net Engineering Materials 1 An Introduction to Properties, Applications and Design www.net Engineering Materials 1 An Introduction to Properties, Applications and Design Third Edition www.net by Michael F. Ashby and David R. Jones Department of Engineering, University of Cambridge, UK Amsterdam Boston Heidelberg London New York Oxford Paris San Diego San Francisco Singapore Sydney Tokyo www.net Elsevier Butterworth-Heinemann Linacre House, Jordan Hill, Oxford OX2 8DP 200 Wheeler Road, Burlington, MA 01803 First published 1980 Second edition 1996 Reprinted 1998 (twice), 2000, 2001, 2002, 2003 Third edition 2005 Copyright # 2005. All rights reserved The right of Michael F.
Ashby and David R. Jones to be identified as the authors 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 www.net 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) (0) 1865 853333, e-mail: permissions@elsevier. You may also complete your request on-line via the Elsevier homepage (http://www.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 63804 For information on all Elsevier Butterworth-Heinemann publications visit our website at http://www.com Typeset by Newgen Imaging Systems (P) Ltd, Chennai, India Printed and bound in Great Britain Working together to grow libraries in developing countries www.net Contents General introduction xi 1.
Engineering materials and their properties 1 1.2 Examples of materials selection 4 www. Price and availability 15 2. The price and availability of materials 17 2.2 Data for material prices 18 2.3 The use-pattern of materials 20 2.5 Exponential growth and consumption doubling-time 23 2. The elastic moduli 29 3.
The elastic moduli 31 3.2 Definition of stress 32 3.3 Definition of strain 35 3.5 Measurement of Young’s modulus 37 3.6 Data for Young’s modulus 38 4. Bonding between atoms 43 4.4 The condensed states of matter 51 4. Packing of atoms in solids 55 5.2 Atom packing in crystals 56 5.3 Close-packed structures and crystal energies 56 www.net vi Contents 5.7 Other simple important crystal structures 62 5.8 Atom packing in polymers 64 5.9 Atom packing in inorganic glasses 65 5.10 The density of solids 66 6. The physical basis of Young’s modulus 73 6.2 Moduli of crystals 74 6.3 Rubbers and the glass transition temperature 76 www.
Case studies in modulus-limited design 85 7.1 Case study 1: a telescope mirror — involving the selection of a material to minimize the deflection of a disc under its own weight.2 Case study 2: materials selection to give a beam of a given stiffness with minimum weight 91 7.3 Case Study 3: materials selection to minimize the cost of a beam of given stiffness 93 C. Yield strength, tensile strength and ductility 97 8. The yield strength, tensile strength and ductility 99 8.2 Linear and nonlinear elasticity; anelastic behavior 100 8.3 Load–extension curves for non-elastic (plastic) behavior 101 8.4 True stress–strain curves for plastic flow 103 8.8 The hardness test 108 8.9 Revision of the terms mentioned in this chapter, and some useful relations 111 9. Dislocations and yielding in crystals 119 9.2 The strength of a perfect crystal 120 9.3 Dislocations in crystals 122 9.4 The force acting on a dislocation 128 9.5 Other properties of dislocations 129 www.net Contents vii 10.
Strengthening methods, and plasticity of polycrystals 131 10.3 Solid solution hardening 132 10.4 Precipitate and dispersion strengthening 133 10.6 The dislocation yield strength 135 10.7 Yield in polycrystals 136 10. Continuum aspects of plastic flow 141 www.2 The onset of yielding and the shear yield strength, k 142 11.3 Analyzing the hardness test 144 11.4 Plastic instability: necking in tensile loading 145 12. Case studies in yield-limited design 153 12.2 Case study 1: elastic design-materials for springs 154 12.3 Case study 2: plastic design-materials for a pressure vessel 159 12.4 Case study 3: large-strain plasticity — rolling of metals 160 D. Fast fracture, brittle fracture and toughness 167 13.
Fast fracture and toughness 169 13.2 Energy criterion for fast fracture 170 13.3 Data for Gc and Kc 175 14. Micromechanisms of fast fracture 181 14.2 Mechanisms of crack propagation, 1: ductile tearing 182 14.3 Mechanisms of crack propagation, 2: cleavage 184 14.4 Composites, including wood 186 14.5 Avoiding brittle alloys 187 15. Case studies in fast fracture 191 15.2 Case study 1: fast fracture of an ammonia tank 192 15.3 Case study 2: explosion of a perspex pressure window during hydrostatic testing 195 15.4 Case study 3: cracking of a polyurethane foam jacket on a liquid methane tank 198 15.5 Case study 4: collapse of wooden balcony railing 202 www.net viii Contents 16. Probabilistic fracture of brittle materials 209 16.2 The statistics of strength and the Weibull distribution 212 16.3 Case study: cracking of a polyurethane foam jacket on a liquid methane tank 216 E.2 Fatigue behavior of uncracked components 224 www.3 Fatigue behavior of cracked components 228 17.2 Fatigue data for uncracked components 238 18.4 The notch sensitivity factor 240 18.5 Fatigue data for welded joints 241 18.6 Fatigue improvement techniques 242 18.7 Designing-out fatigue cycles 244 18.8 Checking pressure vessels for fatigue cracking 246 19.
