Metal Machining Theory and Applications by Thomas Childs

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Metal Machining Theory and Applications by Thomas Childs

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Contents

Preface vii
1 Introduction 1
1.1 Machine tool technology 3
1.2 Manufacturing systems 15
1.3 Materials technology 19
1.4 Economic optimization of machining 24
1.5 A forward look 32
References 34
2 Chip formation fundamentals 35
2.1 Historical introduction 35
2.2 Chip formation mechanics 37
2.3 Thermal modelling 57
2.4 Friction, lubrication and wear 65
2.5 Summary 79
References 80
3 Work and tool materials 81
3.1 Work material characteristics in machining 82
3.2 Tool materials 97
References 117
4 Tool damage 118
4.1 Tool damage and its classification 118
4.2 Tool life 130
4.3 Summary 134
References 135
5 Experimental methods 136
5.1 Microscopic examination methods 136
5.2 Forces in machining 139
5.3 Temperatures in machining 147
5.4 Acoustic emission 155
References 157
6 Advances in mechanics 159
6.1 Introduction 159
6.2 Slip-line field modelling 159
6.3 Introducing variable flow stress behaviour 168
6.4 Non-orthogonal (three-dimensional) machining 177
References 197
7 Finite element methods 199
7.1 Finite element background 199
7.2 Historical developments 204
7.3 The Iterative Convergence Method (ICM) 212
7.4 Material flow stress modelling for finite element analyses 220
References 224
8 Applications of finite element analysis 226
8.1 Simulation of BUE formation 226
8.2 Simulation of unsteady chip formation 234
8.3 Machinability analysis of free cutting steels 240
8.4 Cutting edge design 251
8.5 Summary 262
References 262
9 Process selection, improvement and control 265
9.1 Introduction 265
9.2 Process models 267
9.3 Optimization of machining conditions and expert system applications 283
9.4 Monitoring and improvement of cutting states 305
9.5 Model-based systems for simulation and control of machining
processes 317
References 324
Appendices
1 Metals’ plasticity, and its finite element formulation 328
A1.1 Yielding and flow under triaxial stresses: initial concepts 329
A1.2 The special case of perfectly plastic material in plane strain 332
A1.3 Yielding and flow in a triaxial stress state: advanced analysis 340
A1.4 Constitutive equations for numerical modelling 343
A1.5 Finite element formulations 348
References 350
2 Conduction and convection of heat in solids 351
A2.1 The differential equation for heat flow in a solid 351
A2.2 Selected problems, with no convection 353
A2.3 Selected problems, with convection 355
A2.4 Numerical (finite element) methods 357
References 362
3 Contact mechanics and friction 363
A3.1 Introduction 363
A3.2 The normal contact of a single asperity on an elastic foundation 365
A3.3 The normal contact of arrays of asperities on an elastic foundation 368
A3.4 Asperities with traction, on an elastic foundation 369
A3.5 Bulk yielding 371
A3.6 Friction coefficients greater than unity 373
References 374
4 Work material: typical mechanical and thermal behaviours 375
A4.1 Work material: room temperature, low strain rate, strain hardening
behaviours 375
A4.2 Work material: thermal properties 376
A4.3 Work material: strain hardening behaviours at high strain rates and
temperatures 379
References 381
5 Approximate tool yield and fracture analysis 383
A5.1 Tool yielding 383
A5.2 Tool fracture 385
References 386
6 Tool material properties 387
A6.1 High speed steels 387
A6.2 Cemented carbides and cermets 388
A6.3 Ceramics and superhard materials 393
References 395
7 Fuzzy logic 396
A7.1 Fuzzy sets 396
A7.2 Fuzzy operations 398
References 400
Index 401

