Third edition Materials Selection in Mechanical Design Michael F. ashby
Materials selection in Mechanical Design Third edition Michael f. Ashby ELSEVIER BUTTERWORTH AMSTERDAM BOSTON● HEIDELBERG· LONDON· NEW YORK· OXFORD PARs。SAND|EGo· SAN FRANC|ScO·S| NGAPORE. SYDNEY· TOKYO
Materials Selection in Mechanical Design Third Edition Michael F. Ashby AMSTERDAM BOSTON HEIDELBERG LONDON NEW YORK OXFORD PARIS SAN DIEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO
Butterworth-Heineman Linacre House, Jordan Hill, Oxford OX2 8DP 0 Corporate Drive, Burlington, MA 01803 First published by Pergamon Press 1992 Second edition 1999 Copyright o 1992, 1999, 2005 Michael F. Ashby. All rights reserved The right of Michael F. Ashby to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988 otocopying or storing in amay be reproduced in any material form(including No part of this publication or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the ns of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England WIT 4LP. Applications for the copyright holder's written ermission to reproduce any part of this publication should be addressed Permissions may be sought directly from Elsevier's Science and Technology Rights Department in Oxford, UK: phone: (+44)(0)1865843830, fax:(+44)1865 853333 e-mail: permissions @elsevier. co. uk. You may also complete your request on-line via theElsevierhomepage(http://www.elsevier.com),byselecting"customerSupport and then Obtaining Permissions British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging in Publication Data A catalog record for this book is available from the Library of Congress ISBN0750661682 For information on all elsevier butterworthheinemann publicationsvisitourwebsiteathttp://books.elsevier by Newgen Imaging Systems(P)Ltd, Chennai, Ind Printed and bound in Italy Working together to grow libraries in developing countries www.clsevicr.comiwww.bookaid.orgIwww.sabre.org elsevier BOOK AID Sabre Foundation
Butterworth-Heinemann Linacre House, Jordan Hill, Oxford OX2 8DP 30 Corporate Drive, Burlington, MA 01803 First published by Pergamon Press 1992 Second edition 1999 Third edition 2005 Copyright # 1992, 1999, 2005 Michael F. Ashby. All rights reserved The right of Michael F. Ashby to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988 No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1T 4LP. Applications for the copyright holder’s written permission to reproduce any part of this publication should be addressed to the publisher Permissions may be sought directly from Elsevier’s Science and Technology Rights Department in Oxford, UK: phone: (þ44) (0) 1865 843830, fax: (þ44) 1865 853333, e-mail: permissions@elsevier.co.uk. You may also complete your request on-line via the Elsevier homepage (http://www.elsevier.com), by selecting ‘Customer Support’ and then ‘Obtaining Permissions’ British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging in Publication Data A catalog record for this book is available from the Library of Congress ISBN 0 7506 6168 2 For information on all Elsevier Butterworth-Heinemann publications visit our website at http://books.elsevier.com Typeset by Newgen Imaging Systems (P) Ltd, Chennai, India Printed and bound in Italy Working together to grow libraries in developing countries www.elsevier.com | www.bookaid.org | www.sabre.org
Preface Materials, of themselves, affect us little; it is the way we use them which influences our lives. Epictetus, AD 50-100, Discourses Book 2, Chapter 5 New materials advanced engineering design in Epictetus'time. Today, with more materials than ever before, the opportunities for innovation are immense. But advance is possible only if a pro- cedure exists for making a rational choice. This book develops a systematic procedure for selecting materials and processes, leading to the subset which best matches the requirements of a design. It is unique in the way the information it contains has been structured. The structure gives rapid access to data and allows the user great freedom in exploring the potential of choice. The method is available as software, giving greater flexibility. The approach emphasizes design with materials rather than materials"science", although the underlying science is used, whenever possible, to help with the structuring of criteria for selection. The first eight