ABSTRACT

In order to study the early stages of plastic deformation with initial defect under the action of all indenter, the nanoindentation processes of the single crystal aluminum thin film were simulated using the. quasicontinuum method. The load vs displacement response curves and strain energy vs displacement curves of the single crystal aluminum thin film with initial defect and defect-free were presented, respectively. The nanoindentation processes under influences of the initial defect were investigated about dislocation nucleation, dislocation emission, Peierls stress and load necessary for dislocation emission. The results demonstrate that the load vs displacement response curves experience many times abrupt drops with the emission of dislocations beneath the indenter. The initial defect is found to be insignificant on nucleation and emission of the l(st) and 3(rd) dislocation dipoles, but has a distinct effect on the 2(nd) dislocation dipole. The nucleation and emission of the 2(nd) dislocation dipole is postponed obviously because of the effect of initial defect, and then crack propagation is accompanied. The strain energy of single crystal aluminum thin film and Peierls stress of dislocation dipole beneath the indenter increase with deformation processes due to the severe lattice distortion in the thin film. Before the cleavage occurs, the load necessary for the 2nd dislocation dipole nucleation and emission increases in nanoindentation with initial defect, oil the contrary, it decreases after the cleavage occurred. The nanobardness and Peierls stress in this simulation show a good agreement with relevant theoretical and experimental results.