Molecular dynamics simulation of laser assisted grinding of GaN crystals

Abstract

Gallium nitride crystal is a typical difficult-to-machine material due to its distinct anisotropy, high brittleness, and high hardness. The molecular dynamics simulations of traditional grinding and laser assisted grinding of GaN single crystals with a single grit were performed, and the influences of the laser power density on grinding force, stress distribution, material damage mechanism, subsurface damage depth, and abrasive wear were systematically studied. The results demonstrated that dislocations, stacking faults, hexagonal-to-cubic phase transition, and amorphous transition were generated during both traditional grinding and laser assisted grinding processes. Compared with the traditional grinding, laser assisted grinding with an appropriate laser power density reduced the grinding force, stress distribution, phase transition percentage, dislocation loop length, subsurface damage depth, and wear damage of the abrasive. However, excessive laser power densities caused deeper subsurface damage depth and severer amorphous damage for the rake face of the abrasive particle, which seriously deteriorated the integrity of the ground surface and subsurface. The results not only enhance the understanding of material removal and damages under the coupling actions of the laser and abrasive machining, but also provide a theoretical basis for parameter optimization during the machining of GaN single crystals.