chapters require little prior knowledge: a first-year grasp of materials and mechanics is enough. The chapters dealing with shape and multi-objective selection are a little more advanced but can be omitted on a first reading. As far as possible the book integrates materials selection with other aspects of design; the relationship with the stages of design and optimization and with the mechanics of materials, are developed throughout. At the teaching level, the book is intended as the text for 3rd and 4th year engineering courses on Materials for Design: a 6-10 lecture unit can be based on Chapters 1-6; a full 20+ lecture course, with associated project work with the associated software uses the entire book s Beyond this, the book is intended as a reference text of lasting value. The method, the charts and les of performance indices have application in real problems of materials and process selection; and the catalogue of"useful solutions"is particularly helpful in modelling-an essential ingre- dient of optimal design. The reader can use the book(and the software)at increasing levels of sophistication as his or her experience grows, starting with the material indices developed in the case studies of the text, and graduating to the modelling of new design problems, leading to new material indices and penalty functions, and new-and perhaps novel-choices of material. This continuing education aspect is helped by a list of Further reading at the end of most chapters, and by a set of exercises in Appendix E covering all aspects of the text. Useful reference material is assembled in appendices at the end of the book Like any other book, the contents of this one are protected by copyright. Generally, it is an infringement to copy and distribute materials from a copyrighted source. But the best way to use he charts that are a central feature of the book is to have a clean copy on which you can draw try out alternative selection criteria, write comments, and so forth; and presenting the conclusion of a selection exercise is often most easily done in the same way. Although the book itself is copyrighted, the reader is authorized to make unlimited copies of the charts, and to reproduce these, with proper reference to their source, as he or she wishes M.F. Ashby Cambridge, July 2004 The CES materials and process selection platform, available from Granta Design Ltd, Rustat House, 62 Clifton Road, Cambridge CBI 7eg,Uk(wwW.grantadesign.com)
Preface Materials, of themselves, affect us little; it is the way we use them which influences our lives. Epictetus, AD 50–100, Discourses Book 2, Chapter 5. New materials advanced engineering design in Epictetus’ time. Today, with more materials than ever before, the opportunities for innovation are immense. But advance is possible only if a procedure exists for making a rational choice. This book develops a systematic procedure for selecting materials and processes, leading to the subset which best matches the requirements of a design. It is unique in the way the information it contains has been structured. The structure gives rapid access to data and allows the user great freedom in exploring the potential of choice. The method is available as software,1 giving greater flexibility. The approach emphasizes design with materials rather than materials ‘‘science’’, although the underlying science is used, whenever possible, to help with the structuring of criteria for selection. The first eight chapters require little prior knowledge: a first-year grasp of materials and mechanics is enough. The chapters dealing with shape and multi-objective selection are a little more advanced but can be omitted on a first reading. As far as possible the book integrates materials selection with other aspects of design; the relationship with the stages of design and optimization and with the mechanics of materials, are developed throughout. At the teaching level, the book is intended as the text for 3rd and 4th year engineering courses on Materials for Design: a 6–10 lecture unit can be based on Chapters 1–6; a full 20þ lecture course, with associated project work with the associated software, uses the entire book. Beyond this, the book is intended as a reference text of lasting value. The method, the charts and tables of performance indices have application in real problems of materials