Nanoindentation and cutting simulations of gallium phosphide using molecular dynamics

Gallium phosphide (GaP) has innovative optical applications possibilities due to its refractive index of 3.3 at 600 nm wavelength. A recent example is solid immersion lens with submillimetre apertures. However, in ultra-precision (UP) machining, challenges such as tool wear and brittle-ductile cutting are still evident. A method to understand the UP-cutting mechanisms, and consequently the tool wear is molecular dynamics simulations (MD). This work presents an application of MD simulations in nanoindentation and cutting conditions. Nanoindentation simulations shown a brittle-ductile transition under the indenter, a hardness compatible with experimental data, and good performance of structure identification algorithms. Based on the nanoindentation simulation analysis, machining simulation were performed and a ductile behaviour was observed, though the main cutting mechanism was brittle. Since experimental data and the nanoindentation simulation points out an expressive ductile behaviour, more machining simulations with different tool geometries and cutting parameters should be made for a better understanding of tool wear and phase transitions.