Modern Metal Fatigue Analysis

Modern Metal Fatigue Analysis

There have been major advances in methods of fatigue life estimation over the past 30 years. Allowable stresses can now be estimated to an accuracy of a few percent. Much of this knowledge is available in research papers but is not readily available to designers. This new publication is intended to bridge the gap between research and design.

Table of Contents

v 1 INTRODUCTION TO FATIGUE
1.1 Introduction
1.2 Description of the applied loading
1.3 Endurance curves
1.4 Generalising fatigue data
1.5 Other factors which influence fatigue strength
1.6 Chapter contents
1.7 References
2 UNIAXIAL STRAIN-LIFE FATIGUE ANALYSIS
2.1 Introduction
2.2 True stress and strain
2.3 Fatigue life relationships
2.4 Cyclic stress-strain relationships
2.5 Material response to a sequence of strains
2.6 Effect of mean stress
2.7 Analysing local strain histories
2.8 The Smith-Watson-Topper relationship
2.9 Application of stress concentrations
2.10 Analysing nominal strain histories
2.11 Local strain analysis from a cycle histogram
2.12 Analysis of cast iron
2.13 Applicability of local strain analysis
2.14 Summary of strain-life equations
2.15 References
3 LOCAL STRAIN MATERIALS DATA
3.1 Introduction
3.2 The cyclic stress- strain curve
3.3 The strain-life curve
3.4 Practical testing
3.5 Approximating materials data
3.6 Applicability of materials data
3.7 References
4 SIGNAL PROCESSING FOR FATIGUE ANALYSIS
4.1 Introduction
4.2 Rainflow cycle counting
4.3 Level crossing analysis
4.4 Peak and valley counting
4.5 Range counting
4.6 Summary
4.7 References
5 FATIGUE ANALYSIS USING STRESS-LIFE (S-N) CURVES
5.1 Introduction
5.2 Application of stress concentrations
5.3 Complex load histories 98
5.4 Calculation of fatigue stress reserve factors 107
5.5 Analysis Of Variable Amplitude Stress Histories 109
5.6 Estimating materials fatigue data 112
5.7 Applicability of S-N curves 113
5.8 References 115
6 STRESS CONCENTRATIONS
6.1 Introduction 117
6.2 Fatigue strength reduction factor 122
6.3 Summary 130
6.4 References 130
7 BIAXIAL FATIGUE
7.1 Introduction 133
7.2 Stress and strain relationships 135
7.3 Static yield criteria 145
7.4 Multiaxial fatigue using equivalent stress or strain 147
7.5 Critical plane analysis 167
7.6 Wang-Brown criterion 170
7.7 Effects of mean stress 171
7.8 Dang Van criterion 181
7.9 Summary of fatigue-life relationships 183
7.10 References 185
8 FATIGUE ANALYSIS FROM FINITE ELEMENT MODELS
8.1 Introduction 187
8.2 Terminology of finite element analysis 187
8.3 Analysing a linear elastic model with single applied load history (Figure 8.3) 189
8.4 Analysing a linear elastic model with multiple applied loads 191
8.5 Analysing a sequence of data sets 194
8.6 Frequency-domain finite element analysis. 195
8.7 Other types of loading 195
8.8 Output 196
8.9 Speed considerations 197
8.10 Accuracy of results 198
8.11 Elastic-plastic FEA 199
8.12 Recent developments 199
8.13 Summary 200
8.14 References 200
9 USING STATISTICS IN FATIGUE
9.1 Introduction 201
9.2 Gaussian distribution 202
9.3 The Weibull distribution 206
9.4 Failure probability in design 207
9.5 References 208
10 CRACK PROPAGATION
10.1 Introduction 209
10.2 The purpose of fracture mechanics 209
10.3 Stresses at the crack tip
10.4 Fracture toughness
10.5 Plasticity
10.6 Multiaxial stresses at the crack tip
10.7 Stress corrosion cracking
10.8 Crack propagation
10.9 Crack propagation calculations for complex components.
10.10 Reference
FATIGUE OF WELDED STEEL JOINTS
11.1 Introduction
11.2 Weld classification
11.3 Fatigue life curves
11.4 Calculation of applied stress
11.5 Effect of mean stress
11.6 Effect of material UTS
11.7 Calculation of probability of failure
11.8 Practical fatigue calculations
11.9 Hot-spot approach to fatigue of welds
11.10 Structural stress approach to fatigue of welds
11.11 References and further reading
FATIGUE ANALYSIS FROM THE PSD
12.1 Introduction
12.2 Why fatigue analysis from PSD's?
12.3 Early methods of fatigue analysis from the PSD
12.4 Calculation of rainflow ranges from a PSD
12.5 Summary
12.6 References
FATIGUE TEST SIGNALS AND CUMULATIVE DAMAGE
13.1 Introduction
13.2 Constant amplitude tests
13.3 Block loading test programs
13.4 Editing signals to remove small cycles
13.5 Effect of larger cycles
13.6 Generic test signals
13.7 Summary
13.8 References
PRACTICAL FATIGUE ANALYSIS
14.1 Introduction
14.2 Locating strain gauges
14.3 Data recording
14.4 Short term recording or long term analysis
14.5 Sampling signals
14.6 Length of measured data
14.7 Peak-valley extraction with cycle omission
14.8 Interpreting analysis results
14.9 References
APPENDIX 1. THE VERITY STRUCTURAL STRESS METHOD INDEX

The contents have been developed as course notes for training courses presented to engineers who need to apply fatigue knowledge in engineering design, fatigue testing and failure investigation. Course delegates regularly report that much of the course material is new information. The book will also be of value to undergraduates on mechanical engineering courses.

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