and process selection; and the catalogue of ‘‘useful solutions’’ is particularly helpful in modelling — an essential ingredient of optimal design. The reader can use the book (and the software) at increasing levels of sophistication as his or her experience grows, starting with the material indices developed in the case studies of the text, and graduating to the modelling of new design problems, leading to new material indices and penalty functions, and new — and perhaps novel — choices of material. This continuing education aspect is helped by a list of Further reading at the end of most chapters, and by a set of exercises in Appendix E covering all aspects of the text. Useful reference material is assembled in appendices at the end of the book. Like any other book, the contents of this one are protected by copyright. Generally, it is an infringement to copy and distribute materials from a copyrighted source. But the best way to use the charts that are a central feature of the book is to have a clean copy on which you can draw, try out alternative selection criteria, write comments, and so forth; and presenting the conclusion of a selection exercise is often most easily done in the same way. Although the book itself is copyrighted, the reader is authorized to make unlimited copies of the charts, and to reproduce these, with proper reference to their source, as he or she wishes. M.F. Ashby Cambridge, July 2004 1 The CES materials and process selection platform, available from Granta Design Ltd, Rustat House, 62 Clifton Road, Cambridge CB1 7EG, UK (www.grantadesign.com)
Acknowledgements Many colleagues have been generous in discussion, criticism, and constructive suggestions I particularly wish to thank Professor Yves Brechet of the University of Grenoble; Professor Anthony Evans of the University of California at Santa Barbara; Professor John Hutchinson of Harvard University; Dr David Cebon; Professor Norman Fleck; Professor Ken Wallace; Dr. John Clarkson; Dr Hugh Shercliff of the Engineering Department, Cambridge University; Dr Amal Esawi of the American University in Cairo, Egypt; Dr Ulrike Wegst of the Max Planck Institute for Materials Research in Stuttgart, Germany; Dr Paul Weaver of the Department of Aeronautical Engineering at the University of Bristol; Professor Michael Brown of the Cavendish Laboratory, Cambridge, UK, and the staff of Granta Design Ltd, Cambridge, UK
Acknowledgements Many colleagues have been generous in discussion, criticism, and constructive suggestions. I particularly wish to thank Professor Yves Bre´chet of the University of Grenoble; Professor Anthony Evans of the University of California at Santa Barbara; Professor John Hutchinson of Harvard University; Dr David Cebon; Professor Norman Fleck; Professor Ken Wallace; Dr. John Clarkson; Dr. Hugh Shercliff of the Engineering Department, Cambridge University; Dr Amal Esawi of the American University in Cairo, Egypt; Dr Ulrike Wegst of the Max Planck Institute for Materials Research in Stuttgart, Germany; Dr Paul Weaver of the Department of Aeronautical Engineering at the University of Bristol; Professor Michael Brown of the Cavendish Laboratory, Cambridge, UK, and the staff of Granta Design Ltd, Cambridge, UK
Features of the Third edition Since publication of the Second Edition, changes have occurred in the fields of materials and mechanical design, as well as in the way that these and related subjects are taught within a variety of curricula and courses. This new edition has been comprehensively revised and reorganized to address these. Enhancements have been made to presentation, including a new layout and two- colour design, and to the features and supplements that accompany the text. The key changes are outlined below K ey changes New and fully revised chapters Processes and process selection( Chapter 7) Process selection case studies( Chapter 8) Selection of material and shape( Chapter 11) Selection of material and shape: case studies( Chapter 12) Designing hybrid materials( Chapter 13) Hybrid case studies( Chapter 14) Information and knowledge sources for design( Chapter 15) Materials and the environment( Chapter 16) Materials and industrial design( Chapter 17) Comprehensive appendices listing useful formulae; data for material properties; material indices; and information sources for materials and processes