Laser Shocking Nano-Crystallization and High-Temperature Modification Technology (eBook)

Preface 5
Contents 8
About the Author 11
1 General Introduction 12
Abstract 12
1.1 Laser Shock Wave and Laser Shock Processing 12
1.2 Recent Development of Laser Shock Processing 15
1.3 Practical Applications of LSP 17
1.4 Scope of This Book 18
References 19
2 LSP Numerical Simulation 21
Abstract 21
2.1 Introduction 21
2.2 A Finite Element Analysis of Thermal Relaxation of Residual Stress in Laser Shock Processing Ni-based Alloy GH4169 22
2.2.1 Introduction 22
2.2.2 LSP Simulation 23
2.2.2.1 Thermal Relaxation 23
2.2.2.2 Experimental Materials and Parameters 24
2.2.3 Results and Discussion 26
2.2.3.1 Simulation of Thermal Relaxation of Residual Stress 26
2.2.3.2 Analytical Model for Thermal Relaxation in GH4169 27
2.2.4 Summary 28
2.3 Comparison of the Simulation and Experimental Fatigue Crack Behaviors in the Nanoseconds Laser Shocked Aluminum Alloy 29
2.3.1 Introduction 29
2.3.2 Simulation Methods 30
2.3.2.1 Fracture Analysis Software 30
2.3.2.2 Crack Growth Model 30
2.3.3 Experimental Methods 32
2.3.3.1 Sample Preparation 32
2.3.3.2 Experimental Parameters 33
2.3.4 Results and Discussions 33
2.3.4.1 Residual Stress Distributions 33
2.3.4.2 Microscopic Analysis of Macroscopic Fracture 34
2.3.4.3 Numerical Calculation of I-Type Cracks 36
2.3.4.4 Improvement in Fatigue Life by LSP 37
2.3.5 Summary 39
References 39
3 Laser Shock Processing at Elevated Temperature 42
Abstract 42
3.1 Introduction 42
3.2 Mechanical Properties and Residual Stresses Changing on 00Cr12 Alloy by Nanoseconds Laser Shock Processing at High Temperatures 43
3.2.1 Introduction 43
3.2.2 LSP on Fatigue Properties at Room Temperature 44
3.2.3 LSP on Fatigue Properties at Elevated Temperature 46
3.2.3.1 Yield Strengths 47
3.2.3.2 Effects of LSP on Cycle Times 48
3.2.3.3 Effects of LSP on Axial Strain 48
3.2.4 LSP on Residual Stresses at Elevated Temperature 50
3.2.4.1 Residual Stress 50
3.2.4.2 Stress and Strain 51
3.2.4.3 Fracture Morphology 53
3.2.4.4 Microstructure Morphology 53
3.2.5 Conclusions 55
3.3 High-Temperature Mechanical Properties and Surface Fatigue Behavior Improving of Steel Alloy Via Laser Shock Peening 55
3.3.1 Introduction 56
3.3.2 Experiments and Analysis 57
3.3.3 Results and Discussions 58
3.3.3.1 Residual Stress 58
3.3.3.2 Fatigue Cycle Life 60
3.3.3.3 Fracture Surface 60
3.3.4 Conclusions 62
3.4 Metallographic Structure Evolution and Dislocation Polymorphism Transformation of 6061-T651 Aluminum Alloy Processed by Laser Shock Peening: Effect of Tempering at the Elevated Temperatures 63
3.4.1 Introduction 64
3.4.2 Experimental Procedures 65
3.4.2.1 Material and Technical Parameters 65
3.4.2.2 Surface Topography and Roughness 66
3.4.2.3 Measurements of Residual Stress 66
3.4.2.4 Measurements of Micro-Hardness 66
3.4.2.5 Microstructure Observations 67
3.4.3 Results and Discussions 67
3.4.3.1 Effects of LSP on Residual Stresses at Different Temperatures 67
3.4.3.2 Micro-Mechanism Changing of Residual Stress Relaxation 70
3.4.3.3 Effects of LSP on Grain and Precipitated Phase 72
3.4.3.4 Metallographic Structure Evolution at Elevated Temperature 73
3.4.3.5 Surface Topography and Roughness 75
3.4.3.6 Micro-Hardness Changing 77
3.4.3.7 Strengthening Mechanism 79
3.4.3.8 Dislocation Configuration 82
3.4.4 Conclusions 83
References 83
4 Influence of LSP on Stress Intensity Factor of Hole-Edge Crack 88
Abstract 88
4.1 Introduction 88
4.2 Stress Intensity Factor Changing on the Hole Crack Subject to Laser Shock Processing and Influence of Compressive Stress 89
4.2.1 Introduction 89
4.2.2 SIF Formula 91
4.2.3 Experimental Procedures 95
4.2.4 Analysis Model 95
4.2.4.1 Residual Stresses 95
4.2.4.2 3D Stress Intensity Factor 97
4.2.4.3 Correction of 3D Intensity Factor in Shocking Zone 100
4.2.5 Results and Discussion 105
4.2.6 Conclusions 107
4.3 Investigation of Stress Intensity Factor on 7050-T7451 Aluminum Alloy by High Strain Rate Laser Shock Processing 108
4.3.1 Introduction 108
4.3.2 Experiments and Method 109
4.3.3 Results and Discussions 110
4.3.3.1 SIF Effect on Fatigue Crack 110
4.3.3.2 Residual Stress on the Fatigue Crack 113
4.3.3.3 Fracture Morphology 115
4.3.4 Conclusions 117
4.4 A Model for Reliability and Confidence Level in Fatigue Statistical Calculation 118
4.4.1 Introduction 118
4.4.2 Analysis of Statistics Model 119
4.4.3 LSP and Fatigue Experiment 121
4.4.4 Revision of Statistics Model 122
4.4.5 Conclusions 127
References 127
5 Conversion Model of Graphite 131
Abstract 131
5.1 Introduction 131
5.2 A Conversion Model of Graphite to Ultra-nano-crystalline Diamond via Laser Processing at Ambient Temperature and Normal Pressure 132
5.2.1 Experiment and Method 132
5.2.2 Results 133
5.2.3 Discussion 135
5.2.3.1 Phase Transition Mechanism 135
5.2.3.2 Growth Restriction Mechanism 137
5.2.4 Conclusions 138
References 138