Ashby Materials Selection in Mechanical Design 4th Vol.1 (1)

Ashby Materials Selection in Mechanical Design 4th Vol.1 (1)

(Parte 1 de 5)

Materials Selection in Mechanical Design

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Materials Selection in Mechanical Design Fourth Edition

Michael F. Ashby


Butterworth-Heinemann is an imprint of Elsevier 30 Corporate Drive, Suite 400 Burlington, MA 01803, USA

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© 2011 Michael F. Ashby. Published by Elsevier Ltd. All rights reserved.

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This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein).

Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary.

Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility.

To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein.

Library of Congress Cataloging-in-Publication Data Ashby, M. F. Materials selection in mechanical design / Michael F. Ashby. — 4th ed. p. cm. Includes index and readings. ISBN 978-1-85617-663-7 1. Materials. 2. Engineering design. I. Title. TA403.6.A74 2011 620.1'1–dc22 201002069

British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library.

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CHAPTER 1 Introduction1
1.1 Introduction and Synopsis2
1.2 Materials in Design2
1.3 The Evolution of Engineering Materials4
1.4 The Evolution of Materials in Products8
1.5 Summary and Conclusions12
1.6 Further Reading12
CHAPTER 2 The Design Process15
2.1 Introduction and Synopsis16
2.2 The Design Process16
2.3 Types of Design20
2.4 Design Tools and Materials Data21
2.5 Function, Material, Shape, and Process23
2.6 Case Study: Devices to Open Corked Bottles24
2.7 Summary and Conclusions27
2.8 Further Reading27
CHAPTER 3 Engineering Materials and Their Properties31
3.1 Introduction and Synopsis32
3.2 The Families of Engineering Materials32
3.3 Materials Information for Design35
3.4 Material Properties and Their Units38
3.5 Summary and Conclusions54
3.6 Further Reading5
CHAPTER 4 Material Property Charts57
4.1 Introduction and Synopsis58
4.2 Exploring Material Properties59
4.5 Further Reading95
CHAPTER 5 Materials Selection—The Basics97
5.1 Introduction and Synopsis98
5.2 The Selection Strategy9
5.3 Material Indices106
5.4 The Selection Procedure115
5.5 Computer-aided Selection120
5.6 The Structural Index122
5.7 Summary and Conclusions123
5.8 Further Reading123
CHAPTER 6 Case Studies: Materials Selection125
6.1 Introduction and Synopsis126
6.2 Materials for Oars127
6.3 Mirrors for Large Telescopes130
6.4 Materials for Table Legs134
6.5 Cost: Structural Materials for Buildings138
6.6 Materials for Flywheels142
6.7 Materials for Springs146
6.8 Elastic Hinges and Couplings151
6.9 Materials for Seals154
6.10 Deflection-limited Design with Brittle Polymers155
6.1 Safe Pressure Vessels160
6.12 Stiff, High-damping Materials for Shaker Tables165
6.13 Insulation for Short-term Isothermal Containers169
6.14 Energy-efficient Kiln Walls172
6.15 Materials for Passive Solar Heating175
Precision Devices178
6.17 Materials for Heat Exchangers181
6.18 Heat Sinks for Hot Microchips186
6.19 Materials for Radomes189
6.20 Summary and Conclusions194
6.21 Further Reading194
CHAPTER 7 Multiple Constraints and Conflicting Objectives197
7.1 Introduction and Synopsis198
7.2 Selection with Multiple Constraints199
7.3 Conflicting Objectives203
7.4 Summary and Conclusions211
7.5 Further Reading211
7.6 Appendix: Weight Factors and Fuzzy Methods212
and Conflicting Objectives217
8.1 Introduction and Synopsis218
8.2 Multiple Constraints: Light Pressure Vessels218
High-performance Engines2
High-field Magnets226
8.5 Conflicting Objectives: Table Legs Again232
for Must-have Electronics233
Disk-brake Caliper237
8.8 Summary and Conclusions241
CHAPTER 9 Selection of Material and Shape243
9.1 Introduction and Synopsis244
9.2 Shape Factors246
9.3 Limits to Shape Efficiency257
9.4 Exploring Material-shape Combinations260
9.5 Material Indices That Include Shape265
9.6 Graphical Coselecting Using Indices269
9.7 Architectured Materials: Microscopic Shape270
9.8 Summary and Conclusions274
9.9 Further Reading276
CHAPTER 10 Case Studies: Material and Shape277
10.1 Introduction and Synopsis278
10.2 Spars for Human-powered Planes279
10.3 Forks for a Racing Bicycle282
10.4 Floor Joists: Wood, Bamboo, or Steel?284
10.5 Table Legs Yet Again: Thin or Light?287
10.6 Increasing the Stiffness of Steel Sheet289
10.7 Shapes that Flex: Leaf and Strand Structures291
10.8 Ultra-efficient Springs293
10.9 Summary and Conclusions296
CHAPTER 1 Designing Hybrid Materials299
1.1 Introduction and Synopsis300
1.2 Holes in Material-property Space303
1.3 The Method: “A + B + Configuration + Scale”305
1.4 Composites307
1.5 Sandwich Structures316
1.6 Cellular Structures: Foams and Lattices328

