3-dimensional modeling of laser repetitive pulse heating: a phase change and a moving heat source considerations

Abstract

Laser repetitive pulse heating may offer thermal integration at the workpiece surface during laser material processing. However, the condition 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 considered. In modeling the process, an electron kinetic theory approach 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 method employing an explicit scheme is introduced to solve the governing equations. In the analysis, conduction and phase change processes are taken into account and the laser beam is considered as scanning the surface with a constant velocity. The repetitive pulses are introduced such that the ratio of successive pulse intensity to the first pulse intensity 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 separately. Moreover, the condition for the thermal integration and isothermal heating are introduced. It is found that the temperature profiles do not follow the pulse profile and that thermal integration is possible for the low power intensity ratio considered in the present study.