Krombholz: Einhundert Jahre für die Landtechnikindustrie (Maschinenbauverlag, Frankfurt 1997), in German FAO: World reference base for soil resources (Food and Agriculture Organization of the United Nations, Rome 1998) ISO: ISO 14689-1:2003: Geotechnical Investigation and Testing. Identification and Classification of Rock. Part 1: Identification and Description (ISO, Geneva 2003) D.G. Rossiter: Lecture Notes Principles of Soil Classification (International Institute for Aerospace Survey and Earth Sciences (ITC), Enschede 2001) K.T. Renius: Traktoren: Technik und ihre Anwendung (BLV, München 1985) H.-D. Kutzbach: Allgemeine Grundlagen Ackerschlepper, Fördertechnik. Lehrbuch der Agrartechnik, Vol. 1 (Parey, Berlin 1989), in German W. Söhne: Druckverteilung im Boden und Bodenverformung unter Schlepperreifen, Grundl. Landtech. 5, 49–63 (1953), in German H. Schwanghart: 3.3 Reifen – Reifen/Bodenverhalten Tyres – Tyre/Soil-Performance. In: Jahrbuch Agrartechnik – Yearbook Agricultural Engineering, Vol. 16, ed. by H.J. Matthies, F. Meier (Landwirtschaftsverlag, Münster 2004) pp. 67–72, in German D. Lemser: Radlader sind nicht nur Baumaschinen, Schüttgut 4, 298–309 (2002) J. Pantermöller: Funktionalität und Design bei Radladern, Tiefbau 113(4), 237–240 (2001), WISSENSPORTAL http://www.baumaschine.de, in German DIN: DIN 24080: Earth-Moving Machinery (Beuth, Berlin 1979), in German C. Holländer: Untersuchungen zur Beurteilung und Optimierung von Baggerhydrauliksystemen, Fortschritt-Ber. VDI Reihe 1, Vol. 307 (VDI-Verlag, Düsseldorf 1998), in German J. Forche: Antriebsmanagement für Hydraulikbagger, Baumaschinentechnik 26, 33–40 (2004), in German J. Weber, E. Lautner: Intelligente Baumaschinensteuerungen und alternative Antriebssysteme, Baumaschinentechnik 2004, Schriftenreihe der Forschungsvereinigung Bau- und Baustoffmaschinen, Vol. 26 (Frankfurt 2004) pp. 41–48, in German G. Kunze, H. Göhrung, K. Jacob, M. Scheffler (eds.): Baumaschinen Erdbau- und Tagebaumaschinen (Vieweg, Braunschweig 2003), in German

References

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Applications in Mechanical Engineering

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14.39 14.40

14.41

14.42

14.43

14.44

Part B 14

14.45 14.46

14.47

14.48

14.49

14.50

14.51 14.52

14.53

14.54

Terminology and Commercial Specification (ISO, Geneva 2006) ISO: ISO/DIS 18651:2005: Building Construction Machinery and Equipment. Internal Vibrators for Concrete (ISO, Geneva 2005) ISO: EN 12418:2000: Mansory and Stone Cutting-Off Machines for Job Site-Safety (ISO, Geneva 2000) ISO: ISO 11375:1998: Building Construction Machinery and Equipment. Terms and Definitions (ISO, Geneva 1998) G.Y. Frenkel: Application of Robotics and Manipulators in the Construction Industry: Construction and Progress in Science and Technology (Znanye, Moscow 1988) p. 64, in Russian V. Araksyan, V. Volkov: Mechanization and Automation of Heavy and Labor-Intensive Works (Znanye, Moscow 1985) p. 64, in Russian G.Y. Frenkel: Robotization of Work Processes in Construction (Stroyizdat, Moscow 1987) p. 174, in Russian Y.A. Vilman: Fundamentals of Robotization in Construction (Vysshaya Shkola, Moscow 1989) p. 271, in Russian R. Krom: Robots in the Building Industry (KROM, Sassenheim 1997) S. Singh: The State-of-the-Art in Automation of Earthmoving (Robotics Institute Carnegie Mellon Univ., Pittsburg 2002) E. Budny, M. Chlosta, W. Gutkowski: Sensitivity of the Optimum Bucket Trajectory in Controlled Excavation, Automation in Construction (Elsevier, Amsterdam 1999) pp. 99–110 E. Budny, M. Chlosta, W. Gutkowski: Optimal control of an excavator bucket positioning, 19th ISARC Proc. (ISARC, Washington 2002) E. Budny, M. Chlosta, W. Gutkowski: Loadindependent control of a hydraulic excavator, Automat. Constr. 12(3), 245–254 (2003) E. Budny, M. Chlosta, W. Gutkowski: A bucket discharge control for a backhoe excavator, 21st ISARC Proc. (ISARC, Washington 2004) P. Vähä, M. Skibniewski: Dynamic model of excavator, ASCE J. Aerosp. Eng. 6(2), 148–158 (1993) P. Vähä, M. Skibniewski: Cognitive force control of excavators, ASCE J. Aerosp. Eng. 6(2), 159–166 (1993) Council for Construction Robot Research: Construction Robot System Catalog in Japan (Japan Robot Association, Tokyo 1999) M. Skibniewski, R. Kunigahalli: Chap. 17: Automation in Concrete Construction. In: Concrete

14.55

14.56 14.57

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14.59

14.60

14.61

14.62 14.63

14.64

14.65

14.66

14.67

14.68

14.69

14.70

Construction Engineering Handbook (CRC, Boca Raton 1997) IAARC: Robots and Automated Machines in Construction (Int. Association for Automation and Robotics in Construction (IAARC), Watford 1998) Fujita Corp.: Robots for Construction (Fujita Corp., Tokyo 2005) PENTA OCEAN Construction Corp.: Faces on Automatic Oriented Sheltered Building Construction (PENTA OCEAN Construction Corp., Tokyo) Obayashi Corp.: Big Canopy Automation System for High-rise Reinforced Concrete Buildings, Techn. Res. Inst. Rep., Vol. 640 (Obayashi Corp., Tokyo 2003) J. Maeda: Development and Application of Automated High-Rise Building Construction System, Vol. 14 (Shimizu Tech. Res. Bull., Tokyo 1995) M. Skibniewski, C. Hendrickson: Automation and robotics for road construction and maintenance, ASCE J. Transport. Eng. 116(3), 261–271 (1990) M. Skibniewski, C. Hendrickson: Analysis of robotic surface finishing work, ASCE J. Constr. Eng. Manag. 114(1), 53–68 (1988) M. Skibniewski: Robotics in Civil Engineering (Van Nostrand Reinhold, Boston 1988) p. 233 Y. Zhou, M. Skibniewski: Construction robot force control in cleaning operations, ASCE J. Aerosp. Eng. 7(1), 33–49 (1994) M. Skibniewski: Robot Implementation Issues for the Construction Industry. In: Human-Robot Interaction, ed. by M. Rahimi, W. Karwowski (Taylor Francis, New York 1992) pp. 347–366 M. Skibniewski: A framework for decision making on implementing robotics in construction, ASCE J. Comput. Civil Eng. 2(2), 188–201 (1988) C. Haas, M. Skibniewski, E. Budny: Robotics in civil engineering, Microcomp. Civil Eng. 10(5), 371–381 (1995), Special Issue: Robotics in Civil Engineering M. Skibniewski, S. Nof: A framework for programmable and flexible construction systems, Robotics Autonom. Syst. 5, 135–150 (1989) J. Russell, M. Skibniewski: An ergonomic analysis framework for construction tasks, Constr. Manag. Econ. 8(3), 329–338 (1990) J. Russell, M. Skibniewski, J. Vanegas: A framework for a construction robot fleet management system, ASCE J. Constr. Eng. Manag. 116(3), 448–462 (1990) M. Skibniewski, J. Russell: Construction robot fleet management system prototype, ASCE J. Comput. Civil Eng. 5(4), 444–463 (1991)

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Enterprise Or 15. Enterprise Organization and Operation

Francesco Costanzo, Yuichi Kanda, Toshiaki Kimura, Hermann Kühnle, Bruno Lisanti, Jagjit Singh Srai, Klaus-Dieter Thoben, Bernd Wilhelm, Patrick M. Williams 15.1 Overview.............................................. 1268 15.2 Organizational Structures ...................... 1271 15.2.1 Introduction ............................... 1271 15.2.2 Enterprise: Main Functions ........... 1274 15.2.3 Organization and Tasks ................ 1274 15.2.4 Classical Forms of Organization ..... 1276 15.3 Process Organization, Capabilities, and Supply Networks ............................ 1279 15.3.1 The Capability Concept ................. 1280 15.3.2 Extending the Capability Concept to Processes and Supply Networks . 1281 15.3.3 Application Perspectives and Maturity Models.................... 1288 15.3.4 Operational Process-Based Capabilities ................................ 1288 15.3.5 The Supply Network Capability Map........................................... 1289 15.4 Modeling and Data Structures................ 1290 15.4.1 Introduction ............................... 1290 15.4.2 Definitions ................................. 1291 15.4.3 Guidelines of Modeling (GoM) ....... 1293 15.4.4 Important Models and Methods .... 1293 15.5 Enterprise Resource Planning (ERP) ........ 1303 15.5.1 Resources and Processes .............. 1303 15.5.2 Functionalities of ERP Systems ...... 1304 15.5.3 ERP Procedures ........................... 1304 15.5.4 Conclusions and Outlook .............. 1307 15.6 Manufacturing Execution Systems (MES).. 1307 15.6.1 Information-Interoperable Environment (IIE) ........................ 1309 15.6.2 Development of Prototype Application Systems..................... 1313 15.7 Advanced Organization Concepts............ 1314 15.7.1 Lean Production.......................... 1315 15.7.2 Agile Manufacturing .................... 1315 15.7.3 Bionic Manufacturing .................. 1316 15.7.4 Holonic Manufacturing Systems .... 1316 15.7.5 The Fractal Company.................... 1317 15.7.6 Summary ................................... 1321

Part B 15

Organizations (derived from the Greek word organon, meaning tool) are instruments for enterprise objectives fulfilment. These objectives are to perform and produce products and services. Engineering and industrial production emphasize human-initiated, controlled, and deliberately executed combinations and transformations of resources by energy and information for the supply of market goods and products. Therefore organizations in engineering and manufacturing include the planned and purposeful action of human beings. In order to meet such objectives, formal groups of people with shared goals concerning transformation execution and output performance are configured. Any arrangements of resources devoted to objective fulfilment constitute operations functions, or for short, operations. Technical devices can be provided to execute operations for transformation steps. The amounts of labor involved can be coped with faster and with better quality by planned division into packages assigned to individuals for well-coordinated (repetitive) execution. For the individuals involved, operations represent tasks to be fulfilled. Combinations and syntheses of tasks and responsibilities in total constitute organization structures or parts of organizations. In this section, the focus of our attention is on noncontractual and contractual types of collaborations among independent enterprises, pooling their core competencies to form socalled enterprise networks, aiming to achieve a common goal. The enterprise networks considered are composed of two or more partners collaborating under a variety of bilateral relationships [15.1].

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15.8 Interorganizational Structures ............... 1321 15.8.1 Cooperation................................ 1322 15.8.2 Alliances .................................... 1323 15.8.3 Networks ................................... 1325 15.8.4 Supply Chain .............................. 1326 15.8.5 Virtual Organizations ................... 1327 15.8.6 Extended Enterprise .................... 1328 15.8.7 Virtual Enterprise ........................ 1329 15.9 Organization and Communication .......... 1330 15.9.1 Terms, Definitions, and Models ..... 1330 15.9.2 Challenges Concerning the Internal Embodiment of Communication Processes......... 1332

15.9.3 Methods of Embodiment, Organization Models, and the Management of Communication....................... 1333 15.9.4 Conclusions and Outlook .............. 1335 15.10 Enterprise Collaboration and Logistics .... 1337 15.10.1 Dimensions of Enterprise Networks................. 1337 15.10.2 Analysis of Enterprise Collaborations.......... 1343 References .................................................. 1354

15.1 Overview

Part B 15.1

Planning in enterprises is the definition of enterprise objectives and the anticipation of activities that are necessary to meet these objectives. In manufacturing companies, engineering focuses on transformations of materials into products and market goods by deliberate use of resources. Resource planning means the coordination of human experts, materials, technology, operations, and orders to be executed with the ultimate goal of tuning their operation. Plans (the result of planning), i. e., how all the objectives may be achieved by optimal setups and processes, may cover short-, mid-, and long-term planning horizons. Logistics comprises all activities of planning, implementing, and controlling efficient, effective flows as well as storage of goods, services, and related information from their point of origin to their point of consumption. Seamlessly integrated logistics for the purpose of meeting customer requirements is the ultimate goal of logistics. Its achievement is generally restricted by the availability of resources, technologies, and capabilities. Recent cutting-edge research envisions logistic setups as part of a wider organizational context, as the organizational structures determine all activities and operations along the relevant value chains. Organization and operations are studied by a number of disciplines. Relevant issues may concern technical, social, cultural, and economic areas. First scientific approaches originated in administrative, and later technical and economical, contexts as well as contributions made by organization theory. Later, efforts in sociology, psychology, political sciences, contingency theory, systems theories, and management sciences appeared.

Organizations (from the Greek organon, meaning tool) are instruments to achieve enterprise objectives. Enterprises and manufacturing companies emphasize organizational solutions for specific business areas, drawing results from all the disciplines and approaches mentioned above. For a given set of objectives there are most appropriate organizational setups for arranging groups of people. The clear distinction of these groups from their environments motivates the institutional meaning of the term organization, i. e., that they are all part of the same institutional organization. In this sense, organizations are institutions whose primary purpose is to accomplish established objectives. Rational organizational behavior is best achieved through defined rules and formal authority maintained by control and coordination. For enterprises, the context of organizations and operations is a strategic field, as smooth, efficient operations are decisive for prosperous business development. Therefore these areas are the subject of substantial research progress and ongoing dynamic developments. Resource planning focuses on sequences of operations, which take up resources, time, space, and expertise in order to produce the intended outcome. Such sequences of operations – also called processes (from the Latin processus) – include all activities of analyzing, controlling, implementing, and improving, e.g., by harmonized sequences of operations (batch or flow mode) and arrangements of machines and equipment. A well-known result of elaborate process planning frequently referred to is the assembly line, based on detailed labor division and precise work flow design. All these basics of

Enterprise Organization and Operation

supported are accounting, enterprise resource planning (ERP), manufacturing execution (MES), and process control. Specific modeling languages and models of enterprises, organizations, and processes as well as software frameworks are used to provide formalizations and software codes. Organization and ICT may therefore generally be envisioned as complementary domains, profiting from each other’s progress. Driven by an ultimately competitive organization principle (lean production), industrial organization is actually subject to a paradigmatic shift. Fewer restrictions, faster development of markets, and the spread of technology have outdated familiar mass-production setups. Substantial efforts have been invested in overcoming the strictly functional principles of labor division in favor of dynamic organizational structures. Emphasis is placed on renewal of company culture, human-centered organization, and decentralized management. The common main feature is that human creativity and improvisation is given greater decision power. More flexible and efficient enterprise organization approaches have appeared, such as as agile manufacturing, holonic manufacturing, bionic manufacturing, and the fractal company. Widening objectives and increasing demands for company know how, capabilities, and knowledge for engineering and manufacturing are the reasons for enterprises to loosen their organizational rules and open up their organization structures. New market opportunities, improved flexibility, quicker innovations, and better chances in local markets are the opportunities. Interorganizational structures in the form of virtual organizations, extended enterprises, or collaborative network organizations are the appropriate setups. Aided by revolutionary ICT developments, such as the World Wide Web and global communication standards, instruments for the support of distributed organization structures are continuously improving; as equipment becomes mobile and wearable at work, individuals in industrial organizations may even work simultaneously and distributed globally on the same tasks. Communication and collaboration are now considered crucial skills in such distributed enterprise organizations. The collaborative networked organization, characterized by communication skills and totally networked structures, is emerging as an organization model for the future, in which instruments that support the collection and update of enterprise knowledge are of growing interest. For decades the classical approach of an enterprise was to invest in the required resources and thus to plan

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the organization are outlined in the first section of this Chapter. Moreover economic intentions result in objective systems favoring organizational setups for the repetition of tasks (the learning curve) by adequate design of task structures and job assignments. Individuals, facilities, and tasks are assigned in a manner consistent with the objectives, in order to obtain clear, unambiguous responsibilities, organization charts (organigrams), operations plans, and job descriptions are provided, representing the full description of a hierarchical organizational setup. Less repetitive jobs, relying on fewer routines and therefore requiring more improvisation, require more flexible team organization principles, engaging selforganization and autonomous groups of skilled people. The teams as units may be orientated by (self-similar) subordinate objective systems that may be derived from the overall objectives. Project organizations are very short-term structural setups for temporary enterprises, where task definitions, labor division, responsibilities, and objectives are supplied from scratch. Projects may be seen as independent organization types as well as embedded in other longterm organization structures. Very widespread and widely applied descriptions of organizations envision companies’ organizations or entire process chains as consisting of a set of linked skills and capabilities. All procedures and routines to support the efficient execution of process steps are considered to be a part of this process organization. Process organizations select and optimize alternative means to transform material or objects as well as technologies by using capabilities and competencies. Thus, evaluating, establishing, developing, shaping, and maintenance capabilities in order to ensure effective and competitive operations and processes generally represent key areas of enterprise organization. For efficient planning, checking, measuring, and correcting of the skills and competencies involved, indicators and benchmarks for best practice are particularly appropriate Electronic data processing (EDP) has particularly triggered the development of organization and operations in enterprises. Software solutions as well as information and communication technology (ICT) implementations provide strong support for organizations as well as processes. Well-established logistics and procedures for planning and control have been made available as software packages for organization and operations management. The functions most frequently

15.1 Overview

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Applications in Mechanical Engineering

Part B 15.1

and realize production process by using its own resources. This has changed dramatically. Today no single enterprise is able to provide all manufacturing resources and competencies necessary for the realization of everchanging customer demands. There are at least three areas in which industry anticipates change and for which it must be prepared: shrinking margins, flexibility, and technology. Networked collaboration between enterprises merits greater attention. Current studies on this issue focus on important features for successful long-term collaboration (e.g., trust) as well as the management of knowledge. As business relationships between companies and their distributed sites’ complementary skills and manufacturing abilities become much closer, logistics is also affected. These changes cause the emergence of interorganizational enterprise structures, which themselves cause growth in the complexity of intra- and interenterprise logistics. Enterprise networks as a dynamic interenterprise configuration of manufacturing resources and competencies have become a promising alternative to provide required manufacturing infrastructure. Such networks include a whole range of processes in a value chain, as they do not only include supply operations of planning, sourcing, manufacturing, and logistics, but also product development activities such as research and development (R&D), innovation, product design, engineering, and customer-related activities of marketing, sales, and service. The flow of parts through a production network has usually been preplanned by a central control system. Such central control fails in the presence of highly fluctuating demand and/or unforeseen disturbances, as is regularly the situation today. To manage such dynamic networks with low work-in-progress and short throughput times, autonomous control approaches are appropriate. The application of autonomous control in production networks leads to a coalescence of material flow and information flow and enables every unit to manage and control its flow process autonomously. Moreover such a strong focus on customer orientation with increasing transportation volumes results in higher supply frequencies as well as atomization of cargo into units. Conflicts in the objectives of logistic processes call for adaptive logistic process setups, which directly derives from changes in the production organizations. Logistics service providers need to connect their information systems: interaction rather than integration is the means to connect. The use of agent technology and

adequate organizational structures might enable these challenges to be met. Heterarchies and self-controlling units supported by multi-agent systems, intelligent load carriers, wireless communication, and ubiquitous computing are seen as the main ingredients of future logistics systems. The research work generally required in logistics planning is the transfer of methods for decentralized and autonomous control strategies that have been developed for production systems. Here too, autonomous control means decentralized coordination of intelligent logistics objects. These intelligent objects make autonomous decisions based on local information. The dynamics of such systems relies on the elements’ local decision-making, generating the global behavior with newly emerging characteristics. Since all intelligent self-controlling objects are elements in a network, information and negotiation are the results of collaboration. Therefore in logistics the greatest challenges to boosting competitiveness are concerned with organizational issues, rather than technical concerns. The design of collaboration is a fuzzy topic at best; however, one can gain insight into network design by analyzing the type of collaboration the company needs and the capabilities the company has to offer. Bearing in mind these facts, Sect. 15.10 on enterprise collaboration and logistics places an emphasis on network and cooperation issues. Supply chain management (SCM) approaches have been considered to be useful, particularly for traditional industry where intelligent enterprise network setups are still viewed with caution. However, cutting-edge industry processes have advanced towards knowledge-driven supply network philosophies, which rely on collaboration and high-end ICT applications. Analyzing typological issues of enterprise networks will support:

• • •

Systematic problem analysis and solution synthesis with respect to cooperating enterprises A more structured view of the vast amount of possible real-life cases of industrial cooperation by characterizing these cases in a systematic way The analysis of cases and relevant types of industrial cooperation with respect to typical problems related to decision-making, production planning, etc.

Moreover competitive logistics includes efficient, accurate transfer of customer demands to the upstream supply partners and full interoperability between all partners. In spite of all the efforts to implement and operate technical and organizational standards such as as vendor-managed inventory, factory-gate pricing or col-

Enterprise Organization and Operation

15.2 Organizational Structures

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Table 15.1 DIN terms and classifications for manufacturing operations

Manufacturing operation

Explanation

• Original forming (casting and molding)

• . . . is defined as the manufacturing of a solid body from unformed substance (metals are cast, plastics are molded) • . . . is defined as a plastic change in the form of a solid body which does not change the mass or the cohesion of the body • . . . is manufacturing through changing the form of a solid body, thereby diminished its locally cohesion • . . . is defined as a process in which two or more bodies are linked, united, or assembled • . . . is defined as a layer-adding process to spread a formless substance over a surface of a solid body, e.g.,for protection • . . . is the summary heading for various techniques to change material properties on the atomic level

• Further forming (mechanical forming) • Cutting • Joining • Coating

• Material property alteration

Examples • Extrusion, casting

• Bending, drawing, rolling, pressing • Turning, milling, grinding, sawing • Welding, soldering, bonding, sticking • Painting, cladding

• Tempering, hardening, quenching, nitriding

Table 15.2 Overview of the main functions of an enterprise

Procurement

Operations

Sales and distribution

Comprises all kinds of operational Appears at the end of the overall progoods and services, or is rather duction process. The sale of products the realization of all intended mea- concludes the operational circle by sures for the fulfilment of operational initiating the reflow of cash resources tasks (immaterial as well as material goods). Goods and services contain immaterial and material goods Integrating processes: provide the connections between the processing locations and fulfil the following main functions: – Transportation – Handling – Storage Securing processes: provide a smooth procedure for the main processes and fulfil the following main functions: – Quality assurance – Maintenance – Supply and disposal similar functions, e.g., milling, drilling, and coating, in the same location. One characteristic of the flow principle is the arrangement of the equipment along the prevailing sequence of operations to be executed. The flow principle is initially derived from the product/object to be produced; therefore the term product/object-oriented principle is commonly used as well. Flow ideas date

back to 1913, when Henry Ford introduced this principle to assemble cars, enormously increasing total effectiveness [15.6]. Production cells (production groups) concentrate all machinery and equipment covering sets of functions and technological operations necessary for the production of product or part families. Enriched by control, planning, and handling tasks, production nests have

Part B 15.2

Provides all goods and services necessary for the whole production process: – Raw materials – Supplies – Consumables

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Table 15.3 Overview of the enabling functions of an enterprise

Function

Description

Research and development

Methodical and systematic detection as well as determination and solution of causal impacts to enlarge technical knowledge Basically the following procurement objects are distinguished: – Operating resources – Raw materials and supplies – Staff Capacitated and quantitative planning of the entire production that should be realized in the upcoming period (resulting in a production programme) Providing the required employees to fulfill the following main functions: – Personnel requirements planning – Personnel procurement – Personal development – Personnel applications planning – Personnel discharge Providing financial funds of any kind for the execution of operations functions Supply of all the required documents for control and monitoring processes, which guarantee minimum expenditure for the manufacturing of products Production of geometrically defined solid objects by means of combining basic production factors Combination of individual units into modules or/and product In addition to the name sales, other terms are applied in practice include distribution, selling, turnover, and marketing Increases of customer loyalty by: – Efficient complaints management – Return of defect and surplus goods – General conditions for delivery and service (e.g., warranties)

Procurement

Production planning Personnel planning

Financial planning Scheduling Manufacturing

Part B 15.2

Assembly Marketing and sales After-sales service

good flexibility, high transparency, and short lead times. However, employees have to have high levels of qualifications and more skills; good levels of motivation and self-responsibility are expected. At stationary work places a number of different functions and processes are performed on site, without having to moving the objects to be produced.

15.2.2 Enterprise: Main Functions Generally the enterprise’s organizational setup is visualized by using diagrams (organization charts) using principal functions descriptions such as procurement, operations and sales, and distribution, thereby integrating functions (e.g., transportation) and securing functions (e.g., quality assurance). These main functions represent aggregations of operations, therefore

the terminology main processes is used as well [15.7]. The overall objective is to create value by planned input of resources. In this sense, the enterprises’ main functions represent segments of value chains (compare Tables 15.2 and 15.3) [15.8]. Main functions and enabling functions are generally used for manufacturing companies. A frequently used organization chart by main functions is given in Fig. 15.3.

15.2.3 Organization and Tasks Combinations and syntheses of tasks and responsibilities together constitute structures of organizations or parts of organizations [15.9]. For the individuals assigned, operations and functions represent tasks to be fulfilled. Task analysis decomposes comprehensive (en-

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erations, and control. The combination of all of these function elements results in the total process, which is also referred to as the value chain. Process capabilities are measures of the acceptability of variations of the process. Usually variations in processes are interpreted as a statistical issue by engaging the characteristics of the normal probability distribution. Ambitious process capability objectives include Six-Sigma programs, implying 3.4 defect parts per million (ppm) and requiring elaborate instruments for process capability development.

15.3.1 The Capability Concept

Part B 15.3

Generally [15.17–19] capabilities are provided by a set of resources, networked together into a process (routine) for competitive advantage. The use of the term capabilities, describing firm competitiveness and business development, has a particularly rich history. The early literature on resources and capabilities has links with some of the seminal work on rent creation and the mechanisms to achieve this, the Ricardian perspective on resource picking and the Schumpeterian perspective of capability building [15.20]. The best usage of a firm’s bundle of resources is discussed by Penrose in her original work, extending it to the area of firm services [15.21]. The resource-based view (RBV) perspective [15.17, 22] emerged in the 1980s, incorporating a broader definition of resources as a firm’s strengths and weaknesses, and as any assets (tangible and intangible), that are semipermanently linked to the firm [15.22]. Others have suggested an all-encompassing definition of resources, such as “all assets, capabilities, organizational processes, firm attributes, information, knowledge etc.” [15.23]. More recently, the resourcebased view (RBV) has regained prominence under the basic premise that resources and capabilities provide the basic direction for a firm’s strategy, and are the primary sources of profit [15.17, 24–27]. The term capability has been used interchangeably with a multitude of terms such as strategic resources, organizational routines, and core competencies, meta competencies, and these perhaps require some reflection as part of the historical context. Early RBV thinking suggested that the attributes of a firm’s physical, human, and organizational capital that enable a firm to conceive and implement strategies that improve its efficiency and effectiveness are firm resources [15.22]. The separation of the capabilities element from the firm’s bundle

of resources [15.21] was captured in the seminal paper on core competencies by Prahalad and Hamel [15.28], suggesting that core competencies (essentially those capabilities that deliver competitive advantage) should provide:

• • •

Potential access to a wide variety of markets A significant contribution to the perceived customer benefits of the end product A competence that is difficult for competitors to imitate

and that this is likely if the competence is a complex harmonization of individual technologies and production skills. Barney [15.17] argues that the potential of firm resources to generate sustained competitive advantage is governed by four empirical indicators: value, rareness, imitability, and substitutability. Enterprise resources may be classified into:

• • •

Physical capital resources (extended to include access to raw materials) Human capital resources: internal firm personnel, and also their relationships Organizational capital resources: reporting structures, planning, controlling and coordinating systems, and relationships within the firm and those with its environment

Two factors determine the value (rent-earning potential) deliverable from resources and capabilities [15.25]:

• •

Sustainability (in terms of durability, transparency, transferability, and replicability) Appropriability (the allocation of rents where property rights are not fully defined)

Various aspects of capabilities and resources in terms of value-creating potential have been developed, including: interfirm resource complementarities [15.29] (rather than similarities) that allow firms to learn new and valuable capabilities, combinative capabilities [15.30], and whether capabilities should be outcome focused, targeted at a particular desired end [15.31]. Alternative models identifying capability development approaches describe how competitive advantage may be created and sustained. Teece et al. [15.32] recognized the need to extend the RBV into the development and renewal of resources

Enterprise Organization and Operation

•

Superior rents derived from the ability to destroy and rebuild specialized inimitable resources or routines over time [15.37]

Table 15.5 Resources, processes and performance outcomes

• •

Doubts cast on the stage theory of internationalization as new and small firms prosper (showing similarities to doubts about maturity-model stagewise developments) Dynamic capabilities, i. e., specific processes that firms use to alter their resource base, as sources of competitive advantage [15.38]

The process-based perspective is given prominence by some authors [15.39], who argue that processes (and not resources) provide competitive advantage for the achievement of specific performance outcomes. This process perspective sits in between the RBV barriers to imitation thinking and the market forces approach (Table 15.5, based on [15.39]). The concept of a capability lifecycle [15.40] has been introduced, incorporating the founding, development, and maturity of capabilities into several altered forms. This provides an interesting link to maturity models. Table 15.6 summarizes the key concepts, their evolution, and their implications for supply network operations.

15.3.2 Extending the Capability Concept to Processes and Supply Networks The increasing reliance of firms on supply network partners for innovation, product replenishment, and service has complemented the traditional interfirm competition model with that of the competing supply networks model. The evolution of the RBV therefore needs to take on board that the organizational routines span firm boundaries, and are not just about the interfaces within the firm, but that these network capabilities that provide competitive advantage may nevertheless follow the RBV tradition of being rare, valuable, difficult to imitate, and not easily substitutable.

Operations Resources ‘what they are’

Markets ←→

BARRIERS TO IMITATION thinking Transform scarce resource to strategic resource (Wernerfelt 1984) Inside-out model approach (Hayes 1985, Ferdows and De Meyer 1990) Firm specific factors [15.19]

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Processes provide competitive advantage [15.21]

←→

Performance outcomes ‘what they do’

BARRIERS TO ENTRY thinking Competitive context (Anders 1984) Market influences (Hill 1984) Outside-in model approach (Miles and Snow 1984) Industry and market forces

Part B 15.3

and by taking a process perspective involving the competencies of both internal and external resources. The focus however has been on the integration of external resources into the firm and the balancing of the resource mix as part of its development and renewal in a dynamically changing business environment. Dyer and Singh [15.33] suggest that a firm’s resources may span firm boundaries, and that these may be embedded in interfirm resources and capabilities. This relational view of interorganizational competitive advantage suggests an intermediate unit of analysis that sits between the firm-based perspectives in the extant and traditional RBV approach [15.17], and the industrystructure-based perspectives of Porter [15.26]. A parallel is drawn in the manufacturing networks arena [15.34], where there are specific capabilities of a network of manufacturing plants over and beyond those at the factory plant level. The evolutionary economics approach examines the implications of variation, selection, and retention. Nelson and Winter’s [15.35] framework is based on routines as the fundamental unit of analysis, and discusses their efficiency and effectiveness. Their definition of routines is indistinguishable from the RBV definition of capabilities. Authors adopting the microeconomics approach have focused on measuring the attributes of firm resources and capabilities and correlating them with performance and, in the language of Makadok [15.36], form part of the resource picking school whilst others following the evolutionary approach form part of the capability building school of thought. Capability concepts that have been developed in the 1990s [15.24] include:

15.3 Process Organization, Capabilities, and Supply Networks

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Table 15.6 Perspectives on resources and capabilities – implications for supply network operations

Author/year

On resources

On capabilities (or routines)

Ricardo 1817

Some limited resources are inelastic

Resource picking (as an activity that takes place before resource acquisition)

Ricardian perspective on resource picking as a basis for competitive advantage

Schumpter 1950

Resource deployment and capability building

Capability building (an activity that takes place after resource acquisition)

Schumpterian perspective on capability building as a basis for competitive advantage

Penrose 1959

Tangible things (physical goods) and human resources . . . can be defined independent of their use (pg 24/25)

Bundles of resources

Resources are plant, equipment, land, FGs, WIP . . . and skilled and unskilled labor

Firms are bundles of resources/services

routines are regular and predictable patterns of activity of the firm

Production routines, R&D, procedures, policies, . . . they are behavioral, inheritable, and persistant

Focuses on efficiency and effectivness of routines

Nelson and Winter 1982/2002

Example of resources and capabilities

On competitive advantage/outcomes

Part B 15.3

Daft 1983

All assets, capabilities, organizational processes, firm attributes, information, knowledge etc. controlled by a firm that . . .

. . . enables the firm to conceive of and implement strategies that improve its efficiency and effectiveness

Wernerfelt 1984

Any strength or weakness of a firm, . . . tangible and intangible assets which are tied semipermanently to the firm (Caves 1980)

Resources are machinery, brand names, in-house technology, efficient procedures, employment of skilled people, capital, trade contacts, etc.

Hayes and Wheelwright 1984

Structure/infrastructure?? (hardware/software – Slack 2005)

Structural elements are hardware/assets; infrastructural items are software/intangible assets

Structural and infrastructural capabilities of individual units (plants)

Resource position barriers, attractive resources, supplementary (similar) resources, complementary resources, resourceproduct matrix synergies

Enterprise Organization and Operation

15.3 Process Organization, Capabilities, and Supply Networks

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Table 15.6 (cont.)

On resources

On capabilities (or routines)

Example of resources and capabilities

On competitive advantage/outcomes

Prahalad and Hamel 1990

Key corporate resources include Internal coordination and learning skills that cannot be acquired easily

A competence that is difficult for competitors to imitate; . . . is likely if the competence is a complex harmonization of individual technologies and production skills

core competences are . . . coordination, learning, complex harmonization of individual technologies, and production skills

A core competence that is difficult for competitors to imitate

Barney 1991

Resources are the inputs, or basic units, that go into the production process

Capabilities (or potential competencies) of a firm are generated from a team of resources, networked together into a process (routine) for competitive advantage

Resources are assets, people skills, . . . capabilities are generated from a team of resources networked together into a process or routine for competitive advantage

Sustainable competitive advantage is possible if resources are valuable, rare, imperfectly imitable, and not substitutable; resource heterogeneity is a source of competitive advanatge

Are strengths that firms can use to conceive of and implement their strategies

Physical capital (Williamson 1975), human capital (Becker 1964), organizational capital (Tomer 1987)

. . . strengths . . . that enable firms to conceive and implement their strategies

Grant 1991

Rent-earning potential from resources and capabilities governed by degree of sustainability and appropriability

Harrison et al. 1991/2001

Resource complementarity

Barney 1992

Core competences focus on the technological and production expertise at specific points in the value chain

Resource complementarity is not similarity Capabilities are more broadly based, encompassing the entire value chain. They are visible to the customer.

Resource complementarity allows firms to learn new and valuable capabilities Entire chain concept, visbility to the end customer

Part B 15.3

Author/year

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Table 15.6 (cont.)

Author/year

On resources

On capabilities (or routines)

Example of resources and capabilities

Amit Schoenmaker 1993

Component competence terminology used to capture resources

Capabilities refer to a firm’s capacity to deploy resources, usually in combination, using organizational processes, to effect a desired end

They are information-based, tangible or intangible processes that are firm specific and are developed over time through complex interactions among the firm’s resources. They can abstractly be thought of as intermediate goods generated by the firm to prove

Peteraf 1993 Teece et al. 1997

Supply inelasticity becomes a source of competitive advantage Firm-specific assets that are difficult if not impossible to imitate

Part B 15.3

Dynamic capabilities as the ability to integrate, build, and reconfigure internal and external competencies to address rapidly changing business environments

Assets are difficult to transfer . . . because of transaction costs, transfer costs, and that they may contain tacit knowledge Shi and Gregory 1998

Barney 1999

On competitive advantage/outcomes

Superior deployment of internal resources is a necessary competitive requirement

Managerial processes and organizational (dynamic) capabilities

. . . the development and renewal of resources, and the integration and balancing of resources

Internal and external resources, resource mix, internal managerial processes, resource development, and renewal Networks of plants have additional capabilities that stem from their geographical dispersion, product and process structure/infrastructure

internal firm manufacturing network

Should be balanced by a broader perspective of assessing the relative capabilities of the firm and partners when formalizing the wider SC network

Realative capabilities of the firm and partners are an important factor

Enterprise Organization and Operation

15.3 Process Organization, Capabilities, and Supply Networks

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Table 15.6 (cont.)

Author/year

On resources

On capabilities (or routines)

Example of resources and capabilities

On competitive advantage/outcomes

Eisenhart and Martin 2000

Local abilities or competences that are fundamental to competitive advanatge

Dynamic capabilities, as specific processes that firms use to alter their resource base, as sources of competitive advantage

Resources are specialized equipment, geographic location, and human expertise.

Does not explicitly include spatial (geographic) dispersion

Winter 2003

Lewis 2003

Strategic resources – as equivalent to capabilities – scarce, imperfect mobility, imperfect substitution/imitation (Wernerfelt 1984/1985)

Competence includes all resource and capability notions

Tangible (assets) versus intangible (Nanda 1996) resources

Processes (Penrose 1959, Nanda 1996) (and not resources) provide competitive advantage; resources ⇒ processes ⇒ performance outcomes (Martilla and James 1977)

Evolution of capabilities that encompass operational capabilities (collection of routines that directly contribute to production output or service) and dynamic capabilities (routines that build, integrate or reconfigure operational capabilities)

Parallels with PLCM. Use of terms widely used in maturity models . . . foundation stage, development stage, maturity stage, etc.

Introduces the concept of a capability lifecycle. Focus is on organizational and team capabilities (coordination) and not on the performance of individual tasks

Specifically, RBV theory promotes concepts that are, from a supply network perspective, incomplete as they are:

• •

Single-plant focused, i. e., their focus is on the structural/infrastructural capabilities of individual units [15.41] and they are not manufacturing network based Single-firm focused, i. e., not supply network oriented

•

Internal assessments with few references to external network-dependent capabilities, i. e., they tend to focus on core (component) products, or internal managerial processes and organizational (dynamic) capabilities [15.32] and not multifirm (network) capabilities

The need for a more operational and network perspective of capabilities has been emphasized in the most recent literature:

Part B 15.3

Helfat and Peteraf 2003

An organizational capability is a high-level routine (or collection of routines) that, together with its implementing input flows, confers upon an organization’s management a set of decision options for producing significant outputs of a particular type

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Table 15.7 Supply network maturity models (adapted from Srai and Gregory [15.42])

Related cluster

Author

Maturity level 1 2

3

4

5

None

Functional integration Partial

Internal integration Formal

External integration Culturally embedded

Poirer 2001

Internal SC optimization

Network formation

Value chain constellation

Full network connectivity

Hines et al. 1997

No coherent strategy

Piecemeal coordination

Systematic coordination

Network coordination

Uncertainty

Awakening

Enlightenment Wisdom

Uncertainty

Regression

Awakening

Enlightenment Certainty

Stable formal system approach Design SCs according to product type

Continual improvement emphasized Find the frontier before optimizing Crossenterprise collaboration Network development

Supply network design SC evolution model Design maturity

Stevens 1989 Fraser and Moultrie 2001

Baseline

None

Supply network connectivity e-Business development framework Supplier coordination

Total network efficiency

Part B 15.3

Quality maturity Quality management

Crosby 1979 Crosby 1996

Certainty

SC processes development and application ISO 9004

ISO

No formal approach

Reactive approach

Inventory Mgmt

Kavanaugh 2002

Become customercentric first

SCOR model

SCM 2004

Functional focus

Acknowledge uncertainty, then exploit it Internal integration

Supplier development

Hines et al. 1997

External accreditation

CRM phases

Forrester 2002

Channel integration

Reactive problem solving Process redesign

External integration Systematic development programme Continuous optimization

Best-in-class performance Pay attention to systems integration

6

Enterprise Organization and Operation

15.3 Process Organization, Capabilities, and Supply Networks

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Table 15.7 (cont.)

Related cluster

Author

TPM – autonomous maintenance

Shirose 1992

Initial cleaning

TPM steps

Shirose 1996 FMCG practice

Preparation and buy-in Functional excellence

Eliminate contamination sources Formal kick-off Service and integration

Carnegie Mellon 2002

Initial

FMCG SC model Software assessment

Maturity level 1 2

3

4

5

Create and maintain standards

Inspection

Autonomous inspection

Execution

Establishment

Repeatable

Integrated network and collaboration Defined

Beyond known capabilities Managed

6

Optimizing

Product and service enhancement Szakonyi 1994 McGrath 1996

Not recognized Informal

Initial efforts

Skills

Methods

Functional

Cross functional

NPD cycle time var. 2 Service organization

McGrath 1996 Aerospace practice

Informal

Functional

Service lifecycle Mgmt

McCluskey 2004

Discrete support and services Baseline service

Integrated support and services Operational efficiency

Project excellence Through-life capability

Enterprisewide and integrated Portfolio excellence Output solutions

•

•

The resource-based view (RBV) in which the superior deployment of internal resources as a necessary competitive requirement should be balanced by a broader perspective of assessing the relative capabilities of the firm and partners when formalizing the wider supply chain (SC) network [15.43]. Networks of plants have additional capabilities that stem from their geographical dispersion, and product and process structure/infrastructure [15.34].

Customer support excellence

Responsibil- Contities Imp’t

Collaborative

Structured to grow

It may be argued that taking an external-to-firm supply network perspective challenges the basic premise of RBV of internal resources, perhaps adopting some elements of the external environment alluded to in Porter’s competitive positioning work. However, by distinguishing between closely linked supply network partners and the organizational routines and processes between them, and thus removing ownership as an artificial barrier to what constitutes available resources, maintains the philosophical links between the RBV of the firm and the supply network capabilities of closely coupled partners.

Part B 15.3

R&D effectiveness NPD cycle time

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Table 15.8 Supply network capabilities

Capability

Focus and key questions

Organizational capability (team focus)

Focus Q.

Primary capability (outcome specific)

Focus Q.

Metacapability

Focus

(outcome specific)

Q.

Traditional focus is at the firm level, team selection Do we have the right organizational structure and people? Strive for optimum organizational structure. Operates at the functional and cross-functional level with a focus on process development and maturity Do we have the right processes? Strive for higher levels of operational process maturity. Firm strategy, firm and supply network performance with the focus on primary-capability selection Do we have the right capability sets (profile)? Strive for optimum business model. Is resource configuration a strategic variable?

Part B 15.3

15.3.3 Application Perspectives and Maturity Models

of stagewise evolution from a basic foundation level through to a leading-edge state of process excellence.

Maturity models have been used in a number of applications, in particular in the areas of business excellence models, software development, and process improvement, including in the areas of operations management, engineering, information technology (IT), and adjacent fields. They generally use qualitative assessments or statements to capture stages of capability evolution, but may also be supported by additional descriptive accounts and by quantitative measures. However, quantitative performance measurement across supply networks and across industry sectors is difficult [15.44], facing the combined challenges of consistency, context, and accurate key performance indicator (KPI) assessments. Consequently the various analytical tools struggle to discriminate the best from the rest. In addition, alignment of operational capabilities with business goals is a key dimension that is not generally covered. The supply network capability map (SN capability map) capability map attempts to address these shortcomings by taking a holistic perspective of a broad set of capabilities. Five clusters of capability are identified covering supply network design, network connectivity, network performance, enabling process excellence, and new product development. Table 15.7 summarizes, against each of the five supply network capability clusters, some of the related maturity models used in both the academic and practice literature. These maturity models vary greatly in their level of detail but have a common approach: the notion

15.3.4 Operational Process-Based Capabilities The extension of capabilities to beyond the firm, and to supply networks in particular, makes for a processbased analysis to capability development, as well as an outcome-based assessment at the strategic level. A central issue is the development of primary capabilities developed from established processes or routines. These processes are well recognized and are often difficult to implement, but are nevertheless standard routines. They have been embraced by a whole variety of organizations. Imitation, although difficult, is possible and generally practised. They include complex processes (such as Six Sigma, total productive maintenance (TPM), total quality management (TQM), and Kanban systems), processes that have been well documented. They are regarded as transferable processes or routines that in supply network terms exist within and between functions, and across firms. Metacapabilities, on the other hand, or higher-order capabilities, involve selective resource picking, tradeoff approaches to arrive at a particular set of primary capabilities (a particular capability profile). The selection process seeks to achieve a particular outcome or alignment to the business model, and thereby provides for a unique metalevel capability that is generally far less well understood. These metacapabilities are company (or supply network) specific, customer rel-

Enterprise Organization and Operation

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15.4.2 Definitions The starting point of the consideration of modeling within the field of organizational structures within industrial settings is the term system enterprise. This can be described as a set of entities and a set of relations between these elements [15.46]. A system is defined as a structured formation, which is delimited or assumed to be delimited from the environment. It consists of a set of elements (parts) which affect each other due to fixed relations. According to [15.47], there are various views to analyze systems thoroughly:

• • •

The functional view, which understands system as an input/output system (I/O system) whereby the transformation of input data to output data describes the function of the system The structural view, which focuses on elements and relations between these elements The hierarchical view, which focuses on the fact that a system might be composed by a set of multiple subsystems and belong to a supersystem

According to [15.48] and [15.46] an enterprise can be understood as a system that is:

• • • • • •

Real (physical, observable – not theoretical) Open (relations to environment exist) Complex (large and continuously changing number of elements and relations) Probabilistic (prediction of future behavior has a certain probability) Artificial (created by humans) Dynamic (properties of elements and relations are variable over time)

A model of a system is a constructed, simply changeable, and easily understandable system that represents a hardly changeable, complex system regarding a certain problem or aspect. Therefore, only the corresponding relevant elements are mapped into the model. In general, models will only represent a subset of all the information that a system contains. Therefore, they are only projections of the original system to model systems that can be used to answer specific questions about the structure and behavior of the original system. Various types of models can be distinguished. This distinction can be based on the set of questions that can be answered by a certain type of model as well as the viewpoint of the original system that they represent.

Part B 15.4

tioned above, may implement computer support through computer-aided design (CAD), computeraided manufacturing (CAM), computer-aided process planning (CAPP), or production planning and control (PPC). Computer-integrated manufacturing (CIM) is the sum of the production systems information flows, managing all areas through central databases. EDP has not only contributed to the support of organizations and processes, it has made technologies and information flows more intelligent, e.g., by integrating advances in information and communication technology (ICT) into the application/processing of relevant information. Examples are computer numerical control (CNC), net communication technologies such as field busses or industrial ethernet, advanced software design concepts such as object orientation and agent-oriented programming, and ontology-based contract protocols, to mention only some of the highlights of the last decade. Interoperability requirements and the variety of ICT solutions, offered by increasingly modular setups of devices and software programs, highlight the importance of technical, ICT, and organizational standards, elaborated by national, European, and international institutions, engineering associations, and interest groups (e.g., the Institute of Electrical and Electronics Engineers (IEEE), VDI, ISO, and DIN). To support the engineering and execution of operations and processes within industrial settings using EDP based on advances in ICT it is necessary to provide the relevant information in an electronically processable manner. Therefore, the relevant information has to be integrated into model-based structures. These models separate the relevant information from the rest of the information available within industrial settings and structure it in a manner that abides by the requirements of EDP. They enables structured information collection, representation, and processing at all levels and for all purposes within industrial settings. Hence, models are an essential part of the successful application of EDP within industrial settings. One important field of application of EDP-based information processing is the engineering and execution of organizational structures within industrial settings, i. e., the engineering and execution of business and business-like manufacturing processes. In the following section we will discuss this field of interest with respect to information modeling-related terms, methods, tools, and models.

15.4 Modeling and Data Structures

Enterprise Organization and Operation

Modeling languages and modeling methods provide the basis for modeling technologies. While modeling languages define the syntax of models, modeling methods define their semantics. To increase the applicability of modeling languages and modeling methods and reduce modeling risks and costs, reference models are used. A reference model provides the structures, properties, relation, and behavior of objects of an application domain in a general and usable form, supporting the creation of specific models by adaptation. Usually, reference models consist of various submodels or views, describing the modeled facts in varying levels of detail, and varying points of view on the original system [15.51]. Often-used viewpoints are the static structure of a system and the behavior of the execution of the system to be modeled. The benefits achieved due to usage of reference models are:

• • •

The recognition of weak points and the resulting improvements The documentation of existing workflows The standardization of terminology

A framework to ensure the objectivity and correctness of modeling is provided by guidelines of modeling (GoM), the goal of which is to provide design recommendations for modeling to improve the quality of models beyond the matching of syntactic rules [15.51]. The guidelines of modeling (GoM) are given as follows:

•

• • • • •

General principle of correctness: – Correct reflection of the mapped issue (semantically, the described structure/described behavior; syntactical, the consideration of notation rules) General principle of relevance: – Documentation of the relevant issues regarding the respective view – No mapping of irrelevant information General principle of efficiency: – Modeling activities shall be performed with a suitable cost–value ratio, e.g., through the use of reference models and support of reuse General principle of clearness: – Structure – Clarity – Readability (intuitive) General principle of comparability: – Comprehensive application of modeling rules – Goal: consolidation of independently created (sub)models General principle of systematic setup: – Well-defined interfaces to corresponding models (e.g., input data of the process model/reference to data model)

Applications of models are constrained by the method chosen for modeling. Models and methods cannot be combined arbitrarily. The following applications are available as modeling methods:

• •

Description of functional structures (aspects of operations in production systems) Mapping of functions and specification of organizations (system analysis)

15.4.4 Important Models and Methods 15.4.3 Guidelines of Modeling (GoM) As mentioned above the modeling process requires a well-structured organization and well-defined inputs and outputs to reach the modeling objectives of providing a view of a system to answer dedicated sets of questions.

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In this subsection examples of architectures, reference models, as well as modeling languages and methods relevant within to the field of organization modeling will be described. Thereby, the main characteristics of the different levels of model system design supported by them will be emphasized.

Part B 15.4

A special type of a reference model is an architecture. An architecture defines the basic structure of a system resulting from a set of complementary and superimposing substructures and partially complementary viewpoints on the overall system. The architecture determines the structure of a system using two layers. On the one hand, the architecture establishes the model of the regarding system. Thus, it defines the object layer. On the other hand, the architecture defines rules that have to be considered during the development of the system [15.52]. Modeling architectures, as the most powerful but also most application-domain-oriented technology, form the top level of modeling technologies. They provide sets of models with fixed modeling syntax as well as model semantics related to the application domain. Thereby, they enable fast and efficient model system design and analysis by adapting inherent reference models to the original modeled system.

15.4 Modeling and Data Structures

Enterprise Organization and Operation

the RUP lifecycle is available as a work breakdown structure, which has to be customized to address the specific needs of a project. The RUP lifecycle assumes that a project has four phases (Fig. 15.28):

•

•

Inception phase: In this phase the business case which includes business context, success factors, and financial forecast is established and complemented by basic business use case models, project plans, initial risk assessments, cost assessments, stakeholder considerations, project descriptions, and requirement descriptions. Elaboration phase: in this phase the problem domain analysis is made and the basic architecture of the intended system is developed. This is done by developing use-case models in which the use-cases and the actors have been identified, identifying significant use cases, and revising business cases and risks.

•

•

15.5 Enterprise Resource Planning (ERP)

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Construction phase: In this phase, the main components and features of the intended system architecture and behaviour are designed. This phase is the main design phase developing the concrete system implementation. Transition phase: In the transition phase, the product will be moved from the development organization to the end user, i. e. the product will be delivered. In the case of an organization or a complex system the organization/system will be established.

The RUP provides a methodology for organization/system design fixing semantics of the results of different design phases. Intentionally it is not connected to special models and modelling techniques. Nevertheless, very often UML and SysML (depending of the intended domain of the result) are applied within RUP execution.

15.5 Enterprise Resource Planning (ERP) 15.5.1 Resources and Processes As all software systems, also enterprise resource planning systems are based on models of the business processes regarded. The easiest way to built up these models is to use the given information base in the company. As all companies use bills of material (BOMs) and work sheets or bills of operations (BOOs) the information concerning:

• • • •

Machine (cut, drill, mill, deform etc.) Move (transport, insert, eject etc.) Unite (assemble, weld etc.) Separate (saw, split, etc.)

may be read out and used for planning and process modelling. Figure 15.29 shows a manufacturing flow model on the basis of BOM and BOO information. In ERP, a number of worksheets and bills of material are interlinked in order to obtain routing, process, and flow models as the data input for enterprise resource planning and control [15.70, 71]. In order to define the full manufacturing processes all resources are assigned to functions and operations that are necessary. In the ERP context, resources are workforces, skills, objects, and equipment. ERP uses

Part B 15.5

Enterprise resource planning defines the task of enterprises to optimise plans for the most efficient input of all available resources. As these activities are generally computer supported, the term of ERP is actually used to describe software or software implementations to operate and optimize a number business processes in companies [15.68]. Enterprise resource planning systems attempt to integrate all data and processes of an enterprise organization into a unified software system. Formerly used terms have been also production planning and control (PPC), materials requirement planning (MRP) and manufacturing resources planning (MRP II) [15.69]. Revolving plans are generated for the production programs as well as for the allocation and expected demand of resources like production capacities or inventory. Forecasts and customer orders (primary demands) are broken down to the finished goods’, aggregates’ and parts’ levels (secondary requirements) using a set of well established procedures (net requirements calculation, lot sizing calculation). Moreover ERP also includes a number of administrative functions, as accounting or billing. In order to give an overview on ERP functions, the key procedures that are implemented shall be detailed in formal terms that clearly differentiate the resources regarded.

