The influence of residual stress on incipient plasticity in single-crystal copper thin film under nanoindentation

The incipient plastic deformation of single-crystal copper thin film with in-plane residual stress under Hertzian nanoindentation is studied using molecular dynamics simulation. The result reveals that the residual stresses significantly influence the surface strength and dislocation nucleation behavior of material: (i) the indentation hardness decreases with tensile residual stress, while it increases with moderate compressive residual stress, but it may drop down under higher compressive residual stress; (ii) the dislocation nucleation depth and its slip direction also vary with different residual stress state. This demonstrates that residual stress may influence incipient plasticity not only on the threshold value but also on the initial dislocation nucleation behavior under indentation.