Engineering materials 1 an introduction to properties, applications and design 3rd ed ashby jones

.elsolucionario www.elsolucionario.net www.elsolucionario.net Engineering Materials www.elsolucionario.net An Introduction to Properties, Applications and Design www.elsolucionario.net www.elsolucionario.net www.elsolucionario.net Engineering Materials Third Edition by Michael F Ashby and David R H Jones Department of Engineering, University of Cambridge, UK Amsterdam  Boston  Heidelberg  London  New York  Oxford Paris  San Diego  San Francisco  Singapore  Sydney  Tokyo www.elsolucionario.net An Introduction to Properties, Applications and Design www.elsolucionario.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 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: (ỵ44) (0) 1865 843830, fax: (ỵ44) (0) 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 7506 63804 For information on all Elsevier Butterworth-Heinemann publications visit our website at http://www.books.elsevier.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.elsevier.com | www.bookaid.org | www.sabre.org www.elsolucionario.net The right of Michael F Ashby and David R H Jones to be identified as the authors of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988 www.elsolucionario.net Contents General introduction xi Engineering materials and their properties Introduction Examples of materials selection A Price and availability 15 The price and availability of materials 17 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Introduction Data for material prices The use-pattern of materials Ubiquitous materials Exponential growth and consumption doubling-time Resource availability The future Conclusion 18 18 20 21 23 24 26 27 B The elastic moduli 29 The elastic moduli 31 3.1 3.2 3.3 3.4 3.5 3.6 Introduction Definition of stress Definition of strain Hooke’s law Measurement of Young’s modulus Data for Young’s modulus Bonding between atoms 4.1 4.2 4.3 4.4 4.5 Introduction Primary bonds Secondary bonds The condensed states of matter Interatomic forces Packing of atoms in solids 5.1 Introduction 5.2 Atom packing in crystals 5.3 Close-packed structures and crystal energies 32 32 35 36 37 38 43 44 45 48 51 51 55 56 56 56 www.elsolucionario.net 1.1 1.2 www.elsolucionario.net Contents 5.4 5.5 5.6 5.7 5.8 5.9 5.10 Crystallography Plane indices Direction indices Other simple important crystal structures Atom packing in polymers Atom packing in inorganic glasses The density of solids The physical basis of Young’s modulus 6.1 6.2 6.3 6.4 6.5 Introduction Moduli of crystals Rubbers and the glass transition temperature Composites Summary Case studies in modulus-limited design 7.1 7.2 7.3 Case study 1: a telescope mirror — involving the selection of a material to minimize the deflection of a disc under its own weight Case study 2: materials selection to give a beam of a given stiffness with minimum weight Case Study 3: materials selection to minimize the cost of a beam of given stiffness C Yield strength, tensile strength and ductility The yield strength, tensile strength and ductility 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 Introduction Linear and nonlinear elasticity; anelastic behavior Load–extension curves for non-elastic (plastic) behavior True stress–strain curves for plastic flow Plastic work Tensile testing Data The hardness test Revision of the terms mentioned in this chapter, and some useful relations Dislocations and yielding in crystals 9.1 9.2 9.3 9.4 9.5 Introduction The strength of a perfect crystal Dislocations in crystals The force acting on a dislocation Other properties of dislocations 58 60 61 62 64 65 66 73 74 74 76 78 81 85 86 91 93 97 99 100 100 101 103 106 106 107 108 111 119 120 120 122 128 129 www.elsolucionario.net vi www.elsolucionario.net 10 Strengthening methods, and plasticity of polycrystals 10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8 Introduction Strengthening mechanisms Solid solution hardening Precipitate and dispersion strengthening Work-hardening The dislocation yield strength Yield in polycrystals Final remarks 11 Continuum aspects of plastic flow 11.1 11.2 11.3 11.4 Introduction The onset of yielding and the shear yield strength, k Analyzing the hardness test Plastic instability: necking in tensile loading 12 Case studies in yield-limited design 12.1 12.2 12.3 12.4 Introduction Case study 1: elastic design-materials for springs Case study 2: plastic