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Part B

Applications in Mechanical Engineering

Table 15.9 Description of important ERP procedures (SCH – scheduling; EOQ – economic order quantity) ERP procedures

R

S

T

b(t)

r(t)

Operators D

SIC

R1

–

Discrete

Yes

Yes

MRP

R1

BOM

Discrete

Yes

Yes

MRP II

R1 , R2 , R3 , R4 R1 , R3 , R4

BOM

Discrete

Yes

Yes

Time dependencies

Discrete

–

–

Material requirement? Inventory? Material requirement? Resource requirement? Resource inventory? Order due date feasible?

CSP

R1 , R2 , R4

Working plan

Discrete

Yes

Yes

Kanban

R1

–

–

SCH

–

Part B 15.5

(e.g., tools). SIC application does not assume a complete bills of materials or other information detailing the setup of products or aggregates. Material Requirement Planning (MRP) The MRP procedure may consider all materials and parts that are listed in the bill of materials (BOM); the interrelations set up between the products are used for the computation of the requirements. A (given or forecasted) production programme is broken down into requirements at all levels of the product (on a deterministic basis). In order to determine throughput times and accurate quantities, delays and waste factors are added to the BOM relations (calendar dates, delay times, lot sizes, volumes, and economic order quantities). Generally the products, parts, and aggregates (BOM positions) that are considered by MRP are expensive, difficult to supply, or discontinuous in demand. Two alternative modes are applied:

• •

Order-driven MRP, which breaks down the demand per order Program-driven MRP, which breaks down the demands for all BOM positions, using complex net requirement calculations on the basis of inventory levels

Resource requirement? (time, capacity, lot) Minimum inventory?

E

A

Order EOQ

Next low inventory level

Order EOQ Order release

Next BOM position Resource list

Order release order split/ concurrent procedure Load shift sequencing queuing

Subsequent time span (forward/ backward) Subsequent process step

Card release

Next card

Manufacturing Resource Planning (MRP II) As sketched above, MRP II extends MRP to interenterprise contexts. It uses universal descriptions independent of industry branches [15.77]. Planning and control is applied to multistage value chains. MRP II is characterized by a strong material focus as well, strictly separating lot sizing and capacity loading [15.78]. All process steps are planned and scheduled. Capacity planning activities are a part of standard software activity. Scheduling Procedure For an approximate determination of due dates and dates for execution of process steps the time consumptions to be expected for the order executions is considered. Resulting schedules for R1 (materials, parts, final products, etc.), R2 (machines, lines, etc.), and R4 (auxiliary equipment, tools, measuring technology) anticipate order allocations as well as order execution and finish constellations (Gantt charts) [15.79]. One-of-a-kind production may require more elaborate (graph-theorysupported) procedures such as the critical-path method (CPM), the project evaluation and review technique (PERT) or the metra potential method (MPM) [15.14] for scheduling. The benefits of production scheduling include setup cost and inventory reduction, increased production efficiency, labor load leveling, and real-time order information.

Enterprise Organization and Operation

Capacitated Scheduling (CSP) Capacity requirement and scheduling generates detailed plans and schedules for machines, equipment, and materials, feasible to be executed in manufacturing areas [15.80]. A special case is the capacitated lot-sizing lead-time problem (CSLP), where smooth loads are generated by time and/or assignment shifts using sequencing algorithms as well as order-split logics and queuing rules. Kanban Kanban is a procedure that controls the flow of material by pulling parts as needed through the manufacturing system. A part is manufactured if and only if a part of this kind has been taken out of the buffer. The procedure allows minimum inventory, ensuring highest order availability at the same time. Kanban (Japanese for “card”) is used for the control of mass production and large series throughputs. For each part a standard lot size and minimum inventory level are defined, represented by the number of cards released into the process. Using the ERP formalization as introduced above, all described procedures may be categorized as shown in Table 15.9.

ERP applications are widespread in enterprise organizations. Applied properly, they provide many advantages. Nevertheless the most elaborate ERP procedures also exhibit weaknesses regarding flexibility (dynamic routing or rush orders) and interoperability (with other systems, such as MES). Problems are caused by newly arriving high-priority production orders, since the running production cannot be modified. ERP implementations are often seen as too rigid and too difficult to adapt to the specific workflow and business processes of some companies [15.81]. Also, in areas related to software implementation, expected ERP benefits may not be fully attained as:

• •

•

Customization of the ERP software is limited. Some customization may involve changing of the ERP software structure, which is usually not allowed. Re-engineering of business processes to fit the industry standard prescribed by the ERP system may lead to a loss of competitive advantage. Many of the integrated links need high accuracy in other applications to work effectively. A company may achieve minimum standards, then, over time dirty data will reduce the reliability of some applications. The system may be overengineered with respect to the actual needs of the customer.

To improve ERP applications, potential is seen in more intensive cooperation [15.82]. Concepts such as built-to-order supply chain (BOSC), efficient customer response (ECR) [15.83], and continuous replenishment planning (CRP) [15.75] are discussed, aiming for smoother flows. Multiple forecasts within supply networks, changing demand patterns, and general synchronization problems call for collaborative planning, forecasting, and replenishment (CPFR) [15.84]. Nevertheless these approaches, even if accompanied by firm alignments via very rigid standards, as proposed by the Voluntary Interindustry Commerce Standard Association (VICS) [15.83] are still considered immature [15.85]. Their operation is laborious, as they ignore fundamental problems of collaboration involving diverse self-interested actors with conflicting motivations. With changing organizations in enterprises, ERP logics and software solutions have to be redeveloped too. Currently the vendors of ERP software are working on solutions to avoid the shortfalls listed above [15.85]. The developments are oriented towards advanced industrial organization concepts [15.86], greater flexibility, and variability of product and process data [15.87]. First solutions draw from networked control concepts and the latest ICT devices, e.g., radiofrequency identification (RFID) and multi-agent systems (MAS).

15.6 Manufacturing Execution Systems (MES) To manage the optimization and control problems accruing in larger manufacturing systems, which also include large amounts of numerically controlled (NC) equipment, manufacturing execution systems (MES) have been designed. Presently, manufacturing execution systems incorporate algorithms for short-term

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production planning and control. According to the specification of the Manufacturing Enterprise Solutions Association (MESA) [15.88], MES covers 11 functionalities, as listed in Table 15.10. For efficient implementation of these 11 functions several specific architectures have been developed.

Part B 15.6

15.5.4 Conclusions and Outlook

•

15.6 Manufacturing Execution Systems (MES)

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Part B

Applications in Mechanical Engineering

Table 15.10 Main functions of MES

MES functionality

Attributes

Resource allocation and status

• Shows resources, including reservation and dispatching of machines, tools, labor skills, materials, and other equipment • Provides read/write access to documents and data that must be available to enable the necessary work • Performs sequencing of resource operations and functions based on priorities, attributes, characteristics, and/or recipes • Reflects specific features of the scheduled resources such as necessary activities for process setup and possible process sequences • Prepares the flow of units to be produced such as jobs, orders, batches, lots, and work orders • Creates dispatch information presenting the sequence • Manages the control of information containing units (forms, files, records, etc.) relevant for a manufacturing unit • Provides an interface to collect all data such as interoperational production data and parametric data that are included in the controlled documents of a resource • Manages status information of personnel, including time and attendance reporting as well as certification tracking • Provides real-time analysis of measurements collected from the resources before, during, and after the manufacturing process • Monitors the manufacturing process resources and automatically corrects resource behavior or provides decision support to operators • Controls activities to maintain resources to ensure their availability for manufacturing and ensure scheduling for periodic or preventive maintenance • Provides visibility of the current status of the manufacturing processes and the current state of resource activities • Creates a historical record • Provides up-to-the-minute reporting of actual manufacturing results and its comparison with past history and expected business results

Operations/detailed scheduling

Dispatching production units Document control Data collection and acquisition Labor management Quality management

Part B 15.6

Process management Maintenance management Product tracking and genealogy Performance analysis

The most popular class of systems focuses on resource allocation, scheduling, and dispatching on the one hand, and data collection and acquisition on the other hand. As the overall complexity of MES is increasing (as manufacturing systems become more complex), architectures have been adapted with distributed functionalities and to develop distributed MES systems [15.89]. Special effort has been invested in the field of intelligent distribution of the necessary decisions. One major technology used within this field is agent-based

systems. All of these efforts reflect similar structures dealing with negotiating orders and resource entities [15.90]. Another field of major interest is the interfacing of data sources relevant for MES system behavior. An advanced architecture in this field is the open robot interface for the network (ORiN) – one of the most important data collection and acquisition architectures – which offers interoperability of different functionalities with the possibility of integrating systems from different vendors.

Enterprise Organization and Operation

15.6.2 Development of Prototype Application Systems

Application System for Machine Tools Without Network Interface Examples of accessing operational information from machine tools without network interfaces without a major conversion process include:

• •

Acquisition of operational status through the machine tools operation panel/switchboard or digital input output (DIO) Estimation of a machine tool’s cutting load by measuring the electrical current of the spindle amplifier

NC controller comments as well as variables in the external output command of the NC program can be exported through the RS232C interface of the NC controller through the use of macro functions. Additionally an external direct numerical control (DNC) computer

can manage the operational status of a machine tool if that machine tool is running a DNC system. Accessing information using an external output with macro functions may be adopted for machine tools without a network interface. Ethernet-to-RS232C converters can be used to integrate this system as a very economical solution. The corresponding system configuration is shown in Fig. 15.38. There are also cases (such as when using a CAD/CAM system) where MES-level information such as product name, date of delivery, and tool information are known right after the NC program is made. In such cases, the external output commands from the macro function for the MES-level information can be inserted directly into the NC program. The format of the comment information from the external output is based on the robot action command (RAC) [15.96] specification that was developed by the ORiN consortium. Once the NC program has been prepared it is transmitted to the NC controller of the machine tool. The comment information can then be used for setting up the machine tool by viewing the display panel of the NC controller. The comment information is then output through the RS232C interface of the NC controller, which is synchronized with the execution of the NC program. Subsequently, the comment information is sent to the RAC2RaoSQL, which is an application system for receiving the RAC data through a transmission control protocol (TCP)/internet protocol (IP) socket or virtual COM port on a network using the Ethernet-to-RS232C converter. After the RAC2RaoSQL receives the comment information it is written to the IIE. The configuration of the test system consisted of a factory site and a remote site. The factory site had a developed prototype system for a turning machine with an IIE. A client computer, using a web browser, was prepared at the remote site and connected to the factory over the internet using a virtual private network (VPN). Figure 15.39 shows an example of the indicator screen on the client computer. The NC program’s name, executing sequence number, the product’s name, date of delivery, scheduled production count, actual production count, and the process name of the executing NC program can all be seen in this example.

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Part B 15.6

An Application System for Open NC Machine Tools and MES Applications For a manufacturing system line consisting of one transfer robot and two machine tools, integrated with OpenMES [15.94] as shown in Fig. 15.35, the mechanism of the interoperable system is shown in Fig. 15.36. The equipment class of the OpenMES has been mapped to the RaoSQLController class of RaoSQL. The other OpenMES classes and other ORiN classes have been mapped to the RaoSQLItem class of RaoSQL. Provider software as interface software between devices and ORiN for the machining tool and the transfer robot have been developed using the APIs of each controller with Microsoft’s Visual C++. However, because OpenMES uses Java, a software interface between OpenMES and RaoSQL using a Java wrapper was developed. Test operation of the prototype was performed using the three-dimensional (3-D) layered information viewing environment (3-D LIVE) [15.95]) which was developed in advance. Conventional 3-D LIVE was developed as an application system that uses RAO information directly. The ability to show MES-level information together with device-level information became possible by changing the information reference source in 3-D LIVE to the IIE, as shown in Fig. 15.37.

15.6 Manufacturing Execution Systems (MES)

Enterprise Organization and Operation

15.7.1 Lean Production

1. Produce only what is ordered and only when it is ordered. Apply this to product, organization, as well as product features; otherwise there will be waste. 2. Investigate any mistake with the highest priority and find solutions for strict mistake avoidance. 3. Everybody involved in production is obliged to improve products and processes continuously. To implement these rules, a set of methods is proposed (frequently using Japanese language terms) that may be interpreted as patterns of lean production. The rules most frequently referred to are (not always strictly applied in the original Toyota sense):

• • •

Kanban (use card), a material flow and inventory control procedure, supporting just-in-time production and minimizing lead time as well as inventory levels Kai zen (improve the good), prescribing the continuous improvement process (CIP) Six Sigma, calling upon statistical backgrounds to achieve waste ratios, measured in parts per million (ppm)

• • • •

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The five S’s: seiri (sort out), seiton (clean up), seiso (keep proper), seiketsi (make orders your rules), and shitsuke (improve all things continuously) as simple rules of behavior for everybody in the organization Management by view: all processes are visible and transparent in order to recognize irregularities immediately Poka yoke, technique to obtain error-free transformations and moves Quality circle (QC, TQM): readiness to improve the quality of all processes, executed by teams Jidoka, to stop process steps (including the impressive pull the emergency line option) if errors are detected/assumed

For the implementation of the methods and rules, ten steps to lean production are recommended: 1. Eliminate waste 2. Minimize inventory 3. Maximize flow 4. Pull production from customer demand 5. Meet customer requirements 6. Do it right, first time 7. Empower workers 8. Design for rapid changeover 9. Partner with suppliers 10. Create a culture of continuous improvement Instead of devoting resources to extensive planning, the Toyota production system focuses on reducing system response time by enabling the production system to adapt instantly to market demands. All automobiles are made to order, resulting in a number of effects: delivery on demand, minimization of inventory, maximization of the use of multiskilled employees, flattening of the management structure, and concentration of resources where they are needed. Lean production shows revolutionary attributes, providing an enormous productivity boost [15.104]. Therefore other companies (even competitors) have tried to adapt this methodology and integrate it into their corporate strategies, coining terminologies of X–production systems (where X is the company or brand name) that summarize rules and methods as mandatory parts of multisite company-wide standards (footprints).

15.7.2 Agile Manufacturing Agile manufacturing [15.105] was developed from the synthesis of a lot of companies with individual abili-

Part B 15.7

Since the MIT studies on the machine that changed the world [15.100] lean production has become one of the most frequently discussed organization concepts. Lean production is an assembly-line manufacturing methodology developed originally for the manufacturing of automobiles, derived from the theory of constraints [15.101]. It is also known as the Toyota production system (TPS) [15.102]. Many practical approaches that are also referred to as lean manufacturing (lean management, lean company, lean enterprise etc.) are motivated by this methodology, or originate from Toyota production system blueprints. The guideline for lean production can be formulated as to get the right things to the right place at the right time, first time, while minimizing waste and being open to change. Lean manufacturing can be classified as a team-centered organization specification. While developing the principles of lean production [15.103], it was discovered that, in addition to eliminating waste, the methodology leads to improved product flow and better quality. There is no established theory for lean production, but theoretical grounds may be found in the theory of constraints. However detailed methods and rules for the successful operation of lean are outlined. The most cited rules (simplified) are:

•

15.7 Advanced Organization Concepts

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Part B

Applications in Mechanical Engineering

Part B 15.7

ties or responsibilities, which come together in a joint venture. It was intended to be able to use the sum of abilities and resources of all the partners together. These joint-venture companies are called virtual companies, able to reshape and change quickly. The implementation of agility aims for intensive exploitation of organizational knowledge. For this purpose individuals are motivated to collaborate closely in dynamic teams focusing on clearly defined opportunities in the market [15.106]. Employees and information are the key factors that should ensure the superiority of agile companies compared with the surrounding competition. Agile manufacturing aims to enable an increase in performance of companies by achieving major steps toward flexibility and time to market. Hence, the value chain has to be compatible with fast movement of products to market. The main target of agile manufacturing is the development of durable success in an environment of continuous and nonpredictable change. For success the times of processes inside the value chain have to be in accordance with the fast movement of products to market. The agile approach aims to serve mass markets, but all individual wishes of the customers should be granted. Cooperation with other enterprises helps to produce new products faster and cut costs, reducing the risks for all partners. Usually joint ventures – vertical and horizontal mergers within the value chain – establishing virtual companies are the strategic aim. A characteristic of this concept can be identified is the rapid change of the structure of the networked organizations. This includes all efforts to make use of the latest information and communication systems as well as the integration of fast reprogrammable technologies in production [15.107]. Within the agile concept the employee is the focus; the necessity for a high level of knowledge and education is clear. The employee must act as an entrepreneur in the company and must be actively engaged in all relevant processes, because of the low and simple level of organization. The dynamic development of a team actively helps to develop the creative and innovative talents of other members of the teams. Management assists by developing company culture, supporting creativity, and being open to experiments and risk-taking by the employees. Leadership is based on motivation, support, and especially on building trust.

15.7.3 Bionic Manufacturing Recognizing that even so-called flexible manufacturing systems are not able to fulfil the demands of customer-specific parts production, the bionic manufacturing system (BMS) was developed [15.108]. BMS is an approach that aims to master the future demands of manufacturing systems through the application of technology that mimics the nature of living beings. The core idea of the BMS is the creative system, in which the materials provide the necessary information to the manufacturing equipment. Intelligent methods respond to this information using flexible and autonomous technical units. BMS draws on the results of artificial life research, by embedding DNA-type information into the materials to be processed. Material with this stored information is passed onto the manufacturing system so the product can be built accordingly. Information is transferred to the operating manufacturing system, offering the following characteristics:

• • • •

Ability to learn and identify necessary tasks Ability for self-maintenance Ability for communication Ability for self-creation to acquire new product and technology knowledge [15.109]

The product collects further information and passes this on as recycled raw material back to the manufacturing system, which interprets the information again and develops further. The basic information (for example, the method to move = car) survives as DNA information, whereas the bionic manufacturing system information enables the system to develop independently and adapt to cultural and temporary demands. This far-reaching vision has remained in fashion for a long time and currently miniaturized transponder technologies such as RFID are enabling powerful solutions of this kind [15.110].

15.7.4 Holonic Manufacturing Systems Holonic manufacturing systems (HMS) may be envisioned as specific interpretations of BMS, as HMS are also able to adapt and incorporate new products, new organizational structures, and new technologies. Holonic organizations (or holarchies) support the setup of very

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Part B

Applications in Mechanical Engineering

Table 15.11 Six key attributes of advanced organization concepts

Part B 15.7

Fractal

Holon

Bionic

Agile

Lean

Origin

Geometry

Physics

Biology

Nature

Theory of Constraints

Analogy

Fractal

Molecule

Organism

Agility

Mechanics

Key principles

• Self-similar • Self-organization • Self-optimization • Processorientation • Vitality and dynamic

• Self-similarity • Autonomy • Distributed intelligence

• Autonomy • Cooperation • Selforganization • Selfoptimization

• Enrich the customer • Master change • Resources • Cooperate to compete

• Perfect firsttime quality • Waste minimization • Continuous improvement • Pull processing • Flexibility • Long-term relationship with suppliers

Methods of structuring

• Product structure • Equipment • Employees • Flow of material

• Tasks and their similarity

• Knowledge base of autonomous elements

• Potential of supply and demand

• KAIZEN • POKA YOKE • KAN BAN

Objective

• Cohesive organization structure along the value chain • Minimizing interfaces

• Mutability • Ecologically sensitive • Robustness

• Dynamic adaptation and organizational ability to learn

• Adequate flexibility of the production system to react to market changes

• (MUDA) (Japanese for ‘eliminate waste’

Appearance

• Divisions with variable organization structure

• Event-driven communication between machines

• Sender– recipient relationship between resources and material

• Flexible organization structure • Interdisciplinary teams • Flat management structures

• JIT • Pull • Value stream

Configurable • Employees resources • Divisions

• Equipment

• Elements with inheritable knowledge (equipment) • Elements with learnable knowledge (material)

• Employees • Production and information technologies

• Objects • Equipment

Development • Skills and social of competencies resources

• Distributed systems

• Evolution of knowledge

• Syntheses of resources

• Best-practice benchmarks

Enterprise Organization and Operation

(Fig. 15.45): the agency, the agent community, the CMU community, and the lookup service [15.126]. The main benefits of PABADIS are improved order and resource flexibility and the generic interface structures of the control units – the control building blocks. The integration of a new order or a new product only requires the specification of the related set of manufacturing process data. Product and order agents are generic and therefore valid for each possible application case. This avoids the implementation of new agent types when changes occur. These properties and the internet compatibility of the PABADIS architecture has attracted the attention of leading vendors and users of planning and control systems for manufacturing. Within the PABADIS’PROMISE approach the PABADIS architecture will be improved and extended to all levels of control [15.110].

15.7.6 Summary Fierce competition and saturated markets have forced enterprises to cope with the diversity in customer requirements and the speed of the demands of the markets. Organizations had to become more flexible, versatile, adaptable, and reconfigurable in structure. It is evident that this paradigm shift has generated radical innovations in organization. Of the numerous progresses, the most important generic concepts have been outlined in this Section. These approaches are characterized and compared in terms of their key attributes in Table 15.11.

15.8 Interorganizational Structures Individual organizations are characterized by a mission, which states the scope and principles of their business. A mission tends to have a restricted focus with respect to market and product/service, even though, particularly for large corporate companies operating in different market sectors and product/service areas, the mission statement may consist of a general statement of intent. Throughout their evolution, companies continuously face new challenges derived from the evolution of products, technology, and markets, and face the need to acquire improved governance capability over the market and the product/service lifecycle, while being compelled to cope with limited resources in terms of

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finance, disciplinary competence, capacity, and risk sustainability. Without addressing issues associated with monopolies and vertical trusts, this increase of control can be pursued either through internal growth of a company (possibly using merger and acquisition levers), or by seeking cooperation with external entities (Fig. 15.46). Further progresses in ICT, especially the maturity of the World Wide Web (WWW), offering as-yetunknown possibilities to transfer/store huge volumes of information throughout the globe, accelerates further decentralization. Dispersed production units may cover product segments, functional units or entire production stages, dissolving boundaries within and between

Part B 15.8

interference [15.118]. If objectives of an unit are not achieved, the company top level must be involved: However, depending on the unit’s ability to profit from the opportunities in dynamic environments, the company may lower its influence on the unit, allowing or even supporting autonomous activities of (self)-optimization, (self)-organization, and (self)structuring. Figure 15.44 illustrates only one case of the companies’ meshed control loops established by SoA interactions or interferences. Higher structure levels of the company are represented by SoAs, self-similarly containing all corresponding SoA structures. Increase of market complexity (uncertainty, turbulence, and unpredictability) may force the company to expand the spaces of activities. More-foreseeable steadier conditions reduce complexity. Such conditions make smaller SoAs more effective, in the limit degenerating to a point a the origin for uniform mass production. The SoA model can therefore be envisioned as a generalization of the job definition in the hierarchical organization. Based on the SoA setup as outlined, negotiation and decision procedures between the units can be formalized and assigned to software agents. Making use of internet technology as well, a next-generation control architecture aiming at adaptable manufacturing equipment, flexible integration of different types of control systems, and distributed control devices for the execution of manufacturing orders can be derived: e.g., the plant automation based on distributed systems (PABADIS) architecture [15.125]. A PABADIScompatible control system consists of four components

15.8 Interorganizational Structures

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Part B

Applications in Mechanical Engineering

An additional consideration is cost to market to develop new products or services at lower risk and shared risk to retain market share, where market share is traded against development cost, or to penetrate new markets, possibly by working with a recognized partner in a market segment to open opportunities at lower risk and cost. When alliances involve several partners, it is usual to refer to them as constellations, as in the example of the alliance setup by MIPS in the early 1990s for the development of the innovative reduced-instruction-set computer (RISC) technology (Fig. 15.51). Alliances imply the joining of companies to pursue common, shared objectives, tend to have a limited number of partners, and are usually associated to particular kinds of cooperation:

•

•

Part B 15.8

Alliances are the mechanism used to achieve results that would not be within the reach of individual entities, or in general to minimize risks and organizational costs of particularly challenging or expensive initiatives. An alliance may also be a safeguard mechanism through which otherwise competing entities perform a high-risk activity together so that failure of the initiative cannot lead to a strong competitive edge for nonparticipating parties (as in the development of radically new technologies).

Sometimes alliances represent a real alternative to mergers and acquisitions, to enable greater market competitiveness, as in the case or commercial airlines, which enter code-sharing agreements to improve their market reach and their capability to satisfy the requirements and expectations of their own customers. In some cases, alliances provide a trial environment for mergers, allowing for testing and tuning of evolved, integrated business processes for the new integrated company. Conversely collaboration on specific products and services allows organizational cooperation without the risks and inherent costs of merger or acquisitions. From the point of view of management issues, the establishment of specific collaborations schemes with external entities meets several objectives:

• • • •

Keeping the focus of interaction on specific business objectives Allowing for the control of advancement and efficiency of activities Improving the interaction capability between different entities, focusing on joint strengths in the alliance Achieving cost-effective routes to market

Alliances can be managed through joint legal entities, i. e., separate companies with stock-holding shared among the partners, or on a pure contractual basis (typically assuming the contractual form of joint ventures). While in any case partners maintain their individual business focus, they allocate resources to the common initiative, and tend to establish an independent management office so to ensure that agreed mutual obligations and business focus is maintained throughout the life of the alliance through a central point of control, communication, and responsibility. The business concept for the alliance, particularly when in the form of joint creative developments (as in the case of alliances for the exploration and development of radically new technologies), may change over time, and the existence of an independent management entity helps to identify the most appropriate organization evolution strategies that are capable of accommodating the needs and expectations of all partners. Whether through actual or virtual collocation, human resources are usually allocated to alliances on a full-time basis, as in the case of large projects in integrated companies. This is likely to raise several issues in partners’ personnel management strategies associated with the possible loss of feeling of belonging by deployed personnel and to frequent problems in the management of professional careers and the difficulty of ensuring adequate recollocation of personnel within partner companies at the closure of joint operations. Even in the case of alliances that may lead to substantial benefits to partners and to significant evolution of core business (so-called strategic alliances), partner companies maintain their individuality. They are driven [15.131] to frame their cooperative initiatives within the global company strategy, which may well include an alliance strategy as a policy to achieve company vision and goals, but which cannot be substituted by a single strategic alliance, as that would de facto result in the same level of risk for the company as before, thus missing out on the main benefits yielded by the alliance. As a final note, it is worth quoting the top ten factors identified by Benjamin Gomes-Casseres [15.132] for the success of an alliance: 1. Have a clear strategic purpose: treat alliances as tools of a business strategy. 2. Find fitting partners: select partners with compatible goals and complementary capabilities. 3. Specialize: allocate tasks and responsibilities in accordance with each party’s best capabilities.

Enterprise Organization and Operation

4. Create incentives for cooperation: the cooperative attitude must be nurtured, particularly when partners were formerly rivals. 5. Minimize conflicts between partners: allocate roles in such a way to avoid pitting one against the other in the market. 6. Share information: communication develops trust and keeps projects on target. 7. Exchange personnel: personal contacts and site visits are essential for maintaining communication and trust. 8. Operate with long time horizons: sharing a vision strongly supports the solution of short-run conflicts. 9. Develop multiple joint projects: successful projects can help when other projects enter critical phases. 10. Be flexible: alliances are open-ended dynamic relationships that need to evolve in pace with their environment and in pursuit of new opportunities. Those factors imply an underlying company strategy based on time to market, cash flow, investment, the availability of resources, and the capability to manage alliances in line with organizational investment cycles for new products and the natural lifecycle of products to secure maximum revenue.

Compared with alliances, networks provide a looser kind of relationship [15.133], as they imply multiple close but nonexclusive relationships, whereas alliances imply the creation of a joint enterprise, at least over a limited domain. Networks generally exist on the basis of complementarities and potential synergy among members, which lead joining companies to associate with the network a greater opportunity for acquiring and retaining a competitive edge in the market: 1. To reduce uncertainty: the relationships developed through the network allow for avoiding the uncertainty associated with impersonal, nonrepeatable, and purely exchange-based market transactions. 2. To provide flexibility: the network provides a greater expectation of immediate resource reallocation, and allows for looser constraints in the establishment of joint product/service-specific initiatives. 3. To provide capacity: the likely availability of individual network members’ spare capacity allows companies to reliably pursue opportunities that lie beyond their own contingent capacity while improv-

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ing the management of contingencies in day-by-day operations. Furthermore, the network allows for the rapid provision of resources and skills which are lacking in a company through access to qualified resources from other known members. 4. To provide information: members of networks have easier access to industrial intelligence, as open information constitutes one of the mechanisms for establishing relationships and one of the principal reasons for members to join. A network is expected to offer to its members relationships that can lead to profits in the future. Based on this motivation to join, the power of a member has [15.134] five main sources: economic base, technologies, range of expertise, trust, and legitimacy, i. e., the characteristics that are most likely to support the success of initiatives by other members. Such expectations lead to governance principles that are close to historical socioeconomic organizations founded on reputation (both individual and acquired through belonging to groups of qualified members, such as a family or a clan) and on the provision of services and favors, which do not offer immediate reciprocity but which are aimed at strengthening relationships in view of future opportunities. The networking principle is applied as a mechanism for both dominated cooperation and for cooperation among equals. Cooperation domination is typical of advanced supply chains and extended enterprises (see below), whereas peer-to-peer-based networks constitute a characteristic dynamic entity which needs specific management provisions to be maintained. The peer-to-peer network is not a substitute organizational form for the integrated firm, even though collaborative business operations are usually conducted in accordance with classic customer–supplier relationships; roles are nonetheless dynamic and vary with business opportunities, and depend on contingent conditions that are mainly related to commercial positioning, competence ownership, dimension, and geographical location. As there is no stable leadership in these structures, the relationship glue tends to vanish with time, even for networks which are strongly focused on specific market sectors or composed of members with close geographical locations. There is therefore a need for a network entity, which is in charge of representing the network identity and of nurturing network relationships, typically through the provision of shared services at the technical, technological, commercial or legal level.

Part B 15.8

15.8.3 Networks

15.8 Interorganizational Structures

Enterprise Organization and Operation

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15.8.5 Virtual Organizations The term virtual organization appeared in the 1990s to qualify groups of companies that establish cooperative operations through the extensive use and exploitation of new information and communication technologies. This classification does not imply a specific kind of relationship, so that both dominated cooperation and peer-to-peer cooperation are included. In particular, when the paradigm of virtual organization is applied to supply chains, the expression extended enterprise is used, whereas for virtual organizations among equals it is common to use the terms virtual corporation or virtual enterprise. The paradigm of virtual organizations responds to the need to improve the effectiveness and efficiency of cooperation among multiple organizations. In fact, unless the scope of the collaboration is particularly simple, the interaction among independent organizations (and possibly individual professionals) results in a huge number of problems, resulting from the need for harmonization of cultures, processes, and policies. Virtual organizations leverage the capabilities of ICT to enforce advanced work methods in the partners’ organizations, with the aim of establishing operations that use all mechanisms available to the vertically integrated enterprise, while maintaining the greatest level of flexibility in terms of capacity and capability. The role of ICT is particularly relevant for ensuring team working through virtual collocation, integrated management of development and manufacturing planning, rapid administrative management and efficient cost controlling, and information sharing as well as knowledge management. This capability allows virtual organizations to have geographically dispersed partners which are selected to have the best capability as required by the scope of the organization, compatible with existing constraints, and pursuing maximum mutual profitability. Due to their openness and dynamics, virtual organizations are particularly subject to the issue of trust creation and maintenance, unless they can leverage pre-existing relationships as in the case of partners belonging to the same network. Special care is needed in particular for the management of knowledge in virtual organizations, as the increase of communication flows requires that knowledge is more freely exchanged among participants. Nonetheless, one of the most beneficial characteristics of this type of structure, i. e.,, its capability to evolve

Part B 15.8

It is becoming frequent in modern supply chains built for particularly complex products, such as aircrafts, that the manufacturer and first-tier suppliers enter into risk-sharing agreements that provide the manufacturer with additional financing sources in the development phase and reduce the risk that it must sustain; to balance this additional risk, suppliers require higher visibility on strategic decisions and on the reliability of market projections, which tends to strengthen the relationships and the mutual trust, at least for uppertier levels. The manufacturer keeps in any case the role of architect, which implies responsibility for the specification of component requirements (as a minimum at a functional level) and of boundary and interface requirements. The supply chain is then governed through contractual agreements/orders, which specify the scope of provisioning and the conditions for supply (planning and scheduling, delivery methods, invoicing and payments, etc.). Management of the chain is consequently driven by contractual provisions, with communication flows that are usually associated with expediting and advancement reporting, as well as on compliance of deliveries with requirements. Operations in a supply chain and its effectiveness [15.136] can be evaluated through its modeling in accordance with the supply-chain operations reference (SCOR) approach. This methodology was developed in the late 1990s by the Supply Chain Council to model and evaluate supply chains. The value chain is described as a sequence of standard processes, namely the make, source, deliver, plan, and return processes. The contribution of each participant in the value chain can be described by at least one of these processes, which leads at the top level to the general architecture of the supply chain. Figure 15.52 provides an example of how SCOR describes a supply chain. This top level can be specified at the level of process categories (level 2) and detailed process elements (level 3). It is obvious that SCOR also focuses on supply chains to describe and monitor existing value chains with the objective of achieving optimization. The benefit of the SCOR model is that it provides standardized processes which allow one to model the whole intercompany value chain with a single method – if, of course, all network partners agree to this standard.

15.8 Interorganizational Structures

Enterprise Organization and Operation

where deviations and misunderstandings may have a larger impact on final cost and time to market. The ICT infrastructure of the extended enterprise allows the collaborative phases to be extended through the lifecycle, resulting in a substantial improvement in effort alignment. Due to the increased responsibility allocated to suppliers through the process of co-design, extended enterprise leaders tend to adopt a risk-sharing strategy to ensure organizational motivation for best performance. While being enforced through legal agreements, the additional risk taken on by suppliers is enacted through greater openness of strategic information, which flows from top to bottom of the hierarchical chain of suppliers. The improvements achieved through the extended enterprise concept are therefore related to the establishment of common methods, reflecting harmonized interfacing at the boundaries of individual supplies and leading to:

• •

Increased ease of communication in the hierarchical path The capability to allow for cross communication among suppliers to improve cooperation capability

• • •

Improving reaction time to contingencies Simulating and planning operating conditions Monitoring and controlling flows of materials and associated product data.

15.8.7 Virtual Enterprise The virtual enterprise (often referred to as a virtual corporation [15.133]) is a particular form of virtual organization that is characterized by the precision of its scope/mission and by the actual creation of an organi-

zational structure that can be substantially independent of original organizational structures in the participating companies. The enterprise is typically composed of companies that provide different functions, in accordance with their capabilities and individual strategic goals. A virtual enterprise constitutes a single electronic business entity [15.133], without a physical structure. Although the enterprise is presented as a real company, it is not typically associated with a legal entity, as outlined in the European research project ALIVE (advanced legal issues in virtual enterprise) [15.138], where the contractual framework of joint ventures was found to be most appropriate for this kind of cooperation. The partnership composition of a virtual enterprise is essentially dynamic, to better fit evolving requirements and market contingencies; the greatest benefit of this feature is to ensure that the competitiveness conditions sought at the establishment of the enterprise are maintained throughout its life, but calls for specific formally agreed policies to ease the replacement of partners due to the democratic character of the enterprise. A virtual enterprise is not dominated by one partner, but is a cooperation among equals, with governance systems that must ensure equal participation in strategic decisions. The virtual enterprise organizational structure is orthogonal to the partners’ organization; by its very nature, the virtual enterprise’s organization and process can be ideally fitted to the product/service to be developed and/or provided to customers; nonetheless, due to the enterprise’s temporary nature, it is not possible to establish and empower hierarchical relationships, and personnel hierarchical dependencies and power at partner companies must be reflected in the roles and processes of the cooperative corporation in order to prevent conflicts due to the allocation of responsibility for tasks. The constitution of a virtual enterprise is usually associated with the identification of a business opportunity by a company which does not have the capability individually to pursue such an opportunity, the equivalent of the role of the architect for networks [15.139], i. e., the entrepreneur and possibly the provider of the inspirational vision. Based on the opportunity identified a new role has been introduced for virtual enterprises: the business integrator [15.140], i. e., the role devoted to:

• •

Selection of partners Setup of governance structure, methods, and tools

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Part B 15.8

From the point of view of performance and cost, extended enterprises tend to leverage digital procurement systems not only for the exchange of administrative information during operations, but also for bidding and auction phases, even though such practice is applied with particular care for supplies that cannot be classified as commodities, due to the relevance of co-design contributions. Thanks to the degree of digitalization and to the increased information flows, the extended enterprise is expected to perform substantially as an optimized single integrated vertical enterprise, with significant improvements in the capability of:

15.8 Interorganizational Structures

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Part B

Applications in Mechanical Engineering

Table 15.12 Comparison of integrated and virtual corporations [15.133]

Organizational dimensions

Integrated corporation

Virtual enterprise

Organization structure Decisions Culture

Formal and flexible Ultimately by fiat Recognizable, encouraging employees to identify Clear us and them High overheads From the board, ex officio

Flexible network, flat By discussion and consensus Pluralist, linked by overlapping agendas Variable Minimal overheads Through possession of competences in demand; being the brand company

Boundaries Management Power

• •

Guidance to align internal partners’ processes to the operation of the virtual enterprise Management of operations for the enterprise

Part B 15.9

More than in other types of cooperative work, the virtual enterprise derives its effectiveness from the motivation of the partners, which is usually founded on a shared vision and complementary individual goals, and from a high level of trust and confidence among the partners. This is why networks are the natural breeding environment for virtual enterprises, which can work on existing relationships, whereas specific methods have been developed [15.137]

to assess objectively the readiness of potential partners to join specific common business opportunities. More so than for extended enterprises, in which (at least) the systemic knowhow for a product is held by the single leading organization, virtual enterprises show criticalities in the management of pre-existing and generated knowhow that must be mastered to allow for dynamic reconfiguration of the partnership as required for the best chance of success. To summarize, it is worth reporting the table proposed by Child [15.133] for comparison of integrated and virtual corporations (Table 15.12).

15.9 Organization and Communication Organizations constantly exchange information. By means of their manifold interactions, information and communication become determining factors in their competitive performance. Organizations that learn create more knowledgeable workforces for operations and process innovation, generating highly flexible organizations in which people will adapt to new ideas and changes through shared visions.

15.9.1 Terms, Definitions, and Models Every kind of successful development of a company is based on the intra-organizational acquisition of knowledge, the development of knowledge, and its economical realiation. Basically, knowledge can be characterized by two features. On the one hand, knowledge represents information provided directly by the brain, or that can be retrieved quickly from information memories available to human beings. On the other hand, knowledge is related to the context of the ac-

quirer. People must be able to display their information directly by means of a model-like illustration of realistic relations, conditions, and procedures – referring to means of intermediation (i. e., language) – in such a way that the information is purposeful and can be applied in a practice-oriented context. The obtainment of knowledge by means of purposerelated handling and application by employees occurs in two fundamental acquisition modes:

• •

Original acquisition through one’s own experience Derivative acquisition of knowledge through communication

In this respect, communication comprises all relations and tools of communication both within and outside a company, serving as the interaction with the system’s surrounding or further units within the enterprise. It is characterized by the influence that one organism exerts on another with the intention of purposeful and targeted

Enterprise Organization and Operation

• • • • • •

Derivation (internal or external information) Degree of formalization and structuring (formal and conditioned, or informal and unconditioned information) Condition (primary or secondary information) Area of embodiment and application (special or general information) Quantifiability (quantifiable or nonquantifiable information) Programmability (programmable or nonprogrammable information)

The degree of formalization of information is essential for the internal embodiment of the informa-

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tion process and, accordingly, for the reliability of information processes in the course of operations. Structured information and its formal, i. e., organizationally ruled, course of communication includes all communication procedures, which by means of structuring, purposefulness, and repetition are related to the entrepreneurial task. Informal communication describes those communication contacts which are not conditioned by organizational regulations. They influence the social relations between the interlocutors and the atmosphere of the communication. In the case of largely consistent circumstantial conditions this is characterized by a balance that is typical for enterprises, which in the case of changing conditions often drifts to the disadvantage of informal communication. Informal communication is frequently one of the first measures taken to respond to altered circumstances within the production process [15.142]. As a result, typical phenomena that appear include:

• • •

Increasing bustle and consultations within production and attached areas Accumulation and temporal extension of meetings (for example, production conferences) Increase of the error ratio due to an increasing proportion of informal communication

Being carried by the aforementioned established procedures for information processing, information can be subdivided into data, signs, and signals and thus transferred by coded means. The fundamental information process – as a preliminary stage of communication and knowledge development – is executed in three steps:

• • •

Information gathering Information processing Information transfer

Based on the information process and the information gathered through it, the communication process can be explained according to the model by Shannon and Weaver (Fig. 15.54) [15.143]. Production and the necessity to organize the corresponding information and communication processes lead to the need to establish appropriate information processes and communicative relations, which should contain as high a fraction of formal communication as possible.

Part B 15.9

exchange of information through a common interaction space (operational task). The amount (and also the intensity) and quality (and also content) of possibilities for communication are mainly determined by the organization model in the enterprise. In addition to various structuring criteria resulting from different types of activities (depends on the production program) and its interrelations, this often depends on technical, technological, and economical necessities (utilization). Only in recent times have communication-oriented criteria for production gained significance, due to the increase of more-complex products and production programs in conjunction with the parallel extension and increased development of technology. The foundation of communication is information, which is defined as a purposeful extract of applicable issues, aiming for the achievement of a target or the solution of a problem. The amount of information – clustered and purposeful, specifically directed towards an issue, processed in such a way that it will be generally accepted, checked and transferable – becomes knowledge. Furthermore, nonpurposeful, latent issues are also labeled as information since this kind of information can at any time be combined or condensed into knowledge by means of purpose-related references. Information therefore constitutes an image of the environment surrounding us and the various components and procedures used by humans to orient themselves in the world and to recognize and influence it [15.141]. Information as the basis for communication and the development of knowledge linked with it can be standardized according to different features and consequently evaluated by form-oriented methods. Some of the most important features are:

15.9 Organization and Communication

Enterprise Organization and Operation

nication is not a successive process. An apparent sign of this is the neglect of the corporate identity (CI) concept during the internal communication, for instance. Moreover, further approaches for avoiding problems arise from the existing company structures and organizations described above, which are caused by:

• • •

The lack of institutional and formal rules for voting and decision (such as, tasks without continuance, definite rules as job instructions, obligatory nature) The lack of organizational fixation and improper handing over of responsibility when coordinating diverse communication tools (contact point) Problems in the case of prompt integration of subsidiary companies with increased independent status (content-related summary)

This is accompanied by obstructions in personnel and corporate culture such as:

• •

• •

15.9.3 Methods of Embodiment, Organization Models, and the Management of Communication The following elements of embodiment are regarded as the result of corporate development in the company and as general limitations to this embodiment:

• • • •

Using ambition for reward (striving for gratification, meaning not only money) Response to individualization and regional peculiarities (considering individual and regional–cultural behavior patterns) Participation and integration of all people concerned (integrating employees into the process of embodiment) Focusing on dialogue (mental stimulation, identification, and appreciation)

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Credibility, objectivity, and comprehensibility of both information and the communication process [15.145]

Furthermore, the following assumptions apply to its conception and realization:

• • • • • • • •

Feedback marks the core of communication. Information also means the obligation to acquire it. The information portfolio within the company has to be transparent. A communicative infrastructure forms the basis for systematic communication. The combined employment of media and tools is essential for successful communication. Transfer of information is related to the demand and target group. Information ought to be clear, intelligible, and restricted to the essential facts. Communication complies with an integrative appearance of the company.

Being a decisive factor, the mode of organization of operational procedures has a major impact on the design options for communicative processes within an enterprise. Basically it is the case that, the higher the degree of autonomy of an organizational unit, the higher the demands concerning the availability of information and, accordingly, concerning the required communication process (see also Sect. 15.1) [15.146]. Based on these preliminary remarks, the organization of the structure and procedure of corporate communication gains special importance in securing the realization of the company’s objectives on a long-term basis. The corporate vision of the company in conjunction with the strategic goals and the development of resulting essential achievements lead to significant input parameters for the purposeful embodiment of communication processes [15.147]. The need for steady improvement of corporate communication requires frequent changes of structural and procedural organization patterns, since these – as described above – significantly determine the embodiment options, efficiency factors, and effects of communicative media. Generally, the procedure in this respect occurs as presented in Fig. 15.55. Methods used for these analyses are:

• • •

Portfolio analyses Cross-impact-analyses Questionnaires, for instance, concerning employee satisfaction

Part B 15.9

• • •

Incomplete understanding of integrated communication in top and middle management Existence of subcultures with highly different ways of thinking and behavioral patterns Fear of loss of competence Lack of feeling for integration Lack of professionalism of the responsible personnel Lack of willingness to cooperate and coordinate, and to receive information Fear of supervision

•

15.9 Organization and Communication

Enterprise Organization and Operation

The cross-impact-analysis addressed that problem. By means of a formalized, qualitatively supported method, it enables the evaluation of different incidence rates of states by experts, making it tangible as the embodiment method at the same time. The observed incidents (measures) are evaluated depending on the direction and strength of the context and the diffusion period. Accordingly, the probability of an incident occurring and its impact on another incident can be related. A team assembled of mainly interdisciplinary experts evaluates:

• • • •

The incidents considered to be relevant The individual rates of each incident The moment of occurrence of each incident in the case of a given incidence rate of 0.5 The influence of an incident on another

active elements reactive elements critical elements inactive elements

AS > AIS , AS < AIS , AS > AIS , AS < AIS ,

PS < AIS , PS > AIS , PS > AIS , PS < AIS .

As a result of this analysis, a realization plan can be issued. For the realization of communication strategies, a multitude of options are currently available. Some example communication media are:

• •

Worker and information journals Postings, blackboard announcements, info systems, wall newspapers

• • • • • • • • •

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Internal information services, circulars, newsletters, infomails Specific as well as interdisciplinary information sessions Press reviews Company broadcasting Events such as open days and information sessions concerning the company Videos, pictorial documentation, compact discs (CDs) Annual reports Internet presentations, intranet platforms Introductory texts Trade-fair stands

15.9.4 Conclusions and Outlook Production systems constantly exchange relevant information with the external environment. As a result, the quality of internal and external communication is of inestimable value for companies. Following the current thrust towards innovation caused by the widespread usage of information technology, information processes as well as the availability of information as the basis for acquiring knowledge have been accelerated. As a consequence, conceptual and creative solutions are becoming increasingly important, purposefully integrating the new options for the embodiment of communication processes within organizational structures (Fig. 15.58). Much attention is being paid to interorganizational learning. Through learning alliances, firms can speed up capability development and minimize exposure to technological uncertainties by acquiring and exploiting knowledge developed by others. However, learning introduces self-organization, which makes it difficult to guide. Modeling agents [15.151] help discover such emergent behavior inherent to a multi-agent situation consisting of large groups of loosely coupled agents that work together on tasks. Interoperability of agents is required, and their negotiation strategy will depend on their organizational role (motivational quantity) [15.152]. Collaboration may be expanded beyond the current concepts into complex organizations spontaneously emerging from dynamic versatile environments [15.153,154]. Self-organization and self-similarity help to reduce organizational and process complexity by fractalization. By using topological and systemic methods, supported by the theory of complexity, power-

Part B 15.9

Based on this evaluation, an influence matrix can be constructed, thereby recording the intensities of the incidents with respect to each other (Fig. 15.57). For the evaluation of the influence intensities, a closed discrete rating scale is used. From the summation of the line or column sums – respectively labeled as active and passive sums – and their relation to the average influence sum (that is AS or PS/number of elements), conclusions can be drawn about the influence probabilities of certain measures. Based on the relation between these figures, the elements can be subdivided into active elements, reactive elements, critical elements, and inactive elements, thereby providing clues for the utilization of the measures. Thus, the term of active elements (AS < AIS, PS < AIS) for instance means that the measures have to be changed deliberately, since these determine the entire system in question [15.150]. The elements are characterized by cross-impact-analysis as follows

•

15.9 Organization and Communication

Enterprise Organization and Operation

Supply Chain Type of Collaboration. A supply chain is

a set of activities by which several enterprises (termed nodes) agree to contribute their expertise towards the completion and supply of a common end-product. A simplified model of a supply chain is depicted in Fig. 15.74. Each node in the supply chain acts as a customer as well as a supplier. In the customer mode, it receives (buys) unfinished goods from upstream suppli-

ers, uses its core competence to add value to the product, and passes (sells) them onto the next node downstream in the chain. In traditional manufacturing, the supply chain could span raw-materials suppliers right through to the consumer of the end-product, thus encompassing all the intermediate activities of manufacturing, storage, distribution, and delivery. The supply-side limit of the supply chain is dictated by the criticality of the raw materials. The term raw materials is relative and highly dependent on the market and product sector. It also includes the issues of how readily the raw materials are available in the marketplace in which the supply chain is operating. The distribution side of the supply chain need not be restricted to the final consumer. Indeed, with the emerging environmental and associated recycling issues, enterprises involved in the disposal of the product at the end of its useful life may well form part of this supply chain. A supply chain need not be a sequential set of nodes. In fact, in real life it will often take the form of an enterprise network. The concept of supply chains evolved long before the advent of ICT. Basic research related to supplychain management (SCM) has been carried out since the 1960s. However, it was in the 1980s that market pressures on producers and suppliers, and the emerging ideas of just-in-time (JIT) manufacturing, gave impetus to the study of SCM and its wider acceptance; thus it formally became an integral part of manufacturing and operations research jargon. SCM entails coordination with customers and suppliers. In order to operate efficiently all nodes across the supply chain must operate in a synchronous mode, providing a rapid and high-quality response to the events. In the dynamics of real life, perturbations to planned events will always occur. Unplanned events (changes in the customer order, delayed delivery of materials, machine breakdown, etc.) will cause deviations from scheduled activities. Furthermore, it is the accumulation of perturbations across the supply chain that can make the whole venture very inefficient. As an example, consider two cases: 1. The customer changes the order composition: this effect will ripple and amplify upstream in the supply chain as other nodes sequentially readjust their operations to incorporate this change. 2. Materials are not delivered according to agreed schedules: this effect will ripple and amplify downstream in the supply chain as other nodes sequentially readjust their operations to incorporate this change. Like the market, the production floor is

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Part B 15.10

cooperative relationships between enterprises, as dictated by modern-day market conditions, would not be possible. By improving the transparency of interorganizational infrastructures and implementing the advanced organizational approaches, cooperative and flexible solutions can become feasible. These technologies have now become a prerequisite for highly economic enterprise cooperations. Whereas classical IT solutions supported mainly the rationalization of the production process, ICT solutions of the 1990s tried to reduce the transaction costs as well, thus forming an integral part of the collaboration. Without appropriate ICT-based approaches and infrastructures, effective cooperative relationships between enterprises would not be possible. This has given the manufacturers more choices in terms of in-house product development and outsourcing. By improving the transparency of interorganizational product development as well as order processing ICT enables cooperative and flexible solutions. Various studies have shown that ICT could reduce the coordination costs that result from outsourcing activities and therefore stimulate cooperation between firms [15.177]. Important IT developments that enable interorganizational cooperation also include the development of standards for exchanging information, e.g., EDIFACT (electronic data interchange for administration, commerce and transport) and STEP (standard for the exchange of product data) [15.178], the reduction of prices for computational power of processors, and the interconnectivity of communication networks, resulting in the Internet and the like. Williamson’s transaction cost theory also predicts that weighing economies of scale against transaction costs leads to the outsourcing of activities that have been carried out so far inside the organization [15.175]. Enterprise collaborations have also driven the requirements and developments in the information and telecommunication technologies; for example, developments in EDI (electronic data interchange) technology and STEP protocols to facilitate the transfer of design data and indeed product models between partners has redefined the concept of collaboration to new levels.

15.10 Enterprise Collaboration and Logistics

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Part B

Applications in Mechanical Engineering

also dynamic. Therefore, the same effect will be observed if there was production perturbation, say due to a machine breakdown at one of the nodes. In either case, the only way to counteract either of these effects is to have larger inventories. Perturbations occurring at two different nodes (due to different reasons) will further amplify the noise in the system. Hence, information lags, delivery lags, demand volatility, unsynchronized ordering, over- and underordering, lumpy ordering, and chain accumulations will all contrive to make demand become more volatile further along the supply chain. The primary requirements of the operational phase of any supply chain are the minimization of inventory and lead times across the whole chain. To achieve this:

• • • Part B 15.10

• • • •

Partners in the supply chain need to have a clear understanding (contractual or otherwise) as to what is expected from each partner. This is also true for the respective expectations. Both material and information flow systems need to be streamlined. Various functions within a node, such as marketing, sales, purchasing, production planning, and production control, must communicate effectively with one another. Information exchange among the nodes must occur efficiently for a supply chain to operate effectively. Information and decision support systems at nodes must be able to respond dynamically to meet the ever-changing needs and communicate accordingly to the affected nodes of the supply chain. The industry is moving from being product led to being customer led, and those in the supply chain will need to change their ways of operating to respond to this change. Issues such as quality management and continuous improvement are often part of the contractual agreement when the supply chain is set up.

