1 Introduction 1
1.1 Fatigue Problems in Marine Structures 1
1.2 Current Practices of Fatigue Strength Assessments and Their Deficiencies 2
1.3 Historical Overview of Metal Fatigue 3
1.4 FLP Methods 6
1.4.1 CFD Theories 6
1.4.2 FCP Theories 17
1.5 The Layout of the Book 22
References 23
2 Current Understanding of Fatigue Mechanisms of Metals 31
2.1 Introduction 31
2.2 Difierent Phases of the Fatigue Life 32
2.3 Crack Initiation Mechanisms for Different Metals 34
2.3.1 Definition of a Crack Initiation 34
2.3.2 Fatigue Crack Initiation in Slip Bands 35
2.3.3 Crack Initiation Along the Grain Boundary(GB) 36
2.3.4 Crack Initiation at Inclusions 36
2.3.5 Slip Band and Dislocation in Single Crystal Metal 39
2.3.6 Slip Band and Dislocation in Polycrystal Metal 39
2.3.7 Fatigue Mechanism of Ultrafine-Grained Materials 41
2.4 FCP Mechanisms 42
2.4.1 Stage Ⅰ FCP 43
2.4.2 Stage Ⅱ Crack Growth and Fatigue Striation 44
2.5 Some Important Issues in Crack Growth 47
2.5.1 Short Crack 48
2.5.2 Crack Closure 50
2.5.3 Effect of Loading Sequence 52
2.5.4 Surface Effects 54
2.5.5 Environmental Effects 55
2.6 Fatigue Crack Growth Mechanism of Small Defects 57
2.6.1 Engineering Initial Crack Size of Structures 57
2.6.2 Definition of Short Crack and Long Crack 58
2.6.3 Crack Growth Threshold and Intrinsic Crack Length 59
2.6.4 Equivalent Crack Length for Short and Long Crack 61
2.7 Summary 62
References 63
3 Current State-of-the-Art of UFLP 69
3.1 Introduction 69
3.2 Unified Approach for Three Regions of FCP 69
3.3 Unified Approach to the Stress Ratio Effect or Mean Stress Effect 70
3.4 Unified Approach for Long-and Physically Short-Crack Growth 73
3.5 Unified Approach for Initiation and Propagation 76
3.6 Unified Approach for High and Low Cycle Fatigue 77
3.7 Unified Approach for Fatigue and Creep 77
3.8 Basic Ideas of Our UFLP Method 83
3.9 Summary 84
References 85
4 Basic Concepts of Fracture Mechanics 91
4.1 Introduction 91
4.2 Types of Cracks 92
4.3 Types of Opening Modes for a Cracked Body 94
4.4 SIFs 95
4.4.1 Definition 95
4.4.2 Calculation Methods of SIFs 97
4.4.3 Typical Examples of SIFs 98
4.4.4 Plasticity Limitations of the SIFs Based on LEFM 99
4.4.5 Extensions of the SIFs Based on LEFM 100
4.5 Fracture Toughness 102
4.5.1 Definition 102
4.5.2 Testing 103
4.5.3 Trends 104
4.6 Crack Tip Plasticity 105
4.6.1 Plastic Zone for Plane Stress 105
4.6.2 Plastic Zone for Plane Strain 107
4.6.3 Plastic Zone Under Real Stress State 108
4.7 Summary 111
References 112
5 Development of a UFLP Method for Marine Structures 117
5.1 Introduction 117
5.2 A General Procedure for the UFLP Method 117
5.2.1 The General Function Format of the Fatigue Crack Growth Rate Curve for the UFLP Method 117
5.2.2 Calculation of Fatigue Life 118
5.3 Development of a Unified Fatigue Crack Growth Rate Model 120
5.3.1 The Crack Growth Rate Model for Constant Amplitude Loading 120
5.3.2 The Improved Crack Growth Rate Model Under VA Loading 124
5.3.3 Establishment of Cycle-by-Cycle Integration Procedure 128
5.3.4 Discussion of Model Parameters 131
5.4 Engineering Approaches to Determine the Parameters in the Improved Model 140