Supplements to the Third Edition Material selection charts Full color versions of the material selection charts presented in the book are available from the following website. Although the charts remain copyright of the author, users of this book are authorized to download, print and make unlimited copies of these charts, and to reproduce these for aching and learning purposes only, but not for publication, with proper reference to their owner- shipandsourceToaccessthechartsandotherteachingresourcesvisitwww.grantadesign.com/ ashbycharts. htm Instructor's manual The book itself contains a comprehensive set of exercises. Worked-out solutions to the exercises are freely available to teachers and lecturers who adopt this book. To access this material online pleasevisithttp://books.elsevier.com manuals an nd follow the instructions on screen
Features of the Third Edition Since publication of the Second Edition, changes have occurred in the fields of materials and mechanical design, as well as in the way that these and related subjects are taught within a variety of curricula and courses. This new edition has been comprehensively revised and reorganized to address these. Enhancements have been made to presentation, including a new layout and twocolour design, and to the features and supplements that accompany the text. The key changes are outlined below. Key changes New and fully revised chapters: Processes and process selection (Chapter 7) Process selection case studies (Chapter 8) Selection of material and shape (Chapter 11) Selection of material and shape: case studies (Chapter 12) Designing hybrid materials (Chapter 13) Hybrid case studies (Chapter 14) Information and knowledge sources for design (Chapter 15) Materials and the environment (Chapter 16) Materials and industrial design (Chapter 17) Comprehensive appendices listing useful formulae; data for material properties; material indices; and information sources for materials and processes. Supplements to the Third Edition Material selection charts Full color versions of the material selection charts presented in the book are available from the following website. Although the charts remain copyright of the author, users of this book are authorized to download, print and make unlimited copies of these charts, and to reproduce these for teaching and learning purposes only, but not for publication, with proper reference to their ownership and source. To access the charts and other teaching resources, visit www.grantadesign.com/ ashbycharts.htm Instructor’s manual The book itself contains a comprehensive set of exercises. Worked-out solutions to the exercises are freely available to teachers and lecturers who adopt this book. To access this material online please visit http://books.elsevier.com/manuals and follow the instructions on screen
xiv Features of the Third Edition Image bank The Image Bank provides adopting tutors and lecturers with PDF versions of the figures from the book that may be used in lecture slides and classsygstruc entations. To access this material please visit http:/books.elsevier.com/manualsandfollowthe tions on screen The CES EduPack CES EduPack is the software-based package to accompany this book, developed by Michael Ashby nd Granta Design. Used together, Materials Selection in Mechanical Design and CES EduPack provide a complete materials, manufacturing and design course. For further information please see thelastpageofthisbookorvisitwww.grantadesign.com
Image bank The Image Bank provides adopting tutors and lecturers with PDF versions of the figures from the book that may be used in lecture slides and class presentations. To access this material please visit http://books.elsevier.com/manuals and follow the instructions on screen. The CES EduPack CES EduPack is the software-based package to accompany this book, developed by Michael Ashby and Granta Design. Used together, Materials Selection in Mechanical Design and CES EduPack provide a complete materials, manufacturing and design course. For further information please see the last page of this book, or visit www.grantadesign.com. xiv Features of the Third Edition