This can only be achieved through excellence in communications among the supply-chain partners. This requires an open, scalable, flexible communications solution that provides both seamless communications and the ability to adapt rapidly to changes in supply-chain structure. The Internet is one possible solution because it has the distinct advantage of being a completely open, global communications system, with deep market penetration.

As we will see in the following sections, the emergence of affordable Internet-based ICT technologies is pushing the frontiers of enterprise collaboration to new levels and, as a result, the emergence of new paradigms from the supply chain type of collaboration: extended and virtual enterprises. Extended Enterprise Type of Collaboration. The tra-

ditional view of business organizations is no longer valid [15.179–181]. Instead of speaking of industrial collaboration, however, one uses the term extended enterprise when referring to a new paradigm for manufacturing. The extended enterprise is a term frequently used in today’s business literature to reflect the high level of cooperation between organizations. Browne et al. [15.179] argue that computer-integrated manufacturing (CIM) will enable interenterprise networking across the value chain. Manufacturing systems are no longer confined to a single factory, but cross enterprise boundaries. Integration of operations of independent organizations with the operations of suppliers and customer can result in extended enterprises. Furthermore, the market sector is not restricted to manufacturing but many other business areas such as financial services, distribution, and information services have formed closer relationships that can be termed as extended enterprises. Extended enterprises are evolutionary in nature. Let us take an example. Two organizations have known each other and conducted business in a supply chain for some time. During this period of collaboration a sufficient level of trust has developed to automate the sharing of day-to-day operational data. This integration will be preceded by the realization of the importance of each organization of the other in its business plans. Therefore, each of the organizations will be prepared, if necessary, to invest in modern ICT tools for the effortless sharing of information. The fact that they are willing to invest in their collaboration will imply that they are committed to a long-term relationship. It is this seamless exchange of relevant operational information on top of an existing longterm (and successful) relationship that distinguishes the extended enterprise form other forms of long-term collaboration such as a supply chain. It should also be noted that ICT are enabler technologies and a necessary (though not sufficient) condition for an extended enterprise to exist. It is the integration of the respective information and decision systems and the respective production processes that link them closely enough (within the agreed bounds) to be analogous to the be-

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Part B

Applications in Mechanical Engineering

• •

boundaries of the value chain; for example, why restrict the starting point of the value chain to raw materials; why not extend it to their mining? Furthermore, raw materials for one value chain could very well be a finished product for another value chain, e.g., ball bearings, electric motors, transformers/power supply units, etc. Technology permitting, an extended enterprise can take the form of a complex enterprise network in which each enterprise can be seen as a node. The relationship between a set of nodes in an extended enterprise can be hierarchical or nonhierarchical.

Part B 15.10

Virtual Enterprise Type of Collaboration. Unlike the extended enterprise formation in which, more often than not, existing supplier/buyer (or supply chain) relationships are strengthened through the usage of ICT technologies, the availability of ICT technologies can initiate the formation of entirely new enterprise networks. A virtual enterprise is one manifestation of organizational response to the dynamism and globalization of today’s markets. The baseline for a virtual enterprise is the customer needs. These needs can be extensive and unique (e.g., a large project-based contract) or small but with numerous variations; for example a number of complementary companies specializing in the repair and maintenance of household items may form a virtual enterprise to provide a comprehensive service to their potential customers. These services might include the maintenance of house structure, all forms of energy supplies, telecommunication and entertainment links, repair/maintenance of household durables such as cookers, washing machines, refrigeration equipment, and the recycling and waste disposal. Each of these services will require unique core competencies. Thus, several small specialist companies can increase their potential customer base by pooling their competencies. The attractiveness for the customer of such an enterprise will be that there will be only a single contact point for most of their household-related problems. From the above argument we can note that there needs to be pooling of more than one core competence for the formation of virtual enterprise. Taken literally, there is nothing new in small companies joining forces to strengthen their marketability. However, it is the availability of ICT technologies that has given small enterprises entirely new platforms to collaborate efficiently to supply effective product/service. Thus, it should be noted that ICT are enabling technologies and

a necessary (though not sufficient) condition for a virtual enterprise to exist. Business partners in virtual enterprises can retain the individual agility of the consortium members to undertake their own business operations and quiet possibly participate in other EE or VE type of projects simultaneously [15.184, 186]. As information and communications technologies overcome the constraints of time and distance, it has become possible to create virtual organizations. Those independent companies, temporarily linked by ICT networks, share skills and costs, and can access each other’s markets. Some authors define virtual enterprises as temporary networks of independent companies engaged in providing a product or service. Childe [15.160] defined the evolution of virtual enterprise as: and “. . . in the extreme, the principal company may have no premises and may not perform what is generally seen as manufacturing work – it may only consist of functions such as design and production management, acting as the co-ordinator of activities in the cooperating companies. In this case, the company becomes a virtual enterprise, appearing to its customers as a supplier of goods and services, but with no internal production activities.” In such a scenario, virtual enterprises are often project based and usually operate in niche markets. Thus they form, reform, and dissolve based on the market dynamics and the opportunities it provides. Forbairt [15.187] depicts the virtual enterprise as a response to the speed and globalization of the digital age. It is an enterprise that may have no physical head office or center and very few full time workers, and that exists as a combination of specific skills and competencies of individuals or enterprises. A virtual enterprise may be set up with the objective of providing one particular type of product or service. When the market for that product or service declines, the virtual enterprise dissolves, its members finding new partners to pursue new opportunities. In the global village, companies who survive and prosper are agile, flexible, and adaptable and constantly seek to maximize their unique advantages. Compared to an original enterprise, according to Scholz [15.188], a virtual enterprise is always characterized by the absence of specific physical attributes/features such as a common administration or a common legal status. These features are replaced by the application of sophisticated information and communication infrastructures and mutual confidence (common understanding). Skyrme [15.189] emphasizes the growth of networking, both human and technological, and argues that this

Enterprise Organization and Operation

ration to maintain integrated and ever-changing data files on customers, products, and production and design methodologies. They therefore speak of it in terms of patterns of information and relationships that will appear less as a discrete enterprise and more as an evervarying cluster of common activities of suppliers and their downstream customers in the midst of a vast fabric of relationships. These relationships will be built on principles such as joint destiny, trust, and sharing information. The virtual corporation of Davidow and Malone is described as almost edgeless, with permeable and continuously changing interfaces between company, supplier, and customers. Nevertheless, Davidow and Malone stress the importance of brand names and product identity. A virtual corporation is identified by the activities carried out and the products delivered. In fact, a virtual corporation is defined through the product or product line it produces. Møller [15.191] defines the virtual enterprise from the supply-chain point view. This concept is used to characterize the global supply chain of a single product in an environment of dynamic networks of companies engaged in many different relationships. The companies in a virtual enterprise coordinate their internal systems with other systems in the supply chain, and simultaneously participate in other virtual enterprises and adapt to changes. In principle, small and medium-sized companies participating in a virtual enterprise gain access to the resources of a large organization while retaining the agility and independence of a small one. Skyrme [15.189] suggests that the following benefits may be obtained through the construction of a virtual enterprise:

• • • • •

Access to a wide range of specialized resources Presentation a unified face to large corporate buyers That individual members retain their independence and continue to develop their core competencies Reshaping of the enterprise and changing of members according to the project or task in hand That there is no need to worry about divorce settlements as in formal joint ventures

Therefore, a virtual enterprise can be defined as a network of independent organizations that jointly form an entity committed to provide a product or service, because from the customer’s perspective as far as that product/service is concerned, these independent organizations, for all practical and operational purposes, are virtually acting as a single entity/enterprise. Taken

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is creating a virtual world with virtual products and services, virtual workplaces, and virtual organizations. The virtual products and services are produced, delivered and sold through electronic networks, e.g., telebanking and telemarketing, significantly reducing the costs of many activities and creating opportunities to reach distant markets easily. The virtual workplaces include teleworkers, who work in a location-independent manner (sometimes at home), and flexible offices. Virtual organizations work in teams and cooperate across company boundaries to create the organization necessary for and appropriate to specific projects, thereby gaining significant flexibility in the use of people. This virtual world is the broad social environment for the establishment of the virtual enterprise in manufacturing. The intelligent manufacturing systems (IMS) project [15.190] defines the virtual enterprise as the next generation of manufacturing enterprise, which consists of a globally distributed assembly of autonomous work units linked primarily by the goal of profitably serving specific customers and operating in an environment of abrupt and often unanticipated change. Davidow and Malone [15.180] echo a similar sentiment when they suggest that networks of cooperating manufacturers are the industrial strategy for structuring and revitalizing corporation for the 21st century. They term these networks virtual corporations. We believe that this definition of virtual corporation is rather generic, as it also encompasses many of the principles of electronic commerce. The virtual enterprise described in this section is a more formal definition depicting the nature of relationship between two (or more) organizations engaged in providing a real product or service, as opposed to some virtual product. Our interpretation of virtual enterprise can be considered as a subset of virtual corporation as defined by Davidow et al. In their book Virtual Corporation [15.180] they present their vision of 21st century industries, which will be built around “a new kind of product, delivering instant customer gratification in a cost-effective way.” These products have a very rich service component that is often more important than the tangible characteristics of the product. They can be produced in several locations and offered in a great number of models and formats. Davidow et al. call these products virtual products. They believe that a manufacturing company will not be an isolated facility of production, but rather a node in the complex network of suppliers, customers, engineering, and other service functions. The real-time adaptation of the virtual product to customer needs requires the virtual corpo-

15.10 Enterprise Collaboration and Logistics

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from this perspective, we can identify the following as major characteristics of the virtual enterprise:

• • •

• • •

The (two or more) partners in the virtual enterprises are individuals and independent companies who come together and form a temporary consortium to exploit a particular market opportunity. Within the scope of collaboration, partners share vision and work towards shared goal. Partners in virtual enterprises make extensive use of ICT technologies for communication and sharing information. Most of the day-to-day information exchange among the partners will almost always be automatic and without human interference. Virtual enterprises assemble themselves based on cost effectiveness and product uniqueness without regard to organization size or geographic location. Unlike SCs or EEs, virtual enterprises, once formed, will have a unique dynamics, new identity, and quiet possibly a new name. The efficiency of the virtual enterprise is greatly determined by the speed and efficiency with

•

• • •

which information can be exchanged and managed among business partners. Efficient collaborative engineering, production, and logistics require effective electronic management of engineering and production information. Thus it is a prerequisite that participating enterprises have sufficiently sophisticated IT and decision support tools and mechanisms to make this integration possible. Virtual enterprises pool costs, skills, and core competencies to provide world-class solutions that could not be provided by any one of them individually. Therefore, virtual enterprises often focus on complete products or solutions as opposed to providing partial solutions in a value chain. Decisions are jointly arrived at by making best use of the competencies among the partners. Virtual enterprises will often be complex networks in which each enterprise can be seen as a node. The relationship between a set of nodes in a virtual enterprise will mostly be nonhierarchical in nature.

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15.154 A.-L. Barabasi: Network theory – the emergence of the creative enterprise, Science 308(5722), 639–641 (2005) 15.155 H. Kühnle: Fractal extended enterprise: Framework and examples for multi-party supply chains. In: Modern Industrial Engineering and Innovation in Enterprise Management, IEEM 2005, Vol. 1, ed. by Y. Shuping, C. Xiaohui, Y. Yu (2005) pp. 211–217 15.156 A. Lomi, E.R. Larsen: Dynamics of OrganizationsComputational Modeling and Organization Theories (The MIT Press, Cambridge 2001) 15.157 R. Dekkers: (R)Evolution, Organizations and the Dynamics of the Environment (Springer, New York 2005) 15.158 K. Miller: Communication Theories: Perspectives, Processes, and Contexts, 2nd edn. (McGraw-Hill, New York 2004) 15.159 K.-D. Thoben: Kundenspezifische Produktion –y Prinzipien, Methoden und Werkzeuge, Habilitation Thesis (Universitaet Bremen, Bremen 2000) 15.160 S.J. Childe: The extended enterprise – a concept of co-operation, Prod. Planning Control 9(4), 320–327 (1998) 15.161 B. Kiesel, J. Klink: Die Renaissance der Kooperation, ZWF 93 1-2, 18–21 (1998), (in German) 15.162 G. Reinhart, S. Brandner: Produktdaten- und Prozeßmanagement in virtuellen Fabriken, Produktdatenmanagement 1, 4–8 (2000), (in German) 15.163 S.L. Goldman, R.N. Nagel, K. Preiss: Agile Competitors and Virtual Organizations: Strategies for Enriching the Customer (Van Nostrand Reinhold, New York 1994) 15.164 S. Wurche: Strategische Kooperationen – Theoretische Grundlagen und praktische Erfahrungen am Beispiel mittelständischer Pharmaunternehmen (Dt. Univ.-Verl., Wiesbaden 1994), in German 15.165 P.B. Evans, T.S. Wurster: Strategy and the new economics of information, Harvard Bus. Rev. 75(5), 70–93 (1997) 15.166 H. Håkansson, I. Snehotna: No business is an island: The network concept of business strategy, Scand. J. Manage. 4(3), 256–270 (1989) 15.167 H. Håkansson, I. Snehotna (Eds.): Developing Relationships in Business Networks (Routledge, London 1995) 15.168 J.C. Anderson, H. Håkansson, J. Johanson: Dyadic relationships within a business network approach, J. Market. 58, 0 (1994) 15.169 B. Axelsson: The development of network research – a question of mobilization and perseverance. In: Industrial Networks. A New View on Reality, ed. by B. Axelsson (Routledge, London 1992) 15.170 J.A. Carlisle, R.C. Parker: Beyond Negotiation (Wiley, Chichester 1989) 15.171 P. Smith Ring, A.H. van de Ven: Structuring cooperative relationships between organizations, Strategic Manage. J. 13(7), 483–498 (1992)

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References

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Part C

Complem Part C Complementary Material for Mechanical Engineers

16 Power Generation Dwarkadas Kothari, Vellore, India P.M.V. Subbarao, New Delhi, India 17 Electrical Engineering Seddik Bacha, Grenoble, France Jaime De La Ree, Blacksburg, USA Chris Oliver Heyde, Magdeburg, Germany Andreas Lindemann, Magdeburg, Germany Antje G. Orths, Fredericia, Denmark Zbigniew A. Styczynski, Magdeburg, Germany Jacek G. Wankowicz, Warsaw, Poland 18 General Tables Stanley Baksi, Koblenz, Germany

1521

B.6

Design of Machine Elements by Oleg P. Lelikov

The author would like to thank Dr. Juri Postnikov for his great collaboration and efforts in the preparation of this chapter. B.7

Manufacturing Engineering by Thomas Böllinghaus, Gerry Byrne, Boris Ilich Cherpakov (deceased), Edward Chlebus, Carl E. Cross, Berend Denkena, Ulrich Dilthey, Takeshi Hatsuzawa, Klaus Herfurth, Horst Herold (deceased), Andrew Kaldos, Thomas Kannengiesser, Michail Karpenko, Bernhard Karpuschewski, Manuel Marya, Surendar K. Marya, Klaus-Jürgen Matthes, Klaus Middeldorf, Joao Fernando G. Oliveira, Jörg Pieschel, Didier M. Priem, Frank Riedel, Markus Schleser, A. Erman Tekkaya, Marcel Todtermuschke, Anatole Vereschaka, Detlef von Hofe, Nikolaus Wagner, Johannes Wodara, Klaus Woeste

The author would like to express his thanks to all his colleagues from leading welding institutions and departments for their deep interest and active cooperation in revising the section “Joining Technology”, and to representatives of the Deutscher Verband für Schweißen und verwandte Verfahren e.V. (German Association for Welding and Related Processes) in Düsseldorf for writing the essential analytical introduction. In particular, I owe thanks to my colleague Dr.Ing. J. Pieschel from the Institute of Joining and Beam Technology at the Otto von Guericke University in Magdeburg for his careful editorial preparation of the manuscript.

Acknowl.

Acknowledgements

1523

About the Authors

Chapter B.13, Sect. 13.2

Daimler AG X944 Systems Integration and Comfort Electric Sindelfingen, Germany [email protected]

Gritt Ahrens received the PhD degree from the Department of Engineering Design and Methodology at the Technical University of Berlin. She developed a method for capture and management of product requirements and substantiated its practical applicability. Since 2001 she has been developing and optimizing various processes in the context of car development at Mercedes-Benz Cars Development (Daimler AG).

Seddik Bacha

Chapter C.17, Sect. 17.4

Université Joseph Fourier Grénoble Electrical Engineering Laboratory Grenoble, France [email protected]

Professor Seddik Bacha received the Engineering and Magister degree from École Nationale Polytechnique of Algiers in 1982 and 1990, and the PhD and HDR degrees in 1993 and 1998 from Polytechnic Institute of Grenoble, France, respectively. He is presently the manager of the Power System Group in the Grénoble Electrical Engineering Laboratory and Professor at the Université Joseph Fourier, Grenoble. His interests are power electronics systems, power quality, and renewable energy.

Stanley Baksi

Chapter C.18

TRW Automotive, Lucas Varity GmbH Koblenz, Germany [email protected]

Stanley Baksi received the BA degree in Engineering in 2000 from Visvesvaraya National Institute of Technology and the MSc in Mechanical Engineering from California State University, Long Beach. He completed his doctoral research on rapid bone reconstruction using reverse engineering at Otto-von-Guericke University, Magdeburg, in 2007. Since January 2008 he has been a Project Engineer with TRW Automotive providing computer-aided engineering support for the development of automotive brakes.

Thomas Böllinghaus

Chapter B.7, Sect. 7.4.8

Federal Institute for Materials Research and Testing (BAM) Berlin, Germany [email protected]

Professor Thomas Böllinghaus received the Dr.-Ing. degree in 1995 from the Helmut-Schmidt-University, Hamburg, and qualified there as a Professor for Materials Science and Welding Technology in 1999. He then became head of Division V.5 Safety of Joined Components at the Federal Institute for Materials Research and Testing (BAM), Berlin. Since 2003 he has been Vice President of BAM and became Honorary Professor for Failure Analysis and Failure Prevention in the Faculty for Mechanical Engineering at the Otto-von-Guericke University, Magdeburg in 2008. His research interests focus on hydrogen-assisted cracking of structural metallic materials, numerical simulation of hydrogen transport and cracking, hot cracking phenomena in welds, and failure analysis and lifecycle evaluations of joined components.

Alois Breiing

Chapter B.9, Sect. 9.6

Eidgenössische Technische Hochschule Zürich (ETH) Institut für mechanische Systeme (IMES) Zentrum für Produkt-Entwicklung (ZPE) Zurich, Switzerland [email protected]

Alois Breiing is a retired Professor (Titularprofessor) at ETH Zürich. He was a Lecturer (Privatdozent) at the Institute of Mechanical Systems. He has 23 years of experience as an aerospace engineer in the Development and Design Department of the aerospace company Dornier. Beginning in 1985 he worked at the Institute of Design and Construction Methods of ETH Zurich (now the Institute of Mechanical Systems), starting as a Senior Researcher and Section Leader. He received a doctor’s degree in 1991. He gave lectures in machine design. The main topics of his research work were evaluation and decision processes.

Authors

Gritt Ahrens

1524

About the Authors

Chapter B.14, Sect. 14.1

Institute of Mechanized Construction and Rock Mining Warsaw, Poland [email protected]

Dr. Eugeniusz Budny is a Professor of Mechanical Engineering and Emeritus Director of the Institute of Mechanized Construction and Rock Mining (IMBiGS) in Warsaw, Poland. He began his career as an automotive industry product designer and then moved to the construction equipment manufacturing industry, specializing in the design of single-bucket excavators, hydraulic drives, and hydraulic engineering machine controls. Since 1977 he has been engaged in the mechanization of construction work. Professor Budny served as President of the International Association for Automation and Robotics in Construction (IAARC) and has been Chair of ISO/TC 195 and the Polish Committee for Standardization in the field of building construction machinery since 2005.

Authors

Eugeniusz Budny

Gerry Byrne

Chapter B.7, Sects. 7.3.1, 7.3.2

University College Dublin School of Electrical, Electronic and Mechanical Engineering Belfield, Dublin 4, Ireland [email protected]

Gerry Byrne F.R.Eng. is the Professor of Mechanical Engineering and Director of the Advanced Manufacturing Science Research Centre at University College Dublin (UCD), Ireland. He has over 30 years of experience with high-precision manufacturing processes, surface engineering, and aspects of surface microstructuring. He is an expert in the field of cutting processes and has published extensively. He is a Fellow of the International Academy for Production Engineering (CIRP) and a Member of the Council of that Academy. He is an International Fellow of the Royal Academy of Engineering, UK, and of the Society of Manufacturing Engineers, USA.

Edward Chlebus

Chapter B.7, Sect. 7.5

Wrocław University of Technology Centre for Advanced Manufacturing Technologies Wrocław, Poland [email protected]

Professor Edward Chlebus is Director of the Institute of Production Engineering and Automation at Wrocław University of Technology, Poland, and the Head of the Centre for Advanced Manufacturing Technologies (CAMT). His main research areas are design methodology and CAx and PDM/PLM systems, rapid prototyping, reverse engineering, modeling, optimization, and simulation of production processes. He is a Contractor for six International Projects in FP6, Leonardo da Vinci, and ERA Net. He is also a Graduate of the University of Connecticut Business School.

Mirosław Chłosta

Chapter B.14, Sect. 14.1

IMBiGS – Institute for Mechanized Construction and Rock Mining (IMBiGS) Warsaw, Poland [email protected]

Miroslaw Chlosta received the M.S. degree from Warsaw Technical University in 1980. In that year he began work at IMBiGS as a Research Associate. He received the PhD degree from IMBiGS in 2003 and was an Assistant there from 2003 onwards. His research interests are mainly in CAD and robotics in the building industry.

Norge I. Coello Machado

Chapter B.8, Sect. 8.1

Universidad Central “Marta Abreu” de Las Villas Faculty of Mechanical Engineering Santa Clara, Cuba [email protected]

Norge Coello Machado received the Dipl.-Ing. degree from the Universidad of Santa Clara in 1982 and the Dr.-Ing. degree from the University of Magdeburg, Germany, in 1989. From 2003 he was Temporary Professor at the University of Magdeburg, Germany. His research interests are mainly in the use of statistical methods in quality management, quality engineering, and measurement technology.

About the Authors

Chapter B.15, Sect. 15.8

Alenia Aeronautica Procurement/Sourcing Management Department Pomigliano (NA), Italy [email protected]

Graduated in Aeronautical Engineering in 1977 in Naples, Italy, Francesco Costanzo has a long experience in design and industrialization processes at Alenia Aeronautica (formerly Aeritalia) until 1983. He was then in charge of process and information management with responsibility for CAE/CAD/CAM until 2000. Later he was responsible for the information systems of the A380 program in Alenia and has been head of Procurement Direction/Sourcing Management as Supplier Value Creation Manager, with focus on processes and information for Alenia’s supply chain. Currently Costanzo is a Senior Consultant in processes for procurement and the digitization of supply chains.

Carl E. Cross

Chapter B.7, Sect. 7.4.8

Federal Institute for Materials Research and Testing (BAM) Joining Technology Berlin, Germany [email protected]

Carl Cross received the B.Sc., MSc, and PhD degrees in Metallurgical Engineering from the Colorado School of Mines. He has worked in welding research for over 30 years in both industry and academia, specializing in solidification defects and weldability testing of nonferrous alloys. Currently he is a Senior Scientist at BAM (the German Federal Institute for Materials Research and Testing), investigating the critical conditions needed to initiate and grow hot cracks.

Frank Dammel

Chapter B.4, Sect. 4.3

Technical University Department of Mechanical Engineering/ Institute of Technical Thermodynamics Darmstadt, Germany [email protected]

Frank Dammel is a postdoctoral scientific assistant (Akad. Oberrat) at the Institute of Technical Thermodynamics at the Technische Universitaet Darmstadt. His main field of research is phase-change phenomena with an emphasis on numerical simulations.

Jaime De La Ree

Chapter C.17, Sect. 17.3

Virginia Tech Electrical and Computer Engineering Department Blacksburg, VA, USA [email protected]

Jaime De La Ree received the PhD degree from the University of Pittsburgh, Pittsburgh, PA, USA in 1984. He worked at the ECE Department at Virginia Tech and became Assistant Department Head in 2004. His teaching and research interest is in the areas of electric machinery and power systems protection. He is the recipient of several Outstanding Teaching Awards from both the University of Pittsburgh and Virginia Tech.

Torsten Dellmann

Chapter B.13, Sect. 13.1

RWTH Aachen University Department of Rail Vehicles and Materials-Handling Technology Aachen, Germany [email protected]

Dr. Torsten Dellmann is a Professor of Rail Vehicles and MaterialsHandling Technology at RWTH Aachen University, Germany. He obtained the Dr. degree in materials-handling technology from RWTH Aachen in 1986. Prior to joining the RWTH Aachen University as a professor he worked as Managing Director for Knorr-Bremse MRP Systems for Rail Vehicles. His current research is focused on innovative braking systems as well as innovative undercarriages and guiding technology for rail vehicles.

Authors

Francesco Costanzo

1525

1526

About the Authors

Chapter B.7, Sects. 7.3.1, 7.3.2, 7.3.3

Leibniz University Hannover IFW – Institute of Production Engineering and Machine Tools Garbsen, Germany [email protected]

Professor Denkena earned the PhD degree at Leibniz University Hanover, Germany, in 1992. He then became Manager Standards Engineering at Thyssen Production Systems in Auburn Hills, USA (1993–1995). Back in Germany he served as Manager Mechanical Development at Thyssen Hüller Hille in Ludwigsburg for 1 year before he went to Bielefeld as Manager Engineering and Development for Gildemeister Turning Machines. Since 2001 he has been a Professor at the Leibniz University Hannover and the Head of the Institute of Production Engineering and Machine Tools.

Authors

Berend Denkena

Ludger Deters

Chapter B.5

Otto-von-Guericke University Institute of Machine Design Magdeburg, Germany [email protected]

Ludger Deters is Professor of Machine Elements and Tribology at the Otto-vonGuericke University of Magdeburg. He received the PhD degree from the Mechanical Engineering Department of the University of Clausthal in 1983. From 1983 to 1994 he worked in executive positions in different development and design departments of the machine-building industry. His current main research activities include tribology, slider and rolling bearings, wheel/rail contacts, and friction and wear of combustion engine parts.

Ulrich Dilthey

Chapter B.7, Sects. 7.4.3, 7.4.4, 7.4.7

RWTH Aachen University ISF Welding and Joining Institute Aachen, Germany [email protected]

Professor Dr.-Ing. Ulrich Dilthey holds degrees in Mechanical Engineering/Production Engineering and a doctorate from RWTH Aachen University, where he was research assistant in the ISF, the Welding and Joining Institute of the RWTH Aachen. He has many years of working experience in leading positions of worldwide operating companies in the fields of mechanization, automation, and robotics. From 1989 to 2007 he was Professor of Welding Manufacturing Processes and Director of the ISF. In July 2008 he was elected the President of the International Institute of Welding (IIW).

Frank Engelmann

Chapter B.9, Sects. 9.1–9.4

University of Applied Sciences Jena Department of Industrial Engineering Jena, Germany [email protected]

Frank Engelmann studied mechanical engineering at the Engineering Department at the University of Magdeburg. After he finished his studies he worked as Managing Director for a production business while also working at the University of Magdeburg, where he received the PhD degree. His research activities focus on secondary explosion protection and on biomedical technology. In October 2007 Frank Engelmann joined the University of Applied Sciences in Jena, Germany, as a full professor.

Ramin S. Esfandiari

Chapter A.1

California State University Department of Mechanical & Aerospace Engineering Long Beach, CA, USA [email protected]

Dr. Esfandiari is Professor of Mechanical and Aerospace Engineering at the California State University, Long Beach. He received the PhD degree from the University of California at Santa Barbara in Applied Mathematics with emphasis on optimal control theory. He has published numerous research papers in refereed journals in the areas of distributed control and numerical methods. He is the author/coauthor of three textbooks and author of a MATLAB manual.

Jens Freudenberger

Chapter B.3, Sect. 3.1

Leibniz-Institute for Solid State and Materials Research Dresden Department for Metal Physics Dresden, Germany [email protected]

Dr. Jens Freudenberger is Head of the Department for Metal Physics and Supervisor of the Pulsed High-Magnetic-Field Laboratory at the IFW, Dresden. His current research is dedicated to plastic deformation and metal forming. He is an expert in materials science and solid-state physics with particular interest in materials such as superconductors, high-strength nanostructured conductors, and magnetic materials.

About the Authors

Chapter B.13, Sect. 13.1

RWTH Aachen University Institute for Automotive Engineering Aachen, Germany [email protected]

Professor Dr.-Ing. Stefan Gies received the doctor degree in 1993 from Aachen University at the Institute for Automotive Engineering (IKA), where he was employed as a Scientific Research Engineer between 1989 and 1993 and Chief Engineer from 1993 until 1994. From 1994 to 2000, he was with Ford AG and changed in 2000 to Audi AG, where he was Manager of vehicle dynamics and driving comfort with steering systems, suspension, wheels/tires, chassis controls. Since 2007, he has been a Professor at RWTH Aachen University and the head of IKA.

Joachim Göllner

Chapter B.3, Sect. 3.6

Otto-von-Guericke University Institute of Materials and Joining Technology Department of Mechanical Engineering Magdeburg, Germany joachim.goellner@mb. uni-magdeburg.de

Dr. Joachim Göllner is a Lecturer for materials and corrosion. He habilitated from Otto-von-Guericke University Magdeburg, Germany, and is the Head of a research group. His research interests are in electrochemical noise and the development of corrosion test methods. He has authored more than 150 publications and is a member of various professional societies.

Timothy Gutowski

Chapter B.9, Sect. 9.5

Massachusetts Institute of Technology Department of Mechanical Engineering Cambridge, MA, USA [email protected]

Timothy Gutowski is a Professor of Mechanical Engineering at the Massachusetts Institute of Technology. He received the PhD degree in Mechanical Engineering from MIT, the M.S. degree in Theoretical and Applied Mechanics from the University of Illinois, and the B.Sc. degree in Mathematics from the University of Wisconsin. His current research interests focus on the relationship between manufacturing and the environment. He was Director of MIT’s Laboratory for Manufacturing and Productivity for 10 years and Associate Department Head of Mechanical Engineering from 2001 to 2005.

Takeshi Hatsuzawa

Chapter B.7, Sect. 7.6

Tokyo Institute of Technology Precision and Intelligence Laboratory Yokohama, Japan [email protected]

Takeshi Hatsuzawa received the Dr. Eng. degree from Tokyo Institute of Technology in 1993. After 12 years at the National Research Laboratory of Metrology, he became Associate Professor in the Tokyo Institute of Technology in 1995, and full professor in 2002. His current research is focused on MEMS and NEMS applications in biochemistry using biotechnology.

Markus Hecht

Chapter B.13, Sect. 13.3

Berlin University of Technology Institute of Land and Sea Transport Systems Department of Rail Vehicles Berlin, Germany [email protected]

Marskus Hecht obtained his industrial experience at the Swiss Locomotive and Machine Works Winterthur, working on radially steered bogies and low-noise equipment. Since 1997 he has been Professor for Rail Vehicles at Berlin University of Technology (TU). His research fields are wheel–rail interaction, vehicle design, vehicle acoustics, and safety. He works in several EU projects and is a member of various advisory boards. Since 2005 he has been Director of the Institute of Land and Sea Transportation at TU Berlin. He is responsible for the vehicle-related part of the postgraduate master study on Public Transport Management at Ruhr Campus, Essen, and is Advisory Professor at Tongji University Shanghai.

Authors

Stefan Gies

1527

1528

About the Authors

Authors

Hamid Hefazi

Chapter B.13, Sect. 13.4

California State University Mechanical and Aerospace Engineering Department of Mechanical and Aerospace Engineering Long Beach, CA, USA [email protected]

Hamid Hefazi received the PhD degree in Aerospace Engineering from the University of Southern California in 1985. He is currently Professor and Chair of mechanical and aerospace engineering and Director of the Boeing Technology Center at California State University, Long Beach. His research activities include computational fluid dynamics (CFD), aerodynamic design optimization, aeroacoustics, hydrodynamics, neural networks, and advanced optimization methods.

Martin Heilmaier

Chapter B.3, Sects. 3.1, 3.4

Technical University Department of Physical Metallurgy Darmstadt, Germany [email protected]

Professor Martin Heilmaier graduated in Materials Science from the University of Erlangen-Nuremberg. From 2002 he was Professor for Materials Testing at the Otto-von-Guericke University, Magdeburg. Since October 2008 he holds the chair for Physical Metallurgy at the TU Darmstadt. His research is dedicated to the synthesis and properties of structural materials such as refractory metal silicide alloys and intermetallic alloys for high-temperature applications.

Rolf Henke

Chapter B.13, Sect. 13.1

RWTH Aachen University Institute of Aeronautics and Astronautics Aachen, Germany [email protected]

Since 2006, Professor Rolf Henke has been Head of the Institute of Aeronautics and Astronautics at RWTH Aachen University. He has 20 years of experience working for Airbus R&T, in charge of large technology projects at the aircraft level including flight testing. At Aachen University, his current research projects include seamless air transport, conceptual aircraft design, development of high-lift systems, investigation of wake vortices, and aircraft component and trajectory noise. He is a member of the executive board of the German aerospace society (DLR).

Klaus Herfurth

Chapter B.7, Sect. 7.1

Industrial Advisor Langenfeld, Germany [email protected]

Professor Dr.-Ing. habil. Klaus Herfurth is an expert from the foundry industry. He earned the Dr.-Ing. degree from Technische Universitat Bergakademie Freiberg, Germany in 1963, and his Habilitation in 1979. He is author of 132 technical papers and book and handbook chapters. He was a Teacher at Technische Universitat Chemnitz from 1968 to 2002 in foundry technology and materials science. From 1987 to 2001 he was Manager of the Iron and Steel Casting Technical Group and the Standardization Technical Group of the German Foundrymen’s Association in Düsseldorf. He also worked in R&D at this time in the field of analysis of energy demand in foundries and realization of material and energy savings through castings.

Chris Oliver Heyde

Chapter C.17, Sect. 17.2

Otto-von-Guericke University Electric Power Networks and Renewable Energy Sources Magdeburg, Germany [email protected]

Chris O. Heyde studied electrical engineering at the Otto-von-Guericke University Magdeburg, Germany. He graduated in 2005 with the Dipl. -Ing. degree. He then joined the Chair of Electric Power Networks and Renewable Energy Sources at the Otto-von-Guericke University Magdeburg, Germany as a Research Engineer in 2005. His primary field of interest is network stability.

About the Authors

Chapter B.7, Introduction

AKM Engineering Consultants Bebington, Wirral, UK [email protected]

Andrew Kaldos received the Dipl.-Ing. degree in Mechanical and Production Engineering and Electrical, Instrumentation, and Control Engineering (1966, 1971) and the Dr.- Ing. degree in 1974 from the Technical University of Budapest, Hungary. He then held various positions at the Technical University of Budapest, from 1986 to 1989 at Leeds Polytechnic, from 1989 to 2000 at John Moores University, Liverpool, and since 2007 he has been Managing Director of AKM Engineering Consultants. He is involved in industrial technology transfer in the area of manufacturing engineering by research cooperation with eight departments of six universities in Europe, and development of cooperation with industrial companies.

Yuichi Kanda

Chapter B.15, Sect. 15.6

Toyo University Department of Mechanical Engineering Advanced Manufacturing Engineering Laboratory Kawagoe-City, Japan [email protected]

Yuichi Kanda, is a Professor in the Faculty of Engineering at Toyo University, Japan where he received the M.S. and PhD degrees in Mechanical Engineering. His area of research is advanced manufacturing systems using networks and ultraprecision machining. He is a Fellow of the Japan Society of Mechanical Engineering and is the Chairperson of the FA Control Network committee of JEMA and the Society of Project Management.

Thomas Kannengiesser

Chapter B.7, Sect. 7.4.8

Federal Institute for Materials Research and Testing (BAM) Joining Technology Berlin, Germany [email protected]

Thomas Kannengiesser studied Materials Engineering at Magdeburg University, Faculty of Mechanical Engineering. He was a scientific employee within the scope of a doctoral candidate program of BAM Federal Institute for Materials Research and Testing, Berlin, Germany. Since 2005, he has been Head of the Working Group Testing of Welded Components. His main fields of activity are component weld tests and full-scale tests under defined restraint intensities, cold cracking investigations on small and large specimens, and mobile residual stress measurement on components.

Michail Karpenko

Chapter B.7, Sect. 7.4.2

New Zealand Welding Centre Heavy Engineering Research Association (HERA) Manukau City, New Zealand [email protected]

Dr. Karpenko obtained the Mechanical Engineer degree from the Kiev Polytechnic Institute in 1995. He extended this qualification with the Welding Engineer’s degree (IWE). He completed the PhD degree at the Otto-von-Guericke University, Magdeburg, Germany, in 2001. From 1996 to 2006 he was a Research Fellow at the University of Magdeburg involved in a number of research projects in laser welding, drilling, and hybrid and plasma welding. In 2006 Dr. Karpenko took over the position of the NZ Welding Centre Manager in Manukau, New Zealand.

Bernhard Karpuschewski

Chapter B.7, Sects. 7.3.1, 7.3.2, 7.3.3

Otto-von-Guericke University Department of Manufacturing Engineering Magdeburg, Germany [email protected]

After receiving the PhD degree and holding the Chief Engineer position at the University of Hannover, Germany, Bernhard Karpuschewski worked for 1.5 years as Associate Professor at Keio University, Japan, and then for 4.5 years as a Full Professor for Production Technology at TU Delft, The Netherlands. Since 2005 he has been Full Professor and Managing Director of IFQ in Magdeburg. He is a Fellow of the International Academy for Production Engineering (CIRP), and the current Chairman of Abrasive Processes.

Authors

Andrew Kaldos

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About the Authors

Toshiaki Kimura

Chapter B.15, Sect. 15.6

Japan Society for the Promotion of Machine Industry (JSPMI) Production Engineering Department Technical Research Institute Tokyo, Japan [email protected]

Toshiaki Kimura is an Engineering Leader of the Production Engineering Department at the Technical Institute of the Japan Society for the Promotion of Machine Industry (JSPMI). His interests and research areas are methodologies and application systems of manufacturing support systems using information technologies. He is a member of the JSME and the JSPE.

Authors Dwarkadas Kothari

Chapter C.16

VIT University School of Electrical Sciences Vellore, TN, India [email protected]

Prof. D.P. Kothari is Former Director (in charge) of IIT, Delhi. He is currently Vice Chancellor of VIT University, Vellore. He is FNAE, FNASc, SMIEEE, MIEE, FIE (India), National Khosla Award Winner for Life Time Achievements in engineering. He has co-authored 20 books and more than 540 research publications, and has guided 28 PhD and 59 masters theses. His area of research interest is power and energy system engineering, operation, control, reliability, and optimization.

Hermann Kühnle

Chapter B.15, Sects. 15.1, 15.2, 15.4, 15.5, 15.9

Otto-von-Guericke University Institute of Ergonomics Factory Operations and Automation Magdeburg, Germany [email protected]

Hermann Kühnle is Full Professor for Factory Operation and Manufacturing Systems and Executive Director at the Otto-von-Guericke University of Magdeburg. Hermann Kühnle has worked on approaches and concepts for high-performance organizations on the base of fractal geometry and complexity theory, and implemented these structures in many world market-leading companies. He has been involved in numerous research projects with international partners of global dimensions. Hermann Kühnle is a member of several international scientific committees.

Oleg P. Lelikov

Chapter B.6

Bauman Moscow State Technical University Moscow, Russia

Professor Lelikov received the degree as Mechanical Engineer from Bauman Moscow State Technical University (BMSTU) in 1965, and in 1969 the academic status of Candidate of Technical Sciences. Since 1971 he has been working in the Department of Design Principles of Machines. Since 1992 he has been Professor at BMSTU, carrying out research on power-train loading, roadholds of multiaxial and multi-drive cars, safety of the multiple-unit reducer mechanisms, efficiency of gearings, ballscrew assemblies, and computer-aided design of machine components. He is an editor of one of the volumes of the Russian mechanical engineering encyclopedia in 40 volumes.

Andreas Lindemann

Chapter C.17, Sect. 17.4

Otto-von-Guericke University Institute for Power Electronics Magdeburg, Germany [email protected]

Andreas Lindemann holds the Dr.-Ing. degree in Electrical Engineering. For 10 years he was responsible for the development of power semiconductor components in industry. Being appointed Professor of Power Electronics at Helmut-SchmidtUniversität, Hamburg, in 2004, he now holds the Chair for Power Electronics at Otto-von-Guericke University Magdeburg, Germany.

About the Authors

Chapter B.15, Sect. 15.8

AST Lonate Pozzolo (VA), Italy [email protected]

Partner and Principal Consultant at AST in Italy, Bruno Lisanti has more than 25 years of experience in technical and management consulting in a wide range of markets (aerospace and defense, energy, automotive, and engineering) and company sizes, including large, small, and medium-sized organizations. Graduating in Nuclear Engineering from the University of Pisa, he is directly involved in consulting services, and in the last 10 years has participated in and coordinated several European research projects on concurrent engineering, virtual organizations, and advanced collaborative approaches, methods, and tools.

Manuel Marya

Chapter B.7, Sect. 7.4.9

Schlumberger Reservoir Completions Material Engineering Rosharon, TX, USA [email protected]

Dr. Marya is Group Leader with Schlumberger Technology Corp., TX. After completing his education in France, Canada, and the USA, where he received the M.S. and PhD degrees (Colorado School of Mines), he spent 3 years at General Motors R&D (MI) and NanoCoolers (TX). Dr. Marya has over 50 publications in materials design and processing to his name and is the recipient of the 2000 AWS Graduate Fellowship Award, 2002 IIW Henry Granjon Prize, and the 2006 AWS William Spraragen Award.

Surendar K. Marya

Chapter B.7, Sect. 7.4.9

GeM-UMR CNRS 6183, Ecole Centrale Nantes Institut de Recherche en Génie Civil et Mécanique Nantes, France [email protected]

Surendar Marya is Professor in Materials Science and Engineering, Physical Metallurgy, and Manufacturing Processes at Centrale Nantes, France. He holds the PhD degree from Punjab University College, India, and the Dr. Es. Sc. degree from the University of Paris Orsay, France. Professor Marya is a technical advisor to several industries and is heavily involved in scientific missions worldwide. He has been a Visiting Professor in the USA, Japan, and Korea, and frequently lectures in Southwest Asia.

Ajay Mathur

Chapter B.11

Simon India Limited Plant Engineering New Delhi, India [email protected]

Ajay Mathur is a Mechanical Engineer graduated from The Maharaja Sayaji Rao University, Baroda, India. He has over 20 years of experience in design and fabrication of pressure vessels, heat exchangers, skid-mounted plants, and fired heater modules for refinery, petrochemical, nuclear, and chemical projects in India and elsewhere.

Klaus-Jürgen Matthes

Chapter B.7, Sect. 7.4.5

Chemnitz University of Technology Institute for Manufacturing/Welding Technology Chemnitz, Germany [email protected]

Klaus-Jürgen Matthes is a Professor of Welding Engineering and Director of the Institute for Manufacturing/Welding Technology at Chemnitz University of Technology. His research interests include welding processes, engineering and design weldments, laser welding of microstructures, and automation and sensor-based monitoring of welding processes. He held the position of Vice President for Research from 1997 to 2003 and has been President of Chemnitz University of Technology since October 2003.

Henning Jürgen Meyer

Chapter B.14, Sect. 14.2

Technische Universität Berlin Berlin Institute of Technology Konstruktion von Maschinensystemen Berlin, Germany [email protected]

Dr. Meyer is a Professor of Machinery System Design at the Berlin Institute of Technology. He studied Mechanical Engineering at the Technische Universität Braunschweig, obtaining the PhD degree in 1998. From 1998 to 2002 he worked in the Wirtgen Group and was responsible for electronic systems in road pavers. His research work is concentrated on self-configuring mobile networks and on driving dynamics and braking systems of commercial vehicles, tractors, and mobile working machines.

Authors

Bruno Lisanti

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About the Authors

Chapter B.7, Sect. 7.4.1

DVS – German Welding Society Düsseldorf, Germany [email protected]

Klaus Middeldorf graduated as a Mechanical Engineer (1982) and received the Doctorate in Materials Science (1986) from the University of Essen. He worked as Project Manager for Paper Production for Procter &Gamble, then took the position of R&D Managing Director at the Federation of Industrial Research Associations, Cologne (1988– 1999). He currently serves as R&D Managing Director, and since 2006 as General Manager, for the German Welding Society (DVS).

Authors

Klaus Middeldorf

Gerhard Mook

Chapter B.3, Sect. 3.5

Otto-von-Guericke University Department of Mechanical Engineering Institute of Materials and Joining Technology and Materials Testing Magdeburg, Germany [email protected]

Professor Mook’s main area of research is nondestructive testing and evaluation as well as structural health monitoring. His work is focused on high-resolution imaging systems suitable for in-field application in aerospace and ground transportation systems. He is the chairman of the Board of University Teachers of the German Society for Nondestructive Testing (DGZfP).

Jay M. Ochterbeck

Chapter B.4, Sect. 4.2

Clemson University Department of Mechanical Engineering Clemson, SC, USA [email protected]

Jay M. Ochterbeck has been a Professor of Mechanical Engineering at Clemson University since 1994. His main fields of research are multiphase flows and heat transfer, capillary-driven loops, heat pipe science and technology, and thermal contact conductance. He is an Associate Fellow of the AIAA and is a member of several professional societies and international committees in thermal sciences.

Joao Fernando G. Oliveira

Chapter B.7, Sect. 7.3.3

University of São Paulo Department of Production Engineering São Carlos, SP, Brazil [email protected], [email protected]

Dr. Oliveira is Professor of Production Engineering at the University of São Paulo, Brazil. His area of research is abrasive machining process and its automation. He has published more than 200 papers and four patents. Currently he is the President of the Institute for Technological Research of the State of São Paulo and a member of the International Academy for Production Engineering.

Antje G. Orths

Chapter C.17, Sect. 17.6

Energinet.dk Electricity System Development Fredericia, Denmark [email protected]

Antje Orths graduated in Electrical Engineering at the TU Berlin and received the PhD degree from the Otto-von-Guericke University Magdeburg, Germany. Afterwards she lead the Critical Infrastructures Group at the Fraunhofer-Institute IFF in Magdeburg. Since 2005 she has been with the Planning Department of Energinet.dk, the Danish TSO for electricity and natural gas. Her research interests are planning issues such as the implementation of wind energy into electric power networks and systems. She is a member of the IEEE, VDE-ETG, and CRIS.

Vince Piacenti

Chapter B.10, Sect. 10.4

Robert Bosch LLC System Engineering, Diesel Fuel Systems Farmington Hills, MI, USA [email protected]

Vince Piacenti received the B.S. degree in Mechanical Engineering from Bradley University in 1976. He spent 7 years at Bosch’s Headquarters working on diesel fuel injection. Currently he is Senior Manager at Bosch in Michigan responsible for hydraulic systems integration. He has experience in all forms of diesel and gasoline fuel injection, and research experience with thermoplastics and alternate fuels.

About the Authors

Chapter B.7, Sect. 7.4.2

Otto-von-Guericke University Institute of Materials and Joining Technology Magdeburg, Germany [email protected]

Jörg Pieschel earned the Dipl.-Ing. and and Dr.-Ing. degrees from Otto-von-Guericke University Magdeburg in 1991 and 1999, respectively. In 2001 he was promoted to Head of Laboratories of the Materials and Joining Technology Institute and Welding Supervisor of the University of Magdeburg. Dr. Pieschel is an International Welding Engineer (IWE) and has specialized on joinability of materials, innovation of laser joining processes, quality assurance, and clarification of welding damages.

Stefan Pischinger

Chapter B.13, Sect. 13.1

RWTH Aachen University Institute for Combustion Engines Aachen, Germany [email protected]

Professor Pischinger studied Mechanical Engineering at RWTH Aachen University. Form 1985 to 1989 he worked as a Research Assistant at the Sloan Automotive Laboratory at MIT until he received the PhD degree for his work on spark ignition. Form 1989 to 1997 he held various positions at Daimler, working on diesel and gasoline engine development, and became project leader for the new Common Rail V8-Diesel engine. Since 1997 he has been Professor at RWTH Aachen University and Director of the Institute for Combustion Engines. Since April 2003 he has also been President and CEO of FEV, an Engineering Services Company in the field of combustion engines and powertrain.

Didier M. Priem

Chapter B.7, Sect. 7.4.9

École Centrale Nantes Department of Materials Nantes, France [email protected]

Didier M. Priem is an Engineer and Laboratory Manager for welding joining and forming technologies. For the last 20 years, he has been actively engaged in electromagnetic and electrohydraulic forming and welding technologies. He holds a patent on the electromagnetic forming of titanium dental parts.

Frank Riedel

Chapter B.7, Sect. 7.4.5

Fraunhofer-Institute for Machine Tools and Forming Technology (IWU) Department of Joining Technology Chemnitz, Germany [email protected]

Frank Riedel graduated as a Mechanical Engineer, receiving the PhD degree and PhD habilitatus in Joining Technology from Chemnitz University of Technology. From 2003 to 2006 he was the Deputy Head of Professorship of Welding Technology and Chief Engineer of the Institute of Manufacturing/Welding Technology at Chemnitz University of Technology. Since 2006 he has been establishing the Department of Thermal Processing at the Fraunhofer-Institute for Machine Tools and Forming Technology in Chemnitz, Germany.

Holger Saage

Chapter B.3, Sect. 3.7

University of Applied Sciences of Landshut Faculty of Mechanical Engineering Landshut, Germany [email protected]

Holger Saage received the PhD degree from the Otto-von-Guericke University Magdeburg. His experience covers various fields of materials science, including alloy development, powder technology, modeling of mechanical properties, and methods of materials analysis. Prior to joining the university he worked as a Materials Analyst in the semiconductor industry (AMD Saxony, Dresden). His current research work focuses on high-temperature materials, especially those with intermetallic phases such as TiAl and Mo silicides.

Shuichi Sakamoto

Chapter B.8, Sect. 8.2

Niigata University Department of Mechanical and Production Engineering Niigata, Japan [email protected]

Shuichi Sakamoto worked as Research Associate of the JSPS in 1989 and 1990. After that he received the PhD degree from Niigata University in 1991. He joined Niigata University in 1991 as a Research Associate, and became Associate Professor in 1998. His research interests are the development of new measuring or detection methods using acoustics, the characteristics of airborne sound-absorbing materials, and noise control.

Authors

Jörg Pieschel

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About the Authors

Chapter B.13, Sect. 13.4

California State University Long Beach, CA, USA [email protected]

Roger Schaufele graduated from Rensselaer Polytechnic Institute in 1949 with a degree in Aeronautical Engineering and obtained a M.S. degree in Aeronautics from CalTech in 1952. During the following years he held a number of key roles including Lead Aerodynamics Engineer for the DC-8 project, Aerodynamicist on the DC-9 and DC-10, and General Manager of Commercial Advanced Products. Since retiring from Douglas in 1989, he has been a part-time faculty member at California State University, Long Beach. He teaches courses in aircraft preliminary design and performance.

Authors

Roger Schaufele

Markus Schleser

Chapter B.7, Sect. 7.4.7

RWTH Aachen University Welding and Joining Institute Aachen, Germany [email protected]

Dipl.-Ing. Markus Schleser studied at RWTH Aachen University and majored in Production Engineering in 2001. From 2001 to 2007 he has been employed as a Research Assistant in the Department of Adhesive Bonding and since August 2007 has been Chief Engineer at the Welding and Joining Institute (ISF) of RWTH Aachen University.

Meinhard T. Schobeiri

Chapter B.12

Texas A&M University Department of Mechanical Engineering College Station, TX, USA [email protected]

Dr. Schobeiri, a Professor of Mechanical Engineering, received his entire engineering education at the Technical University Darmstadt, Germany. He was Group Leader for Gas Turbine Aero-Thermodynamic Design at Brown Boveri Co., Baden, Switzerland. His area of expertise includes unsteady aerodynamics, turbine and compressor aerodynamics design, and nonlinear gas turbine engine dynamic simulations. He is the author of one book and more than 100 technical papers and reports. He is a member of VDI and a Fellow of the ASME.

Miroslaw J. Skibniewski

Chapter B.14, Sects. 14.1, 14.3–14.8

University of Maryland Department of Civil and Environmental Engineering College Park, MD, USA [email protected]

Prof. Skibniewski is the holder of the A. James Clark Endowed Chair in Construction Engineering and Project Management at the University of Maryland, USA. A recipient of Civil Engineering degrees from Warsaw University of Technology and from Carnegie Mellon University and author of over 150 publications, he serves as Editor-in-Chief of Automation in Construction, an international research journal.

Jagjit Singh Srai

Chapter B.15, Sect. 15.3

University of Cambridge Centre for International Manufacturing Institute for Manufacturing Cambridge, UK [email protected]

Jag Srai is currently Head of the Centre for International Manufacturing, Institute for Manufacturing, University of Cambridge, an academic and practice-focused group of some 25 personnel. Before joining Cambridge University, Jag’s previous Director-level roles have been in industry, working for leading multinationals in manufacturing and supply chain management, with over 17 years industrial experience. Jag has a degree in Chemical Process Engineering and is a Chartered Engineer and a Fellow of the Institute for Chemical Engineers.

