分子動力学シミュレーション 結晶の不完全性がナノ切削機構に及ぼす影響の分子動力学シミュレーション

Abstract

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