Contents Preface Features of the Third Edition 1 Introduction 1.1 Introduction and synopsis 1.2 Materials in design 1.3 The evolution of engineering materials 1.4 Case study: the evolution of materials in vacuum cleaners i1224688 1.5 Summary and conclusions 1.6 Further read 2 The design process 2.1 Introduction and synopsis 12 2.2 The design process 2.3 Types of de 16 2.4 Design tools and materials data 17 2.5 Function, material, shape, and process 2.6 Case study: devices to open corked bottles 0 2. 8 Further reading 3 Engineering materials and their properties 3.1 Introduction and synopsis 3.2 The families of engineering materials 3.3 The definitions of material pro operties 3.4 Summary and conclusions 3.5 Further reading 4 Material property charts 4.1 Introduction and synopsis 46 4.2 Exploring material properties 4.3 The material property charts 4.4 Summary and conclusions 4.5 Further reading 5 Materials selection -the basics 5.1 Introduction and synopsis 5.2 The selection strategy 5.4 The selection procedure rial indices 5.3 Attribute limits and mate 85
Contents Preface xi Acknowledgements xii Features of the Third Edition xiii 1 Introduction 1 1.1 Introduction and synopsis 2 1.2 Materials in design 2 1.3 The evolution of engineering materials 4 1.4 Case study: the evolution of materials in vacuum cleaners 6 1.5 Summary and conclusions 8 1.6 Further reading 8 2 The design process 11 2.1 Introduction and synopsis 12 2.2 The design process 12 2.3 Types of design 16 2.4 Design tools and materials data 17 2.5 Function, material, shape, and process 19 2.6 Case study: devices to open corked bottles 20 2.7 Summary and conclusions 24 2.8 Further reading 25 3 Engineering materials and their properties 27 3.1 Introduction and synopsis 28 3.2 The families of engineering materials 28 3.3 The definitions of material properties 30 3.4 Summary and conclusions 43 3.5 Further reading 44 4 Material property charts 45 4.1 Introduction and synopsis 46 4.2 Exploring material properties 46 4.3 The material property charts 50 4.4 Summary and conclusions 77 4.5 Further reading 78 5 Materials selection — the basics 79 5.1 Introduction and synopsis 80 5.2 The selection strategy 81 5.3 Attribute limits and material indices 85 5.4 The selection procedure 93
5.5 Computer-aided selection 5.6 The structural index 5.7 Summary and conclusions 103 5.8 Further reading 104 6 Materials selection -case studies 6.1 Introduction and synopsis 6.2 Materials for oars 106 6.3 Mirrors for large telescopes 6.4 Materials for table legs 114 6.5 Cost: structural material for buildings 117 6.6 Materials for flywheels 6.7 Materials for springs 126 6.8 Elastic hinges and couplings 130 6.9 Materials for seals 6.10 Deflection-limited design with brittle polymers 136 6.11 Safe pre, damping materials for shaker tables 6. 12 Stiff, high 144 6.13 Insulation for short-term isothermal containers 6. 14 Energy-efficient kiln walls 6.15 Materials for passive solar heating 154 6.16 Materials to minimize thermal distortion in precision devices 6.17 Nylon bearings for ships'rudders 160 6. 18 Materials for heat exchangers 163 6.19 Materials for radomes 168 6.20 Summary and conclusions 172 6.21 Further reading 7 Processes and process selection 7.1 Introduction and synopsis 7.2 Classifying processes 177 7.3 The processes: shaping, joining, and finishing 7.4 Systematic process selection 7.5 Ranking: process cost 7.6 Computer-aided process selection 7.7 Supporting information 7.8 Summary and conclusions 215 7. 9 Further reading 216 8 Process selection case studies 219 8.1 Introduction and synopsis 220 8.2 Forming a fan 220 8.3 Fabricating a pressure vessel 223 8.4 An optical table 8.5 Economical casting 8.6 Computer-based selection: a manifold jacket
5.5 Computer-aided selection 99 5.6 The structural index 102 5.7 Summary and conclusions 103 5.8 Further reading 104 6 Materials selection — case studies 105 6.1 Introduction and synopsis 106 6.2 Materials for oars 106 6.3 Mirrors for large telescopes 110 6.4 Materials for table legs 114 6.5 Cost: structural material for buildings 117 6.6 Materials for flywheels 121 6.7 Materials for springs 126 6.8 Elastic hinges and couplings 130 6.9 Materials for seals 133 6.10 Deflection-limited design with brittle polymers 136 6.11 Safe pressure vessels 140 6.12 Stiff, high damping materials for shaker tables 144 6.13 Insulation for short-term isothermal containers 147 6.14 Energy-efficient kiln walls 151 6.15 Materials for passive solar heating 154 6.16 Materials to minimize thermal distortion in precision devices 157 