Table Of ContentINTEGRATED COMPUTER-AIDED
DESIGN OF MECHANICAL SYSTEMS
INTEGRATED
COMPUTER-AIDED DESIGN
OF MECHANICAL SYSTEMS
S. A. MEGUID
School of Mechanical Engineering,
Cranfield Institute of Technology,
Bedford, UK
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© ELSEVIER APPLIED SCIENCE PUBLISHERS LTD 1987
Softcover reprint of the hardcover 1s t edition 1987
British Library Cataloguing in Publication Data
Meguid, S. A
Integrated computer-aided design of
mechanical systems.
1. Engineering design - Data processing
I. Title
620' .00425'0285 TAl 74
Library of Congress Cataloging-in-Publication Data
Meguid, S. A
Integrated computer-aided design of mechanical
systems.
Includes bibliographies and index.
1. Computer-aided design. 2. Engineering design -
Data processing. I. Title.
TA174.M386 1986 620'.00425'0285 86-11607
ISBN -13: 978-94-010-8024-8 e-ISBN -13: 978-94-009-3409-2
DOl: 10.1007/978-94-009-3409-2
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To Eli and
Jenna Danielle
Preface
In this book, the author has presented an introduction to the practical
application of some of the essential technical topics related to
computer-aided engineering (CAE). These topics include interactive
computer graphics (ICG), computer-aided design (CAD), computer
aided analysis (CAA) and computer-integrated manufacturing (CIM).
Unlike the few texts available, the present work attempts to bring all
these seemingly specialised topics together and to demonstrate their
integration in the design process through practical applications to real
engineering problems and case studies.
This book is the result of the author's research and teaching activities
for several years of postgraduate and undergraduate courses in
mechanical design of rotating machinery, computer-aided engineering,
practical applications of finite elements, solid mechanics, engineering
dynamics and properties of materials at Cranfield Institute of
Technology, Oxford Engineering Science and the University of
Manchester Institute of Science and Technology (UMIST). It was soon
realised that no books on the most powerful and versatile tools available
to engineering designers existed. To satisfy this developing need, this
book, on the use of computers to aid the design process and to integrate
design, analysis and manufacture, was prepared.
The main text examines the detailed design principles of the various
mechanical components which are not peculiar to the present case
studies but common to other fields of mechanical engineering. The
design parameters necessary for successful operation are also considered
and the steps taken to ensure maximum life and reliability of the
components are outlined. Although every attempt has been made to
verify the different designs, no responsibility can be accepted for their
performance in practice.
vii
viii Preface
Following a brief introduction of the terminology used, Chapter 2
provides a detailed description of the techniques adopted in three
dimensional automated modelling. Chapter 3 provides a detailed
account of the computer-aided design of two practical case studies
involving the design of (i) a centrifugal peening equipment and (ii) a
fluid coupling. Throughout this work, both 3-D solid modelling and
2-D draughting were interactively utilised to create, manipulate and
retrieve the different geometries. In view of its importance to design,
analysis and manufacture, emphasis was given to solid modelling
representation. Chapter 4 provides a truly practical introduction to the
application of the finite element method to structural stress analysis of
mechanical systems. In Chapter 5, complete static stress analysis and
dynamic response studies are performed on the different designs
examined. In particular, it was desired to demonstrate the versatility of
the techniques adopted in data-handling during model creation, mesh
definition and model checking aspects. Chapter 6 deals with the
computer-integrated manufacturing aspects of the work using the same
data base developed during the modelling stage. Some coverage is also
provided for numerically controlled machines.
The book is intended for mechanical, industrial and manufacturing
engineers, design engineers and engineering managers. The work is also
intended for postgraduates undertaking mechanical, industrial, manu
facturing and production engineering degrees. It is also useful for
technologists, academics and researchers working in the field of CAD/
CAM. The material included is largely self-contained and readers are
required to have some basic knowledge of design, analysis and
manufacture; their awareness of computers will also be valuable.
Finally, I wish to acknowledge the following organisations for giving
permission to reproduce a few relevant diagrams: Structural Dynamics
Research Corporation - SDRC (USA), Tilghman Wheelabrator (UK)
and Vacu-Blast International (UK).
