Contents
1 Laser Welding Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
1.1 Interaction of Lasers and Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
1.1.1 Laser Absorption by Materials and Material Heating . . . . . .
1
1.1.2 Laser Heat Source Model and Laser Heating Effect . . . . . . .
4
1.1.3 Material Melting Under Laser Action . . . . . . . . . . . . . . . . . . .
7
1.1.4 Evaporation of Materials Under Laser Action . . . . . . . . . . . .
9
1.1.5 Laser-Induced Plasma and Its Effects . . . . . . . . . . . . . . . . . . . 10
1.2 Principles and Characteristics of Laser Welding . . . . . . . . . . . . . . . . . 12
1.3 Research on Weld Pool Behavior in Laser Welding . . . . . . . . . . . . . . 14
2 Model of Quasi-Steady Weld Pool Dynamics and Numerical
Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2 Basic Models of Quasi-Steady Laser Welding . . . . . . . . . . . . . . . . . . 20
2.2.1 Governing Equations of the Flow and Heat Transfer
in Quasi-Steady Laser Welding . . . . . . . . . . . . . . . . . . . . . . . . 21
2.2.2 3D Mathematical Model of Deep Penetration Laser
Welding Under Moving Heat Source . . . . . . . . . . . . . . . . . . . . 22
2.2.3 Heat Source Model in Deep Penetration Laser Welding . . . . 26
2.3 Implementation of Numerical Solution . . . . . . . . . . . . . . . . . . . . . . . . 27
2.3.1 Upwind Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.3.2 Staggered Grid Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.3.3 Pressure Correction Method for Solving
Navier-Stokers Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.3.4 SIMPLE Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.3.5 Programming and Solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.4 Physical Properties and Calculation Parameters . . . . . . . . . . . . . . . . . 38
2.5 Effect of Welding Speed on Keyhole Profile . . . . . . . . . . . . . . . . . . . . 39
2.5.1 Temperature Distribution in Deep Penetration Laser
Welding of Titanium Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.5.2 Effect of Welding Speed on Keyhole Size . . . . . . . . . . . . . . . . 43
2.5.3 Effect of Laser Power on Keyhole Size . . . . . . . . . . . . . . . . . . 47
xiii
1 Laser Welding Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
1.1 Interaction of Lasers and Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
1.1.1 Laser Absorption by Materials and Material Heating . . . . . .
1
1.1.2 Laser Heat Source Model and Laser Heating Effect . . . . . . .
4
1.1.3 Material Melting Under Laser Action . . . . . . . . . . . . . . . . . . .
7
1.1.4 Evaporation of Materials Under Laser Action . . . . . . . . . . . .
9
1.1.5 Laser-Induced Plasma and Its Effects . . . . . . . . . . . . . . . . . . . 10
1.2 Principles and Characteristics of Laser Welding . . . . . . . . . . . . . . . . . 12
1.3 Research on Weld Pool Behavior in Laser Welding . . . . . . . . . . . . . . 14
2 Model of Quasi-Steady Weld Pool Dynamics and Numerical
Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2 Basic Models of Quasi-Steady Laser Welding . . . . . . . . . . . . . . . . . . 20
2.2.1 Governing Equations of the Flow and Heat Transfer
in Quasi-Steady Laser Welding . . . . . . . . . . . . . . . . . . . . . . . . 21
2.2.2 3D Mathematical Model of Deep Penetration Laser
Welding Under Moving Heat Source . . . . . . . . . . . . . . . . . . . . 22
2.2.3 Heat Source Model in Deep Penetration Laser Welding . . . . 26
2.3 Implementation of Numerical Solution . . . . . . . . . . . . . . . . . . . . . . . . 27
2.3.1 Upwind Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.3.2 Staggered Grid Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.3.3 Pressure Correction Method for Solving
Navier-Stokers Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.3.4 SIMPLE Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.3.5 Programming and Solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.4 Physical Properties and Calculation Parameters . . . . . . . . . . . . . . . . . 38
2.5 Effect of Welding Speed on Keyhole Profile . . . . . . . . . . . . . . . . . . . . 39
2.5.1 Temperature Distribution in Deep Penetration Laser
Welding of Titanium Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.5.2 Effect of Welding Speed on Keyhole Size . . . . . . . . . . . . . . . . 43
2.5.3 Effect of Laser Power on Keyhole Size . . . . . . . . . . . . . . . . . . 47
xiii