Effect of plasticity and adhesion on the stick-slip transition at nanoscale friction

Abstract

When an external force is suddenly applied to the material interface, how much the critical force is required for the onset of slip? To answer this, we used molecular simulations to study the slip initiation during a nano-scratch. The shear load is applied by a very soft spring to achieve the constant force boundary. Using this model, we studied how much plasticity and adhesion affect the critical shear load. Results show that the slip initiation depends on contact depth because the dominated factor for stick-slip changes from interfacial adhesion in shallow contact to dislocation plasticity in deep contact. Also, the initiation stress of slip depends on temperature; the critical shear stress follows a temperature dependence of ~TlnT when dislocation plasticity prevails.