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 pr ocessing is limited due to the assumptions made in the model. An elect ron-kinetic theory may offer an alternative solution to the problem. C onsequently, in the present study an electron-kinetic theory approach is introduced to model the 3-dimensional laser heating process. The ph ase change and conduction effects are encountered when driving the gov erning equations. To simulate the moving heat source, a scanning veloc ity of the laser beam is considered, in this case, the laser beam scan s the workpiece surface with a constant velocity. The governing heat t ransfer equation is in the form of integrodifferential equation, which does not yield the analytical solution. Therefore, a numerical method employing an explicit scheme is introduced to discretize the governin g equations. To validate the theoretical predictions, an experiment is conducted to measure the surface temperatures of the workpiece substr ate during Nd YAG laser heating process. It is found that the rapid in crease in temperature occurs in surface vicinity due to the successive electron-lattice site atom collisions. The depth of melting zone incr eases as the heating progresses and the temperature remains almost con stant at the melting temperature of the substrate in the surface vicin ity. In addition, the theoretical predictions agree well with the expe rimental findings.