Evaluation of repeated single-point diamond turning on the deformation behavior of monocrystalline silicon via molecular dynamic simulations

A three-dimensional molecular dynamics simulation study is conducted to investigate repeated single-point turnings of a monocrystalline silicon specimen with diamond tools at nanometric scale. Morse potential energy function and Tersoff potential energy function are applied to model the silicon/diamond and silicon/silicon interactions, respectively. As repeated nano-cutting process on surfaces often involve the interactions between the consequent machining processes, repeated single-point diamond turnings are employed to investigate the phase transformation in the successive nano-cutting processes. The simulation results show that a layer of the damaged residual amorphous silicon remained beneath the surface after the first-time nano-cutting process. The amorphous phase silicon deforms and removes differently in the second nano-cutting process. By considering the coordination number (CN) of silicon atoms in the specimen, it is observed that there is an increase of atoms with six nearest neighbors during the second nano-cutting process. It suggests that the recovery of the crystalline phase from the amorphous phase occurred. Moreover, the instantaneous temperature distributions in the specimen are analyzed. Although the tangential force (FX) and the thrust force (FY) become much smaller in the second cutting process, the material resistance rate is larger than the first cutting process. The larger resistance also induces the increase of local temperature between the cutting tool and the amorphous layer in the second cutting process.