6.17 Nylon bearings for ships’ rudders 160 6.18 Materials for heat exchangers 163 6.19 Materials for radomes 168 6.20 Summary and conclusions 172 6.21 Further reading 172 7 Processes and process selection 175 7.1 Introduction and synopsis 176 7.2 Classifying processes 177 7.3 The processes: shaping, joining, and finishing 180 7.4 Systematic process selection 195 7.5 Ranking: process cost 202 7.6 Computer-aided process selection 209 7.7 Supporting information 215 7.8 Summary and conclusions 215 7.9 Further reading 216 8 Process selection case studies 219 8.1 Introduction and synopsis 220 8.2 Forming a fan 220 8.3 Fabricating a pressure vessel 223 8.4 An optical table 227 8.5 Economical casting 230 8.6 Computer-based selection: a manifold jacket 232 vi Contents
8.7 Computer-based selection: a spark-plug insulator 8.8 Summary and conclusions 237 9 Multiple constraints and objectives 239 and 240 9.2 Selection with multiple constraints 9.3 Conflicting objectives, penalty-functions, and exchange constants 245 9. 4 Summary and conclusions 9.5 Further reading 255 Appendix: Traditional methods of dealing with multiple 256 and objective 10 Case studies -multiple constraints and conflicting objectives 10.1 Introduction and synopsis 262 10.2 Multiple constraints: con-rods for high-performance engines 10.3 Multiple constraints: windings for high-field magnets 266 10.4 Conflicting objectives: casings for a mini-disk player 10.5 Conflicting objectives: materials for a disk-brake caliper 10.6 Summary and conclusions 11 Selection of material and shape 11.1 Introduction and synopsis 284 11.2 Shape factors 11.3 Microscopic or micro-structural shape factors 11.4 Limits to shape efficiency 301 11.5 Exploring and comparing structural sections 305 11.6 Material indices that include shape 307 11.7 Co-selecting material and shape 312 11.8 Summary and conclusions 314 11.9 Further reading 12 Selection of material and shape: case studies 317 12.1 Introduction and synopsis 318 12.2 Spars for man-powered planes 319 12.3 Ultra-efficient springs 3 12.4 Forks for a racing bicycle 326 12.5 Floor joists: wood, bamboo or steel? 328 12.6 Increasing the stiffness of steel sheet 331 12.7 Table legs again: thin or light? 333 12.8 Shapes that flex: leaf and strand structures 335 12.9 Summary and conclusions 337 13 Designing hybrid materials 13.1 Introduction and synopsis 340 13.2 Filling holes in material-property space 342 133 The method:“A+B+ configuration+ scale” 346 13.4 Composites: hybrids of type 1 348
8.7 Computer-based selection: a spark-plug insulator 235 8.8 Summary and conclusions 237 9 Multiple constraints and objectives 239 9.1 Introduction and synopsis 240 9.2 Selection with multiple constraints 241 9.3 Conflicting objectives, penalty-functions, and exchange constants 245 9.4 Summary and conclusions 254 9.5 Further reading 255 Appendix: Traditional methods of dealing with multiple constraints 256 and objectives 10 Case studies — multiple constraints and conflicting objectives 261 10.1 Introduction and synopsis 262 10.2 Multiple constraints: con-rods for high-performance engines 262 10.3 Multiple constraints: windings for high-field magnets 266 10.4 Conflicting objectives: casings for a mini-disk player 272 10.5 Conflicting objectives: materials for a disk-brake caliper 276 10.6 Summary and conclusions 281 11 Selection of material and shape 283 11.1 Introduction and synopsis 284 11.2 Shape factors 285 11.3 Microscopic or micro-structural shape factors 296 11.4 Limits to shape efficiency 301 11.5 Exploring and comparing structural sections 305 11.6 Material indices that include shape 307 11.7 Co-selecting material and shape 312 11.8 Summary and conclusions 314 11.9 Further reading 316 12 Selection of material and shape: case studies 317 12.1 Introduction and synopsis 318 12.2 Spars for man-powered planes 319 12.3 Ultra-efficient springs 322 12.4 Forks for a racing bicycle 326 12.5 Floor joists: wood, bamboo or steel? 328 12.6 Increasing the stiffness of steel sheet 331 12.7 Table legs again: thin or light? 333 12.8 Shapes that flex: leaf and strand structures 335 12.9 Summary and conclusions 337 13 Designing hybrid materials 339 13.1 Introduction and synopsis 340 13.2 Filling holes in material-property space 342 13.3 The method: ‘‘A þ B þ configuration þ scale’’ 346 13.4 Composites: hybrids of type 1 348 Contents vii