Vivek Srivastava

Chapter B.3, Sect. 3.3

Corporate Technology Strategy Services Aditya Birla Management Corporation Navi Mumbai, India [email protected]

Vivek’s research interest include room- and elevated-temperature mechanical properties of materials and their relationship with microstructure. He completed the PhD degree at the University of Sheffield, UK, on high-temperature creep of metals and alloys and was awarded the Bournton Medal for his thesis. He has published over ten research papers in international journals and has a deep interest in commercialization of technology.

About the Authors

Chapter B.4

Technical University Darmstadt Institute of Technical Thermodynamics Department of Mechanical Engineering Darmstadt, Germany [email protected]

Peter Stephan is a Professor at the Technische Universitaet Darmstadt and Head of the Institute of Technical Thermodynamics since 1997. His main fields of research are boiling heat transfer, microscale heat and mass transfer, interfacial phenomena, heat pipe technology, and drying and freezing processes. He is president of the VDI Heat and Mass Transfer Committee and is a member of several international thermal science associations.

Zbigniew A. Styczynski

Chapter C.17, Sects. 17.2, 17.7

Otto-von-Guericke University Electric Power Networks and Renewable Energy Sources Magdeburg, Germany [email protected] or [email protected]

Zbigniew Styczynski received the PhD degree from the Technical University of Wrocław, Poland. He worked at the University of Stuttgart, Germany, and in 1999 became Professor and Chair of Electric Power Networks and Renewable Energy Sources at the Otto-von-Guericke University, Magdeburg. From 2002 until 2006 he was the dean of the EE Faculty and since 2006 has been the President of the Centre of Renewable Energy Saxonia-Anhalt, Germany.

P.M.V. Subbarao

Chapter C.16

Indian Institute of Technology Mechanical Engineering Department New Delhi, India [email protected]

Dr. P.M.V. Subbarao is an Associate Professor of Mechanical Engineering Department at IIT, Delhi. He obtained the PhD degree in Mechanical Engineering from IIT Kanpur in 1996. He has developed ultramicro hydropower plants installed in remote rural areas for rural electrification. He has also developed a technology for production of bio-CNG from biogas for use in automobiles. His current research activities include power generation, renewable energy systems, and micro and pico power-generation systems.

Oliver Tegel

Chapter B.13, Sect. 13.2

Dr.-Ing. h.c. F. Porsche AG R&D, IS-Management Weissach, Germany [email protected]

Dr. Oliver Tegel is working at IS-Management in R&D at Porsche AG. Previously, he has managed business process reengineering projects related to various aspects of the car development process. His educational background is in engineering design and design methodology, in which he earned the Doctor degree from the Technical University Berlin, Germany.

A. Erman Tekkaya

Chapter B.7, Sect. 7.2

ATILIM University Department of Manufacturing Engineering Ankara, Turkey [email protected]

Professor Tekkaya completed his doctoral thesis at the University of Stuttgart in 1985. Until 2005 he was Professor at the METU, Ankara. From 2005 he was the Chairman of the Department of Manufacturing at ATILIM University in Ankara, Turkey. From 2007 he was Director of the Institute of Forming Technology and Lightweight Construction. His current research is on numerical simulation of sheet/ bulk metal forming processes and material characterization. He is a member of CIRP and President of the International Cold Forging Group (ICFG).

Klaus-Dieter Thoben

Chapter B.15, Sect. 15.10

University of Bremen Bremen Institute for Production and Logistics GmbH Department of ICT Applications in Production Bremen, Germany [email protected]

After finishing his studies in Mechanical Engineering, Klaus-Dieter Thoben worked as a Research Assistant at the Department of Production Engineering at the University of Bremen, where he received the Doctor of Engineering degree in 1989. He received the state doctorate (Habilitation) in the domain of Production Systems in 2002. In the same year he was appointed Professor for IT Applications in Production Engineering at the University of Bremen. Since 2003 he has been Director of Bremen Institute for Production and Logistics GmbH (BIBA) in the Department of ICT Applications in Production.

Authors

Peter Stephan

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About the Authors

Authors

Marcel Todtermuschke

Chapter B.7, Sect. 7.4.5

Fraunhofer-Institute for Machine Tools and Forming Technology Department of Assembling Techniques Chemnitz, Germany [email protected]

After studying mechanical engineering with major subject welding and manufacturing technologies, Marcel Todtermuschke started working at the University of Technology Chemnitz in the Department of Welding Technology. He worked in various fields such as welding design and finally gained his Doctorate in the field of mechanical joining. Since 2006 he has been concentrating on assembling technologies at the Fraunhofer-Institute for Machine Tools and Forming Technology.

Helmut Tschoeke

Chapter B.10

Otto-von-Guericke University Institute of Mobile Systems Magdeburg, Germany [email protected]

Helmut Tschoeke is a Professor of Reciprocating Machines at the University of Magdeburg. From 1981 to 1995 he worked with Bosch Diesel Division, where he was responsible for development and production of distributor and inline pumps. During his career he has held positions as Chief Engineer and Executive Plant Manager. He is an active member of VDI and member of SAE and the head of the automotive research program at the University of Magdeburg.

Jon H. Van Gerpen

Chapter B.10

University of Idaho Department of Biological and Agricultural Engineering Moscow, ID, USA [email protected]

Jon Van Gerpen has been Professor and Department Head of Biological and Agricultural Engineering at the University of Idaho since July 2004. Before that, he was a Professor of Mechanical Engineering at Iowa State University for 20 years. He received the PhD degree from the University of Wisconsin-Madison in 1984. His current research interests include the production and utilization of biofuels and the development of a nationwide biodiesel education program.

Anatole Vereschaka

Chapter B.7, Sects. 7.3.1, 7.3.2

Moscow State University of Technology “STANKIN” Department of Mechanical Engineering Technology and Institute of Design and Technological Informatics Laboratory of Surface Nanosystems Russian Academy of Science Moscow, Russia [email protected]

Anatoly Vereschaka, who received the PhD and Science Doctor degrees from Moscow State University in 1965 and 1986, respectively, is a Professor of Engineering Technology, Material Cutting Technology, and Surface Engineering Technology in the Department of Mechanical Engineering Technology of Moscow State University of Technology (STANKIN), Russia. His research interests are in the physics of metal cutting processes, design theory and methodology of wear resistance, and functional coating for cutting tools. He is Director of the Research Laboratory of Surface Nanosystems of the Russian Academy of Sciences.

Detlef von Hofe

Chapter B.7, Sect. 7.4.1

Krefeld, Germany [email protected]

Detlef von Hofe was responsible for stationary gas turbine fabrication at Siemens Power Generation until 1991 and has been the Chairman of CEN/TC 121 Welding since 2003. He was the Chief Executive Director and a Member of the Executive Council of the DVS, the German Welding Society until January 2006. He was appointed a Honorary Professor at the Otto-von-Guericke University in Magdeburg, teaching quality assurance in welding technology.

Nikolaus Wagner

Chapter B.7, Sect. 7.4.4

RWTH Aachen University ISF Welding and Joining Institute Aachen, Germany [email protected]

Dipl.-Ing. Nikolaus Wagner studied Mechanical Engineering from 1997 to 2004 at the RWTH Aachen University with an emphasis on production engineering. Since January 2005 he has been working as a Scientific Assistant in the Laser Beam Department of the ISF – Welding and Joining Institute at the RWTH Aachen University. After carrying out research on laser hybrid welding of light metals, he is currently working on laser-beam welding with pressure-sensitive adhesives. He is also doing research in the Cluster of Excellence Integrative Production Technology for High-Wage Countries.

About the Authors

Chapter C.17, Sect. 17.1

Institute of Power Engineering Warsaw, Poland

Jacek Wankowicz received the PhD and Dr. Sc. degrees from the Technical University of Wrocław, Poland. He worked at the Technical University of Wrocław, Poland and Bayero University Kano, Nigeria, and since 1997 has been the Managing Director of the Institute of Power Engineering, Warsaw, Poland. He is a Member of many Supervisory Boards, Member of the IEC, CIGRE and is currently the President of the Polish National Committee of the CIGRE.

Ulrich Wendt

Chapter B.3, Sects. 3.2, 3.7

Otto-von-Guericke University Department of Materials and Joining Technology Magdeburg, Germany [email protected]

Ulrich Wendt studied chemistry and received the Dr. rer. nat. degree for the investigation of a catalytic reaction and a second degree (Habil.) for work on polymer melt crystallization. He heads the Microscopy and Stereology Laboratory and lectures on microscopy, spectroscopy, image analysis, and chemical analysis. His research activities are related to microstructure characterization, topometry, and failure analysis.

Steffen Wengler

Chapter B.8, Sect. 8.2

Otto-von-Guericke University Faculty of Mechanical Engineering Institute of Manufacturing Technology and Quality Management Magdeburg, Germany [email protected]

Steffen Wengler graduated and obtained the Doctor degree in Mechanical Engineering, both from Otto-von-Guericke University of Magdeburg, Germany. His fields of specialization include manufacturing measurement technology and gear metrology, mainly cylindrical involute gears, and gear pairs. Since 1990 he has been Head of the Laboratory for Measurement Technology in the Institute of Manufacturing Technology and Quality Management at this university.

Bernd Wilhelm

Chapter B.15, Sect. 15.7

Volkswagen AG Sitech Sitztechnik GmbH Wolfsburg, Germany [email protected]

Bernd Wilhelm has had a career in the automotive industry, first as Specialist for manufacturing strategies, later as Manager of a Volkswagen assembly line, as Chief Industrial Engineer for the Volkswagen Group, and as Executive Manager of plants in Zaragoza and Brussels. As CEO for Sitech, a subsidiary of VW, he guarantees global seat production for the Volkswagen group and teaches operations planning as a Professor. He chairs leading automobile associations and is a Board Member of the German MTM Society.

Patrick M. Williams

Chapter B.15, Sect. 15.8

Assystem UK Bristol, UK [email protected]

Patrick has been involved in the UK aerospace industry for over 25 years. He qualified with the MSc degree in Technology Management from Universities in Bristol. His career has covered managing programmes in the UK, Europe, and the USA. Recently, Patrick has been involved in European research work in collaborative engineering in aerospace, focusing on management techniques in the supply chain.

Lutz Wisweh

Chapter B.8, Sect. 8.1

Otto-von-Guericke University Faculty of Mechanical Engineering Institute of Manufacturing Technology and Quality Management Magdeburg, Germany [email protected]

Lutz Wisweh received the Dipl.-Ing. and Dr.-Ing. degrees from the University of Magdeburg. In 1999 he was a Visiting Professor at the Niigata University, Japan. In 1999 he had an unlimited Visiting Professorship at the Universidad Central de Las Villas, Cuba. Currently, he is an Extracurricular Professor at the University of Magdeburg. His research interests are mainly in the use of statistical methods in quality management and measurement uncertainty in manufacturing measurement technology.

Authors

Jacek G. Wankowicz

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About the Authors

Authors

Johannes Wodara

Chapter B.7, Sect. 7.4.6

Schweißtechnik-Consult Magdeburg, Germany [email protected]

Professor Wodara was working for many years in speciality areas of welding. He was Head of the Institute of Assembling and Welding Engineering at the Otto-von-Guericke University Magdeburg. He also taught fundamentals of manufacturing in vehicle and aircraft engineering at Hamburg University of Applied Sciences. He has more than 170 publications to his name and is (co)author of several books in the field of welding, soldering, and brazing.

Klaus Woeste

Chapter B.7, Sect. 7.4.3

RWTH Aachen University ISF Welding and Joining Institute Aachen, Germany [email protected]

Dr.-Ing. Klaus Woeste studied Mechanical Engineering from 1994 to 2001 at RWTH Aachen University with emphasis on Production Engineering. From 2001 to 2004 he worked as a scientific assistant at the ISF – Welding and Joining Insitute at the RWTH Aachen University in the Electron Beam Department. From 2004 to August 2007 he was Chief Engineer of the ISF and was responsible for the coordination of scientific projects. He earned his doctorate in 2005. Since August 2007 he has been working in the Innovation Centre R&D of Gottwald Port Technology GmbH, Düsseldorf, Germany

Hen-Geul Yeh

Chapter A.2

California State University Department of Electrical Engineering Long Beach, CA, USA [email protected]

Dr. Hen-Geul Yeh’s research areas are dynamics and adaptive controls, digital signal processing, and digital communication systems. He has been selected twice as the NASA summer faculty fellow, in 1992 and 2003. He was the recipient of four NASA tech brief awards and one NASA new technology award. He was the recipient of the Aerospace Corporation inventor’s award. He has been selected as the Boeing A. D. Welliver faculty summer fellow in 2006. He owns several engineering patents.

Hsien-Yang Yeh

Chapter A.2

California State University Long Beach Department of Mechanical and Aerospace Engineering Long Beach, CA, USA [email protected]

Hsien-Yang Yeh received the PhD degree from the University of Southern California. His research interests include the mechanics of composite materials, fracture mechanics, structural and machine components failure analysis, and nanotechnology applications. Dr. Hsien-Yang Yeh’s research interests include the mechanics of composite materials, fracture mechanics, structural and machine components failure analysis, and nanotechnology applications.

Shouwen Yu

Chapter A.2

Tsinghua University School of Aerospace Beijing, P.R. China [email protected]

Professor Shouwen Yu is a Professor in the Department of Engineering Mechanics at Tsinghua University, Beijing, China. Professor Yu has been working in the field of fracture mechanics and nano/micro/ mesomechanics over the last few decades. From 1985 to 1987 he was with the Institute of Mechanics, Technische Hochschule Darmstadt, Germany as a Visiting Research Fellow under an Alexander von Humboldt Fellowship. Professor Yu was Vice President of Tsinghua University from 1992 to 1999 and Dean of Graduate School of Tsinghua University from 1994 to 1999.

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Detailed Contents

List of Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

XXIII

Part A Fundamentals of Mechanical Engineering

2 Mechanics Hen-Geul Yeh, Hsien-Yang Yeh, Shouwen Yu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Statics of Rigid Bodies Hen-Geul Yeh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.1 Force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.2 Addition of Concurrent Forces in Space and Equilibrium of a Particle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.3 Moment and Couple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.4 Equilibrium Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.5 Truss Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.6 Distributed Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 4 4 7 9 9 10 11 15 16 18 21 22 23 24 24 25 26 27 30 32 33

35 36 36 38 38 39 42 43

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1 Introduction to Mathematics for Mechanical Engineering Ramin S. Esfandiari . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . 1.1 Complex Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.1 Complex Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.2 Complex Variables and Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Differential Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.1 First-Order Ordinary Differential Equations . . . . . . . . . . . . . . . . . 1.2.2 Numerical Solution of First-Order Ordinary Differential Equations . . . . . . . . . . . . . . 1.2.3 Second- and Higher-Order, Ordinary Differential Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Laplace Transformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.1 Inverse Laplace Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.2 Special Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.3 Laplace Transform of Derivatives and Integrals . . . . . . . . . . . . . 1.3.4 Inverse Laplace Transformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.5 Periodic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Fourier Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.1 Fourier Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.2 Fourier Transformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Linear Algebra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.1 Vectors and Matrices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.2 Eigenvalues and Eigenvectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.3 Numerical Solution of Higher-Order Systems of ODEs . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2.1.7 Friction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.8 Principle of Virtual Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Dynamics Hsien-Yang Yeh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.1 Motion of a Particle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.2 Planar Motion, Trajectories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.3 Polar Coordinates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.4 Motion of Rigid Bodies (Moving Reference Frames) . . . . . . . . 2.2.5 Planar Motion of a Rigid Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.6 General Case of Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.7 Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.8 Straight-Line Motion of Particles and Rigid Bodies . . . . . . . . . 2.2.9 Dynamics of Systems of Particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.10 Momentum Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.11 D’Alembert’s Principle, Constrained Motion . . . . . . . . . . . . . . . . . 2.2.12 Lagrange’s Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.13 Dynamics of Rigid Bodies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.14 Planar Motion of a Rigid Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.15 General Case of Planar Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.16 Rotation About a Fixed Axis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.17 Lagrange’s Equations of Motion for Linear Systems . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

44 52 52 52 54 54 56 58 60 60 63 63 64 65 66 66 67 68 69 70 71

Part B Applications in Mechanical Engineering 3 Materials Science and Engineering Jens Freudenberger, Joachim Göllner, Martin Heilmaier, Gerhard Mook, Holger Saage, Vivek Srivastava, Ulrich Wendt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Atomic Structure and Microstructure Martin Heilmaier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.1 Atomic Order in Solid State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2 Microstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.3 Atomic Movement in Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.4 Transformation into Solid State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.5 Binary Phase Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Microstructure Characterization Ulrich Wendt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.1 Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 Crystal Structure by X-ray Diffraction . . . . . . . . . . . . . . . . . . . . . . . . 3.2.3 Materialography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Mechanical Properties Vivek Srivastava . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.1 Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.2 Quasistatic Mechanical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.3 Dynamic Mechanical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

75 77 77 81 87 90 93 98 98 98 100 108 108 108 117

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3.4

4 Thermodynamics Frank Dammel, Jay M. Ochterbeck, Peter Stephan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Scope of Thermodynamics. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.1 Systems, System Boundaries, Surroundings . . . . . . . . . . . . . . . . . 4.1.2 Description of States, Properties, and Thermodynamic Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Temperatures. Equilibria Jay M. Ochterbeck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Thermal Equilibrium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 Zeroth Law and Empirical Temperature . . . . . . . . . . . . . . . . . . . . . . 4.2.3 Temperature Scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

122 122 123 126 127 127 130 131 134 135 136 138 140 141 141 142 154 157 158 183 188 191 196 199 201 204 212 217 218

223 223 224 224 225 225 225 225

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Physical Properties Martin Heilmaier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.1 Electrical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.2 Thermal Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 Nondestructive Inspection (NDI) Gerhard Mook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.1 Principle of Nondestructive Inspection . . . . . . . . . . . . . . . . . . . . . . 3.5.2 Acoustic Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.3 Potential Drop Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.4 Magnetic Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.5 Electromagnetic Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.6 Thermography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.7 Optical Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.8 Radiation Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.9 Health Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 Corrosion Joachim Göllner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.2 Electrochemical Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.3 Corrosion (Chemical) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7 Materials in Mechanical Engineering Ulrich Wendt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.1 Iron-Based Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.2 Aluminum and Its Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.3 Magnesium and Its Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.4 Titanium and Its Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.5 Ni and Its Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.6 Co and Its Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.7 Copper and Its Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.8 Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.9 Glass and Ceramics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.10 Composite Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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First Law of Thermodynamics Frank Dammel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.1 General Formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2 The Different Forms of Energy and Energy Transfer . . . . . . . . . 4.3.3 Application to Closed Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.4 Application to Open Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Second Law of Thermodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.1 The Principle of Irreversibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.2 General Formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.3 Special Formulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Exergy and Anergy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.1 Exergy of a Closed System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.2 Exergy of an Open System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.3 Exergy and Heat Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.4 Anergy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.5 Exergy Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Thermodynamics of Substances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.1 Thermal Properties of Gases and Vapors . . . . . . . . . . . . . . . . . . . . . 4.6.2 Caloric Properties of Gases and Vapors . . . . . . . . . . . . . . . . . . . . . . 4.6.3 Incompressible Fluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.4 Solid Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.5 Mixing Temperature. Measurement of Specific Heats . . . . . . 4.7 Changes of State of Gases and Vapors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7.1 Change of State of Gases and Vapors in Closed Systems . . . . 4.7.2 Changes of State of Flowing Gases and Vapors . . . . . . . . . . . . . . 4.8 Thermodynamic Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8.1 Combustion Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8.2 Internal Combustion Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8.3 Cyclic Processes, Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8.4 Thermal Power Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8.5 Refrigeration Cycles and Heat Pumps . . . . . . . . . . . . . . . . . . . . . . . . 4.8.6 Combined Power and Heat Generation (Co-Generation) . . . 4.9 Ideal Gas Mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9.1 Mixtures of Gas and Vapor. Humid Air . . . . . . . . . . . . . . . . . . . . . . . 4.10 Heat Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10.1 Steady-State Heat Conduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10.2 Heat Transfer and Heat Transmission . . . . . . . . . . . . . . . . . . . . . . . . 4.10.3 Transient Heat Conduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10.4 Heat Transfer by Convection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10.5 Radiative Heat Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

228 228 228 229 229 231 231 232 233 233 234 234 234 235 235 235 235 239 250 252 254 256 256 259 262 262 265 267 268 272 273 274 274 280 280 281 284 286 291 293

5 Tribology Ludger Deters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Tribology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.1 Tribotechnical System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.2 Friction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

295 295 296 301

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5.1.3 Wear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.4 Fundamentals of Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.5 Lubricants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

303 310 315 326

327 329 331 332 334 334 336 336 338 339 341 342 343 344 345 348 348 348 350 352 354 354 355 364 364 365 365 366 366 367 368 368 372 372 373

Detailed Cont.

6 Design of Machine Elements Oleg P. Lelikov . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Mechanical Drives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.1 Contact Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.2 Nature and Causes of Failure Under the Influence of Contact Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Gearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.1 Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.2 Accuracy of Gearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.3 Gear Wheel Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.4 The Nature and Causes of Gearing Failures . . . . . . . . . . . . . . . . . . 6.2.5 Choice of Permissible Contact Stresses Under Constant Loading Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.6 Choice of Permissible Bending Stresses Under Constant Loading Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.7 Choice of Permissible Stresses Under Varying Loading Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.8 Typical Loading Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.9 Criteria for Gearing Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.10 Calculated Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Cylindrical Gearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.1 Toothing Forces of Cylindrical Gearings . . . . . . . . . . . . . . . . . . . . . . 6.3.2 Contact Strength Analysis of Straight Cylindrical Gearings . 6.3.3 Bending Strength Calculation of Cylindrical Gearing Teeth 6.3.4 Geometry and Working Condition Features of Helical Gearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.5 The Concept of the Equivalent Wheel . . . . . . . . . . . . . . . . . . . . . . . . 6.3.6 Strength Analysis Features of Helical Gearings . . . . . . . . . . . . . . 6.3.7 The Projection Calculation of Cylindrical Gearings . . . . . . . . . . 6.4 Bevel Gearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.1 Basic Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.2 The Axial Tooth Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.3 Basic Geometric Proportions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.4 Equivalent Cylindrical Wheels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.5 Toothing Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.6 Contact Strength Analysis of Bevel Gearings . . . . . . . . . . . . . . . . 6.4.7 Calculation of the Bending Strength of Bevel Gearing Teeth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.8 Projection Calculation for Bevel Gearings . . . . . . . . . . . . . . . . . . . 6.5 Worm Gearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.2 Geometry of Worm Gearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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6.6

6.7

6.8

6.9

6.5.3 The Kinematics of Worm Gearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.4 Slip in Worm Gearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.5 The Efficiency Factor of Worm Gearings . . . . . . . . . . . . . . . . . . . . . . 6.5.6 Toothing Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.7 Stiffness Testing of Worms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.8 Materials for Worms and Worm-Wheel Rings . . . . . . . . . . . . . . . 6.5.9 The Nature and Causes of Failure of Worm Gearings . . . . . . . 6.5.10 Contact Strength Analysis and Seizing Prevention . . . . . . . . . . 6.5.11 Bending Strength Calculation for Wheel Teeth . . . . . . . . . . . . . . 6.5.12 Choice of Permissible Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.13 Thermal Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.14 Projection Calculation for Worm Gearings . . . . . . . . . . . . . . . . . . . Design of Gear Wheels, Worm Wheels, and Worms . . . . . . . . . . . . . . . . . . . . 6.6.1 Spur Gears with External Toothing . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.2 Spur Gears with Internal Toothing . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.3 Gear Clusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.4 Bevel Wheels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.5 Gear Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.6 Worm Wheels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.7 Worms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.8 Design Drawings of Gear and Worm Wheels: The Worm . . . . 6.6.9 Lubrication of Tooth and Worm Gears . . . . . . . . . . . . . . . . . . . . . . . Planetary Gears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.2 Gear Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.3 Planetary Gear Layouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.4 Torques of the Main Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.5 Toothing Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.6 Number Matching of Wheel Teeth . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.7 Strength Analysis of Planetary Gears . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.8 Design of Planetary Gears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wave Gears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.1 Arrangement and Operation Principles of Wave Gears . . . . . 6.8.2 Gear Ratio of Wave Gears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.3 Radial Deformation and the Transmission Ratio . . . . . . . . . . . . 6.8.4 The Nature and Causes of Failure of Wave Gear Details . . . 6.8.5 Fatigue Strength Calculation of Flexible Wheels . . . . . . . . . . . . 6.8.6 Design of Wave Gears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.7 Thermal Conditions and Lubrication of Wave Gears . . . . . . . . 6.8.8 Structure Examples of Harmonic Reducers . . . . . . . . . . . . . . . . . . Shafts and Axles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.2 Means of Load Transfer on Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.3 Efficiency Criteria for Shafts and Axles . . . . . . . . . . . . . . . . . . . . . . . 6.9.4 Projection Calculation of Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

375 375 376 377 378 378 378 379 380 380 381 383 388 388 391 391 392 393 394 396 397 398 399 399 401 401 402 402 403 406 406 412 413 415 416 416 417 418 425 426 426 426 428 429 429

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430 436 440 449 449 451 453 459 460 460 461 461 464 465 465 467 467 468 470 471 472 474 477 482 483 483 486 490 501 505 508 510 511 514 516 518 519

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6.9.5 Checking Calculation of Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.6 Shaft Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.7 Drafting of the Shaft Working Drawing . . . . . . . . . . . . . . . . . . . . . . 6.10 Shaft–Hub Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.10.1 Key Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.10.2 Spline Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.10.3 Pressure Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.10.4 Frictional Connections with Conic Tightening Rings . . . . . . . . 6.11 Rolling Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.11.2 Classifications of Rolling Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.11.3 Main Types of Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.11.4 Functions of the Main Bearing Components . . . . . . . . . . . . . . . . 6.11.5 Materials of Bearing Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.11.6 Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.11.7 The Nature and Causes of Failure of Rolling Bearings . . . . . 6.11.8 Static Load Rating of Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.11.9 Lifetime Testing of Rolling Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . 6.11.10 Design Dynamic Load Rating of Bearings . . . . . . . . . . . . . . . . . . . . 6.11.11 Design Lifetime of Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.11.12 The Choice of Bearing Classes and Their Installation Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.11.13 Determination of Forces Loading Bearings . . . . . . . . . . . . . . . . . . 6.11.14 Choice and Calculation of Rolling Bearings . . . . . . . . . . . . . . . . . . 6.11.15 Fits of Bearing Races . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.12 Design of Bearing Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.12.1 Clearances and Preloads in Bearings and Adjustment of Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.12.2 Principal Recommendations Concerning Design, Assembly, and Diagnostics of Bearing Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.12.3 Design of Bearing Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.12.4 Design of Shaft Supports of Bevel Pinions . . . . . . . . . . . . . . . . . . . 6.12.5 Support Design of Worm Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.12.6 Supports for Floating Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.12.7 Supports for Coaxial Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.12.8 Lubrication of Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.12.9 Position of the Adjacent with Bearing Components: Drawing of the Interior Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.A Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.B Appendix B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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7 Manufacturing Engineering Thomas Böllinghaus, Gerry Byrne, Boris Ilich Cherpakov (deceased), Edward Chlebus, Carl E. Cross, Berend Denkena, Ulrich Dilthey, Takeshi Hatsuzawa, Klaus Herfurth, Horst Herold (deceased), Andrew Kaldos, Thomas Kannengiesser, Michail Karpenko, Bernhard Karpuschewski, Manuel Marya, Surendar K. Marya, Klaus-Jürgen Matthes, Klaus Middeldorf, Joao Fernando G. Oliveira, Jörg Pieschel, Didier M. Priem, Frank Riedel, Markus Schleser, A. Erman Tekkaya, Marcel Todtermuschke, Anatole Vereschaka, Detlef von Hofe, Nikolaus Wagner, Johannes Wodara, Klaus Woeste . . . . . . . . 7.1 Casting Klaus Herfurth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.1 The Manufacturing Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.2 The Foundry Industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.3 Cast Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.4 Primary Shaping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.5 Shaping of Metals by Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.6 Guidelines for Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.7 Preparatory and Finishing Operations . . . . . . . . . . . . . . . . . . . . . . . 7.2 Metal Forming A. Erman Tekkaya . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.2 Metallurgical Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.3 Theoretical Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.4 Bulk Forming Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.5 Sheet Forming Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.6 Forming Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Machining Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.1 Cutting Anatole Vereschaka . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.2 Machining with Geometrically Nondefined Tool Edges Anatole Vereschaka . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.3 Nonconventional Machining Processes Joao Fernando G. Oliveira . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 Assembly, Disassembly, Joining Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.1 Trends in Joining – Value Added by Welding Detlef von Hofe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.2 Trends in Laser Beam Machining Jörg Pieschel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.3 Electron Beam Klaus Woeste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.4 Hybrid Welding Nikolaus Wagner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.5 Joining by Forming Marcel Todtermuschke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.6 Micro Joining Processes Johannes Wodara . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

523 525 525 525 527 536 538 548 553 554 554 557 560 568 585 599 606 606 636 647 656 657 668 675 682 686 697

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7.4.7

8 Measuring and Quality Control Norge I. Coello Machado, Shuichi Sakamoto, Steffen Wengler, Lutz Wisweh 8.1 Quality Management Lutz Wisweh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1.1 Quality and Quality Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1.2 Quality Management Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1.3 Quality Management Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1.4 CE Sign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Manufacturing Measurement Technology Steffen Wengler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.2 Arrangement in the Manufacturing Process . . . . . . . . . . . . . . . . . 8.2.3 Specifications on the Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.4 Gauging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.5 Application of Measuring Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.6 Coordinate Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.7 Surface Metrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.8 Form and Position Measuring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.9 Laser Measuring Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Measuring Uncertainty and Traceability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4 Inspection Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

702 706

723 733 734 737 753 760 768 768 769 772 773

787 787 787 787 793 793 793 793 794 795 797 797 800 807 810 812 816 817 818

Detailed Cont.

Microbonding Markus Schleser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.8 Modern Joining Technology – Weld Simulation Thomas Kannengiesser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.9 Fundamentals of Magnetic Pulse Welding for the Fabrication of Dissimilar Material Structures Didier M. Priem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 Rapid Prototyping and Advanced Manufacturing Edward Chlebus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.1 Product Life Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.2 Rapid Prototyping Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.3 Reverse Engineering Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.4 Rapid Tooling Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6 Precision Machinery Using MEMS Technology Takeshi Hatsuzawa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6.1 Electrostatic-Driven Optical Display Device . . . . . . . . . . . . . . . . . . 7.6.2 Design of the Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6.3 Evanescent Coupling Switching Device . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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9 Engineering Design Alois Breiing, Frank Engelmann, Timothy Gutowski . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1 Design Theory Frank Engelmann . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.1 Product Planning Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.2 The Development of Technical Products . . . . . . . . . . . . . . . . . . . . . 9.1.3 Construction Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 Basics Frank Engelmann . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3 Precisely Defining the Task Frank Engelmann . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.1 Task . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.2 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.3 Requirements List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4 Conceptual Design Frank Engelmann . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5 Design Timothy Gutowski . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5.1 Identify Requirements that Determine the Design and Clarify the Spatial Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5.2 Structuring and Rough Design of the Main Functional Elements Determining the Design and Selection of Suitable Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5.3 Detailed Design of the Main and Secondary Functional Elements . . . . . . . . . . . . . . . . . . . . . . . . . 9.5.4 Evaluation According to the Technical and Economic Criteria and Specification of the Preliminary Overall Design 9.5.5 Subsequent Consideration, Error Analysis, and Improvement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6 Design and Manufacturing for the Environment Alois Breiing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.1 Life Cycle Format for Product Evaluation . . . . . . . . . . . . . . . . . . . . 9.6.2 Life Cycle Stages for a Product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.3 Product Examples: Automobiles and Computers . . . . . . . . . . . . 9.6.4 Design for the Environment (DFE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.5 System-Level Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7 Failure Mode and Effect Analysis for Capital Goods . . . . . . . . . . . . . . . . . . . 9.7.1 General Innovations for the Application of FMEA . . . . . . . . . . . 9.7.2 General Rules to Carry Out FMEA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7.3 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7.4 Further Use of FMEA Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

819 819 819 824 828 842 843 843 843 844 845 848 849

849 849 851 852 853 854 856 859 866 866 867 867 868 869 875 875

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11 Pressure Vessels and Heat Exchangers Ajay Mathur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Pressure Vessel – General Design Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1.1 Thin-Shell Pressure Vessel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1.2 Thick-Walled Pressure Vessel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1.3 Heads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1.4 Conical Heads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1.5 Nozzles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1.6 Flanges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1.7 Loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1.8 External Local Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1.9 Fatigue Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Design of Tall Towers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.1 Combination of Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.2 Wind-Induced Deflection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.3 Wind-Induced Vibrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

879 879 879 882 884 891 893 893 894 901 910 911 912 913 913 913 915 916 920 927 929 931 933 939 944

947 947 947 949 950 950 950 950 951 951 951 952 952 952 952

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10 Piston Machines Vince Piacenti, Helmut Tschoeke, Jon H. Van Gerpen . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1 Foundations of Piston Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.2 Ideal and Real Piston Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.3 Reciprocating Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.4 Selected Elements of Reciprocating Machines . . . . . . . . . . . . . . . 10.2 Positive Displacement Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.1 Types and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.2 Basic Design Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.3 Components and Construction of Positive Displacement Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3 Compressors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.1 Cycle Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.2 Multi-Staging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.3 Design Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4 Internal Combustion Engines Vince Piacenti . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.1 Basic Engine Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.2 Performance Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.3 Air Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.4 Fuel Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.5 Ignition Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.6 Mixture Formation and Combustion Processes . . . . . . . . . . . . . . 10.4.7 Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.8 Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.9 Selected Examples of Combustion Engines . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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11.3

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Testing Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3.1 Nondestructive Testing (NDT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3.2 Destructive Testing of Welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4 Design Codes for Pressure Vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.1 ASME Boiler and Pressure Vessel Code . . . . . . . . . . . . . . . . . . . . . . . 11.4.2 PED Directive and Harmonized Standard EN 13445 . . . . . . . . . . 11.4.3 PD 5500 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.4 AD Merkblätter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.5 Heat Exchangers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.6 Material of Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.6.1 Carbon Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.6.2 Low-Alloy Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.6.3 NACE standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.6.4 Comparative Standards for Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.6.5 Stainless Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.6.6 Ferritic and Martensitic Steels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.6.7 Copper and Nickel Base Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

953 953 953 954 954 954 956 958 958 959 959 960 960 960 960 964 964 966

12 Turbomachinery Meinhard T. Schobeiri . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 967 12.1 Theory of Turbomachinery Stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 967 12.1.1 Energy Transfer in Turbomachinery Stages . . . . . . . . . . . . . . . . . . 967 12.1.2 Energy Transfer in Relative Systems . . . . . . . . . . . . . . . . . . . . . . . . . . 968 12.1.3 General Treatment of Turbine and Compressor Stages . . . . . 969 12.1.4 Dimensionless Stage Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 972 12.1.5 Relation Between Degree of Reaction and Blade Height for a Normal Stage Using Simple Radial Equilibrium . . . . . . . 973 12.1.6 Effect of Degree of Reaction on the Stage Configuration . . . 975 12.1.7 Effect of the Stage Load Coefficient on Stage Power . . . . . . . . 975 12.1.8 Unified Description of a Turbomachinery Stage . . . . . . . . . . . . . 976 12.1.9 Special Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 979 12.1.10 Increase of Stage Load Coefficient: Discussion . . . . . . . . . . . . . . 979 12.2 Gas Turbine Engines: Design and Dynamic Performance . . . . . . . . . . . . . . 981 12.2.1 Gas Turbine Processes, Steady Design Operation . . . . . . . . . . . . 981 12.2.2 Nonlinear Gas Turbine Dynamic Simulation . . . . . . . . . . . . . . . . . 989 12.2.3 Engine Components, Modular Concept, and Module Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 990 12.2.4 Levels of Gas Turbine Engine Simulations, Cross Coupling . 992 12.2.5 Nonlinear Dynamic Simulation Case Studies . . . . . . . . . . . . . . . . 996 12.2.6 New Generation Gas Turbines, Detailed Efficiency Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1007 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1009

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1011 1012 1015 1019 1022 1026 1026 1032 1049 1055 1070 1070 1076 1086 1091 1092 1092 1093 1095 1096 1096 1096 1098 1098 1108 1109 1114 1121 1122 1131 1137 1140 1144 1144

Detailed Cont.

13 Transport Systems Gritt Ahrens, Torsten Dellmann, Stefan Gies, Markus Hecht, Hamid Hefazi, Rolf Henke, Stefan Pischinger, Roger Schaufele, Oliver Tegel . . . . . . . . . . . . . . . . . 13.1 Overview Stefan Pischinger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.1.1 Road Transport – Vehicle Technology and Development . . . 13.1.2 Aerospace – Technology and Development . . . . . . . . . . . . . . . . . 13.1.3 Rail Transport – Rail Technology and Development . . . . . . . . 13.2 Automotive Engineering Oliver Tegel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2.2 Automotive Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2.3 Car Development Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2.4 Methods for Car Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3 Railway Systems – Railway Engineering Markus Hecht . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3.1 General Interactions of Modules of a Railway System with Surrounding Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3.2 Track . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3.3 Running Gears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3.4 Superstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3.5 Vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3.6 Coupling Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3.7 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3.8 Air Conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4 Aerospace Engineering Roger Schaufele . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.1 Aerospace Industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.2 Aircraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.3 Spacecraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.4 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.5 Flight Performance Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.6 Airplane Aerodynamic Characteristics . . . . . . . . . . . . . . . . . . . . . . . . 13.4.7 Airplane General Arrangements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.8 Weights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.9 Aircraft Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.10 Stability and Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.11 Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.12 Airplane Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.13 Airplane Maintenance Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1551

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Detailed Cont.

14 Construction Machinery Eugeniusz Budny, Mirosław Chłosta, Henning Jürgen Meyer, Mirosław J. Skibniewski . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.1 Basics Mirosław J. Skibniewski . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.1.1 Role of Machines in Construction Work Execution . . . . . . . . . . 14.1.2 Development of Construction Machinery – Historical Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.1.3 Classification of Construction Machinery . . . . . . . . . . . . . . . . . . . . 14.2 Earthmoving, Road Construction, and Farming Equipment Henning Jürgen Meyer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.2.1 Soil Science and Driving Mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . 14.2.2 Tyres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.2.3 Earthmoving Machinery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.2.4 Road Construction Machinery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.2.5 Farming Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3 Machinery for Concrete Works Mirosław J. Skibniewski . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.1 Concrete Mixing Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.2 Concrete Mixers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.3 Truck Concrete Mixers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.4 Concrete Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.5 Concrete Spraying Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.6 Internal Vibrators for Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.7 Vibrating Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.8 Floating Machines for Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.9 Equipment for Vacuum Treatment of Concrete . . . . . . . . . . . . . . 14.4 Site Lifts Mirosław J. Skibniewski . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.1 Material and Equipment Lifts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.2 Material and Equipment Lifts with Access to Personnel . . . . 14.5 Access Machinery and Equipment Mirosław J. Skibniewski . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.1 Static Scaffolds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.2 Elevating Work Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.3 Hanging Scaffolds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.6 Cranes Mirosław J. Skibniewski . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.6.1 Mobile Cranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.6.2 Small Capacity Portable Cranes, Gantries, and Winches . . . . 14.6.3 Tower Cranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.7 Equipment for Finishing Work Mirosław J. Skibniewski . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.7.1 Equipment for Roofwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.7.2 Equipment for Plaster Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.7.3 Equipment for Facing Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1149 1150 1150 1150 1154 1155 1155 1157 1160 1164 1169 1175 1175 1179 1181 1182 1185 1186 1187 1189 1190 1191 1191 1197 1200 1200 1204 1210 1213 1213 1216 1219 1228 1228 1229 1234

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14.7.4 14.7.5

1553

Floor Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1235 Equipment for Painting Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1237

14.8

1238 1240 1244 1249 1250 1251 1252 1252 1256

1259 1264

15 Enterprise Organization and Operation Francesco Costanzo, Yuichi Kanda, Toshiaki Kimura, Hermann Kühnle, Bruno Lisanti, Jagjit Singh Srai, Klaus-Dieter Thoben, Bernd Wilhelm, Patrick M. Williams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1267 15.1

Overview Hermann Kühnle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1268

15.2

Organizational Structures Hermann Kühnle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.2.2 Enterprise: Main Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.2.3 Organization and Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.2.4 Classical Forms of Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15.3

15.4

Process Organization, Capabilities, and Supply Networks Jagjit Singh Srai . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.3.1 The Capability Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.3.2 Extending the Capability Concept to Processes and Supply Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.3.3 Application Perspectives and Maturity Models . . . . . . . . . . . . . . 15.3.4 Operational Process-Based Capabilities . . . . . . . . . . . . . . . . . . . . . 15.3.5 The Supply Network Capability Map . . . . . . . . . . . . . . . . . . . . . . . . . .

1271 1271 1274 1274 1276 1279 1280 1281 1288 1288 1289

Modeling and Data Structures Hermann Kühnle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1290 15.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1290 15.4.2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1291

Detailed Cont.

Automation and Robotics in Construction Mirosław J. Skibniewski . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.8.1 Automation of Earthwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.8.2 Automation of Concrete Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.8.3 Automation of Masonry Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.8.4 Automation of Cranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.8.5 Automation of Materials Handling and Elements Mounting by Mini-Cranes and Lightweight Manipulators . 14.8.6 Automation of Construction Welding Work . . . . . . . . . . . . . . . . . . 14.8.7 Automation of Finishing Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.8.8 Automated Building Construction Systems for Highand Medium-Rise Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.8.9 Automation and Robotics in Road Work, Tunneling, Demolition Work, Assessing the Technical Condition of Buildings, and Service-Maintenance Activities . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Detailed Cont.

15.4.3 Guidelines of Modeling (GoM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.4.4 Important Models and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.5 Enterprise Resource Planning (ERP) Hermann Kühnle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.5.1 Resources and Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.5.2 Functionalities of ERP Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.5.3 ERP Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.5.4 Conclusions and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.6 Manufacturing Execution Systems (MES) Toshiaki Kimura . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.6.1 Information-Interoperable Environment (IIE) . . . . . . . . . . . . . . . 15.6.2 Development of Prototype Application Systems . . . . . . . . . . . . . 15.7 Advanced Organization Concepts Bernd Wilhelm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.7.1 Lean Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.7.2 Agile Manufacturing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.7.3 Bionic Manufacturing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.7.4 Holonic Manufacturing Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.7.5 The Fractal Company . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.7.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.8 Interorganizational Structures Patrick M. Williams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.8.1 Cooperation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.8.2 Alliances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.8.3 Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.8.4 Supply Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.8.5 Virtual Organizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.8.6 Extended Enterprise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.8.7 Virtual Enterprise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.9 Organization and Communication Hermann Kühnle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.9.1 Terms, Definitions, and Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.9.2 Challenges Concerning the Internal Embodiment of Communication Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.9.3 Methods of Embodiment, Organization Models, and the Management of Communication . . . . . . . . . . . . . . . . . . . 15.9.4 Conclusions and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.10 Enterprise Collaboration and Logistics Klaus-Dieter Thoben . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.10.1 Dimensions of Enterprise Networks . . . . . . . . . . . . . . . . . . . . . . . . . . 15.10.2 Analysis of Enterprise Collaborations . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1293 1293 1303 1303 1304 1304 1307 1307 1309 1313 1314 1315 1315 1316 1316 1317 1321 1321 1322 1323 1325 1326 1327 1328 1329 1330 1330 1332 1333 1335 1337 1337 1343 1354

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Part C Complementary Material for Mechanical Engineers 1363 1365 1365 1366 1366 1366 1367 1367 1367 1367 1367 1367 1367 1368 1368 1368 1369 1370 1371 1371 1372 1372 1373 1374 1374 1374 1375 1375 1375 1376 1376 1377 1377 1377 1377 1378 1378 1378 1378 1378 1378 1379 1379

Detailed Cont.

16 Power Generation Dwarkadas Kothari, P.M.V. Subbarao . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.1 Principles of Energy Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.1.1 Planning and Investments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.1.2 Economics of Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.1.3 Economics of Electricity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.1.4 Economics of Remote Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2 Primary Energies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3 Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3.1 Solid Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3.2 Liquid Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3.3 Gaseous Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3.4 Nuclear Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3.5 Regenerative Energies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.4 Transformation of Primary Energy into Useful Energy . . . . . . . . . . . . . . . . . 16.5 Various Energy Systems and Their Conversion . . . . . . . . . . . . . . . . . . . . . . . . . 16.5.1 Generation of Electrical Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5.2 Steam Power Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5.3 Process of the Rankine Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.6 Direct Combustion System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.6.1 Open-Cycle Gas Turbine Power Plant . . . . . . . . . . . . . . . . . . . . . . . . 16.7 Internal Combustion Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.8 Fuel Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.9 Nuclear Power Stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.9.1 Basic Principles of Nuclear Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.9.2 Types of Nuclear Power Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.10 Combined Power Station . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.10.1 Thermodynamic Analysis of the Combined Cycle System . . . 16.11 Integrated Gasification Combined Cycle (IGCC) System . . . . . . . . . . . . . . . . 16.11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.11.2 Environmental Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.11.3 Efficiency Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.11.4 The Science of Coal Gasification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.11.5 Chemical Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.11.6 Optimal Coal Gasifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.11.7 Classification of Gasifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.11.8 E-GAS Entrained Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.12 Magnetohydrodynamic (MHD) Power Generation . . . . . . . . . . . . . . . . . . . . . . 16.12.1 Principle of MHD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.12.2 General Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.12.3 The Production of Plasma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.12.4 Thermal Ionization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.12.5 Nonequilibrium Ionization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.12.6 MHD Steam Power Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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16.13 Total-Energy Systems for Heat and Power Generation . . . . . . . . . . . . . . . . 16.13.1 Cogeneration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.14 Transformation of Regenerative Energies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.14.1 Wind Energy Power Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.15 Solar Power Stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.15.1 Significant Features of Solar Energy . . . . . . . . . . . . . . . . . . . . . . . . . . 16.15.2 Solar Cells or Photovoltaic Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.15.3 Solar Pond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.15.4 Solar Chimney . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.15.5 Integrated Solar Combined Cycle Power System . . . . . . . . . . . . . 16.16 Heat Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.17 Energy Storage and Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.17.1 Pumped Hydro Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.17.2 Compressed Air Energy Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.17.3 Energy Storage by Flywheels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.17.4 Electrochemical Energy Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.17.5 Thermal Energy Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.17.6 Secondary Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18 Furnaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.1 Combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.2 Ideal Combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.3 Theoretical Dry Air–Fuel Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.4 Theoretical Wet-Air–Fuel Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.5 Pressure Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.6 Emission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.7 Particulate Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.8 Nitrogen Oxide Emission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.9 Thermal NOx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.10 Fuel NOx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.11 Sulfur Dioxide Emission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.12 Solid-Fuel Furnaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.13 Stokers and Grates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.14 Pulverized-Fuel Furnaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.15 Dry-Bottom Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.18.16 Wet-Bottom Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.19 Fluidized-Bed Combustion System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.19.1 Bubbling Fluidized-Bed Combustion . . . . . . . . . . . . . . . . . . . . . . . . 16.19.2 Circulating Fluidized-Bed Combustion . . . . . . . . . . . . . . . . . . . . . . . 16.20 Liquid-Fuel Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.20.1 Special Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.21 Burners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.21.1 Various Types of Burners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.21.2 Liquid-Fuel Burners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.21.3 Gun-Type Burners (Pressure Gun) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.21.4 Pot-Type Burners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1379 1379 1381 1381 1382 1382 1383 1383 1384 1384 1385 1385 1385 1385 1386 1386 1386 1386 1386 1386 1387 1387 1387 1387 1388 1388 1388 1388 1388 1388 1388 1388 1389 1390 1390 1390 1391 1391 1392 1392 1392 1393 1393 1393 1394

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1394 1394 1394 1394 1394 1394 1394 1395 1396 1396 1396 1396 1396 1396 1396 1396 1397 1397 1397 1397 1397 1398 1399 1399 1399 1400 1400 1401 1402 1402 1402 1402 1403 1403 1403 1403 1404 1404 1405 1405 1406 1406 1406 1406 1407 1407 1407

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16.22 General Furnace Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.22.1 Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.22.2 Forced Draft Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.22.3 Induced Draft Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.22.4 Balanced Draft (BD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.22.5 Primary Air Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.22.6 Stacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.22.7 Natural Draft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.22.8 Artificial Draught . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.22.9 Forced Draught . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.22.10 Induced Draught . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.22.11 Balanced Draught . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.23 Environmental Control Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.23.1 Particulate Emission Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.23.2 Electrostatic Precipitators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.23.3 Fabric Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.23.4 Pulse Jet Fabric Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.23.5 Shake-Deflate Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.23.6 Reverse-Air Fabric Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.23.7 Mechanical Collectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.23.8 NOx Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.24 Steam Generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.24.1 Types of Steam Generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.24.2 Boiler Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.24.3 Boiler Water Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.24.4 Shell-Type Steam Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.24.5 Natural Circulation Boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.24.6 Forced Circulation Boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.24.7 Boiling Water Reactors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.25 Parts and Components of Steam Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.25.1 Superheaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.25.2 Radiant Superheater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.25.3 Convective Heat Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.25.4 Pendent Superheater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.25.5 Platen Superheater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.25.6 Reheaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.25.7 Economizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.25.8 Feedwater Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.25.9 Air Preheaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.25.10 Recuperative Air Preheater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.25.11 Rotary or Regenerative Air Preheater . . . . . . . . . . . . . . . . . . . . . . . 16.26 Energy Balance Analysis of a Furnace/Combustion System . . . . . . . . . . . 16.26.1 Performance Analysis of a Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.26.2 Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.26.3 First Law Analysis of Combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.26.4 Boiler Fuel Consumption and Efficiency Calculation . . . . . . . . 16.26.5 Various Energy Losses in a Steam Generator . . . . . . . . . . . . . . . .

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Detailed Cont.

16.27 Performance of Steam Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.27.1 Boiler Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.28 Furnace Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.28.1 Heat Release Rate per Unit Volume qv . . . . . . . . . . . . . . . . . . . . . . . 16.28.2 Heat Release Rate per Unit Wall Area of the Burner Region 16.28.3 Heat Release Rate per Unit Cross-Sectional Area . . . . . . . . . . . 16.28.4 Furnace Exit Gas Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.28.5 Example Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.29 Strength Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.29.1 Mathematical Formulae for Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.29.2 Stress Analysis Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.29.3 Design Pressure and Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.30 Heat Transfer Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.30.1 Heat Exchangers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.30.2 Flow Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.31 Nuclear Reactors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.31.1 Components of a Nuclear Reactor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.31.2 Types of Reactors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.32 Future Prospects and Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Electrical Engineering Seddik Bacha, Jaime De La Ree, Chris Oliver Heyde, Andreas Lindemann, Antje G. Orths, Zbigniew A. Styczynski, Jacek G. Wankowicz . . . . . . . . . . . . . . . . . 17.1 Fundamentals Jacek G. Wankowicz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.1.1 Electric Field Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.1.2 Electric Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.1.3 Alternating Current (AC) Engineering . . . . . . . . . . . . . . . . . . . . . . . . . 17.1.4 Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.1.5 Materials and Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.2 Transformers Zbigniew A. Styczynski . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.2.1 Single-Phase Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.2.2 Instrument Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.2.3 Three-Phase Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3 Rotating Electrical Machines Jaime De La Ree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3.1 General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3.2 Induction Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3.3 Synchronous Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3.4 Direct-Current Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3.5 Fractional-Horsepower Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4 Power Electronics Andreas Lindemann . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.1 Basics of Power Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.2 Basic Self-Commutated Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1409 1409 1409 1409 1410 1410 1410 1410 1412 1412 1413 1413 1414 1414 1414 1414 1414 1415 1418 1418

1421 1422 1422 1424 1428 1434 1439 1442 1442 1446 1447 1448 1448 1451 1454 1456 1458 1461 1461 1462

Detailed Contents

1468 1475 1478 1478 1481 1485 1487 1487 1489 1490 1491 1495 1497 1502 1504 1505 1505 1507 1508 1509

18 General Tables Stanley Baksi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1511

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . About the Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Detailed Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1521 1523 1539 1561

Detailed Cont.