Preface

Improved manufacturing productivity, over the last 50 years, has occurred in the area of
machining through developments in the machining process, in machine tool technology
and in manufacturing management. The subject of this book is the machining process
itself, but placed in the wider context of manufacturing productivity. It is mainly concerned
with how mechanical and materials engineering science can be applied to understand the
process better and to support future improvements.
There have been other books in the English language that share these aims, from a variety
of viewpoints. Metal Cutting Principles by M. C. Shaw (1984, Oxford: Clarendon
Press) is closest in spirit to the mechanical engineering focus of the present work, but there
have been many developments since that was first published. Metal Cutting by E. M. Trent
(3rd edn, 1991, Oxford: Butterworth-Heinemann) is another major work, but written more
from the point of view of a materials engineer than the current book’s perspective.
Fundamentals of Machining and Machine Tools by G. Boothroyd and W. A. Knight (2nd
edn, 1989, New York: Marcel Dekker) covers mechanical and production engineering
perspectives at a similar level to this book. There is a book in Japanese, Modern Machining
Theory by E. Usui (1990, Tokyo: Kyoritu-shuppan), that overlaps some parts of this
volume. However, if this book, Metal Machining, can bear comparison with any of these,
the present authors will be satisfied.
There are also more general introductory texts, such as Manufacturing Technology and
Engineering by S. Kalpakjian (3rd edn, 1995, New York: Addison-Wesley) and
Introduction to Manufacturing Processes by J. A. Schey (2nd edn, 1987, New York:
McGraw-Hill) and narrower more specialist ones such as Mechanics of Machining by P.
L. B. Oxley (1989, Chichester: Ellis Horwood) which this text might be regarded as
complementing.
It is intended that this book will be of interest and helpful to all mechanical, manufacturing
and materials engineers whose responsibilities include metal machining matters. It
is, however, written specifically for masters course students. Masters courses are a major
feature of both the American and Japanese University systems, preparing the more able
twenty year olds in those countries for the transition from foundation undergraduate
courses to useful professional careers. In the UK, masters courses have not in the past been
popular, but changes from an elite to a mass higher education system are resulting in an
increasingly important role for taught advanced level and continuing professional development
courses.
It is supposed that masters course readers will have encountered basic mechanical and
materials principles before, but will not have had much experience of their application. A
feature of the book is that many of these principles are revised and placed in the machining
context, to relate the material to earlier understanding. Appendices are heavily used to
meet this objective without interrupting the flow of material too much.
It is a belief of the authors that texts should be informative in practical as well as theoretical
detail. We hope that a reader who wants to know how much power will be needed
to turn a common engineering alloy, or what cutting speed might be used, or what material
properties might be appropriate for carrying out some reader-specific simulation, will
have a reasonable chance either of finding the information in these pages or of finding a
helpful reference for further searching.
The book is essentially organized in two parts. Chapters 1 to 5 cover basic material.
Chapters 6 to 9 are more advanced. Chapter 1 is an introduction that places the process in
its broader context of machine tool technology and manufacturing systems management.
Chapter 2 covers the basic mechanical engineering of machining: mechanics, heat conduction
and tribology (friction, lubrication and wear). Chapters 3 and 4 focus on materials’
performance in machining, Chapter 5 describes experimental methods used in machining
studies.
The core of the second part is numerical modelling of the machining process. Chapter
6 deals with mechanics developments up to the introduction of, and Chapters 7 and 8 with
the development and application of, finite element methods in machining analysis. Chapter
9 is concerned with embedding process understanding into process control and optimization
tools.
No book is written without external influences. We thank the following for their advice
and help throughout our careers: in the UK, Professors D. Tabor, K. L. Johnson, P. B.
Mellor and G . W. Rowe (the last two, sadly, deceased); in Japan, Professors E. Usui, T.
Shirakashi and N. Narutaki; and Professor S. Ramalingam in the USA. More closely
connected with this book, we also especially acknowledge many discussions with, and
much experimental information given by, Professor T. Kitagawa of Kitami Institute of
Technology, who might almost have been a co-author.
We also thank the companies Yasda Precision Tools KK, Okuma Corporation and Toyo
Advanced Technologies for allowing the use of original photographs in Chapter 1, British
Aerospace Airbus for providing the cover photograph, Mr G. Dean (Leeds University) for
drafting many of the original line drawings and Mr K. Sekiya (Hiroshima University) for
creating some of the figures in Chapter 4. One of us (it is obvious which one) thanks the
British Council and Monbusho for enabling him to spend a 3 month period in Japan during
the Summer of 1999: this, with the purchase of a laptop PC with money awarded by the
Jacob Wallenberg Foundation (Royal Swedish Academy of Engineering Science), resulted
in the final manuscript being less late than it otherwise would have been.
We must thank the publisher for allowing several deadlines to pass and our wives –
Wendy, Yoko, Hiromi and Fukiko – and families for accepting the many working weekends
that were needed to complete this book.