5.4.1 General Methods to Estimate the Model Parameters 140
5.4.2 Estimation Method from Crack Growth Rate Data 141
5.4.3 Estimation Method from a-N Curve 141
5.4.4 Estimation Method from S-N Curve 144
5.4.5 Estimation Method from ε-N Curve 144
5.4.6 Estimation Methods from Available Static Test Properties 147
5.4.7 Estimation of A and m 149
5.5 Capabilities ofthe UFLP Method 150
5.5.1 The Quantitative Analysis ofthe Improved Crack Growth Rate Model 150
5.5.2 Model Validation by Test 152
5.6 Summary 167
References 167
6 Description of Fatigue Loading 173
6.1 The Nature of Fatigue Loading 173
6.2 Load Spectra for CFD Analysis 174
6.3 Generating the Whole Life Loading History from Short Time Measurement 177
6.3.1 Method for Extrapolation of a Load History 177
6.3.2 Choice of Threshold Levels 181
6.3.3 Examples of Extrapolation of Load Histories 182
6.4 Cycle Count Methods 185
6.4.1 Definitions 185
6.4.2 Rainflow Cycle Counting 186
6.4.3 A Practical Example 192
6.5 SLHs for FCP Analysis 194
6.5.1 Definition 194
6.5.2 History 195
6.5.3 Basis of Generation of SLHs 196
6.5.4 Generation of Load-Time Histories 197
6.6 Generating a Pseudo Random Loading History from a Spectra 203
6.7 Summary 204
References 205
7 Some Applications and Demonstrations of UFLP 209
7.1 Introduction 209
7.2 The Fatigue Crack Growth Rate of UFLP 209
7.3 FLP of Specimen with Through-Thickness Crack Under Difierent Fatigue Loading 210
7.3.1 FLP of D16 Aluminum Alloy Specimens Under Different Spectrum Loading 210
7.3.2 FLP of Aluminum Alloy Al 7075-T6 214
7.3.3 FLP of Specimen Made of 350WT Steel Under Different Overload Ratios 218
7.3.4 The Fatigue Crack Growth Prediction of Steel HTS-A Under Multi-Level Block Loading 219
7.4 FLP of Cracked Deck of an Oil Tanker 224
7.4.1 Geometry of the Stifiened Plate 225
7.4.2 The Crack Growth Pattern in the Stifiened Plate 226
7.4.3 Determination of SIFs of the Cracked Stiffened Plate by FEA 226
7.4.4 SIF of the Crack in Stiffened Plate by Weld Residual Stress 230
7.4.5 Fatigue Crack Growth Prediction of the Stiffened Plate 231
7.5 FLP of Submarine Hull Under Different Fatigue Loading Sequence 233
7.5.1 General Equations for Calculating the SIF of a Surface Crack at Welded Toe 233
7.5.2 SIF of Surface Crack Caused by Weld Residual Stress at Weld Toe 235
7.5.3 Fatigue Crack Growth Prediction of Surface Crack at Weld Toe of Submarine Structure 237
7.6 Summary 241
References 242
8 Code Development Based on UFLP for Marine Structures 245
8.1 Introduction 245
8.2 Procedure of UFLP 246
8.3 Fatigue Loading 248
8.3.1 Simplified Fatigue Loading Analysis 249
8.3.2 Fatigue Loading by Direct Calculation 251
8.4 SIF Calculation 253
8.4.1 Planar Flaws and Their Initial Size 255
8.4.2 SIF Range Calculation 256
8.5 Fatigue Crack Growth Law of UFLP for Marine Structural Materials 257
8.5.1 Recommended Fatigue Crack Growth Material Constants for Steels in Marine Environment 258
8.5.2 Simplified Fatigue Crack Growth Law and Threshold(BS7910) 263
8.6 Summary 265
Appendix A：SIF Solutions for Some Typical Cracks 265
References 277
Index 279