design-materials for a pressure vessel Case study 3: large-strain plasticity — rolling of metals vii 131 132 132 132 133 135 135 136 139 141 142 142 144 145 153 154 154 159 160 D Fast fracture, brittle fracture and toughness 167 13 Fast fracture and toughness 169 13.1 Introduction 13.2 Energy criterion for fast fracture 13.3 Data for Gc and Kc 14 Micromechanisms of fast fracture 14.1 14.2 14.3 14.4 14.5 Introduction Mechanisms of crack propagation, 1: ductile tearing Mechanisms of crack propagation, 2: cleavage Composites, including wood Avoiding brittle alloys 15 Case studies in fast fracture 15.1 Introduction 15.2 Case study 1: fast fracture of an ammonia tank 15.3 Case study 2: explosion of a perspex pressure window during hydrostatic testing 15.4 Case study 3: cracking of a polyurethane foam jacket on a liquid methane tank 15.5 Case study 4: collapse of wooden balcony railing 170 170 175 181 182 182 184 186 187 191 192 192 195 198 202 www.elsolucionario.net Contents www.elsolucionario.net Contents 16 Probabilistic fracture of brittle materials 16.1 Introduction 16.2 The statistics of strength and the Weibull distribution 16.3 Case study: cracking of a polyurethane foam jacket on a liquid methane tank 209 210 212 216 E Fatigue failure 221 17 Fatigue failure 223 17.1 17.2 17.3 17.4 Introduction Fatigue behavior of uncracked components Fatigue behavior of cracked components Fatigue mechanisms 224 224 228 230 18 Fatigue design 18.1 Introduction 18.2 Fatigue data for uncracked components 18.3 Stress concentrations 18.4 The notch sensitivity factor 18.5 Fatigue data for welded joints 18.6 Fatigue improvement techniques 18.7 Designing-out fatigue cycles 18.8 Checking pressure vessels for fatigue cracking 237 238 238 239 240 241 242 244 246 19 Case studies in fatigue failure 19.1 Introduction 19.2 Case study 1: high-cycle fatigue of an uncracked component — failure of a pipe organ mechanism 19.3 Case study 2: low-cycle fatigue of an uncracked component — failure of a submersible lifting eye 19.4 Case study 3: fatigue of a cracked component — the safety of the Stretham engine 251 252 264 F Creep deformation and fracture 271 20 Creep and creep fracture 20.1 Introduction 20.2 Creep testing and creep curves 20.3 Creep relaxation 20.4 Creep damage and creep fracture 20.5 Creep-resistant materials 273 274 277 280 282 283 21 Kinetic theory of diffusion 287 21.1 Introduction 21.2 Diffusion and Fick’s law 252 260 288 289 www.elsolucionario.net viii www.elsolucionario.net 406 Chapter 31 Final case study: materials and energy in car design 1=2 fiberglass offer potential weight savings of up to times ð=y Þ on these components This makes possible a saving of at least 30 percent on the weight of the vehicle; if, in addition, an aluminum engine block is used, the overall weight saving is larger still These are very substantial savings — sufficient to achieve the increase in mileage per gallon from 22.5 to 34.5 without any decrease in the size of the car, or increase in engine efficiency So they are obviously worth examining more closely What, then, of the other properties required of the substitute materials? Although resistance to deflection and plastic yielding are obviously of first importance in choosing alternative materials, other properties enter into the selection Let us look at these briefly Table 31.4 lists the conditions imposed by the service environment Consider these in turn Elastic and plastic deflection we have dealt with already The toughness of steel is so high that fracture of a steel panel is seldom a problem But what about the other materials? The data for toughness are given in Table 31.5 But what is the proper way to use toughness values? The most sensible thing to is ask: suppose the panel is loaded up to its yield load (above this load we know it will begin to fail — by plastic flow — so it does not matter whether other failure mechanisms also appear); what is the maximum crack size that is still stable? If this is large enough that it should not appear in service, we are satisfied; if not, we must increase the section This crack size is given (Chapter 13) by pffiffiffiffiffiffiffiffiffi pffiffiffiffiffiffi y a ¼ Kc ¼ EGc Table 31.4 The service environment of the average car Loading Physical environment Chemical environment Static ! Elastic or plastic deflection Impact ! Elastic or plastic deflection Impact ! Fracture Fatigue ! Fatigue fracture Long-term static ! Creep À 40 C < T