17.4.3 Basic Circuits with External Commutation . . . . . . . . . . . . . . . . . . . 17.4.4 Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5 Electric Drives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5.1 General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5.2 Direct-Current Machine Drives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5.3 Three-Phase Drives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6 Electric Power Transmission and Distribution Antje G. Orths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6.1 General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6.2 Cables and Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6.3 Switchgear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6.4 System Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6.5 Energy Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6.6 Electric Energy from Renewable Energy Sources . . . . . . . . . . . . 17.6.7 Power Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.7 Electric Heating Zbigniew A. Styczynski . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.7.1 Resistance Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.7.2 Electric Arc Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.7.3 Induction Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.7.4 Dielectric Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1559

1561

Subject Index

2-D laser cutting 673 3-D printing (3DP) 740, 744 3-D surface structure 816

A

B backscattered electron (BSE) 102 ballistic particle manufacturing (BPM) 740 ball–wedge bonding 699 base body 296 basis 12, 31 bath, molten 669 Bauschinger effect 563 beam 668, 669, 671 beam diameter 669 beam machining (BM) 651 beam penetration 671 beam penetration welding 669

beam splitter 674 belt track, rubber 1165 bendability 593 bending 591 – by buckling 591 – roll 591 – strain 591 Bessel point 806 best-fit 812 biased ply construction 1163 bill of materials (BOM) 1056, 1296 bill of operation (BOO) 1278, 1296 Bingham fluid 325 Bingham paste 325 biodegradable oil 317 bionic manufacturing system (BMS) 1322 blade kinematics 1170 blank holder 594 – pressure 596 blended wing body (BWB) 1027 blind hole 674 – groove 675 block construction 1178 block definition diagram (bdd) 1308 block diagram 1308 block-diagonal matrix 29 block-triangular matrix 29 body in white (BiW) 1059 body-centered cubic (bcc) 79 body-centered tetragonal (bct) 164 boiling water reactor (BWR) 1380 bonding 89 – thermocompression 699 – thermosonic 699 – ultrasonic 699 – wedge–wedge 699 – wire 699 boost chopper 1470 boring 671 boron carbide (B4 C) 217 boron nitride (BN) 217, 624, 631, 636, 637, 640, 655 bottom dead center (BDC) 604, 886, 920 bottoming cycle 1380 Boudouard reaction 1383 boundary – conditions 13 – friction layer 301

Subject Index

Abbe comparator principle 806 abrading process 674 abrasion 304 abrasive waterjet machining (AWJ) 647 absorption 672, 674 AC Controller 1480 accessibility 804 accuracy parameter 602 accurate clear epoxy solid (ACES) 761 ACES injection molding (AIM) 761 acoustic emission analysis 129 acoustic testing 127 Acousto-ultrasonic interrogation 140 acrylonitrile-butadiene-styrene (ABS) 207 AD Merkblätter 964 added value 656 additive 318 adhesion 306 ADI (austempered cast iron) 530 adjoint matrix 30 adjustment, space 810 adsorption of lubricants 313 advanced driver-assistance system (ADAS) 1023 advanced gas-cooled reactor (AGR) 1380 advanced legal issues in virtual enterprise (ALIVE) 1335 affinity diagram 795 age hardening 86 air cycle machine 1101 air transport system (ATS) 1026 aircraft 1027 algebraic multiplicity 31 alignment measuring system 819 allowance 801 aluminum 670, 673 – nitride (AlN) 217 – oxide (Al2 O3 ) 629 American Society of Mechanical Engineers (ASME) 960, 1303

amorphous solid 77 analytic 8 anisotropy 586 anisotropy coefficient 586 – planar 587 apparent contact area 297 application programming interface (API) 1316 aquadraw process 598 architecture of integrated information systems (ARIS) 1300 area reduction 575 – allowable 582 argon 673 Arrhenius law 88 arrow diagram 796 articulated steering 1165 artificial dilatation 670 ASME, PD 5500 & AD code 963 aspect ratio 674 assembly 656 assessment, online 672 augmented matrix 31 austempered ductile iron (ADI) 182 autocentering 811 autofocus sensor 820 autoignition 936 automated building construction system (ABCS) 1246, 1262 automatic cutter control system (ACCS) 1266 automatic tool change (ATC) 524 axial turbine 975, 976 axially moving screw drive 603 axle pivot steering 1165

1562

Subject Index

Subject Index

– layer 297 – lubrication 313 – value problem (BVP) 13 Bragg grating 140 brake – power 921 – specific fuel consumption 922 – thermal efficiency 922 brass 970 Bravais lattice 78 Brayton cycle, regenerative 1378 break mean effective pressure (BMEP) 921 break-in 308 Brinell hardness (BHN) 112, 531 bronze 204, 971 buck chopper 1468 – DC–DC converter 1482 buckling 599 – bending by 591 – limit 571 built-to-order supply chain (BOSC) 1313 bulk forming 554 Burgers vector 83 bursting 599 business – integrator 1335 – process reengineering (BPR) 1320 byproducts 673

C CAD/CAM environment 812 calibrated airspeed (CAS) 1113 calibrating laboratory 823 calibration 811 – standard 811 camber 584 camshaft 949 CANDU reactor 1380 capacity heat 124 capillary steam tube 669 car body 672 car development process (CDP) 1055, 1056 carbon steel 965 carburation 926 cartels 1352 Cartesian coordinate system 4, 807 cast metallurgy 90 casting, vacuum (VC) 762 catalyst, three-way 943

Cauchy – Riemann equations 8 – stress 561 cause–effect diagram 795 cavity geometry 670 cell pump 915 center pendulum pivot steering 1165 ceramics 673, 674 – refractory 214 ceramics, nonoxide 216 chain measuring 804 chain polymerization 204 chamber, combustion 987, 1007 characteristic equation 12, 31 characteristic polynomial 31 characteristic value 12, 30 characteristic vector 30 charge motion control valve (CMCV) 950 charpy V-notch (CVN) 970 chatter mark 581 checklist 794 chemical vapor deposition (CVD) 90, 315, 627 chemical-mechanical planarization (CMP) 646 chemisorption 313, 314 chevron crack 578 chlorofluorocarbons (CFC) 939 circuit, electric 1430 circular cutting method 674 circulation piston machine 915 circumferential velocity ratio 985 circumscribed circle 808, 817 closed-die forging 571 – force–displacement characteristics 572 CNC (computerised numerical control) 635 CO2 laser 669, 673 coating 315 cobalt 629 Coble creep 115 cofactor 28 cogging 572 coherency strain 86 coil ignition 933 cold forging 575 – tool-setup 579 cold milling machine 1174, 1175 cold upsetting 571 collaboration 1344, 1351, 1352 collaborative manufacturing system 1345

collaborative planning, forecasting, and replenishment (CPFR) 1313 collimation 669 column vector 27 columnar-to-equiaxed transition (CET) 721 columns 27 combined Brayton–Rankine cycle 1378 combustion – chamber 987, 1003, 1007 – chamber, low-pressure (LPCC) 1003 – engine 888, 919 – process 673 combustion engine 1024 commercial transport 1027 common-rail (CR) 932 communication 1337 compacted graphite iron (CGI) 182 compaction process 1171 company strategy 1332 comparative vacuum monitoring 141 compensating calculation 812 compensation method 807 competence trust 1348 complex – function 7 – number 4 – plane 4 – variable 7 composite material 76 compressed air energy storage (CAES) 989, 1002 compressed natural gas (CNG) 938 compression – ignition engine 937 – pump 908 – test 564 compression ignited (CI) 1024 compressor 889, 916, 987, 1007 – efficiency 926 – stage 973 computational fluid dynamics (CFD) 1058, 1067 computed tomography (CT) 758 computer numerical control (CNC) 1297 computer-aided – design (CAD) 812, 1297 – manufacturing (CAM) 1297 – manufacturing of laminated engineering material (CAM-LEM) 740 – planning (CAP) 1311

Subject Index

coordinate system, workpiece 810 corporate identity (CI) 1339 correct value 823 corrosion 141, 153, 717 – stress 130 corundum (Al2 O3 ) 640 Coulomb friction model 565 counter-blow hammer 602 counterbody 296 crack depth measurement 130 crack length 722 crank dead center (CDC) 901 crank press 602 crankshaft 897 – drive 897 creep 115 critical pitting temperature (CPT) 151, 969 critical resolved shear stress (CRSS) 186 critical-path method (CPM) 1312 crop harvesting 1177 crossover point 673 crystal 669 – defect 558 – lattice 675 cubic boron nitride (CBN) 624, 636, 637, 640, 655 cubic interstitial lattice 79 Cu–Ni alloy 971 curling 591 customer relationship management (CRM) 1310 cutter control, automatic system (ACCS) 1266 cutting 606, 669 – flat-sheet 673 – laser 652, 673 – method 674 – nozzle 673 – quality 674 – speed 673 – system, two-axle 673 CVD (chemical vapor deposition) 768 cylinder-individual fuel injection (CIFI) 927 cylindricity 817

D data interchange 1311 data processing 1275, 1296 DC–DC converter 1467 dead-zone 577

deep drawing 594 – force 597 – hydromechanical 598 deep welding 668, 672 defect 574, 588 – lattice 77 deflection 671, 958 deformation 806 degree of reaction 978 delivery rate 905 density 671 deposition modeling 739, 745 depth-to-width (D/W) ratio 714 design 657 – computer-aided (CAD) 812, 1297 – guidelines 841 – principles 839 – rules 839 design FMEA 873 design for robotic construction (DfRC) 1246, 1262 design for the environment (DFE) 872 design rules of the preform 571 destructive testing 959 determinant 28 development, product 827 deviation 821 deviatoric stress tensor 562 diagonal 28 diagram 795 – scatter 795 – tree 795 diameter beam 669 diamond (C) 631, 640 diamond-pyramid hardness (DPH) 112 diaphragm metering pump 910 die – cone angle 577 – failures in forging 574 – upsetting 572 dielectric heating 1514 diesel injection 929 diesel multiple unit (DMU) 1076 difference measuring 805 differential equation 9 – linear 9 – nonlinear 9 differential interference contrast microscopy (DIC) 101 diffuse necking 588 diffuser 997, 998 diffusion – bonding 89 – vacancy 89

Subject Index

– process planning (CAPP) 1297 – styling (CAS) 1061 computer-integrated manufacturing (CIM) 1297, 1356 computer-integrated manufacturing open system architecture (CIMOSA) 1300 concentricity 817 conception methods 836 concurrent engineering (CE) 523 condensation chain polymerization 204 conditions, boundary 13 conductivity, thermal 672 conductor 1445 conicity, parallelism 817 conjugate 5 connecting rod 897 connectivity 1350 consistency 325 consistent lubricant 319 constant shear friction model 565 constitutional liquid film migration (CLFM) 722 construction methods 834 contact – area 297 – geometry 300, 304 – time under pressure 602 continuous replenishment planning (CRP) 1313 continuous-cooling-transition (CCT) 165 continuously transmission variable 1180 continuously variable transmission 1180 contour crafting (CC) 739 contractual agreement 1352 contractual trust 1348 control chart 798 control module 950 – electronic (ECM) 942 control unit 932 control valve, charge motion (CMCV) 950 control, numerical (NC) 635, 1319 controlled rectifier 1474, 1480 conventional coil ignition 933 convolution 23 cooling 898 cooperation 1343 cooperative manufacturing unit (CMU) 1325 coordinate measuring machine (CMM) 755, 806

1563

1564

Subject Index

Subject Index

digital input output (DIO) 1319 digital mock-up (DMU) 1026, 1057 digitalization 812 dilatant fluid 325 dilatant paste 325 dilatation, artificial 670 dilatometry 124 diode 1468 diode-pumped 673 dip soldering 701 Dirac delta 20 direct – current (DC) 1454 – injection (DI) 929 – laser fabrication (DLF) 746 – metal deposition (DMD) 739 – metal laser sintering (DMLS) 747, 761 – numerical control (DNC) 1319 – redrawing 596 disassembly 656 disc laser 669 discursive methods 837 dislocation 558 dispersion strengthening 86 displacement pump 889 distance 4 – operating 818 distortion 669 disturbance variable 296 domain of definition 8 Dorn equation 116 double focus 670 double-acting hammer 602 double-fed induction generator (DFIG) 1505 down time 1079 Draft International Standard (DIS) 1300 drag line 674 draw bead 598 draw bending 591 drawing 801 drawing force 596 drawing machine – tube 600 – wire 600 drawing of tube 580 drawing with mandrel 580 dressing 641 drift 804 – velocity 122 drill hole diameter 674 drilling 671, 674 – machine 1177 driving resistance 1161

drop hammer 602 ductile to brittle transition (DBTT) 118 duplex stainless steel 969 dynamic – efficiency 1014 – measurement 800 – traction ratio 1163 dynamically working roller 1171

E earing 586 eccentric screw pump 913 economic order quantity (EOQ) 1312 eddy current 134 eddy-current foil sensor 141 effect analysis 796 effective pressure 921 effective stroke rate 602 efficiency 889, 905, 922, 1014 – mechanical 905, 922 – of the turbine 926 – thermal 922, 989, 993, 1015 – total 606 – volumetric 905, 919, 922 efficient customer response (ECR) 1313 E-GAS entrained flow gasifier 1384 eigensystem 30 eigenvalue 30 – problem 30 eigenvector 30 elastic work 601 elastohydrodynamic lubrication (EHL) 312 electric – circuit 1430 – drive 1484 – drive, drive control 1488 – drive, speed control 1486 – field 1428 – heating 1510 electrical conductivity 122 electrochemical grinding (ECG) 648, 655 electrochemical machining (ECM) 648, 649 electrochemical-discharge machining (ECDM) 648 electro-discharge grinding (EDG) 656 electro-discharge machining (EDM) 647, 648

electrolytic in-process dressing (ELID) 641 electromagnetic compatibility (EMC) 799, 1456 electromagnetic testing 134 electron backscatter diffraction (EBSD) 105 electron beam machining (EBM) 648, 651, 654 electron beam melting (EBM) 751 electron beam welding 678 electron energy loss spectroscopy (EELS) 104 electron probe microanalysis (EPMA) 104 electron spectroscopy for chemical analysis (ESCA) 105 electronic – control module (ECM) 942 – control unit (ECU) 932 – data interchange (EDI) 1311 – data processing (EDP) 1275, 1296 – ignition 934 electrostatic field 1429 electrostatics precipitator (EP) 1402 elementary methods of plasticity 564 emission 939 – thermionic 672 EN13445 961 energy 668 – input 668 – solar 1503 – transfer 973 – volume-specific 890 energy dispersive x-ray spectrometer (EDX) 103 engine – spark ignition 935 – twin-spool 997 – type 919 enhanced functional flow block diagram (EFFBD) 1308 enterprise collaboration 1352 enterprise network 1343, 1351 – hyperarchy-type 1350 enterprise resource planning (ERP) 1270, 1275, 1310 enterprise, virtual 1335 entry into service (EIS) 1027 environmental condition 806 Environmental Protection Agency (EPA) 940 equilibrium 672 equivalent airspeed (EAS) 1113

Subject Index

F face-centered cubic (fcc) 79 factory 1343 – super construction (SCF) 1263 facts of life 1343 failure mode and effect analysis (FMEA) 796 failure tree analysis 796 farming 1176 fast breeder reactor (FBR) 1424 fast Fourier transform (FFT) 715, 817 fatigue 304 – analysis 963 fatty acid methyl ester (FAME) 939 federal air regulation (FAR) 1131 Federation of European Producers of Abrasives (FEPA) 640 feeder 1173 femtosecond 675 ferritic steel 970 fiber 669

fiber Bragg grating 140 field inspection, residual 132 filler wire 671 filling 574 filling level 905 film lubrication, fluid 311 film parameter 300 filtering property 21 fine-edge blanking 671 finish tolerance 801 finite element formulation – explicit dynamic elasto-plastic 568 – implicit static elasto-plastic 568 – rigid-plastic 567 finite element method (FEM) 635 finite element modeling (FEM) 1058 fireclay 215 first-order ODE – explicit form 9 – implicit form 9 – linear 10 – separable 10 fishbone diagram, Ishikawa diagram 795 five-axle laser 673 fixed/floating tubesheet 965 flame 671 flanges 956 flash 571 flashless die forging 572 flat product (plates) 967 flat rolling 582 flatness 817 flat-sheet cutting 673 flow – block diagram 1308 – coefficient 978 – condition 562 – curve 564 – forming 585 – forming process 585 – gasifier 1384 – nonquadratic 588 – rule 563 – stress 562 flow condition, von Mises 562 flow description markup language (FDML) 1315 flue gas desulphurization (FGD) 1404 fluid – Bingham 325 – dynamics 1058, 1067 – film lubrication 311

– force 892 – forming 598 – friction 302 – lubricant 315 – Newtonian 322 – non-Newtonian 325 fluidized-bed combustor (FBC) 1396, 1404 flywheel 603 FMEA (failure mode and effect analysis) 873 focus 671 – depth 669 – diameter 669 – matrix 670 focusability 668, 669 focused factory 1343 focused ion beam (FIB) 103 foil sensor 141 folding 591 footprint 1163 force 806 – rolling 583 force on the transmission 893 force resultant 585 forced draught (FD) 1402 force–displacement curve 575 forces model 1162 forged product – failure 574 forging 571, 572 – closed-die 571 – open-die 568, 571 – radial 572 – spread (cross) 572 form and position measuring 816 form and position tolerance 801 form tolerance 802 formability of sheet metal 588 formation of melt 675 forming 568, 585 forming limit diagram (FLD) 589 forming machine 599, 600 – energy controlled 601 Fourier integral representation 26 Fourier transform infrared spectral analysis 941 Fourier transform pair 25 four-point probe 130 four-quadrant single-phase bridge 1471 four-stroke engine 920 fourth-order Runge–Kutta method (RK4) 11, 33 Fraunhofer Institut für Lasertechnik (ILT) 749

Subject Index

equivalent plastic strain rate 563 Erichson – index (IE) 589 – test 589 etch pit 85 Euler turbine equation 975 Euler’s formula 6 eutectic temperature 97 evaluation 799 evanescent coupling display device (ECDD) 772 evaporating point 672 evaporative laser cutting 673 event driven process chains (EPC) 1304 excavator 1168 – mobile 1169 exhaust gas recirculation (EGR) 941, 944 Expansion Joint Manufacturer’s Association (EJMA) 962 expected standard 1344 explosive forming machine 600 extended enterprise 1333 – major characteristics 1357 extended enterprises (E2) 1328 external current 671 external magnetic field 671 extreme pressure (EP) 626 – additive 314 extrinsic property 81 extrusion 575

1565

1566

Subject Index

Subject Index

free bending 591 free forming 568 free probing system 813 free round bending 591 freeform powder molding (FPM) 740 friction 301, 302 – coefficient 301, 303 – energy 307 – force 301 – hill 583 – mechanism 302 – model 564, 565 – model, constant shear 565 – power 301 – solid 301 – state 301 – type 301 – work 301 fuel 937 – cell 1508 – cell-microturbine power 1379 – injection 926, 927 – injection control system 927 – injection, sequential (SEFI) 927 – supply system 929 – weight 1127 fullerene 80 fullering 571 full-frame construction 1179 function – complex 7 – relationship 830 functional performance 830 furnace exit gas temperature (FEGT) 1395 fused deposition modeling (FDM) 739, 745 fusion laser cutting 673 fusion welding 668 future project office (FPO) 1026

G galling 579 galvo-mirror 669 gamma-ray testing 139 gas generation spool 987 gas jet 672, 673 gas metal arc (GMAW) 972 gas tungsten arc (GTAW) 972 gas turbine 988, 995, 998, 1013 – combined cycle gas turbine (CCGT) 1002 – multispool 996 – shutdown 1003

– single-spool 1005 – startup 1003 – ultrahigh efficiency 995 – ultrahigh-efficiency (UHEGT) 1013 gas turbine engine 987 – component 987 – power generation 987 – single-spool 988 gasoline direct injection 927 gathering 571, 572 gauge 800, 803 Gauss 808, 817 gear pump 911 Geiringer equations 566 general arrangement (GA) 1026 generalized eigenvector 31 generalized enterprise reference model architecture and methodology (GERAM) 1300 generation 812 geometric multiplicity 31 GJL (lamellar graphite cast iron) 947 glass 213 glass ceramics 213 glass measuring 809 global positioning system (GPS) 1270 global village company 1358 GMA torch 683 GMA welding 682 goodwill trust 1348 grader 1170 grades, stainless steel 971 GRAI integrated methodology (GIM) 1302 grain harvesting 1177 graphite iron, compacted (CGI) 182 grease 319, 320 greenhouse gas (GHG) 860 grinding 648, 655 grinding with continuous dressing (CD grinding) 641, 642 Guillet diagram 168

H halide lamp 672 hammer 602 – counter-blow 602 hardening 562 – strain 559 hardness – Rockwell 112 – Vickers 112

hardware-in-the-loop (HIL) 1069 harmonic 24 harvesting, root crop 1178 hazard category 819 head dead center (HDC) 901 heading 571 heads – ellipsoidal 956 – hemispherical 956 – torispherical 956 health monitoring 126, 140 heat – affected zone (HAZ) 966 – capacity 124 – conduction 668 – conduction welding 668 – distortion 671 – exchanger 964 – input 669 – treatment 966 heated flame ionization detector (HFID) 941 heating 1513 heating behavior 675 heavier than air (HTA) 1102 Hecker’s test 589 helix 674 Hencky equations 566 hexagonal closed packed (hcp) 79, 557 high density polyethylene (HDPE) 158, 206, 865 high efficiency machining (HEM) 635 high performance 656 high pressure 673 high-power laser 673 high-pressure combustion chamber (HPCC) 1003 high-pressure turbine (HPT) 985, 1003 high-speed cutting (HSC) 633, 733 high-speed cutting thin-sheet 673 high-speed machining (HSM) 634, 733 high-speed steel (HSS) 626, 628 high-speed thin-sheet cutting 673 high-strength low-alloy steels (HSLA) 178 high-technologies 657 histogram 794 holomorphic 8 holonic manufacturing systems (HMS) 1322 hoop stress 954 HRC (hardness Rockwell cone) 635

Subject Index

humidity 821 humping 670 hydraulic counter-pressure deep drawing 598 hydraulic excavator 1168 hydrodynamic lubrication 311 hydroforming 598 – tube 598, 599 hydrogen-assisted cold cracking (HACC) 717 hydrogen-assisted cracking (HAC) 717 hydrogen-assisted stress corrosion cracking (HASCC) 717 hydromec process 598 hydropower 1506 hydrostatic lubrication 313 hydrostatic stress 562 hyper-elasticity 568 hypo-elastic model 568 hysteresis 804

ideal combustion cycle 888 ideal equivalent plastic strain 569, 575 ideal equivalent plastic strain rate 569 ideal limiting drawing ratio 595 identity matrix 28 IGBT (insulated gate bipolar transistor) 1468 IGBT power semiconductor 1481 ignition 672, 934 – engine compression 937 – temperature 673 – timing 935 illumination 809 image-processing system 810 imaginary axis 4 imaginary part 4 imaging microscopy 105 impact extrusion 575 impedance spectroscopy 141 impression die forging 572 improvement process (CIP) 1321 impulse 20 in situ road maintenance 1175 incoherent 669 incomplete filling 574 index, Erichson (IE) 589 indicated airspeed (IAS) 1113 indicated efficiency 905 indicated power 921 indicating range 804

International Federation for Information Processing (IFIP) 1300 International Marketing and Purchasing (IMP) 1350 interorganizational collaboration 1344 interstitial site 79 intrinsic material property 81 intuitive methods 836 inventory control, statistical (SIC) 1311 inverse 29 inversion point 805 inverter 1467–1480 invertible 29 ion beam 103 ion-induced secondary electron (IISE) 103 iron soldering 701 ironing process 580 irreducible polynomial 22 Ishikawa diagram 795 IT 619, 626

J Java intelligent network infrastructure (Jini) 1325 joining micro process 697 joining techniques 656 JP5 system (JP5) 740 just in time (JiT) 1320 just-in-time (JIT) manufacturing 1355

K kerf 672, 673 key performance indicator (KPI) 1294 keyhole 669 Kikuchi band 105 kinematic hardening 563 kinematically admissible velocity field 565 knock 936 Knoop hardness HK 0.1 640

L labeling 671 Lame’s solution 955 laminar composition 218 laminar jet 674

Subject Index

I

indirect diesel injection (IDI) 929 indirect rapid tooling 762 induced draught (ID) 1402 induction heating 1513 inert gas 673 inertial force 892 – oscillating 893 – rotating 892 information and communication technology (ICT) 1275, 1297 information content 804 information technology (IT) 1350 information-interoperable environment (IIE) 1315 initial condition 9 initial grasping 582 initial-value problem 9 injection 926, 927, 929 – nozzle 675 – port 927 – throttle body 927 innovative 657 input energy 668 input variable 296 inscribed circle 808, 817 inside diameter (ID) 645 inspection equipment 823 inspection method 823 inspection planning 823 Institute of Electrical and Electronics Engineers (IEEE) 1297 insulator 1445 integrated circuit (IC) 217, 699 integrated company 1344 integrated information, architecture of systems (ARIS) 1300 intensity 668, 672, 818 inter granular corrosion (IGC) 959 interaction – tribological 300 interfacial medium 296 interference 821 interferometer 821 interferometric display device (IDD) 768 internal block diagram (IBD) 1308 internal combustion engine (ICE) 919, 1024 International Center for Diffraction Data (ICDD) 99 International Civil Aviation Organization (ICAO) 1020, 1108 International Federation for Automatic Control (IFAC) 1300

1567

1568

Subject Index

Subject Index

laminated object manufacturing (LOM) 737, 740, 744 lamp-pumped 669 landing weight 1127 Lankford parameter 586 Laplace – transform 15 – transform operator 15 – variable 15 laser 668, 818 – fabrication 746 – flash method 126 – head 671 – operating time 672 – photolithography (STEREOS) 740 – radiation 672–674 – scanner 819 – sintering (EOSINT) 740 – system 668 laser beam (LB) 652, 668 – cutting 672 – drilling 674 – machining (LBM) 651 – source 668 – welding 668, 670, 700 – welding, magnetically supported 670 laser cutting (LC) 652, 673 – oxygen 673 laser diodes 669 laser engineered net shaping (LENS) 751 laser sintering 740, 745, 751 laser-assisted cutting – oxygen 673 laser-assisted machining (LAM) 656 LASOX technique 673 lateral resolution 102 lattice – Bravais 78 – defect 77 – primitive cubic 77 launching ratio 670 layer manufacturing (LM) 739 layer, boundary 297, 301 lens system 668, 674 lens, thermal 669 Levy–Mises flow rule 563 life cycle 657, 861 – analysis (LCA) 860 – economic 826 – inventory (LCI) 860 – technical 826 light color 818

light duty vehicles (LDV) 1021 light microscopy 101 light water reactor (LWR) 1380 lighter than air (LTA) 1102 limit of error 804 limiting drawing force 596 linear expansion coefficient 806 linear independence 11 liquefied natural gas (LNG) 938 liquefied petroleum gas (LPG) 938 liquid phase 673 livestock farming 1176 load 958 – tribological 300 load coefficient 978 loader, wheel 1167 localized necking 588 lock bead 598 long-range order (LRO) 77 loss variable 296 low-alloy steel 966 low-density PE (LDPE) 206 lower allowance 801 lower bound method 566 lower heating value (LHV) 922 lower-triangular matrix 28 low-pressure – combustion chamber (LPCC) 1003 – compressor 987 – turbine (LPT) 985, 987, 1003 lubricant 315 – aging 322 – consistent 319 – property 322 – solid 315, 321 lubricating grease 319, 320 lubricating oil 315 lubrication 312, 313 – boundary 313 – mixed 314 – partial 314 – procedures 579 – state 311 lubrication of piston machine 898 Lüder’s strips 588 Ludwik flow curve 589

M machine – piston 886 – rolling 600 – tool 524 – work 885

machining 648, 649 – plasma arc (PAM) 648 – robot-guided 671 – spark erosion (SEM) 647 – ultrasonic (USM) 650 machining beam (BM) 651 magnetic – Barkhausen noise 133 – field 670, 671 – flux inspection 132 – forming machine 600 – particle inspection (MPI) 131 – pulse welding (MPW) 723, 724 – resonance imaging (MRI) 755 – stray flux 131 – testing 131 magnetically supported laser beam welding 670 magneto-fluid-dynamic mechanism 670 magnetohydrodynamics (MHD) 1384 magnitude 4, 6 Magnox 1380 main diagonal 27 maintenance – road 1174, 1175 – total productive (TPM) 1294, 1320 mandrel 580 manual soldering 701 manufacturers weight empty (MWE) 1127 manufacturing 657, 737, 740, 744 – shape deposition (SDM) 740 Manufacturing Enterprise Solutions Association (MESA) 1313 manufacturing execution system (MES) 1275, 1313 manufacturing resources planning (MRP II) 1309 manufacturing system 1356 – bionic (BMS) 1322 – collaborative 1345 – demand/customer driven 1344 manufacturing unit 1325 mapping 8 Markov’s variational principle 567 markup language 1315 martensitic steel 970 mass balancing 894 mass balancing on multi-cylinder machine 895

Subject Index

meridional stress 954 meridional velocity ratio 985 mesh points 11 message channel 1050 metal 668 – deposition 739 – forming 554 – laser sintering 747, 761 – vapor 668, 670, 672 metallic filter 675 metallic material 76 metal-matrix composite (MMC) 631 metering pump 908, 910 method of undetermined coefficients 13 methyl t-butyl ether (MTBE) 943 metra potential method (MPM) 1312 metrology 813 Meyer hardness 112 microanalysis 104 microbiologically influenced corrosion (MIC) 153 microelectromechanical system (MEMS) 768 microjet procedure (LMJ) 674 microjoining 656 microscopy 101 microscopy imaging 105 microsoldering process 701 microstructural failure 574 microsystems technology 697 microtome 101 microwelding 671 – process 698 mild steel 673 mini-excavator 1168 minor 28 mirror 668 mirror, parabolic 670 miscibility gap 97 mixed – friction 302 – lubrication 314 mobile excavator 1169 mobile working machine 1161, 1178 modal matrix 31 mode quality 673 modeling 1058 modulus 6 molten – bath 669 – material 672

– pool 672 – puddle 668 molybdenum 629 moment, rolling 584 monitoring 672 monocrystalline diamond (MCD) 631 MOSFET (metal oxide semiconductor field effect transistor) 1468 MOSFET power semiconductor 1481 motorized air cycle machine (MAM) 1101 multi-agent systems (MAS) 1313 multibeam 670 multisensor technology 808 multi-staging 918 Muntz metal brass 203

N Nabarro–Herring creep 115 nanosecond 675 nanotechnology 657 National Association of Corrosion Engineers (NACE) 966 natural gas 1383 NC 677, 738 Nd:YAG 672, 673 – laser 670, 671 – solid-state laser 669 near-net shaped parts 555 necking 110, 588 neighborhood 8 net positive suction head (NPSH) 907 net-shaped parts 555 network analysis 1443 network types 1346 neutral plane 582 Newtonian fluid 322 nickel (Ni) 629 niobium carbide (NbC) 722 nitrogen 673 NOx -particulate tradeoff 944 nobility of metals 146 noise–vibration–harshness (NVH) 1022 nominal size 801 noncontact probing system 813 nondestructive evaluation (NDE) 126 nondestructive inspection (NDI) 126

Subject Index

material 656 – characteristics 832 – interaction 668 – synthetic 673 materialography 100 materials requirement planning (MRP) 1309 matrix 27 – augmented 31 – block-diagonal 29 – block-triangular 29 – diagonalizable 32 – diagram 796 – element 27 – entry 27 – lower-triangular 28 – modal 31 – nonsingular 28 – rectangular 27 – size 27 – square 27 – transpose 28 – upper-triangular 28 – zero 27 maximum landing weight (MLW) 1127 maximum zero fuel weight (MZFW) 1127 mean down time (MDT) 1079 mean effective pressure (MEP) 921 mean piston speed 921 mean time between failure (MTBF) 1079 measurement 672, 799 – standard 800 – static 800 – uncertainty 818 – value 822 measuring – chain 804 – deviation 822 – force 806 – object 800 – range 804, 815, 818 – room 806 – spot diameter 818 – tolerance 801 – uncertainty 804, 822, 824 mechanical – efficiency 905, 922 – probe system 809 melt 673 melting 751 melting temperature 668 membrane theory 585

1569

1570

Subject Index

Subject Index

nondestructive testing 119, 126 – liquid penetrant examination 959 – magnetic particle examination 959 – radiographic examination 959 – ultrasonic techniques 959 nondispersive infrared (NDIR) 941 nonhomogeneous second-order ODE 13 nonlinear dynamic method 997 non-Newtonian fluid 325 nonoxide ceramics 216 nonproductive time 671 nonquadratic flow 588 nonsingular matrix 28 nonvacuum electron beam welding (NV-EBW) 678 normal direction (ND) 106 nozzle 672, 675, 998 NPSH (net positive suction head) 907 nth root 7 numbering system 171 numerical control (NC) 635, 1319 numerical method 567 numerically controlled equipment (NCE) 1313

O object linking and embedding (OLE) 1315 oblique flying wing (OFW) 1027 Ohm’s law 122 oil 315 – biodegradable 317 – lubricating 315 – mineral 315 – synthetic 316 oil pocket 675 OLE for process control (OPC) 1315 Olsen test 589 one bucket excavator 1168 one excavator bucket 1168 online assessment 672 open connectivity via open standards (OPC) 1315 open robot interface for the network (ORiN) 1314 open-die forging 568, 571 operating distance 818 operating variable 300 operating weight empty (OWE) 1127 operation technology 668

optical fiber 668 optical sensor 671 optical system 674 orange skin 588 order quantity 1312 ordinary differential equation (ODE) 9 – homogeneous 10 – linear 11 – nonhomogeneous 10 – nonlinear 11 – order 9 – particular solution 9 Organisation for Economic Co-operation and Development (OECD) 1018 organization, virtual (VO) 1328, 1333 orientation imaging microscopy (OIM) 105 oscillating inertial force 893 Ostwald ripening 86 output signal 804 over fire air (OFA) 1404 overlap ratio 298 oxide dispersion strengthened (ODS) 217 oxy-gas flame 673 oxygen 673 – jet 673 – laser cutting 673

P package freeze 1060 paper 673 parabolic mirror 670 parallel gap welding 698 parallelism conicity 817 parameter 9 Pareto analysis 795 partial differential equation (PDE) 9 partial frame construction 1178 partial lubrication 314 partially melted zone (PMZ) 721 particulate (PM) 1020 paver tractor 1172 PD 5500 962 pebble bed reactor (PBMR) 1380 Peierls stress 86 penetration beam 671 penetration depth 325 penetration effect 669 penetration testing 137 penetration welding 669

percussion 674 – drilling 674 performance 669, 830 periodic 24 persistent slip band (PSB) 119 phase 6 – shift 821 physical simulation 567 physical vapor deposition (PVD) 90, 315, 627 physisorption 313 picosecond 675 pinhole 670 pipe connection, rotary 1169 piston 898 – acceleration 892 – machine 886, 898 – machine, single rotation 911 – pump 900 – pump, single rotation 912 – ring 898 – speed 891, 921 – travel 891 pitting temperature 151, 969 P-kinematic 1167 plane adjustment 810 plane strain Young’s modulus 593 plane stress condition (PSC) 712 plane stress state 561 planetary rotation piston machine 913 planning and scheduling language on XML specifications (PSLX) 1315 plant automation based on distributed systems (PABADIS) 1327 plant protection 1177 planting machine 1177 plasma 671 plasma arc machining (PAM) 648 plasma beam machining (PBM) 651 plasma diagnostics 672 plastic (permanent) strain 561 plastic strain, total equivalent 564 plasticity 564 plastics 673 plate heat exchangers (PHE) 972 ply construction, radial 1163 point adjustment 811 Poka Yoke 796 polar form 6 pole 18 polyaddition 205 polycondensation 205 polycrystalline (PC) 633

Subject Index

preform process 571 pre-ignition 936 premultiplication 29 press – eccentric 604 – energy controlled 602 – force controlled 602 – hydraulic 605 – knuckle-joint 604 – mechanical 604 – servomotor 605 – stroke controlled 604 – Vincent 603 pressure 821 – bar 1173 – Equipment Directive (PED) 960, 964 – thin-shell vessels 953 – valve (PV) 901 pressurized water reactor (PWR) 1380 pre-stressing 955 preventive – monitoring 801 – technique 794 primitive cubic lattice 77 principal radius 585 principal value 6 principle of superposition 11 principle of volume constancy 561 printed wiring board (PWB) 870 private network 1319 probe element 809 probe system 813, 815 – mechanical 809 problem-resolving technique 794 process 656 – control 799 – control, statistical (SPC) 797 – –decision diagram 795 – emission 672 – FMEA 873 – limit 571 – quality 670 – reliability 669 – stability 670 – tribological 300 – work 600 processing time 671 product – development 827 – life stages 826 – planning 827 – tracking 826 – virtual 1359

production planning and control (PPC) 1297, 1309 product–resource–order–staff– architecture (PROSA) 1323 profile rolling 582 programming interface, application (API) 1316 project evaluation and review technique (PERT) 1312 projection welding 698 protection – plant 1177 – short-circuit current 1497 prototype 812 pseudoplastic fluid 325 pseudoplastic paste 325 puddle 668 pulse 20 – length 675 pulsed – energy 671 – laser 671, 674 – light 669 pump – piston 900 – screw 913 pump power 606 Purdue enterprise reference architecture (PERA) 1302 pure imaginary 4

Q quality 669, 670, 673 – assurance (QA) 524 – capability 795 – control chart 798 – function deployment (QFD) 796 – management methods 793 – management system (QMS) 799 – management, total (TQM) 1294, 1320 – monitoring 672

R radial – forging 572 – ply construction 1163 – turbine 976 radians 6 radiation 668, 674 radiofrequency identification (RFID) 1313 radiographic testing 138

Subject Index

polycrystalline cubic boron nitride (PCBN) 631 polycrystalline diamond (PCD) 631 polyethylene terephthalate (PET) 865 polymer 204 polymer electrolyte fuel cell (PEMFC) 1508 polymerization – chain 204 – condensation chain 204 polymorphic 79 polystyrene-butadien-rubber (SBR) 207 port injection 927 position deviation 821 position tolerance 802 positive displacement compressor 889 positive displacement pump 889 post weld heat treatment (PWHT) 966 potential drop method 130 powder diffraction file (PDF) 99 powder diffraction method 99 powder metallurgy (PM) 89, 628 power 890 – brake 921 – density 669 – generation 990 – lift linkage 1181 – machine 885 – output 668 – quality 1508 – semiconductor 1481 – semiconductor diode 1481 – spectral densities (PSD) 1082 – supply 1391, 1467, 1473, 1474, 1479, 1483 – system distribution 1493 – take-off (p.t.o.) 1179 power system transmission 1493 – cable 1495 – energy storage 1501 – line 1495 – protection 1497 – renewable energy source 1503 – switchgear 1496 powertrain control module (PCM) 950 P-profile 814 practice 657 Prandtl–Reuss equations 568 precipitate coarsening 86 precipitation strengthening 86 precipitator 1402

1571

1572

Subject Index

Subject Index

radioscopy 138 rail vehicle 668 ramp function 20 range 8 – of application 804 – stoichiometry 81 rank 28 Rankine cycle 1378 rapid prototyping (RP) 733, 737 rapid tooling 762 rational unified process (RUP) 1308 reactive ion etching (RIE) 768 reactor 1380, 1424 – pebble bed (PBMR) 1380 – pressurized water (PWR) 1380 – RBMK (Chernobyl type) 1380 real – axis 4 – contact area 297 – part 4 reciprocating machine 886 reciprocating pump 899 recovery 559 recrystallization 559 – temperature 559 rectangular form 4 rectangular matrix 27 rectifier 1467, 1483 – uncontrolled 1474 recycler 1175, 1177 recycling 657 reduced-instruction-set computer (RISC) 1330 reducing 575 reference probe 811 reference-surface probing system 815 reflow soldering 702 refraction index 669 refractometer 821 refractory ceramics 214 regenerative Brayton cycle 1378 regression equation 808 reheat turbine (RT) 989 relaxation, stress 116 reliability 669 reliability, availability, maintainability, safety (RAMS) 1078 remote welding 669, 671 replenishment planning, continuous (CRP) 1313 residual field inspection 132 residual stress 581, 593

resistance – tractive 1162 – welding 698 resistivity 122 resolution 818 resolution lateral 102 resonance testing 129 resonator 673 resource planning 1270, 1275, 1310 resource-based view (RBV) 1286, 1293 resources planning 1309 response time 804 reverse engineering (RE) 753 reverse redrawing 596 revolutions per minute (rpm) 921 risk priority number (RPZ) 875 road maintenance 1174, 1175 road paver 1172 robot access object (RAO) 1315, 1316 robot action command (RAC) 1319 robot resource definition (RRD) 1315 robot-guided machining 671 robots 669 Rockwell hardness 112 rod system 669 roll – bending 591 – forming 591 – straightening 591 rolling 581 – direction (RD) 106 – force 583 – machine 600 – moment 584 – thread 583 room temperature (RT) 206 root crop harvesting 1178 root-mean-square (rms) 300 rotary – pipe connection 1169 – piston machine 886 – piston pump 900 – screw pump 913 – transmission leadthrough 1169 rotatable mirror 671 rotating electric machine 1454 – induction machine 1457 – step motor 1466 – synchronous machine 1460 rotating inertial force 892 roughness 300, 813 – surface 300 round bending 591

roundness 817 rows 27 R-profile 814 rubber belt track 1165 ruby bearing 674 run tolerance 802 Runge–Kutta method 11, 33 run-out 817 rupture 580 – tearing 588

S SA welding 682 Sanders model maker (SMM) 739 scale division value 804 scanner 669, 671 – -based process 671 – system 669 – welding 671 scanning 811 scanning Auger electron spectroscopy (SAM) 105 scanning electron microscopy (SEM) 86, 102 scatter diagram 795 scheduling 1312 Schottky defect 82 scraper 1170 screed 1172 screw drive, axially moving 603 screw press 603 screw pump 913 seam welding 698 secant modulus 210 secondary electron (SE) 102 secondary ion (SI) 103 secondary-ion mass spectroscopy (SIMS) 105 segmented blank-holder 598 selective laser sintering (SLS) 740, 745, 751 selective noncatalytic reduction systems (SNCR) 1404 semiconductor 1445 semiconductor power 1481 sensor, triangulation 820 sequential fuel injection (SEFI) 927 sequential probe 811 severity index 590 SHADOW method 671 shape deposition manufacturing (SDM) 740 shape tolerance 801 shear forming 585 shear strength 558

Subject Index

– implicit 9 – particular 9 – solid 80 space – adjustment 810 – limit payload (SLPL) 1127 – of activity (SoAs) 1325 spark electro-discharge machining (SEDM) 647 spark erosion machining (SEM) 647 spark ignited (SI) 1024 spark ignition engine 935 spattering 670 specific fuel consumption (SFC) 922, 1132 speckle testing 137 spectral analysis 941 spot diameter 818 spot welding 698 spread (cross) forging 572 springback 593 square matrix 27 squareness 817 stability 670 stability condition 568 stacking fault energy 86 stainless steel 673, 966, 969 – grades 971 – superferritic 970 standard 1344 standard hydrogen electrode (SHE) 142 standard rectangular form 5 standardized assessment of readiness and interoperability for cooperation in new product development in virtual organization (ARICON) 1334 start of production (SOP) 1058 state variables 32 state-of-the-art 656 state-variable equations 32 static measurement 800 statically admissible stress field 566 statically working roller 1171 stationary state 668 statistical inventory control (SIC) 1311 statistical process control (SPC) 797 statistical research planning 796 steam turbine operated Rankine cycle 1378

steel 79, 674 – pester 169 – plate 673 steering – articulated 1165 – skid 1165 step function 19 step size 11 stereolithography (SL) 742 stereolithography language (STL) 738 stiffness of forming press 601 stoichiometry range 81 straightness 817 strain – bending 591 – coherency 86 – hardening 559 – rate 563, 569 – rate tensor 561 – softening 562 – total 560 streamlined life cycle analysis (SLCA) 861 stress – Cauchy 561 – corrosion 130 – meridional 954 – relaxation 116 – residual 581, 593 – tensor 561, 562 – true 561 stress field – statically admissible 566 stress state – plane 561 – uniaxial 561 Stribeck curve 303 stroke rate 602 structural 656 structural health monitoring (SHM) 126, 140 structured query language (SQL) 1315 submatrix 27 suitability 672 sum 27 super construction factory (SCF) 1263 supercharging 924 supercritical (SC) 1376 superferritic stainless steel 970 superplasticity 116 superposition 11 supervisory control and data aquisition (SCADA) 1325

Subject Index

shear stress 186 shear turning process 585 sheet forming – high-pressure 598 – processes 555, 585 sheet hydroforming 598 shielded metal arc (SMAW) 972 Shimizu manufacturing system by advanced robotics technology (SMART) 1264 shipbuilding 668 short-range order (SRO) 77 shrink ring 579 silicon carbide (SiC) 217, 640 silicon nitride (Si3 N4 ) 630 silicon wafer 674 similar 31 similarity transformation 31 simple pressure vessel (SPV) 960 simple tension test 564 simple test tension 564 simulative formability test 589 simulative test formability 589 single laser pulse 671 single overhead camshaft (SOHC) 949 single rotation piston machine 911 single rotation piston pump 912 single-phase bridge 1471 singular 28 skew-symmetric 28 skid pick-up 813 skid steering 1165 slag 673 slice(d) file format (SLI) 739 slip 1162 slip band, persistent (PSB) 119 slip line field solution 566 softening strain 562 soil 1161 – pressure 1163, 1164 solar energy 1503 soldering reflow 702 soldering, wave 702 solid friction 301 solid ground curing (SGC) 740, 744 solid lubricant 315, 321 solid lubrication 315 solid solution 80 solidification cracking temperature range (SCTR) 722 solidifying 669 soluble organic fraction (SOF) 941 solution 9 – explicit 9 – general 9, 12

1573

1574

Subject Index

Subject Index

supply chain (SC) 1293, 1354 – management (SCM) 1276, 1310, 1355 – operations reference (SCOR) 1333 surface 668 – characteristic 815 – coating 315 – defect 574, 588 – fatigue 304 – finish tolerance 801 – metrology 813 – mounted device (SMD) 702 – roughness 300 suspension 899 swaging 572 symmetric 28 symmetrically loaded shell of revolution 954 synthetic – materials 673 – natural gas (SNG) 1383 – oil 316 system FMEA 873 system international (SI) 1104 systems engineering 669 systems modelling language (SysML) 1308

T tall towers – wind induced deflection 958 – wind induced vibration 958 – wind load 958 tamper 1173 tantalum carbide (TaC) 629 Taylor principle 803 teach-in 812 tearing 596 technology 656 temperature 821 – for measurement 806 – resistivity coefficient 123 temperature-sensitive material 674 tensile strength, ultimate (UTS) 110 tensor – strain rate 561 – stress 561, 562 test – biaxial stretch 589 – Hasek 590 – hole expansion 589 – hydraulic bulge 590 – Marciniak 590 – Nakamiza 590

– plane torsion 589 – stretch-bend 589 – Swift’s cup 589 – torsion 564 – uniaxial tensile 590 – wedge drawing 589 testing 134, 139, 959 – gamma-ray 139 – nondestructive 119, 126 – phases 829 – radiographic 138 – resonance 129 – speckle 137 – thermographic 135 – ultrasonic 127 – visual 136 tetramethyl ammonium hydroxide (TMAH) 772 textiles 673 texture 582 thermal conduction welding 668 thermal conductivity 672 thermal efficiency 922, 989, 993, 1015 thermal lens 669 thermionic emission 672 thermocompression bonding 699 thermographic testing 135 thermoplastics 206 thermosonic bonding 699 thickness assessment 134 thread rolling 583 three-bar linkage 1181 three-fourth frame 1178 three-way catalyst 943 threshold limit 804 throttle body injection 927 thyristor 1468 – power semiconductor 1481 tillage 1176 tilting error 806 time compression technology (TCT) 733, 737 time-of-flight difference 129 titanium – -aluminum nitride (TiAlN) 627, 628 – carbide (TiC) 628, 629 – carbonitride (TiCN) 628 – diboride (TiB2 ) 217 – nitride (TiN) 627–629 toggle press 602 tolerance 801 – position 802 tool construction 571 top dead center (TDC) 886, 920

top-level aircraft requirements (TLAR) 1026 topographic shell fabrication (TSF) 740 topping cycle 1380 torch 683 torsion test 564 total accumulated crack length (TCL) 722 total efficiency – hydraulic system 606 total equivalent plastic strain 564 total productive maintenance (TPM) 1294, 1320 total quality management (TQM) 1294, 1320 total strain 560 Toyota production system (TPS) 1321 TP-kinematic 1167 trace 30 traceability 822 traction ratio 1163 tractive resistance 1162 tractor 1179 – paver 1172 traffic message channel (TMC) 1050 transfer function 804 transformation – similarity 31 transformer 1448 – instrument transformer 1452 transmission 893 transmission electron microscopy (TEM) 85, 102 transplanter 1177 transpose matrix 28 transversal direction (TD) 106 tree diagram 795 trend 657, 668 trepanning 674 – drilling 674 Tresca flow condition 562 TRIAC power semiconductor 1481 triangulation sensor 820 tribochemical reaction 306, 313 tribological interaction 300 tribological load 300 tribological process 300 tribologically relevant property 296 tribology 295 tribotechnical system (TTS) 296 true strain increment 560 true stress 561 true value 800, 823

Subject Index

U U tube tubesheet 964 ultimate tensile strength (UTS) 110 ultra-high-capacity aircraft (UHCA) 1027 ultrahigh-efficiency gas turbine (UHEGT) 1013 ultrasonic (US) 643 – A-scan 128 – bonding 699 – far field 128 – machining (USM) 650 – near field 128 – pulse-echo technique 128 – sound field 128 – testing 127 – transducer 128 – wave 128 ultra-supercritical steam (USC) 1376 uncertainty 804, 822, 824 uncontrolled rectifier 1474 uniaxial stress state 561 unified numbering system (UNS) 171 uninterruptible power supply (UPS) 1391

unit – circle 7 – impulse 20 – injector 930 – pulse function 20 – ramp function 19 – -step function 18 upper allowance 801 upper bound method 565 upper-triangular matrix 28 upsetting 568 – ratio 569 uptime 599 useful life 307

V vacancy diffusion 89 vacuum casting (VC) 762 vacuum monitoring, comparative 141 valve timing 923 vapor cavity 672 variable, operating 300 variable-speed drive 1467, 1479, 1483 variational principle, Markov’s 567 vector 27 Verein Deutscher Ingenieure (Association of German Engineers, VDI) 1303 vertical take-off and landing (VTOL) 1027 very large commercial transport (VLCT) 1027 vibration 958 vibratory plate 1171 Vickers hardness 112 Vickers hardness number (VHN) 112 Vincent press 603 virtual – corporation 1335 – enterprise 1335 – enterprise, advanced legal issues in (ALIVE) 1335 – organization (VO) 1328, 1333 – private network (VPN) 1319 – products 1359 viscosity 322 – classification 324 – index (VI) 323 visio-plasticity method 567 visual testing 136 volatile organic compound (VOC) 866, 940

volatile organic fraction (VOF) 941 volume constancy 561 volume-specific energy 890 volumetric efficiency 905, 919, 922 Voluntary Interindustry Commerce Standard Association (VICS) 1313 von Mises flow condition 562

W wafer – silicon 674 water jet 673 waterjet machining, abrasive (AWJ) 647 wave 669 wave guide 669, 673 wave soldering 702 wavelength 669, 672 wavelength dispersive x-ray spectroscopy (WDS, WDX) 105 waviness 813 wear 303 – determination 307 – energy density 308 – mechanism 303 – nomogram 310 – phenomenon 306 – profile 306 – rate 308 – type 303 wedge–wedge bonding 699 weld 671 – pool 671 – seam 669 – spatter 672 welding 656, 668, 670–672, 682 – beam penetration 669 – parallel gap 698 – projection 698 – remote 669, 671 – resistance 698 – scanner 671 – seam 698 – speed 669 – spot 698 – thermal conduction 668 wheel loader 1167 wheel-slide protection (WSP) 1030 white light triangulation (WLT) 757 wind energy 1504 wiper bending 591 wire bonding 699 wire drawing machine 600 wire drawing process 579

Subject Index

tube drawing machine 600 tube hydroforming 598, 599 Tubular Exchanger Manufacturer’s Association (TEMA) 964 tubular product 968 tungsten carbide 628 tungsten electrode 671 turbine 926, 974, 987 – equation 975 – operation 1003 – radial 976 – reheat (RT) 989 – row 975 – stage 974 turbocharging 924 turbocompounding 925 turbomachinery 987 turning process 585 TWINFOCUS 670 twinning 557 twin-spool engine 997 twist drilling 674 two quadrant – phase leg 1471 two-axle cutting system 673 two-stroke cycle 920 type of transmission 890

1575

1576

Subject Index

wire electro-discharge machining (WEDM) 649 wiring board 870 wood 673 work 600, 601 – hardening 562 – machine 885 – machine, mobile 1161, 1178 – plan 823 work breakdown structure (WBS) 1329 working chamber 887 working roller 1171

workpiece 668 workpiece coordinate system World Wide Web (www) 1327 W-profile 814 wrinkling 581, 588, 599 Wronskian 11

X X-ray diffraction (XRD) 98 X-ray-exited photoelectron spectroscopy (XPS) 105

Y 810 Yb:YAG laser 669 yield condition 562 Young’s modulus, plane strain 593

Z zero matrix 27 zirconium-corundum (ZrO2 with Al2 O3 ) 640 Z-kinematic 1167

Subject Index

1363

Dwarkadas Kothari, P.M.V. Subbarao

The chapter contains 32 sections. Section 16.1 gives an introduction to the principle of energy supply. This section also provides the state of the art of the economics of various energy resources. Different types of fuels and their characteristics are discussed in Sect. 16.3. The conversion of different forms of energy has been explained in Sect. 16.5. Working principles of different power plants like gas turbines, the internal combustion (IC) engine, fuel cells, nuclear, and combined cycle system are discussed in Sects. 16.6–16.10. Section 16.11 explores the inherent features of the integrated gasification combined cycle system. Various types of gasifiers and their working procedures are explained in this section. Section 16.12 provides updated information about magnetohydrodynamic power generation and detailed information about various types of cogeneration system is also explained in Sect. 16.13. Sections 16.14 and 16.15 explain the transformation of regenerative energies. These sections are mainly devoted to wind and solar energy conversion. Harvesting solar energy using solar ponds and solar chimneys is also explained in this section. The concept and working principle of the heat pump is explained in Sect. 16.16. Section 16.17 contains the information about energy storage and distribution systems. Energy storage is used to offset the adverse effects of fluctuating demands for electricity and to assure a steady output from existing power plants. Various energy storage devices like pumped hydro, thermal energy, and hydrogen energy are described. The furnace is the heart of a power generation system. Understanding its internal features and working principle is very important for a power plant professional. Section 16.18 satisfies these needs. It not only provides the characteristics of furnace combustion, but also provides the emission characteristics of furnace. Recent combustion technologies like fluidized bed combustion, bubb-

ling fluidized bed combustion, and circulating fluidized bed combustion are also explored in Sect. 16.19. Section 16.21 provides more details about the working principles of various types of burners. Inside the furnace the fuel must be evenly dispersed in the combustion airstream such that the fuel and air can come into intimate contact. Failure to achieve this results in unburnt or partially burnt fuel. The burner design attempts to achieve this by using a variety of techniques. Sections 16.22 and 16.23 facilitate understanding of various furnace accessories and technologies available to control emission. The boiler is a key component in modern, coal-fired power plants; its concept, design, type, and integration into the overall plant considerably influence costs. The operating behavior and availability of the power plant are discussed in Sect. 16.24. Details of the various components of a steam generator are provided in Sect. 16.25. Energy balance analysis and the efficiency calculation of furnace are described in Sects. 16.26– 16.28. Thermodynamic calculations such as furnace design, boiler strength calculations, and heat transfer calculations are discussed in Sects. 16.29 and 16.30. Various types of nuclear reactors and their working principles are elaborated in Sect. 16.31. Finally, Sect. 16.32 is devoted to a discussion of future prospects and conclusions.

