Multiscale analysis of delay effect of dislocation nucleation with surface pit defect in nanoindentation

Multiscale simulations using the quasicontinuum (QC) method are performed to understand the nature of delay effect of dislocation nucleation with surface pit defect on the post yield process in nanoindentation. Compared with the nanoindentation on defect-free surface, eight different distances of adjacent boundary between surface pit defect and indenter are taken into account. The investigation shows that the delay effect of dislocation nucleation with surface pit defect is performed by 2–22%, which actually results from the emission of [1¯10] perfect dislocation. The reason of such perfect dislocation emission is exactly a strain competition between the two places of 1st and 2nd largest strain concentration near the load surface. In addition, the spatial extent of influence of delay effect is found to be three times the half contact width of indenter, which is in good agreement with the experimental results.

► We modeled nanoindentation process into a pit surface by a multiscale method. ► The abnormal phenomena of load decline in load–displacement curve are probed. ► The delay effect results from the emission of [1¯10] perfect dislocation. ► Strain competition mechanism is used to explain the perfect dislocation emission. ► The influence extent of delay effect is in agreement with the experimental result.