Engineering Materials 1

322 Pages·1996·13.211 MB·English

by  D R H Jones, Michael F. Ashby

S E C O N D E D I T I O N
' A '
AN INTRODUCTION TO THEIF;
PROPERTIES & APPLICATIONS
Michael F Ashby. David R H Jones
Engineering Materials 1
An lntroduction to their Properties and Applications
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Engineering Materials 1
An Introduction to their Properties and Applications
Second Edition
by
Michael F . Ashby
and
David R. H. Jones
Department of Engineering, University of Cambridge, UK
U T T E R W O R T H
E I N E M A N N
OXFORD AMSTERDAM BOSTON LONDON NEW YORK PARIS
SAN DIEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO
Butterworth-Heinemann
An imprint of Elsevier Science
Linacre House, Jordan Hill, Oxford OX2 8DP
225 Wildwood Avenue, Wobum, MA 01801-2041
First published 1980
Second edition 1996
Reprinted 1997, 1998 (twice), 2000,2001,2002
0 1980, 1996, Michael F. Ashby and David R. H. Jones. All rights reserved.
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asserted in accordance with the Copyright, Designs and Patents Act 1988
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British Library Cataloguing in Publication Data
Ashby, Michael E
Engineering materials. 1. an introduction to their
properties and applications. - 2nd. ed.
1. Materials 2. Mechanics
I. Title 11. Jones, David R. H. (David Rayner Hunkin),
1945-620.1’1
ISBN 0 7506 3081 7
Library of Congress Cataloguing in Publication Data
Ashby, Michael E
Engineering materials. 1. an introduction to their properties and
applicationsby Michael F. Ashby and David R. H. Jones - 2nd. ed.
p. cm.
Rev.ed of Engineering materials. 1980.
Includes bibliographical references and index.
ISBN 0 7506 3081 7
1. Materials. I. Jones, David R. H. (David Rayner Hunkin),
1945-. 11. Ashby, M.F. Engineering materials III. Title
TA403.A69 96-1677
620.1’1-dc20 CIP
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Typeset by Genesis Typesetting, Rochester, Kent
Printed and bound in Great Britain by MFG Books Ltd, Bodmin, Comwall
General introduction
1. Engineering Materials and their Properties 3
examples of structures and devices showing how we select the right
material for the job
A. Price and availability
2. The Price and Availability of Materials 15
what governs the prices of engineering materials, how long will supplies
last, and how can we make the most of the resources that we have?
B. The elastic moduli
3. The Elastic Moduli 27
stress and strain; Hooke’s Law; measuring Young’s modulus; data for
design
4. Bonding Between Atoms 36
the types of bonds that hold materials together; why some bonds are
stiff and others floppy
5. Packing of Atoms in Solids 45
how atoms are packed in crystals - crystal structures, plane (Miller)
indices, direction indices; how atoms are packed in polymers, ceramics
and glasses
6. The Physical Basis of Young’s Modulus 58
how the modulus is governed by bond stiffness and atomic packing; the
glass transition temperature in rubbers; designing stiff materials -
man-made composites
7. Case Studies of Modulus-limited Design 66
the mirror for a big telescope; a stiff beam of minimum weight; a stiff
beam of minimum cost
vi Contents
C. Yield strength, tensile strength, hardness and ductility
8. The Yield Strength, Tensile Strength, Hardness and Ductility 77
definitions, stress-strain curves (true and nominal), testing methods,
data
9. Dislocations and Yielding in Crystals 93
the ideal strength; dislocations (screw and edge) and how they move to
give plastic flow
10. Strengthening Methods and Plasticity of Polycrystals 104
solid solution hardening; precipitate and dispersion strengthening;
work-hardening; yield in polycrystals
11. Continuum Aspects of Plastic Flow 111
the shear yield strength; plastic instability; the formability of metals and
polymers
12. Case Studies in Yield-limited Design 119
materials for springs; a pressure vessel of minimum weight; a pressure
vessel of minimum cost; how metals are rolled into sheet
D. Fast fracture, toughness and fatigue
13. Fast Fracture and Toughness 131
where the energy comes from for catastrophic crack growth; the
condition for fast fracture; data for toughness and fracture toughness
14. Micromechanisms of Fast Fracture 140
ductile tearing, cleavage; composites, alloys - and why structures are
more likely to fail in the winter
15. Fatigue Failure 146
fatigue testing, Basquin’s Law, Coffin-Manson Law; crack growth rates
for pre-cracked materials; mechanisms of fatigue
16. Case Studies in Fast Fracture and Fatigue Failure 155
fast fracture of an ammonia tank; how to stop a pressure vessel blowing
up; is cracked cast iron safe?
E. Creep deformation and fracture
17. Creep and Creep Fracture 169
high-temperature behaviour of materials; creep testing and creep curves;
consequences of creep; creep damage and creep fracture
Contents vii
18. Kinetic Theory of Diffusion 1 79
Arrhenius's Law; Fick's first law derived from statistical mechanics of
thermally activated atoms; how diffusion takes place in solids
19. Mechanisms of Creep, and Creep-resistant Materials 187
metals and ceramics - dislocation creep, diffusion creep; creep in
polymers; designing creep-resistant materials
20. The Turbine Blade - A Case Study in Creep-limited Design 197
requirements of a turbine-blade material; nickel-based super-alloys,
blade cooling; a new generation of materials? - metal-matrix composites,
ceramics, cost effectiveness
F. Oxidation and corrosion
21. Oxidation of Materials 211
the driving force for oxidation; rates of oxidation, mechanisms of
oxidation; data
22. Case Studies in Dry Oxidation 219
making stainless alloys; protecting turbine blades
23. Wet Corrosion of Materials 225
voltages as driving forces; rates of corrosion; why selective attack is
especially dangerous
24. Case Studies in Wet Corrosion 232
how to protect an underground pipeline; materials for a light-weight
factory roof; how to make motor-car exhausts last longer
G. Friction, abrasion and wear
25. Friction and Wear 241
surfaces in contact; how the laws of friction are explained by the
asperity-contact model; coefficients of friction; lubrication; the adhesive
and abrasive wear of materials
26. Case Studies in Friction and Wear 250
the design of a journal bearing; materials for skis and sledge runners;
'non-skid' tyres
viii Contents
Final case study
27. Materials and Energy in Car Design 261
the selection and economics of materials for automobiles
Appendix 1 Examples 273
Appendix 2 Aids and Demonstrations 290
Appendix 3 Symbols and Formulae 297
Index 303
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 tea-spoon buckles as you stir your 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: the elastic modulus; the fracture
toughness; resistance to corrosion; and so forth. Each such group of chapters starts by
defining the property, describing how it is measured, and giving a table of data that we use
to solve problems involving the selection and use of materials. We then move on to the
basic science that underlies each property, and show how we can use this fundamental
knowledge to design 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. Each chapter has a list
of books for further reuding, ranked so that the more elementary come first.
At the end of the book you will find sets of examples; each example is meant to
consolidate or develop a particular point covered in the text. Try to do the examples
that derive from a particular chapter whilesthis 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 grocers 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 lo3G N m-2; and are around 102GNm W2fo r metals’ - in any real design you need
an accurate value, which you can get from suppliers’ specifications; but an order-of-