CHAPTER 8 Case Studies: Multiple Constraints 8.3 Multiple Constraints: Con-rods for 8.4 Multiple Constraints: Windings for 8.6 Conflicting Objectives: Wafer-thin Casings 8.7 Conflicting Objectives: Materials for a Contents vii

1.8 Summary and Conclusions338
1.9 Further Reading339
CHAPTER 12 Case Studies: Hybrids341
12.1 Introduction and Synopsis342
12.2 Designing Metal Matrix Composites342
12.3 Flexible Conductors and Percolation344
and Electrical Conduction347
12.5 Refrigerator Walls349
12.6 Materials for Microwave-transparent Enclosures352
12.7 Connectors That Don’t Relax Their Grip354
12.8 Exploiting Anisotropy: Heat-spreading Surfaces356
12.9 The Mechanical Efficiency of Natural Materials358
12.10 Further Reading: Natural Materials365
CHAPTER 13 Processes and Process Selection367
13.1 Introduction and Synopsis368
13.2 Classifying Processes369
13.3 The Processes: Shaping, Joining, Finishing372
13.4 Processing for Properties388
13.5 Systematic Process Selection392
13.6 Ranking: Process Cost406
13.7 Computer-aided Process Selection411
13.8 Summary and Conclusions413
13.9 Further Reading413
CHAPTER 14 Case Studies: Process Selection415
14.1 Introduction and Synopsis416
14.2 Casting an Aluminum Con-rod416
14.3 Forming a Fan419
14.4 Spark Plug Insulators429
14.5 A Manifold Jacket431
14.6 Joining a Steel Radiator433
14.7 Surface-hardening a Ball-bearing Race435
14.8 Summary and Conclusions436
CHAPTER 15 Materials and the Environment437
15.1 Introduction and Synopsis438
15.2 The Material Life-cycle438
15.3 Material and Energy-consuming Systems440
15.4 The Eco-attributes of Materials442
15.5 Eco-selection447
15.6 Case Studies: Drink Containers and Crash Barriers453
15.8 Further Reading458
CHAPTER 16 Materials and Industrial Design461
16.1 Introduction and Synopsis462
16.2 The Requirements Pyramid463
16.3 Product Character464
Product Personality467
16.5 Summary and Conclusions476
16.6 Further Reading476
CHAPTER 17 Forces for Change479
17.1 Introduction and Synopsis480
17.2 Market Pull and Science Push480
17.4 Product Liability and Service Provision487
17.5 Miniaturization and Multifunctionality489
17.6 Concern for the Environment and for the Individual490
17.7 Summary and Conclusions492
17.8 Further Reading492
APPENDIX A Data for Engineering Materials495

Table A.1 Names and Applications: Metals and Alloys;

Ceramics, Glasses, and Natural Materials497

Polymers and Foams; and Composites,

Temperature, Tg500
Table A.3 Density, ρ502
Table A.4 Young’s Modulus, E504
Table A.5 Yield Strength, σy, and Tensile Strength, σts506
Table A.6 Fracture Toughness (plane strain), KIC508

