MOLECULAR DYNAMICS SIMULATION OF THE INFLUENCE OF CRYSTAL IMPERFECTION ON NANO-MACHINING MECHANISM

Abstract

Establishment of nano-scale machining technologies is required in the field of ultra-precision fabrication where it is important to clarify cutting phenomena such as chip formation, cutting force, surface roughness and sub-surface damage. The present paper investigates the diamond machining of a copper single crystal with atomistic defects by means of molecular dynamics simulation. Postulating the Morse potential, the influence of initial vacancies and duplex cutting on the cutting mechanism is analysed when a (111) plane of the crystal is orthogonally machined in a [101] direction. Existing vacancies and edge dislocations in the copper result in further disorder of the lattice structure and an increase of cutting force owing to the interaction between the defects and the dislocations propagated from the tool tip. These phenomena can be observed at a vacancy density of 0.5%. In the case of the duplex cutting of the perfect crystal, displacement of the work atoms is limited to at or just below the finished surface, requiring a lower cutting force and producing more work atoms removed as a chip. These results suggest that a prerequisite for a damage-free machined surface is that the work material be as pure and perfect as possible.