基于流体力学的金属增材制造过程仿真研究

Chapter 1 Introduction 1
1．1 Background 2
1．2 Motivation 3
1．3 Outline 4
Chapter 2 Investigation of the flow field in Laser-based Powder Bed Fusion
manufacturing 5
2．1 Introduction 7
2．2 Simulation model of the L-PBF printer 10
2．2．1 Problem description 10
2．2．2 Geometric model of the L-PBF printer 11
2．2．3 Numerical model of the L-PBF printer 12
2．3 Simulation results 16
2．3．1 Distribution of the flow field 16
2．3．2 Distribution of the temperature field 21
2．3．3 Distribution of spatter particles 23
2．4 Conclusions 28
References 30
Chapter 3 Investigation of optimizing the flow field with fluid cover in
Laser-based Powder Bed Fusion manufacturing process 33
3．1 Introduction 35
3．2 Simulation model of L-PBF printer 37
3．2．1 Geometry of L-PBF printer with a fluid stabilizing cover 37
3．2．2 Numerical model of printer with a fluid stabilizing cover 37
3．2．3 Mesh of L-PBF printer with a fluid stabilizing cover 39
3．2．4 Model of the fluid stabilizing cover and particles 40
3．3 Simulation results and discussion 43
3．3．1 Influence of the fluid stabilizing cover on the flow field 43
3．3．2 Influence of fluid stabilizing cover on particle distribution and removing rate 47
3．4 Summary and conclusions 51
References 53
Chapter 4 Numerical investigation of controlling spatters with negative pressure
pipe in Laser-based Powder Bed Fusion process 54
4．1 Introduction 56
4．2 Simulation model of L-PBF printer 59
4．2．1 Geometric model of L-PBF printer 59
4．2．2 Numerical model of L-PBF printer 61
4．3 Simulation results and discussions 64
4．3．1 Effect of pipe diameter 68
4．3．2 Effect of outlet flow rate 70
4．3．3 Effect of initial particle velocity 74
4．4 Summary and conclusions 76
References 78
Chapter 5 Evolution of molten pool during Laser-based Powder Bed Fusion of
Ti-6Al-4V 80
5．1 Introduction 82
5．2 Modeling approach and numerical simulation 85
5．2．1 Model establishing and assumptions 85
5．2．2 Governing equations 87
5．2．3 Heat source model 87
5．2．4 Phase change 88
5．2．5 Boundary conditions setup 89
5．2．6 Mesh generation 90
5．3 Experimental procedures 91
5．4 Results and discussions 92
5．4．1 Surface temperature distribution and morphology 92
5．4．2 Formation and solidification of the molten pool 94
5．4．3 Development of the evaporation region 98
5．5 Conclusions 101
References 103
Chapter 6 Simulation of surface deformation control during Laser-based
Powder Bed Fusion Al-Si-10Mg powder using an external magnetic field 107
6．1 Introduction 109
6．2 Modeling and simulation 112
6．2．1 Modeling of L-PBF 112
6．2．2 Mesh model and basic assumptions 113
6．2．3 Heat transfer conditions 114
6．2．4 Marangoni convection 115
6．2．5 Phase-change material 115
6．2．6 Lorentz force 116
6．3 Results 118
6．3．1 Velocity field in the molten pool 118
6．3．2 Lorentz force in the MP 121
6．3．3 Surface deformation of the sample 123
6．4 Conclusions 127
References 128
Chapter 7 Influence of laser post- processing on pore evolution of Ti-6Al-4V
alloy by Laser-based Powder Bed Fusion 131
7．1 Introduction 133
7．2 Experimental procedures 136
7．2．1 Sample fabrication 136
7．2．2 Determination of porosity by micro-CT 137
7．3 Modeling and simulation 140
7．3．1 Numerical model 140
7．3．2 Moving Gaussian heat source 143
7．3．3 Thermal boundary conditions 143
7．3．4 Marangoni effect， surface tension and recoil pressure 144
7．4 Numerical results and discussion 145
7．5 Conclusions 152
References 153
Chapter 8 Evolution of multi pores in Ti-6Al-4V/Al-Si-10Mg alloy during laser
post-processing 157
8．1 Introduction 159
8．2 Experimental procedures 162
8．2．1 Sample preparation 162
8．2．2 Detection of porosity by mirco-CT 162
8．3 Model and simulation 165
8．3．1 Simulation model 165
8．3．2 Gaussian heat source 167
8．3．3 Latent heat of phase change 168
8．3．4 Level-set method 169
8．3．5 Boundary conditions 169
8．4 Numerical results and discussion 171
8．5 Conclusions 177
References 179
Chapter 9 Investigation of laser polishing of four Laser-based Powder Bed
Fusion alloy samples 182
9．1 Introduction 184
9．2 Model and theoretical calculation 188
9．2．1 Physical model and assumptions 188
9．2．2 Governing equations and boundary conditions 190
9．2．3 Simulation results 192
9．3 Experimental methods 195
9．3．1 Sample fabrication 195
9．3．2 Morphology observation by 3D optical profiler 198
9．3．3 Experimental results 199
9．4 Conclusions 206
References 208