Numerical simulation and experimental study of the shape variation influence on stainless steel drilling with picosecond laser

The laser beam tilt induces significant changes in the shape of irradiation on the material surface, thereby affecting the ablation contour. However, the influence of tilted laser beams on micro-hole machining remains confined to a simplistic approach. This paper combines experimental and finite element simulation studies to investigate the impact of the laser angle of the incident (AOI) on micro-hole machining with picosecond lasers. A two-dimensional finite element model, including the two-temperature equation and the deformable geometry module, is established to simulate the ablative process of tilted picosecond laser beams on stainless steel. Single-pulse and multiple-pulse ablations under different AOIs are simulated using the model. Experimental results demonstrate that the inclination angle of micro-holes linearly decreases with increasing AOI, resulting in smoother hole wall surfaces. Simulation results reveal a logarithmic decrease in the peak temperatures of electrons and lattice with AOI, which is attributed to the increase in irradiation area and its influence on peak intensity. Under multiple-pulse irradiation, the ablation contour gradually tilts as AOI increases, and the ablation depth follows a logarithmic decrease with AOI.