Nanoindentation Size Effect Interpreted by the Dislocation Nucleation Mechanism

The instability criterion of atomic structure is used to investigate the nanoindentation size effect based on the dislocation nucleation mechanism. Both the dislocation nucleation location and the emission direction under indentation can be predicted. The nanoindentation size effect for hardness can be interpreted with a critical condition of the dislocation nucleation through adopting an Atomic Finite Element Method which is associated with the instability criterion. The present results agree well with the analytical solution based on the Rice model. The present results show that the nanoindentation size effect with the flat indenter can be expressed by using the dislocation nucleation concept. From dislocation nucleation point of view, the applied average force (hardness) required for dislocation emission is proportional to the inverse of square root of the width of the nano-indenter (contact zone size).