Molecular dynamics simulation of nanomachining process and mechanical properties of nanostructure

Nanomachining and tensile process of Cu (111) plane nanostructures were simulated by molecular dynamics, and the defect behavior during nanomachining process and its effect on mechanical properties of nanostructure were analyzed at atomic scale. The results show that the atoms at the frontage or back of the AFM tip deviated from their initial positions and formed a deformation zone in nanostructure. Dislocations only propagate in surface and subsurface when scratching depth is shallow, and some dislocations formed dislocation loops as there existed stress gradient near tip. The number of residual defects increases and ordering degree of crystal structures decreases with scratching depth increasing. There existed high residual stress in subsurface, especially near the position where tool withdraw nanostructure. The tensile curves of the scratched nanostructure are not smooth, which is related to residual stress and defect at the elastic stage, and to dislocation multiplication and pile-up at the plastic stage. Ordering degree of nanostructure decreases with scratching depth increasing, while ordering degree for small scratching depth at the strain of 0.8 is better than that at the first yielding of strain 0.045.