S. A. MEGUID
Contents
Preface vii
Principal Notations xiii
Chapter 1 Introduction 1
1.1 The Developing Design Process 1
1.2 Design Methodology 3
1.3 Interactive Computer Graphics (ICG) . 5
1.4 Computer-Aided Engineering (CAE) . 7
l.4.l Computer-Aided Design (CAD) . 7
l.4.2 Computer-Aided Analysis (CAA) 8
l.4.3 Computer-Aided Draughting (CAD) 9
l.4.4 Computer-Integrated Manufacturing (CIM) 10
l.5 Initial Graphics Exchange Specification (IGES) . 11
References . 12
Chapter 2 Three-Dimensional Automated Modelling 13
2.1 Automated Computer Graphics 13
2.2 Different Types of Modelling 14
2.2.l Wire-Frame Modelling. 14
2.2.2 Surface Modelling 16
2.2.3 Solid Modelling . 18
2.3 Merits of Solid Modelling 23
2.4 Limitations of Solid Modelling 23
References . 24
Chapter 3 Computer-Aided Design 25
3.1 Introduction . 25
First Case Study: Computer-Aided Design of Centrifugal
Shot-Peening Equipment 26
3.2 The Shot-Peening Process 26
ix
x Contents
3.3 Historical Background . 27
3.4 Design Constraints and Requirements. 29
3.5 Conceptual Designs 30
3.5.1 A Simple Model to Determine the Rotational
Speed of the Wheel 40
3.5.2 Computer-Aided Assembly of the Different
Components of the Wheel Design 42
Second Case Study: Computer-Aided Design of a Fluid
Coupling 52
3.6 Principle of Operation. 52
3.7 Design Constraints and Requirements 54
3.8 Flow Models and Analysis . 55
3.9 Conceptual Design 57
3.10 Evaluation of Coupling Design 71
3.11 Modified Design. 72
3.12 The Need for Engineering Analysis 72
References . 82
Chapter 4 Fundamentals of the Finite Element Method 84
4.1 Introduction . 84
4.2 Fundamental Concept of the Finite Element Method. 85
4.3 Fundamentals of Linear Elasticity 93
4.3.1 Stresses and Strains 93
4.3.2 Stress-Strain Relationships . 95
4.3.3 Plane Stress and Plane Strain 96
4.3.4 Equilibrium Equations 99
4.3.5 Compatibility Equations 99
4.4 Principles of Finite Elements 100
4.4.1 Discretisation of a Body 100
4.4.2 Types of Elements. 100
4.4.3 Division of the Body into Elements 103
4.4.4 Labelling of Nodes 105
4.4.5 Effect of Mesh Refinement and Higher Order
Elements upon Accuracy of Solution 106
4.5 Interpolation Polynomial Functions 109
4.5.1 The Pascal Triangle 110
4.5.2 Lagrange Polynomials . III
4.6 Isoparametric Finite Element Representation 113
4.6.1 Intrinsic Co-ordinate System 113
4.6.2 Isoparametric Elements 113
4.7 Derivation of a General Expression for Element
Stiffness Matrix 114
4.7.1 Isoparametric Elements: Stiffness Formulation 117
4.8 Computer Implementation of Finite Element 119
4.8.1 Automatic Mesh Generation 120
4.8.2 Input Data 120
Contents xi
4.8.3 Element Stiffness Matrix Generation and
Assembly 121
4.8.4 Solution of Simultaneous Equations 122
4.9 Conclusions 123
References 124
Appendix 124
Chapter 5 Computer-Aided Analysis 126
5.1 Introduction . 126
5.2 General Purpose Finite Element Software . 127
5.3 Computer-Aided System for Data Processing 129
5.3.1 Pre-and Post-Processing 129
5.4 Interactive Mesh Generation 131
5.5 Non-Linear Structural Analysis 134
First Case Study: Computer-Aided Analysis of Wheel-
Assembly 135
5.6 Structural Stress Analysis 135
5.6.1 Geometry Definition, Model Preparation and
Model Checking . 135
5.6.2 Applied Loads and Imposed Restraints 139
5.6.3 Static Stress Analysis . 142
5.7 Dynamic Response Studies . 148
5.7.1 Modelling of the Assembly 148
5.7.2 Dynamic Response Analysis 150
Second Case Study: Computer-Aided Analysis of Fluid
Coupling 151
5.8 Structural Stress Analysis and Dynamic Response
Studies . 151
5.9 Conclusions 159
References 160
Chapter 6 Computer-Integrated Manufacturing 162
6.1 Computer-Controlled Machine Tools . 162
6.2 Types of Control Systems for NC Machines. 164
6.3 NC Palt-Programming Languages 166
6.4 NC Programming with Interactive Graphics 167
6.5 Tool Path Generation . 167
First Case Study: Computer-Integrated Manufacturing of
Critical Components of Wheel-Assembly 169
6.6 Choice of Materials 169
6.7 Manufacture of Wheel-Assembly . 170
6.8 Development ofNC Machining Programs 171
6.8.1 Machining of Main Shaft 171
6.8.2 Roughing Cut 174
xu Contents
6.8.3 Finishing Cut 174
6.8.4 Circlips and Undercut Machining 175
6.8.5 Milling Cut of Slots in Discs. 175
Second Case Study: Computer-Integrated Manufacturing
of Fluid Coupling 176
6.9 Choice of Materials and NC Machining Programs 176
6.9.1 Machining of Coupling's Output Shaft 176
6.9.2 Finishing Cut of Rotor 181
6.9.3 Cutter Location Source Files (CLSF) . 187
6.10 Concluding Remarks 189
References 190
Index. 193