Case studies in fatigue failure 251 19.2 Case study 1: high-cycle fatigue of an uncracked component — failure of a pipe organ mechanism 252 19.3 Case study 2: low-cycle fatigue of an uncracked component — failure of a submersible lifting eye 260 19.4 Case study 3: fatigue of a cracked component — the safety of the Stretham engine 264 F. Creep deformation and fracture 271 20. Creep and creep fracture 273 20.2 Creep testing and creep curves 277 20.4 Creep damage and creep fracture 282 20.5 Creep-resistant materials 283 21. Kinetic theory of diffusion 287 21.2 Diffusion and Fick’s law 289 www.net Contents ix 21.3 Data for diffusion coefficients 293 21.4 Mechanisms of diffusion 294 22.
Mechanisms of creep, and creep-resistant materials 299 22.2 Creep mechanisms: metals and ceramics 300 22.3 Creep mechanisms: polymers 307 22.4 Selecting materials to resist creep 309 23. The turbine blade — a case study in creep-limited design 311 23.2 Properties required of a turbine blade 313 www.3 Nickel-based super-alloys 314 23.4 Engineering developments — blade cooling 318 23.5 Future developments: metals and metal–matrix composites 319 23.6 Future developments: high-temperature ceramics 321 23. Oxidation and corrosion 325 24. Oxidation of materials 327 24.2 The energy of oxidation 328 24.3 Rates of oxidation 329 24.
Case studies in dry oxidation 337 25.2 Case study 1: making stainless alloys 338 25.3 Case study 2: protecting turbine blades 339 25.4 Joining operations: a final note 343 26. Wet corrosion of materials 345 26.3 Voltage differences as a driving force for wet oxidation 347 26.4 Rates of wet oxidation 350 26. Case studies in wet corrosion 357 27.2 Case study 1: the protection of underground pipes 358 27.3 Case study 2: materials for a lightweight factory roof 360 27.4 Case study 3: automobile exhaust systems 363 www. Friction, abrasion and wear 367 28.
Friction and wear 369 28.2 Friction between materials 370 28.3 Data for coefficients of friction 373 28.5 Wear of materials 375 28.6 Surface and bulk properties 377 29. Case studies in friction and wear 381 www.2 Case study 1: the design of journal bearings 382 29.3 Case study 2: materials for skis and sledge runners 385 29.4 Case study 3: high-friction rubber 387 I. Designing with metals, ceramics, polymers and composites 391 30. Design with materials 393 30.
Final case study: materials and energy in car design 399 31.2 Energy and cars 400 31.3 Ways of achieving energy economy 400 31.4 Material content of a car 402 31.7 Conclusions 410 Appendix 1 Symbols and formulae 411 Appendix 2 References 419 Index 421 www.net General introduction To the student Innovation in engineering often means the clever use of a new material — new to a particular application, but not necessarily (although sometimes) new in the sense of recently developed. Plastic paper clips and ceramic turbine-blades both represent attempts to do better with polymers and ceramics what had previously been done well with metals. And engineering disasters are frequently caused by the misuse of materials. When the plastic teaspoon buckles as you stir your www.net tea, and when a fleet of aircraft is grounded because cracks have appeared in the tailplane, it is because the engineer who designed them used the wrong materials or did not understand the properties of those used.
So it is vital that the professional engineer should know how to select materials which best fit the demands of the design — economic and aesthetic demands, as well as demands of strength and durability. The designer must understand the properties of materials, and their limitations. This book gives a broad introduction to these properties and limitations. It cannot make you a materials expert, but it can teach you how to make a sensible choice of material, how to avoid the mistakes that have led to embarrassment or tragedy in the past, and where to turn for further, more detailed, help.
You will notice from the Contents list that the chapters are arranged in groups, each group describing a particular class of properties: elastic modulus; fracture toughness; resistance to cor- rosion; and so forth. Each group of chapters starts by defining the property, describing how it is measured, and giving data that we use to solve problems involving design with materials. We then move on to the basic science that underlies each property, and show how we can use this funda- mental knowledge to choose materials with better properties. Each group ends with a chapter of case studies in which the basic understanding and the data for each property are applied to practical engineering problems involving materials.
At the end of each chapter you will find a set of examples; each example is meant to consolidate or develop a particular point covered in the text. Try to do the examples from a particular chapter while this is still fresh in your mind. In this way you will gain confidence that you are on top of the subject. No engineer attempts to learn or remember tables or lists of data for material properties.
But you should try to remember the broad orders of magnitude of these quantities. All foodstores know that ‘‘a kg of apples is about 10 apples’’ — they still weigh them, but their knowledge prevents them making silly mistakes which might cost them money. In the same way an engineer should know that ‘‘most elastic moduli lie between 1 and 103 GN m2; and are around 102 GN m2 for metals’’ — in any real design you need an accurate value, which you can get from suppliers’ spe- cifications; but an order of magnitude knowledge prevents you getting the units wrong, or making other silly, and possibly expensive, mistakes. To help you in this, we have added at the end of the book a list of the important definitions and formulae that you should know, or should be able to derive, and a summary of the orders of magnitude of materials properties.