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CONTENTS
Title page
iCertificate of approval
iiiDeclaration
ivCertificate
vAcknowledgement
viContents
viiList of symbols
xiList of abbreviations
xiiiList of figures
xvList of tables
xxiiiAbstract
xxvChapter 1 Introduction 1-5
Chapter 2 Literature Review 7-41
2.1 Introduction 9
2.2 Fatigue: General aspects 10
2.3 Material response to cyclic loading 14
2.4 Ratcheting phenomenon 16
2.5 Ratcheting: historical background 17 2.6 Parameters affecting strain accumulation during ratcheting 19
2.6.1 Effect of mean stress 20 2.6.2 Effect of maximum stress 24 2.6.3 Effect of Stress Ratio 26
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2.6.4 Effect of Temperature 27
2.6.5 Material dependence 29
2.7 Theory of Ratcheting 33
2.8 Re-appraisal of the current problem 40
Chapter 3 Selected Materials and Their Characterization 43-68
3.1 Introduction 45
3.2 Experimental procedure 45
3.2.1 Material 46
3.2.2 Chemical composition and heat treatment 46 3.2.3 Microscopic examinations and image analyses 47
3.2.4 Hardness measurement 48
3.2.5 Tensile test 49
3.2.6 Fractographic Examination 50
3.2.7 X-ray diffraction 51
3.3 Results and discussion 51
3.3.1 Material and Microstructural Analyses 51 3.3.2 Hardness and tensile properties 58
3.3.3 Fractographic Analyses 65
3.4 Summary 68
Chapter 4 Ratcheting Behaviour of AISI 304LN Stainless Steel
69-98
4.1 Introduction 71
4.2 Experimental procedure 72
4.2.1 Specimen design 72
4.2.2 Ratcheting test 73
4.2.3 X-ray diffraction 74
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4.2.4 Transmission electron microscopy 74
4.3 Results and Discussion 75
4.3.1 Nature of hysteresis loops 75 4.3.2 Effect of stress amplitude on ratcheting strain at
constant mean stress
75 4.3.3 Effect of mean stress on ratcheting strain at constant
stress amplitude
81 4.3.4 Saturation of ratcheting strain 85 4.3.5 Hardening and softening during asymmetric cyclic
loading
85 4.3.6 In-situ variation in substructure and microstructure 89
4.4 Conclusions 98
Chapter 5 Ratcheting Behaviour of Interstitial Free Steel 99-120
5.1 Introduction 101
5.2 Experimental procedure 102
5.3 Results and Discussion 103
5.3.1 Uniaxial ratcheting: nature of hysteresis loops 103 5.3.2 Accumulation of ratcheting strain:
Effect of mean stress and stress amplitude
103 5.3.3 Saturation of ratcheting strain 109 5.3.4 Substructural variation in interstitial free steel 112 5.3.5 Post-ratcheting tensile behaviour 115
5.4 Conclusions 120
Chapter 6 Ratcheting Behaviour of Aluminum Alloy 121-141
6.1 Introduction 123
6.2 Experimental Procedure 124
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6.3 Results and Discussion 125
6.3.1 Uniaxial ratcheting: Nature of hysteresis loops 126 6.3.2 Accumulation of ratcheting strain under varying stress
amplitudes at constant mean stress
129 6.3.3 Saturation of ratcheting strain 134 6.3.4 Post-ratcheting tensile behaviour 135
6.4 Conclusions 140
Chapter 7 Ratcheting Behaviour of α-Brass 143-160
7.1 Introduction 145
7.2 Experimental Procedure 146
7.3 Results and Discussion 147
7.3.1 Uniaxial ratcheting: Nature of hysteresis loops 147 7.3.2 Accumulation of ratcheting strain: effect of stress
amplitude and mean stress
149 7.3.3 Saturation of ratcheting strain 152 7.3.4 Post-ratcheting tensile behaviour 153 7.3.5 Ratcheting behaviour and stacking fault energy 157
7.5 Conclusions 159
Chapter 8 General Conclusions and Scope for Future Research
161-166
References 167-180
Appendix 1 A1 – A3
Appendix 2 A5 – A8
Appendix 3 A9 – A16
Appendix 4 A17–A18