16.1 Principles of Energy Supply.................... 1365 16.1.1 Planning and Investments ......... 1365 16.1.2 Economics of Gas ...................... 1366 16.1.3 Economics of Electricity .............. 1366 16.1.4 Economics of Remote Heating ..... 1366 16.2 Primary Energies .................................. 1367 16.3 Fuels ................................................... 1367 16.3.1 Solid Fuels................................ 1367 16.3.2 Liquid Fuels.............................. 1367

Part C 16

Power Gene 16. Power Generation

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Complementary Material for Mechanical Engineers

Part C 16

16.3.3 16.3.4 16.3.5

Gaseous Fuels ........................... 1367 Nuclear Fuels ............................ 1367 Regenerative Energies ............... 1367

16.4 Transformation of Primary Energy into Useful Energy ................................ 1368 16.5 Various Energy Systems and Their Conversion ............................ 1368 16.5.1 Generation of Electrical Energy ... 1368 16.5.2 Steam Power Cycle..................... 1369 16.5.3 Process of the Rankine Cycle ....... 1370 16.6 Direct Combustion System ..................... 1371 16.6.1 Open-Cycle Gas Turbine Power Plant.............................. 1371 16.7 Internal Combustion Engines ................. 1372 16.8 Fuel Cells ............................................. 1372 16.9 Nuclear Power Stations ......................... 1373 16.9.1 Basic Principles of Nuclear Energy 1374 16.9.2 Types of Nuclear Power Plants..... 1374 16.10 Combined Power Station ....................... 1374 16.10.1 Thermodynamic Analysis of the Combined Cycle System..... 1375 16.11 Integrated Gasification Combined Cycle (IGCC) System ........................................ 1375 16.11.1 Introduction ............................. 1375 16.11.2 Environmental Benefits ............. 1376 16.11.3 Efficiency Benefits ..................... 1376 16.11.4 The Science of Coal Gasification .. 1377 16.11.5 Chemical Reactions.................... 1377 16.11.6 Optimal Coal Gasifiers ................ 1377 16.11.7 Classification of Gasifiers............ 1377 16.11.8 E-GAS Entrained Flow ................ 1378 16.12 Magnetohydrodynamic (MHD) Power Generation ................................ 1378 16.12.1 Principle of MHD ....................... 1378 16.12.2 General Characteristics............... 1378 16.12.3 The Production of Plasma ........... 1378 16.12.4 Thermal Ionization .................... 1378 16.12.5 Nonequilibrium Ionization ......... 1379 16.12.6 MHD Steam Power Plant ............. 1379 16.13 Total-Energy Systems for Heat and Power Generation ............. 1379 16.13.1 Cogeneration ............................ 1379 16.14 Transformation of Regenerative Energies1381 16.14.1 Wind Energy Power Plant ........... 1381 16.15 Solar Power Stations ............................. 1382 16.15.1 Significant Features of Solar Energy.......................... 1382

16.15.2 16.15.3 16.15.4 16.15.5

Solar Cells or Photovoltaic Cells ... 1383 Solar Pond ............................... 1383 Solar Chimney........................... 1384 Integrated Solar Combined Cycle Power System ........................... 1384

16.16 Heat Pump........................................... 1385 16.17 Energy Storage and Distribution ............ 1385 16.17.1 Pumped Hydro Power ................ 1385 16.17.2 Compressed Air Energy Storage ... 1385 16.17.3 Energy Storage by Flywheels ....... 1386 16.17.4 Electrochemical Energy Storage ... 1386 16.17.5 Thermal Energy Storage.............. 1386 16.17.6 Secondary Batteries ................... 1386 16.18 Furnaces .............................................. 1386 16.18.1 Combustion .............................. 1386 16.18.2 Ideal Combustion ...................... 1387 16.18.3 Theoretical Dry Air–Fuel Ratio ..... 1387 16.18.4 Theoretical Wet-Air–Fuel Ratio ... 1387 16.18.5 Pressure Conditions ................... 1387 16.18.6 Emission .................................. 1388 16.18.7 Particulate Emissions ................. 1388 16.18.8 Nitrogen Oxide Emission ............ 1388 16.18.9 Thermal NOx ............................. 1388 16.18.10 Fuel NOx .................................. 1388 16.18.11 Sulfur Dioxide Emission.............. 1388 16.18.12 Solid-Fuel Furnaces ................... 1388 16.18.13 Stokers and Grates .................... 1388 16.18.14 Pulverized-Fuel Furnaces ........... 1389 16.18.15 Dry-Bottom Furnace .................. 1390 16.18.16 Wet-Bottom Furnace ................. 1390 16.19 Fluidized-Bed Combustion System ......... 1390 16.19.1 Bubbling Fluidized-Bed Combustion .............................. 1391 16.19.2 Circulating Fluidized-Bed Combustion .............................. 1391 16.20 Liquid-Fuel Furnace.............................. 1392 16.20.1 Special Characteristics ................ 1392 16.21 Burners ............................................... 1392 16.21.1 Various Types of Burners ............ 1393 16.21.2 Liquid-Fuel Burners .................. 1393 16.21.3 Gun-Type Burners (Pressure Gun) 1393 16.21.4 Pot-Type Burners ...................... 1394 16.22 General Furnace Accessories .................. 1394 16.22.1 Fans ........................................ 1394 16.22.2 Forced Draft Fan........................ 1394 16.22.3 Induced Draft Fan ..................... 1394 16.22.4 Balanced Draft (BD) ................... 1394 16.22.5 Primary Air Fans ........................ 1394 16.22.6 Stacks ...................................... 1394 16.22.7 Natural Draft ............................ 1395

Power Generation

Artificial Draught....................... 1396 Forced Draught ......................... 1396 Induced Draught ....................... 1396 Balanced Draught ..................... 1396

16.23 Environmental Control Technology ......... 1396 16.23.1 Particulate Emission Control ....... 1396 16.23.2 Electrostatic Precipitators ........... 1396 16.23.3 Fabric Filters ............................. 1396 16.23.4 Pulse Jet Fabric Filters................ 1397 16.23.5 Shake-Deflate Filters ................. 1397 16.23.6 Reverse-Air Fabric Filter ............. 1397 16.23.7 Mechanical Collectors ................ 1397 16.23.8 NOx Control .............................. 1397 16.24 Steam Generators ................................. 1398 16.24.1 Types of Steam Generators ......... 1399 16.24.2 Boiler Safety ............................. 1399 16.24.3 Boiler Water Treatment .............. 1399 16.24.4 Shell-Type Steam Generator ....... 1400 16.24.5 Natural Circulation Boiler ........... 1400 16.24.6 Forced Circulation Boiler ............ 1401 16.24.7 Boiling Water Reactors ............... 1402 16.25 Parts and Components of Steam Generator .............................. 1402 16.25.1 Superheaters ............................ 1402 16.25.2 Radiant Superheater.................. 1402 16.25.3 Convective Heat Transfer ............ 1403 16.25.4 Pendent Superheater................. 1403 16.25.5 Platen Superheater.................... 1403 16.25.6 Reheaters................................. 1403 16.25.7 Economizers ............................. 1404 16.25.8 Feedwater Heaters .................... 1404 16.25.9 Air Preheaters ........................... 1405 16.25.10 Recuperative Air Preheater ......... 1405 16.25.11 Rotary or Regenerative Air Preheater ..... 1406

16.26 Energy Balance Analysis of a Furnace/Combustion System............ 1406 16.26.1 Performance Analysis of a Furnace ............................. 1406 16.26.2 Analysis ................................... 1406 16.26.3 First Law Analysis of Combustion . 1407 16.26.4 Boiler Fuel Consumption and Efficiency Calculation .......... 1407 16.26.5 Various Energy Losses in a Steam Generator................. 1407 16.27 Performance of Steam Generator ........... 1409 16.27.1 Boiler Efficiency ........................ 1409 16.28Furnace Design..................................... 1409 16.28.1 Heat Release Rate per Unit Volume qv .................... 1409 16.28.2 Heat Release Rate per Unit Wall Area of the Burner Region .......... 1410 16.28.3 Heat Release Rate per Unit Cross-Sectional Area...... 1410 16.28.4 Furnace Exit Gas Temperature ..... 1410 16.28.5 Example Problem ...................... 1410 16.29 Strength Calculations ............................ 1412 16.29.1 Mathematical Formulae for Stress 1412 16.29.2 Stress Analysis Methods ............. 1413 16.29.3 Design Pressure and Temperature 1413 16.30 Heat Transfer Calculation ...................... 1414 16.30.1 Heat Exchangers ....................... 1414 16.30.2 Flow Resistance ........................ 1414 16.31 Nuclear Reactors................................... 1414 16.31.1 Components of a Nuclear Reactor 1414 16.31.2 Types of Reactors ...................... 1415 16.32 Future Prospects and Conclusion ............ 1418 References .................................................. 1418

16.1 Principles of Energy Supply Energy exists in many forms such as thermal energy, chemical energy, mechanical energy, potential energy, kinetic energy, and nuclear energy. Electrical energy is a desirable form of energy, because it can be generated centrally in bulk and transmitted economically over long distances. The requirement for energy is the demand for so many tonnes of coal, barrels of oil, cubic meters of gas, and so on. With the ever-increasing percapita energy consumption and exponential growth in population, technologists already foresee the end of the Earth’s non-replenishable fuel resources.

16.1.1 Planning and Investments Investment planning for power plants requires a longterm plan, which covers facility investment such as the construction of new power plants or the replacement of existing plants with a newer one in an uncertain environments. Capital investment is a prerequisite for energy development as it is highly capital intensive. Investments in energy plants, equipment, and infrastructure (transportation, availability of fuel, water, communications, environment compatibility etc.) must be viewed

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16.22.8 16.22.9 16.22.10 16.22.11

16.1 Principles of Energy Supply

Power Generation

District heating is already widely used in central core areas of large cities. Many large buildings can be heated by steam or hot water from a single large central combustion plant. Also, space cooling can be provided by using the hot water or steam to actuate an absorptiontype refrigeration plant.

16.2 Primary Energies Primary energy is contained in raw fuels and any other forms of energy received by a system as input to the system. Primary energy is transformed in energy conversion processes to more convenient forms of energy and cleaner fuels. The most important primary energy sources are the carbon-based fossil energy

sources. Fossil fuels (oil, coal, and natural gas) are called nonrenewable energies, and come from the longterm decomposition of plant and animal matter over millions of years. Sun is the main source of energy from which all of the above energy resources are derived.

16.3 Fuels Fuels are chemical substances which may be burned in oxygen to generate heat. They mainly consist of carbon and hydrogen and sometimes a small amount of sulfur or minerals, and may be solid, liquid, or gaseous. Coal and coke are examples of solid fuels. Petroleum oils are usually a mixture of several liquid fuels. Gaseous fuels may be a mixture of gases such as methane (CH4 ), ethane (C2 H6 ) and so on.

16.3.1 Solid Fuels Solid fuel is a term given to various types of solid materials that provide energy. This energy is usually released by combustion. Coal and coke are examples of solid fuels.

16.3.2 Liquid Fuels Most liquid fuels are derived from fossil fuels. These can be classified according to their volatility (the ease with which they evaporate and turn into vapor). The most volatile fuels are gasoline and kerosene. Less volatile fuels are used in diesel engines and residual fuels, of varying viscosities, are often used in boilers. Ethanol produced from the fermentation of sugar is a prominent liquid fuel.

16.3.3 Gaseous Fuels Gas is a preferred fuel, the combustion of which offers more environmental friendliness over the other fossil fuels. It burns more readily and completely than other fuels. Gaseous fuels are the most convenient, requiring the least amount of handling, and are the most maintenance free. Gas is odorless and colorless. Because gaseous fuels are in a molecular form, they are easily mixed with the air as required for combustion, and are oxidized in less time than is required to burn other types of fuel. A mixture of methane (CH4 ) and ethane (C2 H6 ) is an example of a gaseous fuel.

16.3.4 Nuclear Fuels Fuels such as uranium or thorium that can be used in nuclear reactors as a source of electricity are called nuclear fuels. The energy derived during fission or fusion processes is called nuclear energy. Examples of nuclear fuels are: 235 U, 238 U, and 239 Pu.

16.3.5 Regenerative Energies Regenerative or renewable energies are those energy sources or energy carriers that naturally renew themselves within human timescales. Regenerative energies

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cost of waste heat has two components: the production cost at the plant and the distribution cost. The distribution component is calculated from the capital charges and maintenance expense for the pipeline system conveying warm water or steam from the plant to customers.

16.3 Fuels

Power Generation

16.6 Direct Combustion System

The economics of power generation by gas turbines is now quite attractive due to their low capital cost and high reliability and flexibility in operation. Another outstanding feature is their capability to start quickly and to use a wide variety of fuels from natural gas to residual oil or powdered coal.

16.6.1 Open-Cycle Gas Turbine Power Plant The essential components of a gas turbine power plant are the compressor, combustion chamber, and the turbine. The air standard cycle of gas turbine power plant is the Brayton cycle shown in Fig. 16.9. It consists of two reversible adiabatic processes and two constantpressure processes. Gas turbine plants can be operated either in an open or closed system configuration. Analysis

1–2: Work input wcomp = h 2 − h 1 = cp (T2 − T1 ) ,

(16.1)

2–3: Heat input qin = h 3 − h 2 = cp (T3 − T2 ) ,

(16.2)

(16.3)

4–1: Heat rejection qout = h 4 − h 1 = cp (T4 − T1 ) . Isentropic processes  γ   γ p2 v1 T2 γ −1 = = , p1 v2 T1  γ   γ p3 v4 T3 γ −1 = = . p4 v3 T4

(16.4)

(16.5)

(16.6)

Constant-pressure processes p3 = p2 and p4 = p1 ;  γ  γ p2 p3 v1 v4 rp = = = = p1 p4 v2 v3   γ   γ T2 γ −1 T3 γ −1 = = , T1 T4

T2 = T1 (rp )

(16.7)

(16.8)

γ −1 γ

= T1 ρ ,

(16.9)

ρ = (rp ) γ , T3 T3 T4 = = , γ −1 ρ γ (rp )   cp Tρ3 − T1 wnet 1 ηth = = = γ , qin cp (T3 − ρT1 ) rpγ −1     ρ−1 wnet = cp T3 − T1 (ρ − 1) , ρ   T3 = cp (ρ − 1) − T1 ρ   ρ−1 = cp (T3 − ρT1 ) . ρ

(16.10)

and γ −1

(16.11)

(16.12)

(16.13)

(16.14)

The thermal efficiency can also be written as ηth =

3–4: Work output wtur = h 3 − h 4 = cp (T3 − T4 ) ,

where rp is the pressure ratio

1 = ρ

1 γ

rpγ −1

.

(16.15)

It may be noted that in a simple gas turbine cycle the cycle efficiency is a function of the pressure ratio only. The gas turbine inlet temperature is an important parameter of efficiency. The present state of the art temperature is 1570 K, but research on closed-cycle steam cooling of turbine blades, protective surface coating of combustor liners, and new ceramic structural parts of the turbine are areas of research that will lead to higher gas turbine inlet temperatures. Merits and Demerits of the Brayton Cycle

1. Very compact, which is why it is used in aircraft. 2. It demands extremely high quality and costlier fuel. 3. The pressure of the exit gases should always be just above atmospheric pressure. 4. The compressor requires a large power input. In consumes more power than is produced from the steam turbine. 5. It has a lower cycle efficiency, due to the large exhaust loss.

Part C 16.6

16.6 Direct Combustion System

1371

Power Generation

16.11.4 The Science of Coal Gasification Coal gasification involves the chemical reaction of coal, steam, and air or oxygen at high temperatures to produce a mixture of hydrocarbon gases, typically carbon monoxide, carbon dioxide, and methane as well as hydrogen sulfide.

In a coal–steam or oxygen–steam, the homogeneous water-gas shift reaction is also important: CO + H2 O(g) → CO2 + H2 , ΔHR = − 41.0 MJ/kmol .

Hydrogen is added as a reactant in order to increase the quantity of methane. Water gas from which the CO2 has been removed is called synthesis gas. Synthesis gas can also be used to produce methane, or synthetic natural gas (SNG) CO(g) + 3H2 (g) → CH4 (g) + H2 O(g) , 2CO(g) + 2H2 (g) → CH4 (g) + CO2 (g) .

16.11.5 Chemical Reactions Coal combustion, which is the exothermic reaction of coal with oxygen or air to produce carbon dioxide and water, is a fundamental part of coal gasification, using 20–40% of the oxygen or air required for complete combustion. The purpose of this partial combustion is to supply the energy necessary to complete the gasification of the coal particles. C(s) + 12 O2 → CO (partial combustion) , ΔHR = − 1110.5 MJ/kmol ,

(16.34)

where ΔHR is the standard heat of reaction at 298 K and atmospheric pressure This partial combustion reaction is exothermic, that is, it liberates heat, as signified by the negative sign. Furthermore the reaction of carbon does not stop at CO2 , but any remaining oxygen rapidly reacts with CO in the gas phase to produce CO2 CO + 12 O2 → CO2 , ΔHR = − 283.1 MJ/kmol .

(16.40)

In fuel-rich combustion, the sulfur in the coal is released mainly as hydrogen sulfide with a small amount of carbonyl sulfide and the fuel-bound nitrogen is released as elemental nitrogen, ammonia, and hydrogen cyanide. In order to capture the sulfur, lime stone or dolomite may be fed to the gasifier CaO + H2 S → CaS + H2 O .

(16.41)

16.11.6 Optimal Coal Gasifiers Gasifiers convert carbonaceous feedstock into gaseous products at high temperature and elevated pressure in the presence of oxygen and steam. Partial oxidation of the feedstock provides the heat. At operating conditions, chemical reactions occur that produce synthesis gas or syngas, a mixture of predominantly CO and H2 .

(16.35)

(16.36)

This reaction is called the Boudouard reaction. In order to control the high temperatures resulting from the C(s)-O2 reactions, and to increase the heating value of the product gas through the production of hydrogen, steam is often added as a reactant. C(s) + H2 O(g) → CO + H2 , ΔHR = + 131.4 MJ/kmol .

(16.39)

16.11.7 Classification of Gasifiers

The solid carbonaceous material that is not combusted by oxygen reacts endothermically with carbon dioxide, hydrogen, and methane C + CO2 → 2CO , ΔHR = + 172.0 MJ/kmol .

(16.38)

(16.37)

A wide variety of gasifier designs has been developed for different applications and types of fuel used. The important parameters used for selecting the type of gasifiers are temperature, pressure, reactant gases, and the method of contacting. The different types of gasifier used in combined cycle technology are: 1. 2. 3. 4. 5. 6. 7. 8.

The entrained-flow (downflow) gasifier The E-GAS entrained flow (up flow) gasifier The Shell entrained flow (up flow) gasifier The fluidized-bed gasifier The transport reactor gasifier The Lurgi dry ash gasifier The British Gas/Lurgi fixed-bed gasifier The Prenflo entrained bed gasifier

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Part C 16.11

less carbon dioxide is produced. IGCC plants with the flexibility to produce chemicals such as ammonia and hydrogen along with electricity make this a promising technology for future generations.

16.11 Integrated Gasification Combined Cycle (IGCC) System

Power Generation

16.17 Energy Storage and Distribution

A reversed Carnot cycle can be used as heat pump. If the aim is to heat a body or space, the heat is rejected at a high temperature to the body or space and the heat is absorbed at a lower temperature from the ambient air or circulating water. Thus heat is drawn from the atmospheric air and pumped to the space to be heated. Such a cycle is called a heat pump cycle (Fig. 16.27) and the coefficient of performance (COP) for a Carnot reversed cycle heat pump is given by

Heat rejected , Work done T2 , COPCarnot heat pump = T2 − T1 where T1 and T2 are temperatures of source and sink. The efficiency of this device to transfer heat Q R to a high-temperature body is COPCarnot heat pump =

Efficiency =

Energy effect sought . Energy input

16.17 Energy Storage and Distribution Energy storage plays an important role in the competent management of energy resources. The demand for electricity fluctuates with time, which affects the economics of power plants that are normally designed for higher capacity. The ultimate aim of an energy storage device is to reduce the economic losses due to fluctuating demand. When the demand is lower than the capacity, energy is stored. When the demand is higher than the capacity, the stored energy is released. This will provide savings in operating cost and ensure complete customer satisfaction, which can improve the status of the organization in the international market. Finally, energy storage is commonly used in stand-alone applications, where it can serve as an uninterruptible power supply (UPS) unit. The most important energy storage technologies are: 1. 2. 3. 4. 5. 6.

Pumped hydro power Compressed energy storage Flywheels Electrochemical storage devices Thermal energy storage devices Secondary battery energy storage

16.17.1 Pumped Hydro Power Pumped hydro facilities consist of two large reservoirs, one located at the base level and the other located at a different elevation. In pumped hydro, surplus power is utilized to pump the water from the lower reservoir to the upper reservoir, where it can be stored as potential energy. During periods of higher demand, water is sent back into the lower reservoir, passing through hydraulic

turbines that generate electrical power [16.11]. The only drawback in pumped hydro power devices is that their construction cost is very high. The combined efficiency of a pumped hydro system is given by ηcomb. effic. =

Total energy output Total energy input during a charge–discharge cycle

. (16.43)

16.17.2 Compressed Air Energy Storage Excess energy is used to compress air and store it an airtight underground storage cavern. The stored energy is then released during periods of peak demand by expansion of the air through an air turbine. Three types of reservoirs can be used to store compressed air: salt caverns, aquifers, and hard rock caverns. When air is compressed for storage, its temperature increases according to   n−1 p2 n , (16.44) T2 = T1 p1 where n is the polytropic index, and P1 , T1 and P2 , T2 are the pressures and temperatures before and after compression. Various studies have concluded that compressed air energy storage is competitive with combustion turbines and combined-cycle units, even without taking into account its unique benefits in terms of energy storage [16.12]. The layout of compressed energy storage device is shown in the Fig. 16.28. The heat of compres-

Part C 16.17

16.16 Heat Pump

1385

Power Generation

C + O2 → CO2 , 2H2 + O2 → 2H2 O .

(16.46) (16.47)

When the amount of oxygen supplied is insufficient for complete combustion then carbon will be burned incompletely with the formation of carbon monoxide 2C + O2 → 2CO .

(16.48)

The most important parameter to estimate the effectiveness of combustion is called the combustion efficiency, which depends on the following parameters: 1. 2. 3. 4. 5. 6. 7.

Air–fuel ratio Fuel–air mixing Flame temperature Flame shape Fuel residence time Degree of atomization (for liquid fuel) Degree of turbulence

The theoretical air–fuel ratio for complete combustion is known as the stoichiometric ratio. In practice every oxygen molecule does not come into contact with a fuel molecule. In order to ensure complete combustion some amount of air is used to compensate this shortage of oxygen molecules, normally called excess air, and attain complete combustion. Turbulence enhances the proper mixing of fuel and oxygen and hence the combustion efficiency.

16.18.2 Ideal Combustion The generalized ideal combustion equation can be written as   Y K O2 + mH2 O C X HY S Z O K + X + + Z + 4 2 (16.49) → PCO2 + QH2 O + GSO2 . The generalized combustion equation can be written   Y K C X HY S Z O K + X + + Z + O2 4 2   Y K + 3.76 X + + Z + N2 + mH2 O 4 2 (16.50) → PCO2 + QH2 O + RN2 + GSO2 .

The air–fuel ratio can be written A m air . = F mf

(16.51)

16.18.3 Theoretical Dry Air–Fuel Ratio 1 kmole of oxygen and 3.76 mole of nitrogen generate a mixture of 4.76 mole of air. The molecular weight of air is therefore 32 + 3.76 × 28 = 28.84 , 4.76   A m air = F TD mf  4.76 X + Y4 + Z − = 100

(16.52)

K 2



28.84

.

(16.53)

16.18.4 Theoretical Wet-Air–Fuel Ratio Ambient air is always humid in nature so the calculation of the theoretical wet-air–fuel ratio depends on the relative humidity. The specific humidity of air, w (kg) of moisture per kg of dry air. Relative humidity pvapor,act . (16.54) φ= pvapor,sat Amount of moisture in ambient air 4.76 (X + Y/4 + Z − K/2) 28.84w n= (16.55) . 18 Theoretical wet-air–fuel ratio   A m wet,air = F TW mf    4.76 X + Y4 + Z − K2 (28.84 + w18) = . 100 (16.56)

16.18.5 Pressure Conditions Not all boiler furnaces are airtight, especially stokers (boilers that burn solid fuels). Flue gases may escape into the plant area if the furnace pressure is greater than the atmospheric pressure. Other furnace designs may require draft and furnace pressure control. Typically, the furnace pressure is controlled using a balance draft system. The induced draft fan is modulated to maintain the

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Part C 16.18

a gas (the oxidizer), usually O2 , to release heat. The presence of CO2 in the product gas signifies complete combustion whereas CO signifies incomplete combustion. The basic chemical equations for complete combustion are

16.18 Furnaces

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Complementary Material for Mechanical Engineers

Part C 16.18

furnace at a slight negative pressure. Furnace pressure measurement and induced fan control is required. The location of the furnace pressure transmitter is important because the pressure is not uniform within the furnace. If the combustion airflow rate measurement is available, furnace pressure control can be more effective.

tions for the formation of NOx during combustion are [16.15]

16.18.6 Emission

16.18.10 Fuel NOx

The combustion of fuel finally leads to the emission of various gases and particulate matter. The amount and chemical components of these emissions depend on the fuel type, boiler type and size, and the firing method. Different forms of emissions are described below.

16.18.7 Particulate Emissions The particulates present in the stack gases depend primarily on the combustion efficiency and on the amount of ash contained in the fuel. All fuels except natural gas contain some quantity of ash or noncombustible material, which forms the majority of these particulates [16.14, 15].

16.18.8 Nitrogen Oxide Emission The level of nitrogen oxides (NOx ) present in the stack gas depends on many variables; the furnace heat rate levels, temperature, and excess air are the major variables that affect NOx emission levels. NOx is one of the contributors to acid rain and ozone formation, visibility degradation, and human health concerns. Combustion of any fossil fuel generates some level of NOx due to the high temperature and availability of oxygen and nitrogen from both the air and fuel. Based on the method of formation, NOx can be classified as thermal NOx and fuel NOx .

16.18.9 Thermal NOx High-temperature oxidation (above 1200 ◦ C) initiates the formation of NOx , normally called thermal NOx . The nitrogen and oxygen in the air dissociate at higher combustion temperatures and lead to the formation of NOx . Thermal NOx formation is typically controlled by reducing the peak and average flame temperature. Apart from a higher temperature, the formation of NOx is also due to longer residence time and oxygen concentration. Three possible reac-

N2 + O → NO + N , N + O2 → NO + O , N + OH → NO + H .

(16.57) (16.58) (16.59)

Fuel NOx refers to the formation of chemically bound nitrogen in the fuel during combustion. The fuel–air ratio is one of the deciding factors for the formation of fuel NOx . Conversion of fuel-bound nitrogen to NOx is strongly dependent on the fuel–air ratio but is relatively independent of the combustion-zone temperature. The formation of NOx happens at two levels, one is during oxidation of volatile nitrogen and another is from the char during combustion.

16.18.11 Sulfur Dioxide Emission SO2 is an acidic gas formed by the combustion of sulfur in the fuel with oxygen. Dilute sulfuric acid is a major constituent of acid rain. An aqueous solution of sulfurous acid (SO3 ) is formed when sulphur dioxide combines with water. This can easily oxidize in the atmosphere to form sulfuric acid (H2 SO4 ).

16.18.12 Solid-Fuel Furnaces Furnaces that use solid fuels for combustion are normally called solid fuel furnaces. Fuels include, coal, coke, and firewood (wood chips and pellets).

16.18.13 Stokers and Grates There are various ways to introduce coal into the furnace. Stokers play a vital role in distributing coal into the furnace. Stokers are normally differentiated on the basis of how the coal is introduced into the fire. Different types of stokers are: 1. 2. 3. 4. 5.

Traveling-grate stoker Chain-grate stoker Spreader stoker Vibrating stoker Underfeed stoker

Traveling-grate stokers have been in use for the past 50 years and are the most popular way to burn coal in stokers for boilers. In addition to coal, traveling-grate

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16.22.8 Artificial Draught In modern power plants, the draught should be flexible to meet the needs of fluctuating loads and it be independent of atmospheric conditions. To achieve this, the aid of draft fans becomes mandatory; by employing the fans, the height of the chimney can also be reduced. There are two types of fans used for producing mechanical draught: 1. Forced draught (FD) 2. Induced draught (ID)

16.22.9 Forced Draught In this system, the blower (forced draft fan) is located at the base of the boiler near the grate. Air is forced into the furnace by the forced fan and the flue gases are forced to chimney through the economizer and air preheater.

• •

Advantages of the Forced Draught System Since the fan handles cold air, the fan size and the power required are lower. No need for water-cooled bearings because the air being handled is cold.

•

The pressure throughout the system is above atmospheric pressure so that air leakage into the furnace is reduced.

16.22.10 Induced Draught In an induced draught system, a blower (induced draft fan) is placed near (or) at the base of the chimney. The fan sucks the flue gas from the furnace, creating a partial vacuum inside the furnace. Thus atmospheric air is induced to flow through the furnace to aid the combustion of fuel. The flue gases drawn by the fan passes through the chimney to the atmosphere.

16.22.11 Balanced Draught In the induced draught system, when the furnace is opened for firing, cold air enters the furnace and dilates the combustion. In the forced draught system, when the furnace is opened for firing, the high-pressure air will try to blow out suddenly and the furnace may stop. Hence the furnace cannot be opened for firing and inspection in both systems. Balanced draught, which is a combination of induced and forced draught, is used to overcome these difficulties.

16.23 Environmental Control Technology There are many technologies that can be used in industry to reduce the emissions of pollutants to the atmosphere, and these can be applied before, during, or after combustion.

16.23.1 Particulate Emission Control There are several types of equipment available to control particulate matter from the flue gas which includes: 1. 2. 3. 4.

Electrostatic precipitators Fabric filters Mechanical collectors Venturi scrubbers

16.23.2 Electrostatic Precipitators When the ash particles present in the flue gas pass through the electrostatic precipitators (ESP) at a certain velocity, they become charged electrically and are attracted towards the collecting plate, which is normally positively charged.

Figure 16.35 shows a schematic diagram of ESP. The particulate-laden gas, normally laden with flyash, is sent through pipes with negatively charged plates which give the particles a negative charge. The particles are then routed past positively charged plates, or grounded plates, which attract the newly negatively charged ash particles. The particles stick to the positive plates until they are collected. The air that leaves the plates is then clean of harmful pollutants. Velocity is one of the important factors that affect the performance of an electrostatic precipitator. A lower velocity allows more time to collect the ash particles.

16.23.3 Fabric Filters Fabric filters are used to remove particles from the gas stream. They are made up of woven or felted material. Fabric filters are generally in the form of a cylindrical bag. Fabric filters generally operate in a temperature range of 120–180 ◦ C. The choice between ESP and fabric filtration generally depends on coal type, plant size, and boiler type and configuration. The two fundamen-

Power Generation

1. 2. 3. 4.

Flue gas temperature Dew point and moisture content Particle size distribution Chemical composition of the fly ash Fabric filters are classified into three types:

1. Pulse jet fabric filters 2. Reverse-air fabric filters 3. Shake-deflate filters

16.23.4 Pulse Jet Fabric Filters Pulse jet fabric filters use high-pressure air to clean the filter bags, and are provided in standard configurations that are capable of treating gas flow rates up to about 300 000 ACFM (actual cubic feet per minute). Customdesigned units can handle larger flow rates.

16.23.5 Shake-Deflate Filters This kind of filters collect the dust inside the bags as in the reverse-air design. To clean the bags, the top ends are shaken by a driver linkage.

16.23.6 Reverse-Air Fabric Filter The reverse-air fabric filter is a customized design for utility boilers and industrial applications where large volumes of process gas flow (250 000 ACFM and more) must be cleaned. The systems consist of 6–24 structural compartments. Compartments are available with nominal 20 or 30 cm diameter bags with typical bag lengths of 7.31–11 m.

16.23.7 Mechanical Collectors Mechanical dust collectors are often called cyclones. Cyclones are used to remove dust and fibrous material either as the first stage of a scrubber or fabric filter system. Although cyclones are an established form of dust collector, care and application knowledge are required to ensure correct sizing. The arrangement of a cyclone

separator is shown in Fig. 16.36. The basic principle is the centrifugal force created by spinning a gas stream, which is used to separate the particles from the gas. In a conventional cyclone, the gas enters a cylinder tangentially, where it spins in a vortex as it proceeds down the cylinder. A cone section causes the vortex diameter to decrease until the gas reverses on itself and spins up the center to the outlet pipe or vortex finder. A cone causes flow reversal to occur sooner and makes the cyclone more compact. Dust particles are centrifuged toward the wall and collected by inertial impingement. The collected dust flows down in the gas boundary layer to the cone apex where it is discharged through an airlock or into a dust hopper serving one or more parallel cyclone.

16.23.8 NOx Control It is very important to control the level of NOx emitted from power plants. NO2 from the exhaust reacts with sunlight and hydrocarbons to produce photochemical smog and acid rain constituents. The following techniques are used to reduce the level of NOx formation in current practices:

• • •

Low excess air operation Off-stoichiometric combustion, combustion modification Flue gas recirculation and treatment

Low Excess Air Operation This technique involves a reduction in the total quantity of air used in the combustion process. By using less oxygen, the amount of NOx produced is reduced. Off-Stoichiometric Combustion This technique involves the mixing of the fuel and air in a way that reduces the peak gas temperatures and peak oxygen concentrations. Advanced low-nitrogenoxide burners can reduce emissions by up to 30%. Such burners can be installed in either new or existing combustion plants. For a low-NOx burner, sudden heating up and temperature rise is important. In this case the high-temperature zone is very close to the burner compared with a conventional burner, so the pulverized coal is heated very rapidly in order to increase the fractional volatile and nitrogen release according to quantity introduced. Also, the recirculation flow near the center of the burner is important, because hot gas returning to the burner creates a very high-temperature region at this point. Altogether, the modified shape of the flow divider

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tal parameters in sizing and operating bag houses are the air-to-cloth (A/C) ratio (m/s) and the pressure drop (mm water gauge, Pascal or in H2 O). In operation, dustladen gas flows through the filters, which remove the dust particles from the gas stream. The most important factors that affect the performance of fabric filters are:

16.23 Environmental Control Technology

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and the pulverized fuel nozzle, together with an optimized strength of swirl in the air flow, produce a strong internal recirculation and NOx reducing zone in the CIa burner, with longer residence time in this region and reduced unburnt matter. So the result is a reduction of 50% in unburnt carbon and, at the same time, a significant reduction of at least 10% in NOx production. Over Fire Air (OFA) This technique keeps the mixture fuel rich and completes the combustion process using air injection nozzles. Combustion Modifications Flue Gas Recirculation. A second method is to add

some of the flue gas with the combustion air at the burner, normally known as flue gas recirculation. This increases the gas weight which must be heated by the chemical energy in the fuel, thereby reducing the flame temperature. Flue Gas Treatment Selective Noncatalytic Reduction Systems (SNCR). This

technique involves the injection of ammonia (NH3 ) or urea into the hot gas zone where reactions leading to reduction of nitrogen oxides can occur. The reactions are completed within the boiler, and no waste products are generated. There is a risk of ammonia (NH3 ) being emitted into the atmosphere if temperatures are too low, however. SCNR systems are capable of reducing nitrogen oxides by 20–60%. The reactions are 4NH3 + 4NO + O2 → 4N2 + 6H2 O , 4NH3 + 5O2 → 4NO + 6H2 O .

Flue Gas Desulphurization. Precombustion Sulphur Control Technology. Remov-

ing the sulphur before burning is one of the challenging options. There are a verity of techniques available to reduce the sulphur, including coal scrubbing and oil desulphurization. Another removal process is to change the design of the boiler and to install pressurized fluidized-bed combustors (FBC), which remove sulphur from the coal during the burning process. Another process that removes sulphur dioxide from coal during combustion is the integrated gasification combined cycle. Coal is gasified under pressure with a mixture of air and steam which results in the formation of gas which can then be burned to produce electricity. Post-Combustion Sulphur Control Technology. One of the post-combustion sulphur control methods (removing sulphur after burning) is flue gas desulphurization (FGD). In FGD processes, waste gases are scrubbed with a chemical absorbent such as limestone to remove sulphur dioxide. There are many different FGD processes, the main ones being the limestone–gypsum process and the Wellman–Lord regenerative process. Limestone–gypsum FGD involves mixing limestone and water with the flue gases to produce slurry which absorbs the sulphur dioxide. The slurry is then oxidized to calcium sulphate (gypsum) which can then be used in the building trade. FGD technologies can be classified into six main categories: wet scrubbers, spray dry scrubbers, sorbent injection processes, dry scrubbers, regenerable processes, and combined SO2 /NOx removal processes.

16.24 Steam Generators The steam generator is one of the main components in modern coal fired-power plants. Its concept, design, and integration into the overall plant considerably influence costs, operating behavior, and availability of the power plant. The thermal structure of the boiler furnace is shown in Fig. 16.37. Within the steam generator, fuel and air are forced into the furnace by the burner, where burning produces heat; from there fuel gas travels throughout the boiler, the feedwater absorbs the heat, and eventually absorbs enough energy to change into vapor. Boiler makers have developed various designs to extract the most energy from fuel and to maximize its transfer to the water.

Water enters the boiler, preheated, at the top as shown in the Fig. 16.37. The hot water naturally circulates through the tubes down to the lower area where it is hot. The water heats up and flows back to the steam drum, where the steam collects. Not all of the water is turned to steam, so the process starts again. Water keeps on circulating until it becomes steam. Meanwhile, the control system measures the temperature of the steam drum, along with numerous other readings, to determine if it should keep the burner burning, or shut it down. Sensors also control the amount of water entering the boiler, known as the feedwater. A steam generator is normally equipped with

Power Generation

16.24.1 Types of Steam Generators The classification of boilers depends on various phenomena, such as furnace position, the type of fuels used, tube contents, circulation etc.

16.24.2 Boiler Safety Boiler safety is one of the prime aspects while operating the boiler. Operating the pressure above the design pressure is extremely dangerous, so proper control of the pressure inside the steam generator is very important. Though boilers are usually equipped with a pressurerelief valve, if the boiler fails to contain the expansion pressure, the steam energy is released instantly. This combination of exploding metal and superheated steam can be extremely dangerous. The concentration of solids in the boiler should be measured and the boiler blow-down at such intervals as necessary to maintain established limits. Blow-down valves are placed at the lowest point of the boiler for the purpose of blowing sediment or scale from the boiler. They should be maintained in good working order and have to be opened and closed carefully when used. Boilers should always be brought online slowly and cold water should never be injected into a hot system as sudden changes in temperature can warp or rupture the boiler. Because many boilers are fired by natural gas, diesel or fuel oil, special precautions need to be taken. Boiler operators should ensure that the fuel system, including valves, lines, and tanks, is operating properly with no leaks. The low-water cutoff is the most important electrical/mechanical device on a boiler for maintaining a safe water level. If a low-water condition develops, it could very well result in an overheating and explosion of the boiler. The low-water cutoff should be tested at least weekly. To prevent furnace explosions, it is imperative that boiler operators purge the boiler before ignition of the burner. Workers should check the fuel-to-air ratio, the condition of the draft, and the flame to make sure that it is not too high and not smoky. Ventilation systems should also be inspected and maintained to make sure that combustion gases do not build up in the boiler room.

16.24.3 Boiler Water Treatment Efficient performance of the boiler depends upon the quality of the water. The treatment of the boiler feedwater is required to prevent excessive fouling of the heat transfer equipment and the erosion of turbine blades. The common impurities present in the raw water are: 1. 2. 3. 4.

Dissolved solids – calcium, magnesium Suspended solids – mineral matter Dissolved gases – oxygen and carbon dioxide Scum-forming substances – carbonate, chlorate, and sulphate

In the steam boiler industry, high-purity feedwater is required to ensure proper operation of steam generation systems. High-purity feedwater reduces the use of boiler chemicals due to less frequent blow-down requirements. This lower blow-down frequency also results in lower fuel costs. The boiler system loses water through steam and water leaks. Additional water called make-up water is added to the boiler to replace these losses. The amount of make-up water and the level of naturally occurring impurities in this water will determine the type of water treatment required. Boiler heating systems that have very few leaks require a simple water treatment program. All water contains dissolved minerals and these minerals, if allowed to reach high enough levels in the boiler water, will come out of solutions and form as a hard shell on the hot surfaces of the boiler. This hard shell is called scale and is often found on the outside of the fire tubes or the inside of water tubes. Scale insulates the heating surfaces, reducing the ability of the fire tubes to transfer heat from the hot combustion to the boiler water. High stack temperatures or ruptured tubes are common problems related to scale build up. Boiler water also contains dissolved gases such as oxygen or carbon dioxide. These gases, in the presence of water and metal, can cause corrosion. Corrosion eats away the metal, affecting the durability of the boiler. For boiler feedwater treatment, depending on its requirements, a number of processes can be utilized including chemical treatment/lime softening, dual-media filtration, carbon adsorption, conventional reverse osmosis membranes, and final ion-exchange resin polishing. Various methods of pretreatment of water are discussed below.

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basic component like a furnace, economizer, reheater, superheater, evaporator, air preheater, and auxiliary devices.

16.24 Steam Generators

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Lime Soda Process Calcium and magnesium salts are removed using lime and soda ash. The chemical reactions during this process are

Ca(HCO3 )2 + Ca(OH)2 = 2CaCO3 + 2H2 O , MgCl2 + Ca(OH)2 = Mg(OH)2 + CaCl2 , MgSO4 + Ca(OH)2 = Mg(OH)2 + CaSO4 , CaSO4 + Na2 CO3 = CaCO3 + Na2 SO4 , CaCl2 + Na2 CO3 = CaCO3 + 2NaCl . Insoluble components such as calcium carbonate and magnesium hydroxide settle at the bottom. Deaeration The feedwater from the condenser contains dissolved gases such as O2 and CO2 . Oxygen is found in feedwater with a relatively high partial pressure, so, it requires a near saturation temperature to be disassociated from the water. Oxygen in combination with water will attack iron and cause corrosion. This reaction occurs in two steps

Fe2+ + 2OH− = Fe(OH)2 . Then, 4Fe(OH)2 + O2 + 2H2 O = 4Fe(OH)3 Soluble Dissolved Water Insoluble ferrous oxygen ferric hydroxide hydroxide A deaerator is an open-type feedwater heater, in which the steam that is bled from the turbine is mixed directly with water. When the water temperature increases, the dissolved gases reduce.

16.24.4 Shell-Type Steam Generator This is a cylindrical boiler where the shell axis is vertical to the firing floor. Originally it consisted of a chamber at the lower end of the shell, which contained the combustion appliance. The gases rose vertically through a flue surrounded by water. Large-diameter (100 mm) cross tubes were fitted across this flue to help extract heat from the gases, which then proceeded to the chimney. Later versions had the vertical flue replaced by one or two banks of small-bore tubes running horizontally before the gases discharged to the chimney. The steam was contained in a hemispherical chamber forming the top of the shell.

The present vertical boiler is generally used for heat recovery from exhaust gases from power generation or marine applications. The gases pass through small-bore vertical tube banks. The same shell may also contain an independently fired section to produce steam at such times that there is insufficient or no exhaust gas available. In relation to the thermal capacity generated, a shelltype boiler has much higher water contents than a water tube boiler. Therefore, a shell-type boiler is more robust towards load fluctuations or load demands that temporarily exceed the rated boiler capacity. Shell-type boilers are fire-tube boilers, because the products of combustion pass through the boiler tubes. Lancashire and Cornish are examples of shell-type boilers.

16.24.5 Natural Circulation Boiler The distinct features of natural circulation boiler are that natural circulation occurs due to the density difference between the fluids in the down comer and riser or is caused by convection currents that result from the uneven heating of the water contained in the boiler. The natural circulation has been largely used in boilers up to 140 bar. Based upon the position and geometry natural circulation boilers are classified into two types: 1. Vertical-tube type 2. Sloped-tube type Figure 16.39 shows a typical water-tube natural circulation waste heat boiler with steam drum and down comer and riser pipes. Feedwater enters the drum from an economizer. This mixes with the steam/water mixture inside the drum. Down comers carry the resultant cool water to the bottom of the evaporator tubes while external risers carry the water–steam mixture to the steam drum. The heat transfer tubes also act as risers, generating steam. The natural circulation is maintained due to the static head difference and natural convection due to the density differential between the mean down comer density and mean riser density. The down comers are located outside the furnace and away from the heat of combustion. They serve as pathways for the downward flow of relatively cool water. The circulation ratio is defined as the ratio of the mass of steam–water mixture to steam generation. The natural circulation largely depends upon the

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16.24.7 Boiling Water Reactors The fission zone is contained in a reactor pressure vessel, at a pressure of about 70 bar (7 MPa). At the temperature reached (approximately 290 ◦ C), the water starts to boil and the resulting steam is produced directly in the reactor pressure vessel. After the separation of the steam and water in the upper part of the reactor pressure vessel, the steam is routed directly to a turbine

driving an alternator. The steam coming out of the turbine is converted back into water by a condenser after having delivered a large amount of its energy to the turbine. It is then fed back into the primary cooling circuit where it absorbs new heat in the fission zone. Since the steam produced in the fission zone is slightly radioactive, mainly due to short-lived activation products, the turbine is housed in the same reinforced building as the reactor.

16.25 Parts and Components of Steam Generator 16.25.1 Superheaters One of the most important accessories of a boiler is a superheater, which affects improvement and economy in the following ways. The steam that is produced in the boiler has a certain percentage moisture content. Due to the high velocities of the steam inside a turbine, the moisture content of the steam can erode the turbine blades. A superheater is utilized to remove the moisture content in the steam by raising the temperature while keeping the pressure constant. Steam that undergoes this process is referred to as superheated steam. Superheating improves the turbine internal efficiency and hence the lifetime of the turbine. The degree of superheating is a term which is used to describe the temperature difference between the raised temperature and the temperature at constant pressure. A superheater therefore: 1. Increases the capacity of the plant 2. Reduces corrosion of the steam turbine 3. Reduces steam consumption of the steam turbine Depending upon the way heat is transferred, superheaters are classified into three types: 1. Radiant superheaters 2. Convective superheaters 3. Combined radiative and convective superheaters Convective superheaters are normally called primary superheaters and are located near the convective zone of the furnace, whereas radiant and combined superheaters are termed secondary superheaters. Flow Arrangements of the Different Types of Superheater The saturated steam from the drum is sent into the convective superheaters. After the convective superheater

the steam is passed into the radiant superheater, where the heat is absorbed purely by means of radiation. Steam leaving the radiant superheater is sent into the desuperheater, where highly pure water is sprayed directly into the steam. The temperature of the steam leaving the pendent superheater should not exceed the rated value. Superheaters are often divided into more than one stage such as: 1. 2. 3. 4.

A platen superheater A pendent superheater A horizontal superheater A radiant superheaters

16.25.2 Radiant Superheater Radiant superheaters receive energy primarily by thermal radiation from the furnace with little energy from convective heat transfer. Radiant superheaters are located at the furnace exit or turning section. The radiant superheater absorbs more enthalpy at partial loads when compared to the convective type. At lower loads the flow distribution inside the superheater tubes is less uniform. The radiant superheater outlet temperature decreases with increasing boiler output. At higher loads the mass flow rate of the combustion gas is high, because of increased amount of fuel and air for combustion. The convective heat transfer coefficient increases both inside and outside the tubes. Thus the steam receives more heat transfer per unit mass flow rate, and its temperature increases with load. The surface area required to transfer a given amount of energy will be lower due to the higher log mean temperature difference and higher heat transfer coefficient. Hence their cost may be lower in spite of the better grade of materials required.

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the tubes and air flows outside. Since this is a gas-to-gas heat exchanger it requires a huge heat transfer surface area and hence larger size.

16.25.11 Rotary or Regenerative Air Preheater Rotary preheaters works on the counterflow principle, and consist of a rotor and housing. The rotor is normally divided into 12–24 radial divisions of heat transfer elements and is made up of steel sheets. The rotor is driven by an electric motor and is coupled with worm-gear drive that helps to reduce the speed of the rotor device to 2–6 rpm. During the rotation through the flue gas side the heat transfer element absorbs heat which is later given off during the rotation through

the air section. Based on the number of sections rotary preheaters are further classified into three types: bisector, trisector, and quadsector types. Trisector-type air preheaters are divided into three sections: one for the flue gas, one for the primary, and one for the secondary section. In the quadsector type, the secondary air section is divided into two sections, taking up primary air. Control of the leakage of air into the flue gases is very important to avoid energy loss in the system. Various types of sealing systems are normally employed: 1. 2. 3. 4.

Radial sealing system Axial sealing system Circumferential sealing system Shaft sealing system

16.26 Energy Balance Analysis of a Furnace/Combustion System 16.26.1 Performance Analysis of a Furnace The following procedures should be adopted to carry out the performance analysis of the furnace: 1. 2. 3. 4.

Obtain the ultimate fuel analysis Compute the equivalent chemical formula Select the recommended exhaust gas composition Write and balance the combustion equation 

 Y K air C X HY S Z O K + ε4.76 X + + Z − 4 2 + moisture in air + ash moisture in fuel → PCO2 + QH2 O + RSO2 + T N2 + UO2 + V CO + WC + ash .

4. Calculate the total heat transfer area of the furnace Afurnace .

16.26.2 Analysis   Y K C X HY S Z O K + ε4.76 X + + Z − air 4 2 + moisture in air + ash moisture in fuel → PCO2 + QH2 O + RSO2 + T N2 + UO2 + V CO + WC + ash . Dry exhaust gases PCO2 + RSO2 + T N2 + UO2 + V CO

The volume of gases is directly proportional to the number of moles Volume fraction = mole fraction Volume fraction of CO2

Dry Exhaust Gases.

PCO2 + RSO2 + T N2 + UO2 + V CO

(kmol) .

1. Carry out first law analysis to calculate the theoretical combustion temperature. 2. Calculate the total number of moles of wet exhaust gas for 100 kg of fuel n ex.gas = P + Q + R + T + U + V . 3. 100 CV of fuel = n ex.gas cpexhaust gas (Tth − Tatm ) .

(kmol) .

x1 = P

100 . (P + R + T + U + V )

Volume fraction of CO x2 = V CO

100 . (P + R + T + U + V )

Volume fraction of SO2 x3 = R

100 . (P + R + T + U + V )

Power Generation

16.26.3 First Law Analysis of Combustion

100 . (P + R + T + U + V ) Volume fraction of N2 100 x5 = T . (P + R + T + U + V ) These are dry gas volume fractions. Emission measurement devices only indicate dry gas volume fractions.

  Y K C X HY S Z O K + ε4.76 X + + Z − air 4 2 + moisture in air + ash + moisture in fuel → PCO2 + QH2 O + RSO2 + T N2 + UO2 + V CO + WC + ash ,  Q CV + n air h f,air + n fuel h f,fuel

x4 = U

Measurements Volume flow rate of air, volume flow rate of exhaust are obtained from exhaust gas analysis

=

→ x1 CO2 + x6 H2 O + x3 SO2 + x5 N2 + x4 O2 + x2 CO + x7 C + ash ,

n i h f,fluegas,i +



WCV .