Table A.2 Melting Temperature, Tm, and Glass Table A.7 Thermal Conductivity, λ, and Thermal

Expansion, α510
Table A.8 Heat Capacity, Cp512
Table A.9 Resistivity and Dielectric Constant514
Table A.10 Embodied Energy and CO2 Footprint516
Table A.1 Approximate Material Prices, Cm518
Ways of Checking and Estimating Data520
Further Reading523
APPENDIX B Useful Solutionsf or Standard Problems525
Introduction and Synopsis527
B.1 Constitutive Equations for Mechanical Response528

Contents ix

B.3 Elastic Bending of Beams532
B.4 Failure of Beams and Panels534
B.5 Buckling of Columns, Plates, and Shells536
B.6 Torsion of Shafts538
B.7 Static and Spinning Disks540
B.8 Contact Stresses542
B.9 Estimates for Stress Concentrations544
B.10 Sharp Cracks546
B.1 Pressure Vessels548
B.12 Vibrating Beams, Tubes, and Disks550
B.13 Creep and Creep Fracture552
B.14 Flow of Heat and Matter554
B.15 Solutions for Diffusion Equations556
B.16 Further Reading558
APPENDIX C Material Indices559
C.1 Introduction and Synopsis560
C.2 Uses of Material Indices560
APPENDIX D Data Sources for Documentation565
D.1 Introduction566
D.2 Information Sources for Materials566
D.3 Information for Manufacturing Processes589
D.4 Databases and Expert Systems as Software590
D.5 Additional Useful Internet Sites592
APPENDIX E Exercises595
E.1 Introduction to Exercises595
E.2 Material Evolution in Products (Chapter 1)596
E.3 Devising Concepts (Chapter 2)597
E.4 Using Material Properties (Chapter 3)597
E.5 Using Material Property Charts (Chapter 4)599
(Chapters 5 and 6)602
(Chapters 5 and 6)605

E.7 Deriving and Using Material Indices

(Chapters 7 and 8)613
E.9 Selecting Material and Shape (Chapters 9 and 10)622
E.10 Hybrid Materials (Chapters 1 and 12)629
E.1 Selecting Processes (Chapters 13 and 14)633
E.12 Materials and the Environment (Chapter 15)638

E.8 Multiple Constraints and Objectives x Contents


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

Materials influenced lives in Epictetus’ timea ndc ontinuet od os ot oday. In his day, the number of materials was small; today it is vast. The opportunities for innovation that materials offer now are equally immense. But advance is possible only if a procedure exists for making a rational choice from the materials on this great menu, and—if they are to be used—a way of identifying ways to shape, join, and finish them. This book develops a systematic procedure for selecting materials and processes, leading to the subset that best matches the requirements of a design. It is unique in the way that the information it contains has been structured. The structure gives rapid access to data and allows the user great freedom in exploring potential choices. The method is implemented in software* to provide greater flexibility.

The approach here emphasizes design with materials rather than materials “science,” although the underlying science is used whenever possible to help with the structuring of selection criteria. The first six chapters require little prior knowledge: A first-year grasp of materials and mechanics is enough. The chapters dealing with shape and multiobjective 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 relationships with the stages of design and optimization and with the mechanics of material, are develope d throughout. At the teaching level, the book is intended as a text for third- and fourth-year engineering courses on Materials for Design: A 6- to 10-lecture unit can be based on Chapters 1 through 6, 13, and 14; a full 20-lecture course, with project work using the associated software, will require use of the entire book.

* The CES Edu materials and process selection platform is a product of Granta Design ( xi

Beyond this, the book is intended as a reference of lasting value. The method, the charts, and the tables of performance indices have application in real problems of materials and process selection; and the table of data and the catalog of “useful solutions” (Appendices A and B) are particularly helpful in modeling—an essential ingredient in optimal design. The reader can use the content (and the software) at increasing levels of sophistication as his or her experience grows, starting with the material indices developed in the book’s case studies and graduating to the modeling of new design problems, leading to new material indices and penalty functions, as well as new—and perhaps novel—choices of material. This continuing education aspect is helped by the “Further readings” at the end of each chapter and Appendix E—a set of exercises covering all aspects of the text. Useful reference material is assembled in Appendices A, B, C, and D.

