Experimental and Simulation Study of Laser Hole Drilling in Stainless Steel Using Pulsed Nd:YAG Laser

This work presents an experimental and simulation study of percussion laser hole drilling in 1.2mm thick sheet of AISI304 stainless steel. Drilling experiments using NdYAG laser pulses of 1.0 to 7.0ms duration, 0.35 to 2.5J energy as single shots, in addition to a series of 10 pulses of 1ms duration at 10 pulse repetition frequency (prf) have been performed in ambient air. The experimental results have been used for the comparison with the simulation results. COMSOL Multiphysics 5.1 software has been employed to simulate the heating cycles of the 10prf shots, and the 5.0ms single shot. The simulation has been performed in terms of 2D-Axisymmetric, comprising the heat transfer differential equations, phase change to liquid and vapour, laminar fluid flow, adaptive mesh refinement, convection and radiation losses, in addition to heat source propagation velocity. The cooling cycles following pulse extinguishment, using formulated initial thermal condition, have been simulated also for two samples from the 10prf sequence (after the 4th and the 9th pulse), and for the 5.0ms shot. Simulation showed that full cooling occurs within a few tens of milliseconds, and no residual heat would be carried forward to the subsequent heating pulse when operating with low pulse repetition rate.