Indenter Orientation-Dependent Scratch Behavior and Size Effect in Single Crystalline Copper

Abstract

Abstract. The orientation of the pyramidal indenter critically influences slip system activation and dislocation accumulation, thereby complicating the interpretation of tribological responses at small deformation scales. This study systematically investigates the orientation-dependent scratch response and associated size effect of single crystalline copper using a strain gradient crystal plasticity framework. The results reveal that the stabilized scratch depth exhibits variations on the order of 10% depending on indenter orientation. Moreover, the relative inter-side difference in pile-up height can reach the upper tens of percent, indicating pronounced orientation-induced asymmetry. Additionally, scratch hardness does not strictly correlate inversely with scratch depth, as evidenced by that the side-forward orientation produces the greatest depth but not the lowest hardness. For all indenter orientations, increasing the applied load from 0.9 mN to 6 mN leads to a hardness reduction of several tens of percent relative to the low-load value. Furthermore, the influence of indenter orientation on scratch hardness is greater than that of scratch direction.