As in any other book, the contents in this one are protected by copyright. Generally, it is an infringem ent to copy and distribut e materials from a copyrighted source. However, the best way to use the charts that are a central feature of the book, for readers to have a clean copy on which they can draw, try out alternative selection criteria, write comments, and so forth; presenting the conclusion for a selected exercise is often most easily done in the same way. Although the book itself is copyrighted, instructors or readers area uthorized to makeu nlimited copies of thec hartsa nd to reproduce these for teaching purposes, provided a full reference to their source is given.

Many colleagues have been generous with discussion, criticism, and constructive suggestions. I particularly wish to thank Professor Yves Bréchet of the University of Grenoble in France, Professor Anthony Evans of the University of California at Santa Barbara, Professor John Hutchinson of Harvard University, Professor David Cebon, Professor Norman Fleck, Professor Ken Wallace, Professor John Clarkson, Dr. Hugh Shercliff of the Engineering Department of Cambridge University, Professor Amal Esawi of the American University in Cairo, Professor Ulrike Wegst of Drexel University, Dr. Paul Weaver of the Department of Aeronautical Engineering at the University of Bristol, and Professor Michael Brown of the Cavendish Laboratory in Cambridge, UK.

Mike Ashby xii Preface

Features of the Fourth Edition

Since publication of the third edition of this book, changes have occurred in the field of materials and their role in engineering, as well as in the way these subjects are taught in university- and college-level courses. There is increasing emphasis on materials efficiency—design that uses materials effectively and with as little damage to the environment as possible. All this takes place in a computer-based environment; teaching, too, draws increasingly on computerbased tools. This new edition has been comprehensively revised and reorganized to address these. The presentation has been enhanced and simplified; the figures, many of them new, have been redrawn in full color; worked intext examples illustrate methods and results in chapters that are not themselves collections of case studies; and additional features and supplements have been added. The key changes are outlined next.

Key changes ■ Chapter 1, Introduction, has been completely rewritten and illustrated to develop the history of materia ls and the evol ution of materi als in engineering.

■ Engineering Design, introduced in Chapter 2, has been edited, with a full revision of all figures.

■ Material Properties and Property Charts—a unique feature of the book, which appear in Chapters 3 and 4, have been redrawn in full color.

■ Chapter 5 and 6—the central chapters that describe and illustrate selection methods—have been extensively revised with new explanations of the essential selection strategy.

■ Chapters 7 and 8 (Multiple Constraints) have been revised, with in-text examples and more illuminating case studies.

■ Chapters 9 and 10 (Materials and Shape) have been rewritten for greater clarity, with numerous in-text examples in Chapter 9.


■ Chapters 1 and 12, Hybrid Materials, represent a further development of what was in the earlier edition, with a new develop ment of the treatment of sandwich structures and with enhanced case studies.

■ Chapters 13 and 14, Processing, contain sections and figures that emphasize the influence of processing on properties.

■ Chapter 15, Materials and the Environment, is revised, with improved examples and links to the new information.1

■ Chapter 16, Industrial Design, is updated and linked to the second edition of the related text2 on this subject. ■ Chapter 17, Forces for Change, has been updated.

■ Appendices with Tables of Materials Properties, Useful Solutions, Indices, and Data Sources are updated, enlarged and reillustrated. ■ The final appendix contains Exercises that are listed by chapter number.

Material selection charts Full color versions of a number of the Material Selection Charts presented in this book are available . Samples can be found at ashbycharts.htm. This web page also provides a link to a page where users of CES EduPack (details follow) can download further charts and other teaching resources, including PowerPoint lectures. Although the author retains the copyright for the charts, users of this book are authorized to download, print, and make unlimited copies of those available on the site; in addition, they can be reproduced for teaching purposes (but not for publication), with proper reference to their source.

