Simulations of deep drilling of metals by continuous wave lasers using combined smoothed particle hydrodynamics and ray-tracing methods

Abstract

A robust numerical method based on smoothed particle hydrodynamics (SPH) is used to investigate the melt pool expulsion mechanism during high-aspect ratio laser drilling of two different materials: aluminum and 316L stainless steel. The computational model is validated with previously published results which show extremely close matches. The ray-tracing method is combined with SPH method which makes the model capable of taking into account the multiple reflections of laser radiations from the keyhole wall. The drilling velocity is found to be a non-linear function of time, which is dependent on the shape of the heated surface. For a flat surface, the drilling velocity is small, but after the cavity is formed and multiple reflections of laser radiations become significant, the drilling velocity strongly increases. The main driving force of melt expulsion is the repulsive force produced by vapor pressure. The Marangoni stresses are found to provide marginal effect on melt expulsion during deep drilling.