3-dimensional laser heating model including a moving heat source consideration and phase change process
The use of a Fourier heating model in high intensity laser material processing is limited due to the assumptions made in the model. An electron-kinetic theory may offer an alternative solution to the problem. Consequently, in the present study an electron-kinetic theory approach is introduced to model the 3-dimensional laser heating process. The phase change and conduction effects are encountered when driving the governing equations. To simulate the moving heat source, a scanning velocity of the laser beam is considered, in this case, the laser beam scans the workpiece surface with a constant velocity. The governing heat transfer equation is in the form of integro-differential equation, which does not yield the analytical solution. Therefore, a numerical method employing an explicit scheme is introduced to discretize the governing equations. To validate the theoretical predictions, an experiment is conducted to measure the surface temperatures of the workpiece substrate during Nd YAG laser heating process. It is found that the rapid increase in temperature occurs in surface vicinity due to the successive electron-lattice site atom collisions. The depth of melting zone increases as the heating progresses and the temperature remains almost constant at the melting temperature of the substrate in the surface vicinity. In addition, the theoretical predictions agree well with the experimental findings.