Instructor’s manual and Image Bank The book ends with a comprehensive set of exercises in Appe ndix E. Worked-out solutions to the exercises are avai lable, free of char ge, to teachers, lecturers, and professors who adopt the book.

The Image Bank provides tutors and lecturers who have adopted this book with PDF versions of the figures contained in it; they can be used for lecture slides and class presentations.

To access the instructor’s manual and Image Bank, please visit w.textbooks. and follow the onscreen instructions.

1 Materials and the Environment—Eco-informed materials choice (2009) by M.F. Ashby, Butterworth- Heinemann, ISBN 978-1-85617-608-8. 2 Materials and Design—The art and science of materials selection in Product Design, 2nd edition (2009), by M.F. Ashby and K. Johnson, Butterworth-Heinemann, ISBN 978-1-85617-497-8.

xiv Features of the Fourth Edition

The CES EduPack The CES EduPack is a widely used software package that implements the methods developed here. The book does not rely on the software, but the learning experience is enhanced by using the two together to create an exciting teaching environment that stimulates exploration, self-teachin g, and design innovation. For further information, see the last page of this book or visit

Features of the Fourth Edition xv

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Stoneage Bronzeage Ironage Age ofsteel

Age of molecularengineeringAge ofpolymersAge of silicon

GoldGold CopperCopper BronzeBronze


Cast iron

WoodWood SkinsSkins

Fibers GluesGlues

RubberRubber Straw-brickStraw-brick PaperPaper



FlintFlint PotteryPottery




PortlandPortland cementcement FusedFused silicasilica

Pyro-Pyro- ceramicsceramics


Alloy steels

LightLight alloysalloys

Super alloysSuper alloys

Titanium Zirconium AlloysAlloys etc.




EpoxiesEpoxies PolyestersPolyesters


CompositesComposites Metal-matrixMetal-matrix

Ceramic compositesCeramic composites

HighHigh-modulusmodulus polymerspolymers

High-temperature polymers

Glassy metalsGlassy metals Al-lithium alloys Dual phase steelsDual phase steels Microalloyed steelsMicroalloyed steels New super alloysNew super alloys

Gold Copper Bronze


Cast iron

Wood Skins

Fibers Glues

Rubber Straw-brick Paper

BakeliteStone Flint




Refractories Portland cement Fusedsilica Pyroceramics


Alloy steels

Light alloys

Super alloys

Titanium Zirconium Alloys etc.


PE PMMA Acrylics PC PS P


Epoxies Polyesters


Composites Metal-matrix

Ceramic composites

High-modulus polymers

High-temperature polymers

Development Slow:Development Slow: Mostly QualityMostly Quality Control andControl and ProcessingProcessing

Development Slow: Mostly Quality Control and Processing

Glassy metals Al-lithium alloys Dual phase steels Microalloyed steels

Tough engineeringTough engineering

New super alloys

Date Relative importance

Polymers and elastomers

Polymers and elastomers Composites


Ceramics andglassesCeramics and glasses

Metals Metals

The evolution of engineering materials with time. “Relative importance” is based on information contained in the books listed under “Further reading”; plus, from 1960 onward, data for the teaching hours allocated to each material family at U.K. and U.S. universities. The projections to 2020 rely on estimates of material usage in automobiles and aircraft by manufacturers. The time scale is nonlinear. The rate of change is far faster today than at any previous time in history.

Materials Selection in Mechanical Design. DOI: 10.1016/B978-1-85617-663-7.00001-1 © 2011 Michael F. Ashby. Published by Elsevier Ltd. All rights reserved. 1

1.1 Introduction and Synopsis2
1.2 Materials in Design2
1.3 The Evolution of Engineering Materials4
1.4 The Evolution of Materials in Products8
1.5 Summary and Conclusions12
1.6 Further Reading12


“Design” is one of those words that mean all things to all people. Every manufactured thing, from the most lyrical of ladies’ hats to the greasiest of gearboxes, qualifies, in some sense or other, as a design. It can mean yet more. Nature, to some, is divine design; to others it is design by natural selection. The reader will agree that it is necessary to narrow the field, at least a little.

(Parte 1 de 5)