(16.63)

i=1

x1 + x2 + x3 + x4 + x5 = 100 or 1 . Ultimate Analysis of Coal   Y K nC X HY S Z O K + εn4.76 X + + Z − air 4 2 + moisture in air + ash and moisture in fuel

n 

Furnace characterization criteria   1/0.6 Gm f cP 1 Tth Afurnace = − 1 , (16.64) m Tout Tth3 where G is the furnace quality factor, M is the temperature field coefficient, Tth is the theoretical combustion temperature, Afurnace is the total surface area of the furnace, and m f is the mass flow rate of fuel.

where x1 , x2 , x3 , x4 , and x5 are dry volume fractions or percentages.

16.26.4 Boiler Fuel Consumption and Efficiency Calculation

Conservation Species. Conservation of carbon

For any fuel there is a minimum quantity of oxygen required for complete combustion. The amount of air that contains this minimum quantity of oxygen is called the theoretical air; it is the measure of capability of the boiler to transfer heat liberated in the furnace to water and steam. The boiler efficiency may be expressed in any one of the following methods.

n X = x1 + x2 + x7 . Conservation of hydrogen nY = 2x6 . Conservation of oxygen   K Y n K + 2nε X + + Z − 4 2 = 2x1 + x2 + 2x3 + 2x4 + x6 . Conservation of nitrogen   K Y = x5 . εn3.76 X + + Z − 4 2 Conservation of sulfur n Z = x3 . By rearranging the terms, we obtain   Y K air C X HY S Z O K + ε4.76 X + + Z − 4 2 + moisture in air + ash moisture in fuel → PCO2 + QH2 O + RSO2 + T N2 + UO2 + V CO + WC + ash .

16.26.5 Various Energy Losses in a Steam Generator 1. 2. 3. 4. 5. 6. 7. 8.

Heat loss from the furnace surface area Unburned carbon loss Incomplete combustion loss Loss due to hot ash Loss due to moisture in the air Loss due to moisture in the fuel Loss due to combustion-generated moisture Dry exhaust gas losses

The pictorial representation of the Shanky diagram, as shown in Fig. 16.47, represents the various energy losses that take place in a steam generator. The first law analysis steam generator in steady state steady flow (SSSF) mode in molar form (see Fig. 16.48)

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Volume fraction of O2

16.26 Energy Balance Analysis of a Furnace/Combustion System

Power Generation

Losses due to Moisture in Fuel and Combustion Generated Moisture For 100 kg of fuel

Q ML = (M + 9Y )[2442 + csteam (Tg − 25)] (kJ) , (16.69)

where M is the percentage moisture content in the fuel and Y is the combustible hydrogen atoms in the fuel.

Radiation and Unaccounted-for Losses (RUL) This calculation captures losses due to radiation and incomplete combustion resulting in hydrogen and hydrocarbons in the flue gases. While the radiation and unaccounted loss is relatively small, it is difficult to determine accurately. In practice, this loss is 3–5%.

Q RCL = As (h s )(Tsurface − Tamb ) (kW) ,

Losses due to Hot Ash or Slag (ASL) For 100 kg of fuel

Q ASL = Acp,as Tash ,

where cp,ash is the specific heat of ash (0.55– 0.6 kJ/(kg, K)), Tash is the temperature of the ash or slag, and Tash varies from 300 to 800 ◦ C.

(16.70)

(16.71)

where As is the total surface area (m2 ), and h s is the surface heat transfer coefficient.

16.27 Performance of Steam Generator 16.27.1 Boiler Efficiency This is the measure of the capability of the boiler to transfer heat liberated in the furnace into water and steam. The boiler efficiency may be expressed in any of the following methods

or ηboiler =

(HHV − total loss) , HHV

(16.72)

where HHV is the higher heating value of the fuel.

ηboiler =

mass flow rate of steam × (steam heat−feedwater heat) fuel mass × heating value of fuel

16.28 Furnace Design There are two aspects of furnace design. The first is concerned with the generation of the heat; the second part involves the absorption of the heat in the furnace. The amount of fuel can be burned in the given furnace volume, liberating the required amount of heat. The heat release rate and furnace gas temperature are two of the important parameters used for the design of the size of the furnace. The heat release rate is expressed on three different bases: furnace volume (qv ), furnace cross-sectional area, and water wall area in the burner region (qb ). The important thermal characteristic of the furnace for design analysis are:

• • •

Heat release rate per unit cross-sectional area Heat release rate per unit volume Heat release rate per unit wall area of the burner region

16.28.1 Heat Release Rate per Unit Volume qv The amount of heat generated by the combustion of fuel in a unit effective volume of the furnace is given by qv =

m f × LHV Vfurnace

(kW/m3 ) ,

(16.73)

where m f is the designed fuel consumption rate (kg/s), LHV is the lower heating value of the fuel (kJ/kg), Vf is the volume of the furnace (a × b × h f ), and h f is the height of the furnace. The value of qv depends on the coal type and type of furnace. The volumetric heat release rate also depends on the ash characteristic, firing method, and the arrangement of the burners. The proper selection of the volumetric flow

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of steam at constant pressure (1.88 kJ/(kg K)), and Tg is the temperature of exhaust gas.

16.28 Furnace Design

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Part C 16.28

rate in accord with the heat release rate will ensure that fuel particles are substantially burned.

16.28.2 Heat Release Rate per Unit Wall Area of the Burner Region One of the most important regions in the furnace is the burner region. The heat release rate in the burner region is calculated on the basis of the water wall in this region. The heat release rate per unit wall area of the furnace depends on the following parameters [16.16]: 1. 2. 3. 4.

Ash characteristic Fuel ignition characteristics Firing method Arrangement of burners

The heat release rate per unit wall area of the burner region my be written m f LHV (kW/m2 ) , (16.74) qb = 2(a + b)h b where a and b are the width and depth of the furnace, respectively, and h b is the distance between the top edge of the uppermost burner and the lower edge of the lowest burner.

16.28.3 Heat Release Rate per Unit Cross-Sectional Area This is the amount of heat released per unit cross section of the furnace. It is given by m f LHV (kW/m2 ) , (16.75) qf = Afurnace where Afurnace is the cross-sectional area of the furnace in m2 .

16.28.4 Furnace Exit Gas Temperature The furnace exit gas temperature is an important design parameter. It determines the rate of heat absorption by the radiant heating surface in the furnace and that by the convective heating surface of the furnace. The optimum value of the furnace exit gas temperature is 1200–1400 ◦ C.

16.28.5 Example Problem An optimal operation test on a model steam generator gives the following information:

•

Ultimate analysis: C: 63.4%, H: 5.7%, O: 16.8%, N: 10%, ash: 8.9%, moisture: 13%

• • • • •

HHV of coal: 33 318 kJ/kg Combustible solid refuse: 7.5% Dry exhaust gas analysis: CO2 : 15.4%, CO: 0.5%, O2 : 2.8%, N2 : 81.3% Ambient conditions: 50 ◦ C and 100 kPa Temperature of air entering the furnace: 235 ◦ C

Design a PC (pulverized coal) furnace for a steam generator with a thermal capacity of 1000 MW with the following characteristics:

• • • •

Steam generator efficiency of 0.86 Furnace quality factor of 0.406 × 108 Temperature field coefficient of M = 0.405 Thermal capacity of the gas of cp = 1.17 kJ/(kg K)

A furnace can be characterized geometrically by its linear dimensions: front width a, the depth b, and the height h f (Fig. 16.29), which are estimated according to the rated fuel consumption and the thermal, physical, and chemical properties of the fuel to be used. Flow Rate of Fuel

Q boiler = m coal HHVηSG , 1 000 000 = m coal 33 318ηSG , m coal = 34.899 kg/s ; mH O 2 2442 , LHV = HHV − kg of fuel LHV = 323 827 kJ/kg . Here, ηSG is the efficiency of the steam generator. Heat Release Rate per Unit Volume

m f LHV (kW/m3 ) . (16.76) Vf The large content of H and O is largely volatile matter and hence the given composition is bituminous. For bituminous coal the range of value of qv is 0.14–0.20 MW/m3 [16.16]. Substituting the values of qv , m f , and LHV (Table 16.1) we find the volume of the furnace to be qv =

V = 7532.05 m3 . Heat Release Rate per Unit Cross-Sectional Area

This is the amount of heat released per unit cross section of the furnace. It is given by m f LHV (kW/m2 ) , (16.77) qa = Agrade

Power Generation

16.28 Furnace Design

Dry-bottom furnace

Wet (slagging) bottom furnace qv (MW/m3 )

Coal type

qv (MW/m3 )

Open furnace

Half-open furnace

Slagging pool

Anthracite

0.110– 0.140

≤ 0.145

≤ 0.169

0.523–0.598

Semi-anthracite

0.116– 0.163

0.151– 0.186

0.163– 0.198

0.523–0.698

Bituminous

0.14– 0.20

–

–

–

Oil

0.23– 0.35

–

–

–

Lignite

0.09– 0.15

≤ 0.186

≤ 0.198

0.523–0.640

Gas

0.35

–

–

–

Table 16.2 Upper limits of qa for tangentially fired fur-

naces (MW/m2 )

Boiler

Upper limit of qa

capacity (t/h)

ST a ≤ 1300 ◦ C

ST = 1300 ◦ C

ST ≥ 1300 ◦ C

130

2.13

2.56

2.59

220

2.79

3.37

3.91

420

3.65

4.49

5.12

500

3.91

4.65

5.44

1000

4.42

5.12

6.16

1500

4.77

5.45

6.63

a

where Agrade is the cross-sectional area of the grade in m2 m f LHV Agrade = ab = (kW/m2 ) . (16.78) qa Substitute the value of qa , m f , and LHV (Table 16.2) in (16.78) we find the grade area ab = 441.46 m2 . Heat Release Rate per Unit Wall Area of the Burner Region The heat release rate per unit wall area of the burner region may be written

m f LHV 2(a + b)h b

(kW/m2 ) .

Based on the above constraints suitable values for a and b are a = 20.62 m , b = 21.4 m , 1129.8 = 13.44 m . hb = 2(21.4 + 20.62) The volume of the furnace region (Fig. 16.29) is therefore

ST = softening temperature of ash (◦ C)

qb =

Part C 16.28

Table 16.1 Typical values of the volumetric heat release (qv ) in MW/m3

(16.79)

The recommended value of the burner region heat release rate was taken as h b = 1 MW/m3 . 2(a + b)h b = 1129.80 m . 2

Based on Tables 16.1 and 16.3, corresponding to the boiler capacity, the minimum width was chosen as bmin = 6 m and h furnace,min = 11 m.

Vfurnace = h furnace ab a − (d + d + d tan β + d tan α)d , (16.80) 2 ad Vfurnace = h furnace ab − (2d + d tan β + d tan α) , 2 (16.81)

Vfurnace = h furnace ab −

ad 2 2

1411

(2 + tan β + tan α) . (16.82)

Substituting the values of a, b, α, β, and Vfurnace into (16.82) yields h furnace = 19.33 m . To find the height of the hopper we insert the data into   b−e hh = (16.83) tan γ = 14.56 m . 2 From the geometry we calculate the total surface area as a(h f + h b ) + a(h f + h b − d − d tan α − d tan β + d sec α + d sec β) + 2b(h f + h b )   1 − d(d + d + d tan α + d tan β) + 2 h h (b + e) 2 (16.84) + 2ah h cos ec γ .

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Complementary Material for Mechanical Engineers

Part C 16.29

For 100 kg of fuel

Table 16.3 Lower limit of h furnace (m) Boiler capacity (t/h)

65– 75

130

220

420

670

Anthracite Bituminous

8 7

11 9

13 12

17 14

18 17

Substituting all the values into (16.84), the surface area of the furnace is calculated to be 3793.98 m2 . Adiabatic Flame Temperature Ultimate Analysis.

64.4 = 5.283 12 13 = 4.255 H: 5.7 − 9     16.8 8 13 O: − = 0.327 16 9 16 1 = 0.071 N: 14 Ash = 8.9 13 Moisture = 18   Y K C X HY S Z O K + X + + Z − O2 4 2 → 15.4CO2 + 0.5H2 O + 2.8O2 + 81.3N2 + ZH2 O C:

C5.28 H4.25 O0.327 + 4.76 · 1.162 · 6.152air → 5.11CO2 + 0.166H2 O + 0.933O2 + 27.1N2 + 2.13H2 O , n exit (mole of exit gases) = 5.11 + 0.166 + 0.93 + 27.1 + 2.13 = 35.43 , 100 · 33 318 = 35.43 · 40 · (Tth − Tatm ) , Tth = 2624 K . The ash softening temperature is ≥ 1250 ◦ C and Tout ≤ 1250 ◦ C = 1523 K. 100 kg of fuel generates 1056.71 of exhaust flue gas with m gas for a 34.89 kg/s of flow rate of fuel, m gas = 368.68 kg/s. To find Tout we use   1/0.6 Gm f cp 1 Tth − 1 , (16.85) Afurnace = m Tout Tth3 where G is the furnace quality factor, M is the temperature field coefficient, Tth is the theoretical combustion temperature, Afurnace is the total surface area of furnace, and m f is the mass flow rate of fuel. Substituting all these values in (16.85) we find Tout = 1365.95 K. Tout is < 1523 K (ash softening temperature), so the design is safe.

16.29 Strength Calculations Special care must be taken in the design and stress analysis of steam generators because of the application of high pressure and temperature involved in the system. Allowable stresses in the pressure vessel depend on the nature of the loading in the pressure vessel and the response to this loading. Stress can be classified into: 1. Primary stress 2. Secondary stress 3. Peak stress The primary stress is developed by the mechanical load; it can cause mechanical failure of the vessel. An example of this kind of stress is that produced by internal pressure such as in a steam drum. Secondary stress is due to mechanical load or thermal expansion. Peak

stress is concentrated in highly localized area at abrupt geometry changes.

16.29.1 Mathematical Formulae for Stress The basic equation for the longitudinal stress σ1 and hoop stress σ2 in a vessel of thickness of h, longitudinal radius r1 , and circumferential stress r2 , which is subjected to a pressure p is given by p σ1 σ2 + = . r1 r2 h

(16.86)

From this equation, and by equating the total pressure load with the longitudinal forces acting on a transverse section of this vessel, the stresses in the commonly used shells of revolution can be found.

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Part C 16

is a fissionable material and can be extracted from the reactor fuel waste by a fuel reprocessing plant. Plutonium can then be used in the next-generation reactors (fast breeder reactors (FBRs)), thereby considerably extending the life of nuclear fuels. The FBR technology is being intensely developed as it will extend the availability of nuclear fuels at predicted rates of energy consumption to several centuries. Figure 16.54 shows the schematic diagram of an FBR. It is essential that, for breeding operation, the conversion ratio (fissile material generated/fissile material consumed) is more than unity. This is achieved by fast-moving neutrons so that no moderator is needed, although the neutrons do slow down slightly through collision with structural and fuel elements. The energy density/kg of fuel is very high and so the core is small.

It is therefore necessary that the coolant should possess good thermal properties; hence liquid sodium is used. The fuel for an FBR consists of 20% plutonium plus 8% uranium oxide. The coolant, liquid sodium, leaves the reactor at 650 ◦ C at atmospheric pressure. The heat transported in this way is led to a secondary sodium circuit which transfers it to a heat exchanger to generate steam at 540 ◦ C. With a breeder reactor the release of plutonium, an extremely toxic material, make the environmental considerations very stringent. An experimental fast breeder test reactor (FBTR) (40 MW) has been built at Kalpakkam alongside a nuclear power plant. FBR technology is expected to reduce the cost of electric energy so that it compares favorably with that from conventional thermal plants.

16.32 Future Prospects and Conclusion Various advanced power generation technologies have been described in this chapter. Many regions of the world are experiencing fast growing electricity demand. Advanced technologies such as IGCC, ultrasupercritical cycles, and advanced gasification molten carbonate fuel cell cycles allow this electricity demand to be met and emission levels from power plants to meet air quality standards. Fluidized-bed combustion is an environmentally benign and proven technology for the disposal of solid wastes and the generation of electrical energy. Technological advancement will improve the reliability and efficiency of energy conversion process. The integrated gasification combined cycle will be able to exploit various kinds of low-grade energy resources such as biomass, low-grade coal, oil residues etc., for the sake of efficient power production. The development of advanced materials to withstand high temperatures as well as high pressures will enhance the thermal efficiency to 55%. Even a fraction of a percentage improvement in efficiency can mean huge savings in annual fuel cost.

Cogeneration of heat as well as electric power is one of the attractive options from the cost–benefit point of view; it saves 30–40% of fuel input energy. A combined cycle employing cogeneration using a multicomponent fluid such as an ammonia–water mixture will improve the thermal efficiency further. Effective utilization of renewable sources of energy including hydropower, solar, wind, and biomass is one of current the challenging tasks for researchers. The potential of solar power is unlimited; it is our prime task to utilize this energy in a more effective way. The development of solar technology seeks to achieve efficient operation even though solar energy intensity varies according to weather and time of day. With the end of coal reserves in sight in the not too distant future, the immediate practical alternative source of large-scale electric energy generation is nuclear energy. The latest power plant technologies and dedicated research will lead to efficiencies approaching the Carnot efficiency in the near future.

References 16.1 16.2

A. Bejan, G. Tsatsaronis, M. Moran: Thermal Design and Optimization (Wiley, New York 1995) D.P. Kothari, K.C. Singal, R. Ranjan: Renewable Energy Sources and Emerging Technologies (Prentice Hall of India, New Delhi 2008)

16.3

16.4

I. Seikan: Steam Power Engineering: Thermal And Hydraulic Design Principles (Cambridge Univ. Press, Cambridge 1999) M.S. Briesch, R.L. Bannister, I.S. Diakunchak, A. Huber: A combined cycle designed to achieve

Power Generation

16.6 16.7 16.8

16.9

16.10

16.11 16.12 16.13

16.14

16.15

16.16 16.17

J.C. Zink: Who says you can’t store electricity, Power Eng. 101(3), 21–25 (1997) P.G. Hill: Power Generation: Resources, Hazards Technology, and Costs (MIT Press, Cambridge 1977) W.A. Adams: Electrochemical energy storage systems: A small scale application to isolated communities in the Canadian Arctic, Can. Electr. Eng. J. 4, 4–10 (1979) S. Tavoulareas: Multi Pollutant Emission Control Technology Options for Coal Fired Power Plants, US Environmental Production Agency Rep. (EPA, Washington 2005) L.E.J. Roberts, P.S. Liss, P.A.H. Saunders: Power Generation and the Environment (Oxford Univ. Press, Oxford 1990) P. Basu, C. Kefa, L. Jestin: Boilers and Burners: Design and Theory (Springer, New York 2000) G. Wills: Nuclear Power Plant Technology (Wiley, New York 1967)

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16.5

greater than 60% efficiency, ASME J. Eng. Gas Turbines Power 117, 734–741 (1995) R. Kehlhofer, R. Bachmann, H. Nielsen, J. Warner: Combined Cycle Gas and Steam Turbine Power Plant (PennWell, Tulsa 1999) K.W. Li, A.P. Priddy: Power Plant System Design (Wiley, New York 1985) D.P.K. Kothari: Modern Power System Analysis (McGraw-Hill, New York 2006) R.C. Bansal, D.P. Kothari, T.S. Bhatti: On some of the design aspects of wind energy conversion systems, Int. J. Energ. Conv. Manag. 43, 2175–2187 (2002) D.P.K. Kothari, I.J. Nagarth: Power System Engineering, 2nd edn. (Tata McGraw-Hill, New Delhi 2007) B. Kelly: Optimization studies for integrated solar combined cycle system, Proc. Solar Forum 2001 (ASME, Washington 2001)

References

1421

Electrical Eng 17. Electrical Engineering

Electricity is the most flexible form of energy accessible to humans. It can be transported over long distances, and transformed into almost any other kind of energy like heat, radiation or kinetic energy. Electrical engineering is very closely coupled especially to mechanical engineering but also to many other fields of engineering. This chapter will give an overview of the theoretical fundamentals of electric phenomenon and some practical electric processes and application. It should be understood as a basic source of information about the most important issues in electrical engineering. For further reading the references will give a deeper insight into the mentioned scientific fields. The reader will get information about the fundamentals of electrical engineering in Sect. 17.1. Here the physical phenomenon of electric currents and voltages are explained. The electrical aspects of the main electrical machines transformer, generators and motors are explained in the Sects. 17.2, 17.3 and 17.5. Power electronics have become a very important issue in transformation of different forms of electricity and in control of machinery. The reader will be informed about the basic working principles of this scientific field in Sect. 17.4. This chapter places a emphasis on the section Electric Power Transmission and Distribution (17.6). In this section the fundamentals of electricity transport, distributed generation (especially from renewable sources) and the energy system protection are given.

17.1 Fundamentals ...................................... 1422 17.1.1 Electric Field Basics ..................... 1422 17.1.2 Electric Circuits............................ 1424 17.1.3 Alternating Current (AC) Engineering................................ 1428

17.1.4 Networks ................................... 1434 17.1.5 Materials and Components ........... 1439 17.2 Transformers ........................................ 1442 17.2.1 Single-Phase Transformers ........... 1442 17.2.2 Instrument Transformers .............. 1446 17.2.3 Three-Phase Transformers ............ 1447 17.3 Rotating Electrical Machines .................. 1448 17.3.1 General Information .................... 1448 17.3.2 Induction Machines ..................... 1451 17.3.3 Synchronous Machines................. 1454 17.3.4 Direct-Current Machines .............. 1456 17.3.5 Fractional-Horsepower Motors...... 1458 17.4 Power 17.4.1 17.4.2 17.4.3

Electronics ................................. 1461 Basics of Power Electronics ........... 1461 Basic Self-Commutated Circuits ..... 1462 Basic Circuits with External Commutation .......... 1468 17.4.4 Design Considerations.................. 1475

17.5 Electric Drives....................................... 1478 17.5.1 General Information .................... 1478 17.5.2 Direct-Current Machine Drives ...... 1481 17.5.3 Three-Phase Drives ..................... 1485 17.6 Electric Power Transmission and Distribution ................................... 1487 17.6.1 General Information .................... 1487 17.6.2 Cables and Lines ......................... 1489 17.6.3 Switchgear ................................. 1490 17.6.4 System Protection ....................... 1491 17.6.5 Energy Storage ............................ 1495 17.6.6 Electric Energy from Renewable Energy Sources.... 1497 17.6.7 Power Quality ............................. 1502 17.7 Electric Heating .................................... 1504 17.7.1 Resistance Heating ...................... 1505 17.7.2 Electric Arc Heating...................... 1505 17.7.3 Induction Heating ....................... 1507 17.7.4 Dielectric Heating ........................ 1508 References .................................................. 1509

Part C 17

Seddik Bacha, Jaime De La Ree, Chris Oliver Heyde, Andreas Lindemann, Antje G. Orths, Zbigniew A. Styczynski, Jacek G. Wankowicz

1422

Part C

Complementary Material for Mechanical Engineers

17.1 Fundamentals

Part C 17.1

In electric engineering most of the phenomenon can be explained using some fundamental laws. These law are explained in Sect. 17.1.1. In the following subsections the basics about the electric circuits, starting from the DC current, and ending with the explanation of AC circuits with capacitance and inductance [17.1, 2]. The section closes with comments about multi phase networks and the behavior of some materials important for electrical engineering [17.1, 3].

17.1.1 Electric Field Basics Fields and Equations The electromagnetic field (EMF) in any given area of space should comply with the laws of electrodynamics [17.4]. This field can be described by the five field parameters presented in Table 17.1. Based on experimental knowledge, four laws are known to be valid for electromagnetic fields: Maxwell’s laws; in integral form they can be written as Ampère’s, Faraday’s, and Gauss’s laws. Ampère’s Law. The first of Maxwell’s laws is often

called the general Ampère’s law (17.1a)      ∂D J+ H ds = dA ∂t C

(17.1b)

 H ds = I + C

∂ ∂t

  D dA .

 

BdA = 0

(17.1c)

A

Ampère’s law (17.1a) requires that the line integral (circulation) of the magnetic field intensity H around a closed contour s is equal to the sum of the line current I and electric displacement D through the surface A.

A

Gauss’s law states that the net magnetic flux out of any closed surface A is zero. This amounts to a statement about the sources of a magnetic field. For a magnetic dipole, in any closed surface the magnetic flux directed inward toward the south pole is equal to the flux outward from the north pole. The net flux will always be zero for dipole sources. If there were a magnetic monopole source, this would give a nonzero area integral. Furthermore, the divergence of a vector field is proportional to the point-source density, so the form of Gauss’s law for magnetic fields is therefore a statement that there are no magnetic monopoles. Electricity – Gauss’s Law.

 

D dA = Q

c

∂ ∂t

 

BdA

(17.2)

A

Faraday’s law of induction requires that the line integral (circulation) of the electric field intensity E is

(17.5) (17.6) (17.7)

The current density and electric displacement are proportional to the electric field strength, while the flux Table 17.1 Field parameters and symbols

Field parameters Electric field

E ds = −

(17.4)

The electric flux outside any closed surface is proportional to the charge Q. The field parameters are related to three equations (17.5)–(17.7), which refer to materials of different physical properties

Induction – Faraday’s Law.



(17.3)

J = σE , D = εE , B = μH .

A

and

Magnetism – Gauss’s Law.

A

(17.1a)

A

to which is added   J dA I=

equal to the negative time derivative of the magnetic flux density through the surface A.

Magnetic field Electric flow field

Electric displacement Electrical field strength Flux density Magnetic field strength Current density

Symbol D E B H J

1428

Part C

Complementary Material for Mechanical Engineers

siderably more magnetic flux density than air. The magnetic flux density B reinforcement is expressed by B = J + μ0 H = μ0 (M + H) ,

(17.49)

Part C 17.1

where J is the magnetic polarization and M is the magnetization. Ferromagnetic materials show magnetization characteristics in the form of a hysteresis curve B = f (H), see Fig. 17.7a. After initial magnetization to the point A1 , the H field is decreased by reducing the current in the coil, the magnetic flux density B is also reduced, but the B–H curve does not follow the original magnetization curve. Note that at point B1 the current in the coil of a toroid is equal to zero, as is H, yet the residual magnetic flux density B is nonetheless present in the toroid. The residual flux is due to the fact that the magnetic moments of some of the domains in the ferromagnetic materials are still aligned in the same direction. The magnitude of this residual B is called the remanence. If we now reverse the current to reverse the H, the B–H curve will trace a curve B1 H1 , as shown in Fig. 17.7. Note that it takes some negative value of H to null the B field. The value of H1 in the negative direction of the initial magnetization, necessary to nullify the magnetic inductance B field, is called the coercive force or coercivity. If the reverse current is increased beyond this point, the magnetic inductance B begins to reverse and the B–H curve follows the curve H1 A2 . If the current is now reduced, the B–H curve traces a new path A2 A1 . The closed loop A1 B1 H1 A2 A1 is called a hysteresis loop. If the current is varied in a smaller cycle, the corresponding hysteresis loop will be smaller. If the material is brought to saturation in both ends of the magnetization curve, the remanence B is called the retentivity of the ferromagnetic material, and the coercive force H is called the coercivity of the material. In general both soft and hard magnetic materials are useful in electrical engineering. The first are used for constructing magnetic circles in electrical machines (slim hysteresis curve), while hard magnetic materials are used in permanent magnets. Electromagnetic Field Forces An electromagnetic field can be defined by the force it produces. Generally, the force in a field is defined as

1 (17.50) fv = (S× B) − H2 grad μ . 2 The first part of (17.50) gives the current density force, which affects the current leading conductor in the external field from B induction. The second part ap-

pears only for position-dependent permeability and is expressed as a permeable force density. For the length element ds of an electrical conductor the force is expressed as dF = I ( ds × B) .

(17.51)

The force is determined for a cable with length l, which is located in a vertical magnetic field (Fig. 17.7b) F = BIl .

(17.52)

The so-called right-hand rule is applied to determine the direction of the magnetic force. A magnetic force can also be specified for two parallel electrical conductors. The current I1 generates the field strength H at a distance r in conductor 1, in agreement with (17.1a) H = I1 /(2πr) .

(17.53)

A second conductor located at the distance d and carrying the current I2 is affected by the force μ0 I1 I2 (17.54) l. F= 2π d The value of the forces in conductors 1 and 2 is the same. When both the current in the two conductors is in the same direction electrostatic attraction occurs. If, on the other hand, the direction of the current in the two conductors is different then repulsion occurs. Moreover, mechanical tensions are produced on the interface of a magnetic field, between areas with differential permeability. On the interface between iron and air longitudinal pull and lateral pressure develop. If a magnetic field with inductance B passes vertically through a surface that combines areas with μ1 and μ2 , a specific force σ is accrued normal to this surface   1 1 1 B2 . − (17.55) σ= 2 μ1 μ2 When μ1 = μ0 for air and μ2 = μ0 μr  μ0 for iron the electrostatic attraction force through surface A can be defined by 1 2 B A. (17.56) F= 2μ0 This is applied in electromagnets carrying ferromagnetic loads.

17.1.3 Alternating Current (AC) Engineering Alternating Current Quantities For a periodic current waveform i(t) with period T and frequency f = 1/T the following definitions can be written

Electrical Engineering

•

The average value i=

1 T

(17.57)

0

•

0

The average value v and the RMS value V of an alternating voltage v(t) are defined in a similar way. The AC waveform current containing a DC component consists of a fundamental frequency and higher harmonics that are integer multiples of the fundamental frequency. The RMS value of such a current is

2 2 2 . (17.59) I = i + I12 + I22 + I32 + . . . = i + I≈ The deformation of an alternating current through harmonics can be calculated using the distortion factor   2 Ii . (17.60) ki = 1 − I In this case a fundamental current will be defined as (17.61)

where iˆ is the peak value of the current and ω = 2π f is the angular speed. The average value i¯ of the current i (17.57) is zero while the effective value is √ (17.62) I = iˆ/ 2 . The same refers to voltages and therefore vˆ V=√ . (17.63) 2 RMS value of a current I refers directly to the Ohmic resistance by thermal energy dissipated by this both at flow of direct current or its alternating equivalent of defined RMS value which produces the same thermal effect. Active power P produced by current I of given RMS value can be written as T 1 i 2 dt = RI 2 . (17.64) PV = R T 0

Currents like that in (17.61) flow in branches with linear elements if the applied voltages and currents also

Alternating Current Parameters Every alternating current parameter is represented by its:

• • • •

Amplitude Effective value Frequency Phasing (t = 0)

Applying these parameters the current and voltage can be expressed as follows  √  √ 2I ej(ωt+ϕi ) = Re 2I ejωt , (17.65) i = Re with I = I ejϕi  √  √ v = Re 2V ej(ωt+ϕu ) = Re 2V ejωt , (17.66) with V = V ejϕu . Now, by giving the angular frequency ω the current and voltage can be sufficiently described by using the complex parameters I and V , which contain information about the absolute value and phasing. The ratio of I to V is complex and denotes the impedance Z, which consists of the component’s resistance R and reactance X. Its multiplicative inverse gives the admittance Y , which consists of the conductance G and the susceptance B Z = V /I = R + jX , Y = I /V = 1/Z = G + jB .

(17.67) (17.68)

The passive linear elements in alternating current circuits are:

• • •

Ohmic resistance Capacitors Inductors

By using (17.65)–(17.68) it is very easy to evaluate these elements for AC v R = Ri → V R = RI → Z R = R , dv ic = C → Ic = jωCV → Z c , dt Z c = 1/jωC = −jX c , di vl = L → VL = jωL I → Z L , dt Z L = jωL = jX L .

(17.69)

(17.70)

(17.71)

Accordingly, in relation to the voltage the current phase is shifted by −π/2 by an inductor, and by +π/2 by a capacitor. A resistance does not produce an angular phase shift.

Part C 17.1

The effective, root-mean-square (RMS) value

  T 1 i 2 dt (17.58) I = T

i = iˆ cos(ωt + ϕ) ,

1429

have a sine waveform with a fundamental frequency, and transition processes have faded away.

T i dt

17.1 Fundamentals

Electrical Engineering

excitation matrix, and v(t) represents the input signals which result from active elements in the circuit. The solutions to the above equations can be stated as shown in the following expression t x(t) = e

A(t−t0 )

x(t0 ) +

e A(t−τ) Bv(τ) dτ , (17.92)

where x(t0 ) is the initial state vector, which disappears for zero initial conditions. The solution to this problem can also be expressed as the sum of a transient-state component and a steady-state component x(t) = xt (t) + xs (t) .

(17.93)

The steady-state component xs (t) can be solved by commonly used calculation procedures valid for steady-state AC and DC analysis. The transient element xt (t) can be computed in this case with the help of a simplified formula xt (t) = e A(t−t0 ) xt (t0 ) ,

xt (t0 ) = x(t0 ) − xs (t0 ) . It can be seen that the solution of the transient phenomena is reduced to the calculation of the e At component. In order to calculate this element, three main methods are used: – The Sylvester equation – The Cayley–Hamilton theorem – Eigenvalue decomposition with Jordan form representation Among these methods only the eigenvalue transformation will now be explained in an example. Assuming that the state matrix A is square, the eigenvalues for this matrix can be calculated with the help of the formula (17.95)

The calculated values sk are the basis for obtaining the eigenvectors that build the transformation matrix T. This matrix allows us to transfer the square matrix A into Jordan form Aj . The sought component e At can be reformulated as e At = T−1 e Aj t T .

(sI − A)X(s) − X(t0 ) = BV(s) ,

(17.96)

(17.97)

where I is the identity matrix. The input signal is transformed into s-domain by the following integral ∞ Im[ f (t)] = F(s) =

f (t)e−st dt .

(17.98)

0

After solving the much easier algebraic equation in s-domain, the solution needs to be transformed back from the s-domain into time domain

(17.94)

where the initial condition for the above equation is stated as the difference between the initial condition x(t0 ) and the initial condition for the steady-state component at the instant t0

det(A − Is) = 0 .

The elements of the Jordan matrix contain the linear combination of the exponential and polynomial function dependent on the multiplication factors and values of the eigenvalue of the state matrix A. 2. Laplace Transformation Transient phenomena in a network can be calculated with the help of the Laplace transformation as well. Using operator methods based on the Laplace transformation, the state equation can be written in the following form

Im

−1

σ+  j∞

[F(s)] = f (t) =

F(s)est ds . (17.99)

σ− j∞

The initial conditions for the state variables are considered by the Laplace transformation and are contained in the input signals (excitation signals). To obtain the Laplace function, correspondence tables can be a useful tool. The solution of the transient phenomena is obtained by the inversion of the square matrix (Is − A) and multiplication by its excitation vector BV(s) + X(t0 ). As a result of this approach, the polynomial functions for the state variables are obtained and written as Ni (s) (17.100) . xi (s) = Di (s) Assuming that the denominator can be described by the polynomial function with stated poles Di (s) = (s − s1 )m 1 (s − s2 )m 2 . . . (s − sr )m r (17.101)

and that the polynomial order equals n = m 1 + m 2 + . . . mr ,

(17.102)

the state i is represented as the following time function mk r   akl (17.103) t m k −1 esk t , xi (t) = (m k − l)! k=1 l=1

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t0

17.1 Fundamentals

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Part C 17.1

In order to keep the superconductive effect, certain critical values of the current density and external magnetic field cannot be exceeded (Fig. 17.22). Superconductors can be used in energy engineering for electrical machines, distribution feeders, and storage systems. For this purpose, high-temperature superconductors have been designed based on compounds of NbTi (Tc = 9.3 K), Nb3 Sn (Tc = 18.0 K) and V3 Ga. For example, superconductance for a Ni and Ti compound is achieved at a temperature of 4.2 K, a current density of 70 kA/cm2 , and a critical magnetic flux density of 8 T. Due to the low temperature that must be maintained for superconduction, adequate cooling materials – most often liquid helium (LHe) and liquid nitrogen (LN2 ) – and appliances are required. Recently, new technologies have been being developed to obtain high-temperature superconductors in which the superconductive properties appear at temperatures of about 100 K. The compound YBa2 Cu3 O7 , for example, exhibits the zero-resistance effect at 93 K. High-temperature superconductors have the advantage of lower cost and higher efficiency. For example, in order to achieve the superconducting temperature for such materials, cheaper nitrogen instead of high-priced helium can be used. Additionally less energy is needed to maintain the appropriate conditions. However, due to their low critical current density and some problems with the production of superconductor components, their practical application still lies in future.

beck effect states that the generated voltage between two different metal wires connected in one circuit is proportional to the difference of temperatures between the two thermo-elements. One of these joints is usually kept at a fixed reference temperature, for instance in a container filled with water and ice (for a reference temperature of 0 ◦ C). When a copper wire is connected to a constantan wire in one circuit and a temperature difference of 100 K exists, a thermovoltage of 4.15 mV is produced. A second effect, known as the Peltier effect, is the inverse of the Seebeck effect. Current flowing through a thermocouple irrespectively to Joule heat feeds the one brazed point with heat which is dissipated from the other brazed point. The Peltier thermal effect is proportional to the current flowing in the circuit. This phenomenon can be found in various circuit elements subjected to cooling. Materials in an Electric Field Insulation materials are characterized by their relative permittivity εr and electric breakdown strength E d . In an electric field the molecules are polarized by the electric charge. The electric field strength is combined with the polarization by a formula

P = χ e ε0 E ,

(17.119)

where χe = ε1 − 1 is the dielectric susceptibility. Some dielectric materials have a nonlinear relationship between polarization and electric field strength and show ambiguous hysteresis properties. This behavior is called ferroelectricity.

Hall Effect. When current flows through a metal strip

with a rectangular cross-section a magnetic field perpendicular to it generates a voltage between the two opposite margins of that metal strip; this is known as the Hall voltage. This Hall effect can serve to measure the magnetic field. Furthermore, based on this effect the currents in wires can be measured with the help of special equipment. In order to use the Hall effect for measurements, a thin flat blank with a high Hall factor is applied. For example, a Hall-effect probe made of InAs materials achieves a Hall voltage of about 100 mV at currents of about 0.1 A and a magnetic induction of 1 T. Seebeck and Peltier Effects. Two further effects are the

Seebeck and Peltier effects which both concern the thermovoltage. A thermovoltage is produced by two wires connected to each other as a thermocouple. In a closed circuit loop the thermovoltage is noticeable when the two brazed points have different temperatures. The See-

Piezoelectricity. Some crystals can become polarized

by applying pressure or tensile stress. On the opposite edges of the crystal surface charges arise with different signs. Reciprocally, for these materials it is possible to apply an electrical field which causes a change in the length of the material. This change is dependent on the polarization and direction of that field. In general, piezoelectric materials are used for the conversion of electromechanical oscillations. For example, piezoelectric transducers are applied in measurement techniques, microphones, and especially in quartz clocks. The most recent application for piezoelectric transducers is in drive devices and in the field of noise reduction. Photovoltaic Solar Cells. Solar cells are photovoltaic

(PV) elements with a p–n junction in which light irradiation causes the separation between the electrons and p-holes and a voltage can develop [17.8]. The energy

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17.3 Rotating Electrical Machines 17.3.1 General Information

Part C 17.3

Electrical machines convert mechanical energy to electrical energy (generator) or electrical energy to mechanical energy (motor) [17.11]. Energy conversion in almost all motors and generators takes place when a change in magnetic flux is associated with mechanical motion. Each machine consists of at least one stationary part, the stator, and one rotating part, the rotor. According to Faraday’s law, voltages are generated in windings or coils by: 1. Rotating a magnetic field past the windings or coils 2. Rotating the coils through a magnetic field, or 3. By designing the magnetic circuit so its reluctance changes with rotation of the rotor

Nonrotating Machines. Linear machines are nonrotating machines, and their construction can be either induction or synchronous. They are used as short or long stator linear motors.

Types of Construction and Shaft Heights The different types of construction for rotating electrical machines are described in IEC 60034. Machines for industrial use, especially three-phase asynchronous (induction) machines, are produced according to IEC 60072. The construction of the machine is connected with nominal power and protection degree. Degrees of Protection Rotating machines are classified according to their size and protection provided by the enclosure as follows:

Machine Types In general, electrical machines can be divided into three types based on their mode of operation [17.1].

•

Induction Machines. As a general rule induction ma-

•

chines consist of a three-phase stator winding fed with AC currents, and a short-circuit three-phase rotor winding. Power is transmitted from the rotating magnetic field generated by the stator windings, through the air gap, to the rotor, which rotates asynchronously. A special form of this machine may be provided with slip-rings to gain access to the rotor windings. Synchronous Machines. The majority of synchronous

machines have a stator three-phase winding, and a rotor winding energized by a DC source that rotates at a constant speed proportional to the ratio of the applied frequency and the number of poles. For medium-sized and large machines a field coil is used on the rotor, while for small machines permanent magnets may be used instead. Direct-Current Machines. A direct current (DC) machine may be viewed as a synchronous machine inside out. The commutator winding is placed at the rotor whereas the magnetic flux is produced in the stator. This can be achieved with a field coil or permanent magnets. The AC voltages induced in the rotor windings are converted to DC voltages through the action of the mechanical commutator. The commutator is mounted on the rotor shaft and connects groups of coils to the external terminals by means of brushes.

•

Protected against human contact with parts that are under voltage Protected against contact and ingress of foreign bodies Protected against water ingress

This protection is described in IEC 60034-5. The degree of protection is represented by a symbol formed from a number and a letter, which consists of: IP + two digits + sometimes extra letters, e.g., IP 23 S. The first digit of the code is for protection against contact and ingress of foreign parts whose size ranges between 1 mm and 50 mm. The second is for protection against water ingress. The digit 0 means that this machine is not protected (in the order of 0–6 for the first digit and 0–8 for the second digit). The second digit indicates that the machine is protected against either dripping water, dripping water at a tangential deviation up to 15◦ , spray water, shower water, stream water or that the machine is protected from dipping or immersion. The special letters in the IP code are:

• • •

W – weatherproof machine S – machines that are checked for water protection while stationary M – machines that are checked for water protection during operation

Losses and Efficiency Using IEC 60034-2:1972 (IEC 60034-2A:1974 + A1:1995 + A2:1996) the total losses in an electrical

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Part C 17.3

the air gap between the stator and the rotor. This power is called the air-gap power PAG of the machine. After the power is transferred to the rotor, some of it is lost as ohmic losses (the rotor copper loss PRCL ), and the rest is converted from electrical to mechanical power (Pconv ). Finally, the friction and windage lossesPF&W and stray losses Pmisc are subtracted. The remaining power is the output of the motor Pout . Single-Phase Motors In the examples above, it was assumed that the induction machines were fed with a three-phase symmetrical source. Single-phase-fed induction motors, which are important in the small power sector, cannot produce a starting torque because of the missing rotating field in the stator. To solve this problem, a split-phase motor is used in most cases. An extra start-up winding is arranged in addition to the major winding. Through a capacitor (capacitor start motor) or a higher resistance a phase shift of the current in the start-up winding is achieved. After reaching a defined speed the start-up winding can be switched of, e.g., with a centrifugal switch.

Star-point

Terminal

Transformer

Stator core Stator winding

Air filter

Threephase Shaft Rotor auxiliary Rectifier salient generator pole for excitation

Bearing Exciter winding

Cooling

Fig. 17.42 Synchronous generator (ABB)

ment is required to provide the DC power to its field windings. There are two approaches to supply this DC power:

•

From an external DC source to the rotor by means of slip rings and brushes From a special DC source mounted directly on the shaft of the synchronous generator

17.3.3 Synchronous Machines

•

Types Like other electrical machines, synchronous machines may be operated either as a motor or as a generator. In a synchronous generator, a DC current is applied to the rotor winding, which produces a rotor magnetic field. The rotor of the generator is then turned by a prime mover, producing a rotating magnetic field within the machine. This rotating magnetic field induces a three-phase set of voltages within the stator windings of the generator. The rotor of a synchronous generator is a large electromagnet. The magnetic poles on the rotor can be:

The largest electrical machines in the world are synchronous generators (Fig. 17.42). Some can produce as much power as 1700 MW. They are constructed as (twoor four-pole) turbogenerators and are driven, for example, by steam turbines. The power of a synchronous machine is limited by its possible rotor dimension (mechanical stress) and allowable armature current (temperature) (Table 17.3). The limiting power values of two-pole turbogenerators at 50 Hz are described below.

• •

Table 17.3 Synchronous generator power limits

Salient – the magnetic pole sticks out of the rotor surface Nonsalient – the magnetic pole is constructed flush to the surface

Non-salient-pole rotors are normally used for twoand four-pole rotors. Because the rotor is subjected to changing magnetic fields, it is constructed of thin laminations to reduce eddy-current losses. A DC current must be supplied to the field circuit on the rotor. Since the rotor is rotating, a special arrange-

Direct air cooling Indirect air cooling Hydrogen cooling without compressors Hydrogen cooling with 5 bar overpressure Water cooling, two pole Water cooling, four pole

80 MVA 150 MVA 250 MVA 800 MVA 1200 MVA 1700 MVA

Electrical Engineering

Universal Motors These are motors which can work in both DC and AC systems. Nowadays they mostly use onephase alternating current, especially in household

appliances. The major advantage of these machines is that the rotating speed is not bound to the network frequency. For example, a vacuum cleaner that works at a rotating speed of up to 25 000 min−1 can achieve a very high power-to-weight ratio. The universal motor is setup as shown in Fig. 17.56b. The unloaded speed is limited by windage and friction. Because of their capability to operate at high speeds, universal motors of a given horsepower rating are significantly smaller than other kinds of AC motors operating at the same frequency. Universal motors are ideal for home devices such as hand drills, hand grinders, food mixers, routers, and vacuum cleaners. Unfortunately the lifetime of such motors is limited by the lifetime of the brushes, which is about 2500 h.

17.4 Power Electronics 17.4.1 Basics of Power Electronics Power Electronics is basically used to transform one electrical system into another. Major applications are variable-speed drives and power supplies. Configurations as follows are frequently met:

• • • •

Conversion DC → DC, e.g., to supply variablespeed DC drives from a constant-voltage DC line or as step-down DC–DC converters in decentralized power supplies Conversion AC → DC by a rectifier, e.g., to supply variable-speed DC drives or electronics – such as computers, communication equipment etc. – from AC mains Conversion DC → AC by an inverter, e.g., to feed energy generated from a DC source – such as a fuel cell or a photovoltaic generator – into AC mains Conversion AC → AC, e.g., to supply variablespeed AC motor drives by AC mains, or in generator mode to feed the generated electrical energy into mains

It is obvious that the voltage level and – in the case of AC – frequency are the subject of change in the transformation. The aforementioned conversion steps can of course also be cascaded, e.g., first rectifying mains AC into a DC system which is subsequently inverted again to supply a variable-speed AC drive.

Generally speaking, power electronics is used to transmit higher power than signal electronics, covering a range between some 100 W and several megawatts. Its operational principle can easily be derived based on following consideration, following the development of the control of variable-speed DC drives. A higher DC voltage u 1 can basically be reduced to a lower value u 2 = R1 /(R1 + R2 )u 1 − R1 R2 /(R1 + R2 )i 2 with a voltage divider circuit according to Fig. 17.57. It is however obvious that u 2 depends on the load current i 2 ; to keep the voltage u 2 constant for different loads, the voltage divider needs to be adapted. This can be achieved using controllable active devices instead of passive resistors. As an additional constraint power losses pV = (u 1 − u 2 )2 /R1 + u 22 /R2 in the circuit may become undesirably high and lead to low efficiency, especially in the case of a low ratio u 2 /u 1 . To avoid this, only ideally lossless passive devices, i. e., capacitors and inductors, should be used in power electronics along with digitally operated active devices. Semiconductors are therefore used as switches according to Fig. 17.58a. They are either fully conductive, carrying a current |i S |  0 with negligible voltage drop u S ≈ 0, or fully blocking |u S |  0 with minimum leakage current i S ≈ 0; the transients between these steady states need to be short. Unless otherwise stated, the considerations of circuit theory in Sects. 17.4.2 and 17.4.3 therefore assume idealized behavior

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DC Small Power Motors These kinds of motors are mostly used as auxiliary drives in vehicles and are supplied with a battery voltage of either 12 or 24 V. To produce low-cost motors only ferrite magnets are used. The high value of the temperature coefficient of the coercive field strength (about + 0.004 K−1 ) has to be considered as well as the deviation of the demagnetization characteristic in a high negative field strength; it has to be assured that at low ambient air temperature (−20 ◦ C) the start-up short-circuit current does not result in permanent demagnetization.

17.4 Power Electronics

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Part C 17.4

ates in inverter mode; in the case of the other voltage, it takes energy from the source and thus operates as a rectifier. At a given external counter-voltage the current – including its phase angle with respect to the voltage, which determines the power factor cos ϕ – is determined by adjustment of the converter output voltage u L12 . It can therefore be concluded that the considered converter is not only suitable to transform one DC system into another but also to transform DC to AC as an inverter, and vice versa as a rectifier. It thus accomplishes several of the tasks outlined in Sect. 17.4.1. Single-phase bridges are frequently used as an interface between AC mains and a DC link: as inverters they may, e.g., feed electrical energy generated by renewable sources such as photovoltaic cells into the grid; as rectifiers, they may feed a DC link for power supplies. The harmonic content of the current – which needs to be limited in the case of mains connection [17.15] – can be controlled to be low. Three-phase AC machines such as common induction or synchronous machines can be supplied with a corresponding three-phase converter circuit which is obtained when adding a third phase leg to the single-phase bridge, cf. Fig. 17.62b. Corresponding considerations then apply. Figure 17.64b exemplarily shows the generation of a three-phase system of output voltages u L12 , u L23 , and u L31 . Note that the odd number of phases requires the introduction of a three-level modulation scheme which may be implemented with one control voltage u St1 , u St2 , u St3 per phase. Three-phase converters of this kind are a key component of modern variable-speed drives: the machines can be supplied and thus controlled by three-phase AC systems with variable amplitude and frequency. Motor and generator operation of the machine are possible in inverter and rectifier mode of the converter, which is also able to supply the required reactive power. The direction of rotation is defined by the phase sequence of the converter output voltages, depending on the control voltages u St1 , u St2 , and u St3 . Consequently full four-quadrant operation of the drive can be achieved.

17.4.3 Basic Circuits with External Commutation Uncontrolled Bridges Although the circuits considered so far can be used as rectifiers, the conventional topology of rectifier bridges is often preferred. The reason is that it is simpler and needs no control, as is obvious from the schematics shown in Fig. 17.65.

Fig. 17.64a,b Idealized waveforms of pulse width modulated (a) single-phase bridge: from top to bottom –

triangular carrier u T (solid) and sinusoidal control signal u St (dotted) – switching states of T1 − T4 (0 = off, 1 = on) – output voltage u L12 (solid) together with two different load voltages u 12 (dashed) – output currents i L1 at these output voltages (long dashed: inverter operation, short dashed: rectifier operation); (b) three-phase bridge: from top to bottom – triangular carrier u T (solid) and sinusoidal control signals u St1/2/3 (dotted and dashed) – switching states of T1 − T 6 (noninverted 0 = off, 1 = on) – output voltages u L12 , u L23 , and u L31 

To characterize their behavior when connected to the mains, mains voltages are defined to be u n = Uˆ n sin(ωt)

(17.169)

for the single-phase circuit or u L1N = Uˆ n sin(ωt) ,   2π ˆ u L2N = Un sin ωt − , 3   4π u L3N = Uˆ n sin ωt − , 3

(17.170) (17.171) (17.172)

for the three-phase circuit, using the angular frequency of the mains ω = 2π/Tn with cycle duration Tn of one mains period. The RMS value of the √ single-phase or star voltages is therefore Un,RMS = Uˆ n / 2. Unless otherwise stated, a constant DC current i d = Id is further assumed. Regarding the single-phase circuit it is obvious that in the upper half of the bridge the diode with the highest potential of anode, i. e., D1 or D3 , will conduct i d while the other is blocking |u n |; correspondingly in the lower half of the bridge the diode with the lowest potential of cathode, i. e., D2 or D4 , will conduct i d while the other again blocks |u n |. Consequently the switching states described in Table 17.4 occur. The corresponding waveforms are depicted in Fig. 17.66a: the output voltage u di consists of two sinusoidal half waves u di = |u n | per mains period Tn , which is why the circuit is called a two-pulse bridge connection, abbreviated to B2. Its average value can be calculated from (17.169) to be √  2 2 2 Un,RMS . Udi0 = u di (t)dt = Uˆ n = π π Tn

(17.173)

The input current i n is rectangular. Note that a rectangular waveform can be expressed as the sum of

Electrical Engineering

17.4 Power Electronics

1473

Table 17.5 States of the B6 bridge Condition (uncontrolled B6) u L1N ≥ u L2N u L1N ≥ u L3N u L3N ≤ u L2N

u L2N ≥ u L1N u L2N ≥ u L3N u L3N ≤ u L1N

u L2N ≥ u L1N u L2N ≥ u L3N u L1N ≤ u L3N

u L3N ≥ u L1N u L3N ≥ u L2N u L1N ≤ u L2N

u L3N ≥ u L1N u L3N ≥ u L2N u L2N ≤ u L1N

Conducts i d Blocks u L12 Blocks u L12 Conducts i d Blocks −u L31 Blocks −u L23

Conducts i d Blocks −u L31 Blocks u L12 Blocks u L23 Blocks −u L31 Conducts i d

Blocks −u L12 Blocks −u L31 Conducts i d Blocks u L23 Blocks u L23 Conducts i d

Blocks −u L12 Conducts i d Conducts i d Blocks −u L12 Blocks u L23 Blocks u L31

Blocks u L31 Conducts i d Blocks −u L23 Blocks −u L12 Conducts i d Blocks u L31

Blocks u L31 Blocks u L12 Blocks −u L23 Conducts i d Conducts i d Blocks −u L23

id −i d 0

id 0 −i d

0 id −i d

−i d id 0

−i d 0 id

0 −i d id

u L12

−u L31

u L23

−u L12

u L31

−u L23

Devices D1 D2 D3 D4 D5 D6 Input i L1 i L2 i L3 Output u di

or the occurrence of pulse shapes is disadvantageous. Because of their simplicity and ruggedness these circuits are widely used for mains rectification, e.g., to supply drive converters or as input stages of power supplies. Controlled Bridges A means to control the output voltage is frequently desirable. Basically maintaining the previously discussed bridge circuits, this can be achieved by controlling the timing of current commutation through the use of thyristors, which behave similarly to diode but need to be triggered by a gate pulse (Fig. 17.58). The corresponding circuit diagrams are depicted in Fig. 17.68. The principle of operation of a single-phase thyristor bridge is illustrated in Fig. 17.66c. At ωt → π the current will flow through T1 and T4 , which is the state characterized in the middle column of Table 17.4; the input current is thus i n = i d and the output voltage is u di = u n . In a diode bridge, the current would commutate to the other pair of diodes at ωt = π; in a thyristor bridge this cannot happen before the respective thyristors are triggered. This means that the previous switching state is maintained until triggering is applied, at the firing angle ωt = α. The correspondent waveforms are shown in Fig. 17.66c for α = π/4; the output voltage continues to follow the sine wave u di = u n in its negative half wave. The average value thus becomes lower; depending on the firing angle α it

can be calculated to be  2 Udiα = u di (t)dt = Uˆ n cos α π Tn √ 2 2 Un,RMS cos α = Udi0 cos α . = π

(17.175)

Compared to the uncontrolled bridge the trigger delay by α thus leads to a reduction of the average bridge output voltage by a factor of Udiα /Udi0 = cos α. Note that, for α > π/2, Udiα can in this way become negative; a corresponding example with α = 3π/4 is depicted in Fig. 17.66d. Here, however, consideration of the thyristor blocking voltages – see u R1 and u R2 – becomes important: because u n < 0, u R1 = −u n > 0 will, for example, apply for π < α < 2π when T3 is conducting, cf. also Table 17.4. As stated in Sect. 17.4.1, a thyristor with forward current flowing cannot be actively turned off to take over a forward blocking voltage, but it will block a reverse voltage u R > 0 like a diode. It is thus necessary to trigger T3 sufficiently long before α = π to guarantee that a positive reverse voltage u R1 > 0 will be applied to T1 ; if this is not the case, T1 and T3 might conduct at the same time, leading to a potentially destructive short circuit, also called through conduction. If this is observed, the thyristor bridge will operate as an inverter, transferring power Udiα i d < 0 from the DC side to the mains for π/2 < α  π, while it remains a rectifier transferring power Udiα i d ≥ 0 from the mains to

Part C 17.4

u L1N ≥ u L2N u L1N ≥ u L3N u L2N ≤ u L3N

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rent during commutation and thus the related mains disturbance. Device surge current ratings may be important for power-on and the occurrence of mains voltage peaks.

