40
2 Model of Quasi-Steady Weld Pool Dynamics and Numerical Simulation
2.5.1.2 Computational Results and Analysis
The TC4 titanium alloy with radius 0.015 m was calculated by using the established three-dimensional laser welding process dynamics model. Because the thermophysical properties in the high temperature region cannot be obtained, and the
data obtained by extrapolation method cannot accurately reflect the essential characteristics of materials, the thermophysical parameters in the high temperature region
of numerical experiments are all taken as constants. The laser processing parameters
used in numerical experiments are as follows: the laser power is selected between
1600 and 3000 W, and the welding speed is selected between 0.025 and 0.070 m/s.
Figures 2.9 and 2.10 show the temperature distribution on the upper surface of the
workpiece and the temperature gradients before and behind the welding heat source.
In Fig. 2.9, the positive direction of x axis is the moving direction of the workpiece.
As can be seen from Fig. 2.9, the temperature near the center of the heat source
is 3510 K, the shape of the temperature profile is like an ellipse, and the long axis
of the ellipse is parallel to the welding direction. It is easy to infer that the outlet
of the keyhole has the same characteristics. From the distribution characteristics
of the isotherms, the isotherm in front of the keyhole has a considerably higher
density than the isotherm at the back of the keyhole. In Fig. 2.10, the temperature
Fig. 2.9 Temperature distributions in the XOY plane at upper surface of the piecework during deep
penetration laser welding
2 Model of Quasi-Steady Weld Pool Dynamics and Numerical Simulation
2.5.1.2 Computational Results and Analysis
The TC4 titanium alloy with radius 0.015 m was calculated by using the established three-dimensional laser welding process dynamics model. Because the thermophysical properties in the high temperature region cannot be obtained, and the
data obtained by extrapolation method cannot accurately reflect the essential characteristics of materials, the thermophysical parameters in the high temperature region
of numerical experiments are all taken as constants. The laser processing parameters
used in numerical experiments are as follows: the laser power is selected between
1600 and 3000 W, and the welding speed is selected between 0.025 and 0.070 m/s.
Figures 2.9 and 2.10 show the temperature distribution on the upper surface of the
workpiece and the temperature gradients before and behind the welding heat source.
In Fig. 2.9, the positive direction of x axis is the moving direction of the workpiece.
As can be seen from Fig. 2.9, the temperature near the center of the heat source
is 3510 K, the shape of the temperature profile is like an ellipse, and the long axis
of the ellipse is parallel to the welding direction. It is easy to infer that the outlet
of the keyhole has the same characteristics. From the distribution characteristics
of the isotherms, the isotherm in front of the keyhole has a considerably higher
density than the isotherm at the back of the keyhole. In Fig. 2.10, the temperature
Fig. 2.9 Temperature distributions in the XOY plane at upper surface of the piecework during deep
penetration laser welding