Molecular dynamics study on deformation behaviour of monocrystalline GaN during nano abrasive machining.

• Nano abrasive machining of monocrystalline GaN is studied by molecular dynamics simulations. • Deformation of monocrystalline GaN is associated with both the propagation of dislocation and the contact of workpiece/tool. • Dislocation and phase transition are identified in the deformation layer after nano abrasive machining. • Pile-up and elastic recovery of monocrystalline GaN are affected by the stagnation region and slip system. • Effects of cutting velocity, depth of cut and abrasive shape on deformation are systematically investigated. Molecular dynamics simulations are carried out to investigate the nano abrasive machining of monocrystalline gallium nitride (GaN). Effects of the cutting velocity, depth of cut (DOC) and abrasive shape on the atomic strain, stress, temperature, cutting forces, and deformation layer are systematically investigated, aiming at understanding the deformation behaviour of monocrystalline GaN during nano abrasive machining. The results show that the strain, stress and temperature were increased by using the higher cutting velocity, the larger DOC or cub-octahedral abrasive. Being affected by both the average stress and the elasto-plastic deformation zone right ahead the diamond particle, the cutting forces increase with the increase in DOC but decrease under a larger cutting velocity, or when using a cub-octahedral abrasive. The deformation layer in the subsurface is insensitive to the cutting velocity, while impressively shrinks under a larger DOC or cub-octahedral abrasive used. As the stress and temperature rise, the use of higher cutting velocity, larger DOC or cub-octahedral abrasive would facilitate the nucleation of dislocation, phase transition and the development of pile-up. This work can enrich the understanding on the nanoscale deformation mechanism of monocrystalline GaN material during the ultra-precision machining process. [ABSTRACT FROM AUTHOR]