Part C 17.5

The aforementioned control algorithms can be implemented in various ways. Some of them, e.g., for light dimmers according to Sect. 17.4.3, have been realized in integrated circuits; more complex algorithms are frequently programmed in microcontrollers or even digital signal processors. Interfaces between the power section and the control unit need to be defined: typically measurement and status signals are transferred to the control unit whereas logic levels indicating the switching states

of the transistors are transmitted to the power section. The interfaces often include potential separation: while thyristors can be triggered with small transformers, the control of IGBTs or MOSFETs is mainly realized with integrated or discrete driver circuits to charge and discharge their gates; a separate power supply may be required for this purpose. Note that the potential difference between the emitters of T1 and T2 in the phase leg of Fig. 17.59c will vary between virtually zero (when T2 or D2 are conducting) and u Z (when T1 or D1 are on). Because of this kind of fast transients, electromagnetic compatibility including conducted and radiated emissions should already be considered in the design phase.

17.5 Electric Drives 17.5.1 General Information Electric drives deliver the required form of mechanical energy needed to conduct certain technical processes [17.25,26]. These drives are applied in a wide variety of industrial processes and are mainly used in:

• • • • • •

Machine tools Lifts and crane devices Pumps and ventilators Roller mills and calanders Valves and gate valves Positioning facilities and robots

Additionally, they are used in vehicles, particularly railed vehicles. Electrical drives have the following functions:

• • •

Control of torque (forces) and angular speed (speeds) to be compatible with machine operation and technological processes Optimization of machine operation to achieve technical criteria Insurance of minimal power losses during energy conversion

Rotating electrical machines such as induction, synchronous, direct-current machines, and their improved forms are used in these drives. For some purposes, a linear motor can also be used. The drive device structures are addressed to technological processes:

• • •

The electrical machine can be connected directly to the power supply for operation at fixed frequency and voltage. If control and regulation are required, controllable energy supply units must be used. These units mainly consist of power electronics. For speed, position, or torque control with closedloop schemes the principles of cybernetics are applied.

It is therefore obvious that the field of electric drives is multidisciplinary (Fig. 17.72). Steady-State Operation In steady-state operation, the drive device produces a constant torque at a constant angular speed [17.26]. The intersection point between the drive characteristic and load characteristic must ensure stability for the whole drive system. The various characteristics for these machines are often approximated by an ideal constant or quadratic, and rarely linear, relation between the torque produced ML and the angular speed Ω = 2πn/60 (with n in rpm). In the starting range of the machine there are usually particular variations from the ideal characteristics which mainly result from the breakaway torque. Examples of the torque characteristic for working machines and drive devices are presented in Fig. 17.73. At constant voltage drive devices can be described by three typical characteristics in relation to M(Ω) (Fig. 17.73b):

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Part C 17.5

cage in the form of a damper cage. The exciting winding is shorted out with a resistance. When the rotor reaches the synchronization speed, the cage is switched off and the exciting system is switched on. Synchronization can be achieved by the use of a converter with linear frequency and magnitude control. For DC machines, the classic starting method is the stepwise changing of a resistance at constant voltage. To reduce resistance losses during start-up, the currentleading method is mainly used. In this case, the DC machine is run up with the help of a controllable converter, which ensures maximal performance by running permanently at the current limit. This start-up system is characterized by high dynamic. Speed Control In controlled and regulated drive systems the angular speed is changeable with the help of a controller. There are various ways in which such systems can operate:

1. DC machines. The angular speed is controlled by suitable armature voltage regulation. By appropriate settings of the actuator, operation in all four quadrants of the coordinate system M(Ω) is possible. At speeds above the nominal speed, field control (flux control) is also used, although in this case the controlled speed range is limited. Speed control via resistance changes is also possible but it also has a lossy character. Figure 17.75 presents all of the regulation methods for DC drive devices. 2. Induction machines. The simplest method to regulate the speed of an induction machine is by changing the voltage at the clamps of the machine. This is realized with the help of a three-phase controller (Sect. 17.4.2). In this case, the idle speed is not adjustable. Because the relation between the voltage and the produced torque (M ∼ V 2 ) and due to the high losses resulting from higher harmonics, this method is not suitable for high powers and wide control ranges. Thus it is only applied to ventilators with low power. The frequency control method is a low-loss method. In this case, the idle angular speed is adjustable. For this method the voltage needs to be adjusted as proportionally to the frequency V ∼ f (V/ f ). The breakdown torque has a constant value in the range up to the nominal voltage. If the resistance of the stator windings are taken into account, the voltage must be additionally increased for lower fre-

quencies. If the controller is set to maximum gain, the voltage cannot be increased anymore. The frequency, typically the nominal frequency f N of the machine, at this point is called the cut-off frequency. For further regulation the frequency is increased above the nominal frequency f 1 > f N , and the machine works in the field-weakening range, which leads to a decrease of the breakdown torque. These characteristics are shown in Fig. 17.76. There is another conventional method for regulating the speed. By changing the number of poles the speed can be adjusted in fixed steps. The pole number of a Dahlander motor, for example, can be changed in a ratio of 1 : 2. In this case, the threephase winding consists of six winding parts, which can work at variable pole numbers. 3. Synchronous machines. For synchronous machines, the angular speed control can only be realized through variation of the frequency and simultaneous adjustment of the voltage. The power performance of the drive device is restricted by current and voltage limitations. The speed control in the range of 0 ≤ Ω ≤ Ωmax is broken down into three general areas, see the corresponding numbers in Fig. 17.77: a) Constant value of the current and flux: linear increasing the voltage V ∼ Ω; from this relation the power also increases linearly P ∼ Ω. b) Field-weakening range: at constant voltage and current; the power level is maintained as the torque decreases. c) Minimal flux Φmin : both the current and power are decreased. Torsional Vibrations Torsional vibrations can arise due to variable moments, rapid load changes, and short circuits. Due to possible resonances in the electromechanical system, a lot of undesirable effects can appear. In order to investigate the dynamic requirements for shafts, couplings, and gears, computational methods are used in the design stage. For this purpose, the mechanical part of the system is simulated as a multiple-mass system. If necessary the effects of the mechanical alternating torque on the electromagnetic moment need to be taken into account. Electric Braking In electric drive devices, electrical as well as mechanical braking is possible. To achieve this, a reverse torque is produced by operation in the second quadrant of

Electrical Engineering

17.6 Electric Power Transmission and Distribution

1487

17.6 Electric Power Transmission and Distribution 17.6.1 General Information

• • •

Overhead lines and power cables Transformers Switching stations

These devices also include measuring transformers, protection units, and relays. Power networks are distinguished according to their purpose, with different voltage levels and structures. The usual nominal voltages of transmission systems are high voltages of 110, 220, and 380 kV. In special cases the three-phase current is transmitted at an extra high-voltage level of up to 765 kV. Distribution systems are operated at medium voltages of either 10 or 60 kV, while low-voltage supply grids usually work at nominal voltages below 1 kV, i. e., 230 V (single phase) or 400 V (three phase). The related operating frequency for all voltage levels is generally 50 Hz in Europe and 60 Hz in North America and Japan. Other frequencies are also used for special applications such as railway supply systems in Germany, Austria, and Switzerland, which operate at 16 23 Hz. When choosing which basic voltage to use technical and economical factors have to be considered. In the case of long-distance energy transmission voltage stability plays an important role. Additionally, the isolation of the network components must always be able to bear the short-circuit current. Another possibility for the transmission of electric energy is the use of the high-voltage direct-current transmission system (HVDC) at a few hundred kV. This technology is applied either for long distances or for the coupling of two systems with different frequencies and decoupling the short-circuit power of both systems to protect network components in the case of faults. Figure 17.84 shows an example of an urban electric power network structure. The voltage levels for transmission are 380 kV and 110 kV, connected as closed loops. This voltage is then stepped down in transformer stations from 110 kV to the distribution level

Part C 17.6

Electric energy is produced in power plants and consumed by customers located at various distances from the plants. Power networks and related equipment are needed for the transmission and distribution of electric energy from the plant to the customer. Thus the following devices are used:

of 10 kV. This medium-voltage network is connected in open-loop circuits. This is advantageous in the case of faults within the medium-voltage network because the sectioning point can easily be moved within the ring and the customers are quickly reconnected to the grid. If the number of customers connected to a given grid increases, more energy will be transmitted. Therefore, the network capacity must be increased. By increasing the network capacity and the amount of network interconnections the short-circuit power also increases. Ideally, the short-circuit power is the product of the short-circuit current and the rated voltage. This value does not appear in reality but is used for the dimensioning of network components. An increased short-circuit power can be dangerous for network components if a fault occurs because dynamic and thermal effects lead to their destruction. To limit the short-circuit power several actions have to take place. Some of these concern the neutral-point treatment, which has an influence on the resulting short-circuit current. Networks are generally distinguished according to the neutral-point treatment of the transformers. There are isolated neutral points, impedance grounding, and direct grounding. (Figs. 17.85–17.87). When faults occur – especially single-phase faults – some neutral-point structures can continue operation, whereas some others have to be disconnected immediately. Which structures can be used and which must be disconnected depends on the type of neutral-point treatment deployed. The fault-to-earth current is determined mainly by the earth capacitance and must not be higher than 35 A to self-extinguish. During a fault, the network can continue to operate when an isolated neutral point is used. (Fig. 17.85). The isolated neutral point can be applied to small networks with voltages below 30 kV. By using a specific type of impedance grounding (Fig. 17.86) (e.g., an arc suppression coil or neutral grounding reactor), in the case of a phase-to-ground fault, the capacitive components failure current will be compensated by the reactor (Petersen coil). As a result, the residual current of the arc will be small enough to self-extinguish if it has a value below 100 A. The voltages √ in the faultless phases are multiplied by the factor 3 during the fault in one phase. Like the isolated neutral-point network, this type of network can also continue to operate during a fault. Impedance grounding is used for networks with voltages below 110 kV.

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Complementary Material for Mechanical Engineers

The specific values for resistance, inductance, and capacitance per length of a line are minimally dependent on the voltage if the operating voltage is changed Ic =

Vl ωCb √ . 3

(17.196)

Part C 17.6

Line Simulation Figure 17.89 shows an equivalent circuit for one line. A line can be described using:

• • • •

The resistance per unit length R The inductance per unit length L The capacitance per unit length C The conductance per unit length G

The equivalent circuits can have either a T or Π form. In most cases the conductance per length G can be neglected because G  ωC . The line operation can be described using line theory, which helps to determine the voltage and current at each position of a line. Therefore, the line impedance is needed. The impedance is generally identified as the characteristic wave impedance Z W  R + jωL ZW = . (17.197) G + j ωC For a lossless line this can be reduced to a resistive value  L . (17.198) ZW = ZW = C The current and voltage along a line can be represented as a superposition of a forward-running wave (wf ) and one reflected, backward-running wave (wb ). The voltage at the end of a line v2 can be calculated by the summation of both waves v 2 = wf + w b .

(17.199)

The current can be calculated by the difference between wf and wb , divided by the wave impedance i=

1 (wf − wb ) . ZW

(17.200)

The relation between the backward and forward components of the voltage is expressed as a reflection coefficient r, which depends on the terminating

impedance Z a of the line and the wave resistance Z W r=

wf Z − Zw = t . wb Z t + Zw

(17.201)

The reflection coefficient for unloaded operation (Z t = ∞) is r = 1 and for short-circuit operation (Z t = 0) it is r = −1. This results in a voltage of v2 = 2wb for unloaded operation and v2 = 0 for a short circuit. The reflection coefficient is r = 0 for Z t = Z w , in the case of complete adjustment of the terminating impedance. In this case there are no backward-running waves and as a result, the voltage at the end of the line is the same as at the beginning (v2 = wf ). At this point the transmission of maximal power Pn with minimal losses is possible Pn =

VL2 . ZW

(17.202)

This active power Pn is called the natural power. For 380 kV overhead lines it has a value of about 450 MW.

17.6.3 Switchgear Switching Stations Switchgear is a general term covering switching devices and their combination with associated control, measuring, protective, and regulating equipment. Switching stations are needed to collect and distribute electric energy. High-voltage switching stations up to 110 kV are usually located within buildings; higher voltages require outdoor switching stations or special encapsulated switching stations based on SF6 gas technology. Due to its electric strength it can be used in places where insulation with air would take too much space. High-Voltage Switchgear The three types of switchgear, each with a different purpose, are:

•

A circuit breaker is intended to switch both load and short-circuit currents. The switching power can be calculated as a product of the rated voltage and the switching current. It is dimensioned to avoid damage due to the short-circuit current’s dynamic and thermal effects on generators, transformers, switching stations, and lines. It restores quickly after a short circuit and is the most effective but also expensive form of switchgear. It

Electrical Engineering

17.6 Electric Power Transmission and Distribution

trical energy is also referred to as using a renewable energy source, but this depends on the primary energy – the fuel being used. Some of them will now be briefly discussed.

Other Accumulators. Cadmium and nickel batteries are accumulators with an alkaline electrolyte; they are rechargeable and are produced as button cells with a capacity between 10 mA h and 25 A h. The use of electric drives in vehicles depends considerably on the capability to produce storage batteries with a high energy density. However, the lead-acid accumulator with a specific capacity of 30–40 W h/kg, assuming a 2 h discharging time, cannot entirely fulfil these requirements. A promising development is the sodium/sulphur battery with a ceramic electrolyte and liquid sodium and sulphur. An energy density of about 120 W h/kg is achieved with this technology. The sodium/sulphur battery requires a minimum operating temperature of 285 ◦ C.

Solar Energy Solar energy from the sun is the most abundant energy form on the planet. The sun provides energy in two forms – light and heat [17.8]. The thermal energy can be used either for heating (homes, offices, swimming pools etc.) or to power a conventional turbine to produce electricity (a solar thermal power plant). The light energy can be converted into electrical energy directly by using photovoltaic systems.

Other Energy Storage Methods Future development is addressing the possibility of storage of magnetic energy in superconducting coils, in which the current can flow nearly without losses. The coupling in and coupling out of electrical energy is realized by an electronic power converter. Other methods involve the unconventional charging processes with switches, which are converted from a superconducting state into a normal state. A different approach is the use of flywheel storage, which is charged by an electric source and can be discharged depending on the demand for electricity.

17.6.6 Electric Energy from Renewable Energy Sources Renewable energy is sometimes called green energy because it is – in contrast to fossil energy like coal, oil, and gas – not finite. Renewable energy sources are based on regenerating natural primary energy sources (biomass, biogas) or infinite primary energy sources (sun, wind, water). The transformation process into electrical energy has no or only a small effect on the environment and does not contribute to the greenhouse effect and global warming like the conventional burning of fossil sources. The five most common renewable sources – which are finally all solar sources – are hydropower, wind energy, solar energy (thermal as well as photovoltaic), geothermal energy and biomass. Sometimes using fuel cells for the transforming process into elec-

Photovoltaic Energy Systems. Photovoltaic (PV) en-

ergy systems transform light directly into electricity. They use daylight to supply ordinary electrical equipment, for example, household appliances, computers, and lighting. A PV cell consists of two or more thin layers of semiconducting material, most commonly silicon (for the different types of PV see Table 17.7). When the silicon is exposed to light, electric charge carriers are generated and an electric potential develops between the two layers of the material. To balance this potential a charge transport is necessary, which is conducted via metal contacts on both sides of the cell. If an electrical load is connected to the contacts a direct current (DC) will flow. To achieve a higher voltage and power level single cells are connected electrically. For mechanical stability and outdoor use these cells are then encapsulated, usually behind glass, to form a module. The connection of several modules is called a panel or string. The PV module is the principle building block of a PV system and any number of modules can be connected to give the required power with a suitable current and voltage output. Typical modules have a rated power output of around 75–200 W peak (Wp ) each. A typical domestic system of 1.5–2 kWp may therefore contain about 10–24 modules covering an area of 12–40 m2 . The actual power output is dependent on the technology used and the orientation of the array with respect to the sun. An inverter (see Sect. 17.4) is used to convert the comparatively low DC voltage to a compliant AC voltage. The solar generators are suitable for autonomous distributed energy supplies as well for feeding into public networks. Figure 17.100 shows an example of a 10 kWp photovoltaic system.

Part C 17.6

1990s several plants were installed worldwide showing that the economical operation of this system is possible. Developments caused by the liberalization of the energy market may promote this technology.

1497

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Part C

Complementary Material for Mechanical Engineers

defined



h max h>1

G 2h

, (17.210) G1 where G h is the individual RMS value of the quantity G. It can be seen that THD is referred to as the fundamental harmonic. To measure the distortions produced by nonlinear loads of mainly large power networks the total demand distortion (TDD) is introduced

h max 2 h>1 Ih , (17.211) TDD = IL where IL is the peak, or maximum, demand load current at the fundamental frequency. For power quality evaluation the individual harmonic components can be analyzed separately as well. In this case the magnitude of the harmonic cannot exceed the prescribed values that are introduced by standards and norms. Not only harmonics are evaluated in terms of the power quality. Power analysis is also conducted when the current or voltage occurs as a harmonic signal. In such cases the apparent power S is divided into three components  (17.212) S = P 2 + Q 2 + D2 , THD =

Part C 17.7

where P is the active power at each harmonic, Q is the reactive power at each harmonic, and D is called the distortion power, reflecting the relationship between the different harmonic elements. The general relationship between the active power (needed to operate equipment) and the apparent power is P (17.213) PF = , S the power factor. The best conditions for network operation are obtained when this parameter is equal to 1.

Power Quality Improvement A lot of methods are used to improve the power quality. These methods are distinguished in terms of phenomena that need to be compensated. Harmonic mitigation, for example, requires the use of filters. Two main groups of filters can be distinguished: passive and active. Passive filters are constructed by a suitable connection of inductances and capacitances. They are designed to reduce individual harmonics (mainly the fifth) or narrow frequency ranges. Over the last few years, active filters have begun to play an important role in the improvement of network operation in terms of harmonics. These elements are based on semiconductor components and a storage system (battery, supercapacitor, superconductor). By applying suitable switching techniques of the valves in active filters the higher harmonics can be limited. The reactive power in a distribution system has turned out to be an important problem as well. The reactive flow power results in additional losses. To reduce this, capacitor banks are used to compensate the prevailing inductive load. Furthermore, short circuits are another important issue in network operation. A high short-circuit current can contribute to the destruction of distribution elements (wires, transformers). To avoid short circuits, relaying systems are applied. Sudden changes in current can induce current in other wires and also cause the aggravation of the power quality. To limit this type of phenomena shielded cables are utilized. In order to improve the reliability of the network, the designing approach of the power system plays a very important role. Using new numerical techniques, the network can be designed to have more stable operation, and can be monitored to find the distortion source and eliminate it.

17.7 Electric Heating In resistances electric power is converted into heat [17.1, 36]. This process is described by the simple formula Pw = UI cos ϕ = I 2 R = U 2 /R .

(17.214)

The different electric heating procedures vary in terms of the kind of resistance and the nature of the energy source and include resistance, arc, inductive, and

dielectric heating. For a smelting furnace, the first three principles, shown in Fig. 17.110, are used. For the techniques illustrated in Fig. 17.110a,e,f, the heated material itself acts as the resistance, and for the examples shown in Fig. 17.110a,d the heating source is arc plasma. The only practical application of Fig. 17.110c is the arc-heating steel furnace. Most reduction furnaces, for

Electrical Engineering

The suitable power density is only achieved at high frequencies. The following frequencies are authorized for this process: 13.6, 27.12, 40.68, and 433.92 MHz. For the heating process in a microwave radiation field

References

1509

the frequency of 2450 MHz is permitted. When using other frequencies, shielding must be applied in order to achieve EMC compatibility. The mentioned frequencies are produced by electron valve generators.

References

17.2

17.3

17.4 17.5 17.6

17.7 17.8 17.9 17.10 17.11

17.12 17.13 17.14 17.15

17.16 17.17

17.18

17.19

W. Hoffmann, M. Stiebler: Elektrotechnik. In: Dubbel, ed. by K.-H. Grote, J. Feldhusen (Springer, Berlin, Heidelberg 2007), in German K. Küpfmüller, W. Matthis, A. Reibiger: Theoretische Elektrotechnik, 17. Aufl. (Springer, Berlin 2006), in German H. Fischer, H. Hofmann, J. Spindler: Werkstoffe in der Elektrotechnik, 5. Aufl. (Hanser, München 2002), in German G. Lehner: Elektromagnetische Feldtheorie, 5. Aufl. (Springer, Berlin 2006), in German W.-K. Chen: The Circuits and Filters Handbook, 2nd edn. (CRC, Boca Raton 2003) E. Ivers Tiffee, W. von Müch: Werkstoffe der Elektrotechnik, 9. Aufl. (Stuttgart, Teubner 2004), in German D.G. Fink: Standard Handbook for Electrical Engineers, 14th edn. (McGraw-Hill, New York 2000) T. Markvart: Solar Electricity, 2nd edn. (Wiley, Chichester 2000) R.M. DelVecchio: Transformer Design Principles (Gordon Breach, Amsterdam 2001) J.H. Harlow: Electric power transformer engineering (CRC, Boca Raton 2004) IEC: IEC60747-9: Semiconductor devices – Discrete devices – Part 9 – Insulated-gate bipolar transistors IGBTs, 1st edn. (International Electrotechnical Commission, Geneva 2001) E.J. Rothwell: Electromagnetics (CRC, Boca Raton 2001) R.H. Bishop: The Mechatronics Handbook (CRC, Boca Raton 2002) G. Holmes, T. Lipo: Pulse Width Modulation for Power Converters (IEEE Press, Piscataway 2003) IEC: IEC61000-3-2: Electromagnetic Compatibility (EMC) – Part 3–2 – Limits – Limits for harmonic current emissions – equipment input current ≤ 16 A per phase (International Electrotechnical Commission, Geneva 2005) J. Baliga: Modern Power Devices (Wiley, New York 1987) IEC: IEC60747-1: Semiconductor devices – Part 1 – General, 2nd edn. (International Electrotechnical Commission, Geneva 2006) IEC: IEC60747-2: Semiconductor devices – Discrete devices and integrated circuits – Part 2 – Rectifier diodes, 2nd edn. (International Electrotechnical Commission, Geneva 2000) IEC: IEC60747-2-1: Semiconductor devices – Discrete devices – Part 2 – Rectifier diodes – Section 1 –

17.20

17.21

17.22

17.23

17.24

17.25 17.26 17.27 17.28 17.29 17.30

17.31 17.32 17.33 17.34 17.35

blank detail specification for rectifier diodes (including avalanche rectifier diodes), ambient and case-rated, up to 100 A, 1st edn. (International Electrotechnical Commission, Geneva 1989) IEC: IEC60747-2-2: Semiconductor devices – Discrete devices – Part 2 – Rectifier diodes – Section 2 – blank detail specification for rectifier diodes (including avalanche rectifier diodes), ambient and case-rated, for currents greater than 100 A, 1st edn. (International Electrotechnical Commission, Geneva 1993) IEC: IEC60747-6: Semiconductor devices – Part 6: Thyristors, 2nd edn. (International Electrotechnical Commission, Geneva 2000) IEC: IEC60747-8-4: Discrete semiconductor devices – Part 8-4 – Metal-oxide-semiconductor fieldeffect transistors MOSFETs for power switching applications, 1st edn. (International Electrotechnical Commission, Geneva 2004) IEC: IEC60747-15: Discrete semiconductor devices – Part 15 – Isolated power semiconductor devices, 1st edn. (International Electrotechnical Commission, Geneva 2003) R.W. de Doncker, J.P. Lyons: The auxiliary resonant commutated pole converter, Proc. IEEE-IAS Conference (IEEE, Piscataway 1990) pp. 1228–1235 U. Riefenstahl: Elektrische Antriebstechnik, 2. Aufl. (Stuttgart, Teubner 2006), in German J. Vogel: Elektrische Antriebstechnik, 6. Aufl. (Hüthig, Heidelberg 1998), in German W. Leonhard: Control of Electrical Drives (Springer, Berlin, Heidelberg 2001) J.N. Chiasson: Modeling and High-Performance Control of Electric Machines (Wiley, New York 2005) S. Heier: Windkraftanlagen, 4. Aufl. (Stuttgart, Teubner 2005), in German S. Mathew: Wind Energy – Fundamentals, Recourse Analysis and Economics (Springer, Berlin, Heidelberg 2006) E. Hau: Wind Turbines, Fundamentals, Application, Economics (Springer, Berlin, Heidelberg 2006) R. O’Hayre: Fuel Cell Fundamentals (Wiley, New York 2006) G. Hoogers: Fuel Cell Technology Handbook (CRC, Boca Raton 2003) N. Sammes: Fuel Cell Technology (Springer, Berlin, Heidelberg 2006) G.J. Wakileh: Power Systems harmonics – Fundamentals, Analysis and Filter Design (Springer, Berlin, Heidelberg 2001)

Part C 17

17.1

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Part C

Complementary Material for Mechanical Engineers

17.36

M. Rudolph, H. Schaefer: Elektrothermische Verfahren, (Berlin, Springer 1989), in German

17.37

C.J. Erickson: Handbook of Electrical Heating for Industry (IEEE, New York 1995)

Part C 17

1511

General Table 18. General Tables

Stanley Baksi

Table 18.1 Basic dimensions, their symbols, and physical significance Symbol

Physical entity

Meter

m

Length

Kilogram

kg

Mass

Second

s

Time

Ampère

A

Electric current

Kelvin

K

Thermodynamic temperature, temperature difference

Mol

mol

Quantity

Candela

cd

Light intesity

Table 18.3 Prefixes for units Power of ten

Prefix

Symbol

1018

Exa

E

1015

Peta

P

1012

Tera

T

109

Giga

G

106

Mega

M

103

Kilo

k

102

Hekto

h

10

Deka

da

10−1

Deci

d

10−2

Centi

c

10−3

Milli

m

10−6

Micro

μ

10−9

Nano

n

10−12

Pico

p

10−15

Femto

f

10−18

Atto

a

Table 18.4 Units not defined in the Système International

d’Unités (SI) system but commonly used Characteristics of units

Example

Generally used units

Liter (l), hour (h), degree (deg, ◦ )

Units with limited use

Electron volt (eV)

1 kp ≈ 1 daN 1 kp/cm ≈ 1 N/mm 1 mm water column ≈ 0.1 mbar

1 at ≈ 1 bar 1 kp m ≈ 1 daJ 1 PS ≈ 0.75 kW 1 kcal ≈ 4.2 kJ

Table 18.6 Names and abbreviations of English units atm bbl btu bu cwt cal deg F ft gal hp in lb lbf lntn mi pdl shtn yd UK US

Atmosphere Barrel British thermal unit Bushel Hundred weight Calorie Degree Fahrenheit Foot Gallon Horsepower Inch Pound Pound force Long ton Mile Poundel Short ton Yard United Kingdom United States of America

in/s ≡ inch per second; in2 ≡ square inch; in3 ≡ cubic inch

Table 18.9 Nomenclature for astronomical prefixes 106 109 1012 1015 1018 1021 1024 1027

Million Billion Trillion Quadrillion Quintillion Sextillion Septillion Octillion

Mega Giga Tera Peta Exa Zetta Yotta –

M G T P E Z Y –

Part C 18

Basic dimension

Table 18.5 Conversion values to calculate from m–kp–s in the SI system

1512

Part C

Complementary Material for Mechanical Engineers

Table 18.2 Types of units and their explanation Derived SI – units characteristics

Development of symbols for derived SI units description These symbols are developed by combining the basic units of their constituting elements, for example, units of area, volume, velocity, etc. –

Units (combined) without special symbols Units (combined) with special symbols Units (combined) with mixed symbols

These symbols are developed by combining the specific units of their constituting elements and some basic units of measurement. If necessary, a combination of symbols which describe the properties of the measurement

Example m2 , m3 , m/s

Newton (N), Pascal (Pa), Joule (J), Watt (W), Ohm (Ω) Newtonmeter (N m), Pascalsecond (Pa s)

Part C 18

Table 18.7 Roman counting system I ≡ 1 V ≡ 5 X ≡ 10 L ≡ 50 C ≡ 100 D ≡ 500 M ≡ 1000 1 I 10 X 100 C 2 II 20 XX 200 CC 3 III 30 XXX 300 CCC 4 IV 40 XL 400 CD 5 V 50 L 500 D 6 VI 60 LX 600 DC 7 VII 70 LXX 700 DCC S VIII 80 LXXX 800 DCCC 9 IX 90 XC 900 CM Writing direction is from left to right, and the individual values are added to get the value. The lesser values always come after the bigger values. If otherwise, the lesser values have to be subtracted from the bigger values. V, L, D can be written only once. can be written up to three times. I, X, C Examples MCDXCVI 1496 DCLXXIII 673 MDCCCXCI 1891 MCMLXXXI 1981

Table 18.12 Commonly used units in thermodynamic calculations Unita

Symbol

Physical relation

Relation to basic units

Kelvin

K

–

Meter square per second Joule Watt Joule per kilogram Joule per Kelvin Joule per kilogram and Kelvin Watt per meter square Watt per meter square and Kelvin Watt per meter and Kelvin Kelvin per watt Degree Celsius

m2 /s J W J/kg J/K J/(kg K) W/m2 W/(m2 K) W/(m K) K/W ◦C

Thermodynamic temperature, temperature potential Conductivity Heat energy Heat power Specific inner energy Heat capacity Specific heat capacity Heat flux density Heat transfer coefficient Heat conductance Thermal resistance Temperature

a

Both SI and other unit systems (commonly used ones) are presented

– 1 J = 1 kg m2 /s2 1 W = 1 kg m2 /s3 1 J/kg = 1 m2 /s2 1 J/K = 1 m2 /(s2 K) 1 J/(kg K) = 1 m2 /(s2 K) 1 W/m2 = 1 kg/s3 1 W/(m2 K) = 1 kg/(s3 K) 1 W/(m K) = 1 kg m/(s3 K) 1 K/W = 1 K s3 /(kg m2 ) 1 ◦C = 1 K

General Tables

1513

Table 18.8 Conversion of important units from the foot–pound–second (fps) system to the SI system Length Area Volume Velocity Acceleration Mass Force

Pressure

Density Temperature Power Specific heat capacity Thermal conductivity Heat transfer coefficient Viscosity, kinematic Viscosity, dynamic

SI (m-kg-s)

1 ft = yd = 12 in 1 ft2 = 144 in2 1 ft3 = 1728 in3 = 6.22882 gal (UK) 1 gal (US) = 0.83268 gal (UK) 1 ft/s 1 knot = 1.150785 mi/h = 1.6877 ft/s 1 ft/s2 1 lb = cwt/112; 1 shtn = 2000 lb 1 slug = 32.174 lb; 1 lntn = 2240 lb 1 lbf 1 pdl = 0.031081 lbf 1 ft lb = 0.323832 calIT 1 btu = 252 calIT = 778.21 ft lb 1 lb/ft2 = 6.9444 × 10−3 lb/in2 1 lb/in2 = 0.068046 atm 1 atm = 29.92 in Hg = 33.90 ft water 1 lb/ft3 = 5.78704 × 10−4 lb/in3 1 lb/gal = 6.22882 lb/ft3 32◦ F = 0 ◦ C, 212◦ F = 100 ◦ C 1 ft lb/s = 1.8182 × 103 hp = 1.28505 × 10−3 btu/s 1 btu/(lb◦ F) 1 btu/(ft h◦ F) 1 btu/(ft2 h◦ F) 1 ft2 /s 1 lb/(ft s)

1 ft = 0.3048 m; 1 mi = 1609.34 m 1 ft2 = 0.092903 m2 1 ft3 = 0.0283169 m3 1 bu (US) = 35.23931; 1 bbl (US) = 115.6271 1 ft/s = 0.3048 m/s 1 ft/s2 = 0.3048 m/s2 1 lb = 0.453592 kg 1 slug = 14.5939 kg 1 lbf = 4.44822 N 1 pdl = 0.138255 N 1 ft lb = 1.35582 J 1 btu = 1.05506 kJ 1 lb/ft2 = 47.88 N/m2 1 lb/in2 = 6894.76 N/m2 1 atm = 1.01325 bar 1 lb/ft3 = 16.0185 kg/m3 1 lb/gal = 99.7633 kg/m3 1◦ F = 0.5556 ◦ C 1 ft lb/s = 1.35582 W 1 btu/(lb◦ F) = 4.1868 kJ/(kg K) 1 btu/(ft h◦ F) = 1.7306 W/(m K) 1 btu/(ft2 h◦ F) = 5.6778 W/(m2 K) 1 ft2 /s = 0.092903 m2 /s 1 lb/(ft s) = 1.48816 kg/(m s)

Table 18.11 Units commonly used for calculation in mechanics Unita

Symbol

Physical meaning

Relation to basic units

Kilogram Kilogram per second Kilogram meter square Kilogram per cubic meter Cubic meter per kilogram Square meter per second Newton Pascal Joule Watt Newtonmeter Newton per square meter Pascalsecond Joule per cubic meter Ton Gram

kg kg/s kg m2 kg/m3 m3 /kg m2 /s N Pa J W Nm N/m2 Pa s J/m3 t g

Mass Mass flow Mass moment Density Specific volume Kinematic viscosity Force Pressure Work, energy Power Moment Pressure Dynamic viscosity Energy density Mass Mass

– – – – – – 1 N = 1 kg m/s2 1 Pa = 1 kg/(m s2 ) 1 J = 1 kg m2 /s2 1 W = 1 kg m2 /s3 1 J Nm = 1 kg m2 /s2 1 N/m2 = 1 kg/(m s2 ) 1 Pa s = 1 kg/(m s) 1 J/m3 = 1 kg/(m s2 ) 1 t = 1000 kg 1 g = 1/1000 kg

a

Both SI and other unit systems (commonly used ones) are presented

Part C 18

Work

fps (foot-pound-second)

1514

Part C

Complementary Material for Mechanical Engineers

Table 18.10 Space and time units

Part C 18

Unita

Symbol

Physical relation and technical value

Description through the basic units

Meter

m

Length

–

Second

s

Time

–

Square meter

m2

Surface

–

Cubic meter

m3

Volume

–

Meter per second

m/s

Velocity

–

Meter per second square

m/s2

Acceleration

–

Meter cube per second

m3 /s

Volume flow

–

Radian

rad

Angle

1 rad = 1 m/m

Steradian

sr

Three-dimensional angle

1 sr = 1 m2 /m2

Hertz

Hz

Frequency

1 Hz = 1 /s

Radian per second

rad/s

Angular velocity

–

Radian per second squared

rad/s2

Angular acceleration

–

Liter

l

Volume

1 l = 10−3 m3

Degree

◦

Angle

1◦ = π/180 rad

Minute



Angle

1 = π/(180 × 60) rad

Second



Angle

1 = π/(180 × 60 × 60) rad

Minute

min

Time

1 min = 60 s

Hour

h

Time

1 h = 60 min = 3600 s

1 per second

1/s

Frequency

1/min = (1/60) 1/s 1/h = (1/60) 1/min = (1/60)2 1/s

a

Both SI and other unit systems (commonly used ones) are presented

Table 18.13 Commonly used units in electric current calculations Unita

Symbol

Physical relation

Relation to basic units

Ampère

A

Electric current

–

Ampère per square meter

A/m2

Electric current density

–

Ampère per meter

A/m

Electric current distribution

–

Coulomb

C

Electric charge

1C = 1As

Watt

W

Electric power

1 W = 1 kg m2 /s3

Volt

V

Electric potential

1 V = 1 kg m2 /(A s3 )

Farad

F

Electric capacity

1 F = 1 A2 s4 /(kg m2 )

Ohm

Ω

Electric resistance

1 Ω = 1 kg m2 /(A2 s3 )

Siemens

S

Electric conductance

1 S = 1 A2 s3 /(kg m2 )

Coulomb per square meter

C/m2

Electric flux density

1 C/m2 = 1 A s/m2

Volt per meter

V/m

Electric field intensity

1 V/m = 1 kg m3 /(A s3 )

Farad per meter

F/m

Dielectric constant, electric field constant

1 F/m = 1 A2 s4 /(kg m3 )

Ohmmeter

Ωm

Specific electric resistance

1 Ω m = 1 kg m3 /(A2 s3 )

Siemens per meter

S/m

Specific electric conductivity

1 S/m = 1 A2 s3 /(kg m3 )

a

Both SI and other unit systems (commonly used ones) are presented

General Tables

1515

Table 18.14 Commonly used units in magnetic calculations Unita

Symbol

Physical relation

Relation to basic units

Ampère

A

Magnetic potential

–

Ampère per meter

A/m

Magnetic intensity

–

Weber

Wb

Magnetic flux

1 Wb = 1 kg m2 /(A s2 )

Tesla

T

Magnetic induction

1 T = 1 kg/(A s2 )

Henry

H

Inductivity, magnetic conductance

1 H = 1 kg m2 /(A2 s2 )

Henry per meter

H/m

Permeability, magnetic field constant

1 H/m = 1 kg m/(A2 s2 )

1/Henry

1/H

Magnetic resistance

1 /H = 1 A2 s2 /(kg m2 )

a

Both SI and other unit systems (commonly used ones) are presented

Unita

Symbol

Physical relation

Relation to basic units

Candela

cd

Luminosity

–

Candela per square meter

cd/m2

Light density

–

Lumen

lm

Luminous flux

1 lm = 1 cd sr

Lux

lx

Illumination

1 lx = 1 cd sr/m2

Lumen second

lm s

Luminous energy

1 lm s = 1 cd sr s

Lux second

lx s

Exposure

1 lx s = 1 cd sr s/m2

a

Both SI and other unit systems (commonly used ones) are presented

Table 18.16 Physical constants Gravitational constant

G

6.672 × 10−11 N m2 /kg2

Acceleration due to gravity

gn

9.8067 m/s2

Gas constant

R

8314.41 J/(kmol K)

Molar volume

Vm

22.414 m3 /kmol at 1.01325 bar, 0 ◦ C

Avogadro constant

NA

6.0221 × 1026 kmol−1

Loschmidt constant

NL

2.6868 × 1025 m−3

Boltzmann constant

kB

1.3807 × 10−23 J/K

Electric field constant

ε0

8.8542 × 10−12 F/m

Magnetic field constant

μ0

1.2566 × 10−6 H/m

Electric charge

e

1.6022 × 10−19 C

Faraday constant

F

9.6485 × 107 C/kmol

Speed of light in vacuum

c

2.9979 × 108 m/s

Planck constant

h

6.626 × 10−34 Js

Wave drag in vacuum

Γ

376.731 Ω

Stefan–Boltzmann radiation constant

σ

5.6703 × 10−8 W/(m2 K4 )

Planck radiation constants

c1 c2

3.741 × 10−16 W m2 1.438 × 10−2 m K

Wien constant

K

2.8978 × 10−3 m K

Rydberg constant

R

1.09737 × 107 m−1

Static weight of electrons

me

9.109 × 10−31 kg

Radius of an electron

re

2.8178 × 10−15 m

Atomic mass unit

amu

1.6606 × 10−27 kg

Part C 18

Table 18.15 Commonly used units in luminosity calculations

General Tables

Table 18.17 (continued)

1517

Table 18.22 Conversion from dB to pressure or power ra-

tios and vice versa

(b) Constants Velocity of light

c0 = 2.998 × 108 m/s

Static weight of electron

m e0 = 9.110 × 10−31 kg

Avogadro constant

NA = 6.0221 × 1026 kmol−1

Static weight of proton

m p0 = 1.6606 × 10−27 kg

Electric charge of an electron

e = 1.6022 × 10−19 C

Static weight of neutron

m n0 = 1.675 × 10−27 kg

Table 18.23 Important standards and their abbreviations American Gear Manufacturers Association

ANSI

American National Standard Institution

ASTM

American Society for Testing and Materials

API

American Petroleum Institute

BSI

British Standard Institution

CEN

Comité Européen de Normalisation

CENELEC

Comité Européen de Normalisation Electrotechniques

GOST

Government Standard of the former USSR

IEC

International Electrotechnical Commission

ISO

International Organization for Standardization

NF

Normes Françaises

NEN

Netherland Norms

ÖNORM

Austrian Norms

SAE

Society of Automotive Engineers

SNV

Swedish Norms

UNI

Unificazione Nazionale Italiana

DIN

Deutsches Institut für Normung

p/ p0

p2 / p20

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0 1 2 3 4 5 6 7 8 9 10 0 10 20 30 40 50 60 70 80 90 100

1 1.012 1.023 1.035 1.047 1.059 1.072 1.084 1.096 1.109 1.122 1 1.122 1.259 1.413 1.585 1.778 1.995 2.239 2.512 2.818 3.162 1 3,162 10 31.62 100 316.2 1000 3162 10000 31620 100000

1 1.023 1.047 1.072 1.096 1.122 1.148 1.175 1.202 1.23 1.259 1 1.259 1.585 1.995 2.512 3.162 3.981 5.012 6.31 7.943 0.01 1 10 102 103 104 105 106 107 108 109 1010

Part C 18

AGMA

dB

1518

Part C

Complementary Material for Mechanical Engineers

Table 18.18 Basic units for light calculations Measure

Definition

Unit

Mathematical relation

Remarks

Luminous flux

Amount of rays emanating from a light source in all directions Intensity of light rays inside the elementary space anglea . 1 cd is the radiation emitted by a black body perpendicular to its surface [1/(6 × 106 ) m2 ] at 2042.5 K and 1.0133 bar Ratio of light emitted at the source to the light received at a particular surface

Lumen (lm)

φ = dQ/ dt

Light energy emitted per unit time

Candela (cd) cd = m/sr SI basic units

I = dφ/ dω

Stearin candle ≈ 1 cd Bulb (40 W) ≈ 35 cd

Lux (lx) lx = lm/m2

E = φ/A = Iω/A = I/r 2

Summer sunlight 105 lx Living room 10–150 lx Full-moon night 0.2 lx No-moon night 3 × 10−4 lx Full moon 2500 cd/m2 Candle 7500 cd/m2 Bulb 2 × 107 cd/m2 Sun 2.2 × 109 cd/m2 Tube light 44 lm/W Bulb (1000 W) 19 lm/W Bulb (40 W) 11 lm/W

Light intensity

Luminance

Part C 18

Light density

Light intensity per unit of illuminated surface

cd/m2

–

Light yield

Luminous flux per unit of electric power

lm/W

η = φ/P

 Product of luminous flux and lm s Q = φ dt the duration of radiation a The unit steradian (sr) is valid for the space angles. Steradian is the ratio of the surface of a section of a sphere to the square of its radius. If α is the opening angle of a section of a sphere with an area of A = 2πrh, its height is given by h = r[1 − cos(α/2)] = 2r sin2 (α/4). The space angle is defined as ω√= A/r 2 = 4π sin2 (α/4). Special cases: ω = 1 sr for α = 4 arcsin(0.5/ π) = 65.54◦ . For a sphere α = 360◦ and ω = 4πsr. For α = 120◦ is ω = π sr Light range

Table 18.20 Approximated acoustic measures Noise source Siren with funnel without funnel Rotating disk with ultrasonic velocity Schmidt tube Ventilator optimal point Δ p < 2.5 mbara Δ p > 2.5 mbar Escape noise Ma < 0.3a 0.4 < Ma < 1.0 Ma > 2.0 Motor bike 250 cm3 capacity without damper Organ Small gas turbine Suction Exhaust Housing a

η = Pacu /Pmech a 3 –7 × 10−1 1.00 × 10−2 2.50 × 10−1 2.00 × 10−2 1.00 × 10−6 4 × 10−8 Δ p 8(1 × 10−6 – 1 × 10−5 ) (Ma)3 1.0 × 10−4 (Ma)5 2.00 × 10−3

1.00 × 10−3 1 × 10−3 –1 × 10−2 1.00 × 10−4 1.00 × 10−5 1.00 × 10−6

Noise source Diesel engine Cylinder at 800 rpm Cylinder at 3000 rpm Exhaust with turbocharger Electromagnetic loudspeaker Electric motor Special low noise Normal Machines Special class Quiet machines Normal Bad Airplane propeller 2700 kW in test stand Human voice Ship propeller Without cavitation With cavitation

Δ p = compression, Pacu = acoustic power, Ma = mach number, Pmech = mechanical power

η = Pacu /Pmech 4.00 × 10−7 5.00 × 10−6 1.00 × 10−4 5.00 × 10−2 2.00 × 10−8 1.00 × 10−6 3.00 × 10−8 2.00 × 10−7 2.00 × 10−7 3.00 × 10−6 5.00 × 10−3 5.00 × 10−4 1 × 10−9 – 1 × 10−8 1.00 × 10−7

General Tables

1519

Table 18.19 Important terms in acoustic technology Term

Definition

Velocity of sound

Solids



2G(1−υ)

Unit

Remarks

m/s

1000– 5000 m/s

Longitudinal waves in big bodies

cL =

Transversal waves in big bodies

500– 3500 m/s

Liquids

cT = Gς  cD = Eς  c = χς

Gases

c=

Air: 331 m/s at 1 bar, 0 ◦ C Hydrogen: 1280 m/s at 1 bar, 0 ◦ C

Speed of vibrational part

u = a0 ω = 2πa0 f

m/s

5 × 10−8 –1 m/s

Static and dynamic pressure in elastic media

p

N/m2

10−2 – 102 N/m2

Bending waves in bars

 ς(1−2υ)

√

Rubber 50 m/s Water 1485 m/s

x RT

Normal audio waves = 2 × 10−5 N/m2 Piano = 0.2 N/m2 Siren = 35 N/m2 Sound power

Sound energy that passes per unit time through a particular surface area

P

W

1 × 10−12 – 1 × 105 W Audio waves = 1 × 10−12 W Voice ≈ 1 × 10−3 W Siren ≈ 1 × 103 W

Sound intensity

Sound power per unit area

I = P/A = p2 /c p

Sound level

Logarithmic scale for sound pressure

L = 10 lg(P/P0 )

W/m2

1 × 10−11 –1 × 103 W/m2 Audio waves = 1 × 10−12 W/m2 0 – 140 dB

= 10 lg(I/I0 )

Bel

= 20 lg( p/ p0 )

B, dB

P0 = 1 × 10−12 W I0 = 1 × 10−12 W/m2 P0 = 2 × 10−5 N/m2

Sound volume

Measurement of subjective perception of the sound intensity for the ear

Λ = 10 lg(I/I0 )

phon

0 –130 phon Audio wave 0 phon Entertainment 50 phon Pain level 130 phon

Sound absorption factor

Measurement of loss of sound energy in heat due to friction Index a and r indicate absorption and reflection, respectively

α = (Pa − Pf )/Pf

1

For 500 Hz

= ( p2a − p2r )/ p2r

Concrete 0.01 Glass 0.03 Foam 0.36

Logarithmic measurement for R = 10 lg(I1 /I2 ) dB 1 mm-thick steel plate 29 dB sound damping by a wall, Index 1 indicates energy before reflection and 2 indicates energy after reflection Acoustic coefficient Ratio of sound to mechanical η = Pacu /Pmech 1 See Table 18.20 power a0 Amplitude, A surface area, P power, x isentropic exponent, f frequency, E modulus of elasticity, R gas constant, υ Poisson ratio, G modulus of rigidity, T absolute temperature, ς density, χ compressibility Sound damping

Part C 18

Transverse vibrational speed of sound Sound pressure

Mathematical formula

19 K Potassium

37 Rb Rubidium

55 Cs Caesium 87 Fr Francium

4

5

6

Actinoids

Lanthanoids

∗∗

∗

7

3

2

1 H Hydrogen 3 Li Lithium 11 Na Sodium

56 Ba Barium 88 Ra Radium

38 Sr Strontium

4 Be Beryllium 12 Mg Magnesium 20 Ca Calcium

2

∗∗

∗

∗∗

∗

40 Zr Zirconium

22 Ti Titanium

4

41 Nb Niobium

23 V Vanadium

5

24 Cr Chromium

6

42 Mo Molybdenum 71 72 73 74 Lu Hf Ta W Lute- HafTanta- Tungtium nium lum sten 103 104 105 106 Lr Rf Db Sg Law- Ruth- DubSearenerford- nium borgcium ium ium 57 58 59 60 La Ce Pr Nd LanCerPraseo- Neothanum ium dym- dymium ium 89 90 91 92 Ac Th Pa U Actin- Thor- ProUranium ium tactin- ium ium

39 Y Yttrium

21 Sc Scandium

3

8

61 Pm Promethium 93 Np Neptunium

75 Re Rhenium 107 Bh Bohrium

43 Tc Technetium

62 Sm Samarium 94 Pu Plutonium

76 Os Osmium 108 Hs Hassium

44 Ru Ruthenium

25 26 Mn Fe Man- Iron ganese

7

10

11

95 Am Americium

63 Eu Europium

77 Ir Iridium 109 Mt Meitnerium

45 Rh Rhodium

96 Cm Curium

78 Pt Platinum 110 Ds Darmstadtium 64 Gd Gadolinium

46 Pd Palladium

48 Cd Cadmium

30 Zn Zinc

12

66 Dy Dysprosium 97 98 Bk Cf Berke- Calilium fornium

65 Tb Terbium

80 Hg Mercury 111 112 Rg Uub Roent- Unungenium bium

79 Au Gold

47 Ag Silver

27 28 29 Co Ni Cu Cobalt Nickel Copper

9

99 Es Einsteinium

67 Ho Holmium

81 Tl Thallium 113 Uut Ununtrium

49 In Indium

13 Al Aluminium 31 Ga Gallium

5 B Boron

13

51 Sb Antimony

33 As Arsenic

7 N Nitrogen 15 P Phosphorus

15

100 Fm Fermium

68 Er Erbium

101 Md Mendelevium

69 Tm Thulium

83 Bi Bismuth 114 115 Uuq Uup Unun- Ununquadium pentium

82 Pb Lead

32 Ge Germanium 50 Sn Tin

6 C Carbon 14 Si Silicon

14

35 Br Bromine

102 No Nobelium

70 Yb Ytterbium

84 Po Polonium 116 Uuh Ununhexium

85 At Astatine 117 Uus Ununseptium

118 Uuo Ununoctium

86 Rn Radon

54 Xe Xenon

36 Kr Krypton

2 He Helium 10 Ne Neon

18

9 F Fluorine 17 18 Cl Ar Chlor- Argon ine

17

52 53 Te I Tellur- Iodine ium

34 Se Selenium

8 O Oxygen 16 S Sulphur

16

Part C

1

Period

Part C 18

Group 1

1520 Complementary Material for Mechanical Engineers

Table 18.21 Periodic table of chemical elements