3-DIMENSIONAL MODELING OF LASER REPETITIVE PULSE HEATING - A PHASE-CHANGE AND A MOVING HEAT-SOURCE CONSIDERATIONS

Laser repetitive pulse heating may offer thermal integration at the wo rkpiece surface during laser material processing. However, the conditi on for the thermal integration highly depends on the material response to successive laser pulses. In the present study, 3-dimensional laser heating of semi-infinite steel subjected to repetitive pulsation is c onsidered. In modeling the process, an electron kinetic theory approac h is employed and governing equations are derived. Since the governing equations derived are in the form of integro-differential equations, they do not yield analytical solutions. Therefore, the numerical metho d employing an explicit scheme is introduced to solve the governing eq uations. In the analysis, conduction and phase change processes are ta ken into account and the laser beam is considered as scanning the surf ace with a constant velocity. The repetitive pulses are introduced suc h that the ratio of successive pulse intensity to the first pulse inte nsity is kept constant and the cooling period between two consecutive pulses is also kept constant. To investigate the power intensity ratio on the resulting temperature profiles, three ratios are considered se parately. Moreover, the condition for the thermal integration and isot hermal heating are introduced. It is found that the temperature profil es do not follow the pulse profile and that thermal integration is pos sible for the low power intensity ratio considered in the present stud y. (C) 1998 Elsevier Science B.V. All rights reserved.