Transition From Plastic Flow to Fracture During Shear Collision of Nanoscale α ‐Quartz Asperities

Fault slip commonly leads to the collision and wear failure of asperities across broad length scales. Clarifying the multiscale wear failure mechanisms of asperities is essential for understanding the underlying principle of fault friction behavior. In this study, to investigate the still‐debated wear failure modes of nanoscale asperities, we conduct a series of 3‐D molecular dynamics simulations of semi‐spherical α ‐quartz asperity collisions under different boundary conditions, asperity radii ( R ), and contact configurations. The results indicate that both plastic deformation and fracture of α ‐quartz asperities can occur during frictional collision without creating surface grooves. Under constant normal stiffness‐like condition, the failure transition can be mapped by the vertical overlapping distance normalized by R between the summits of two asperities, as a function of R . Under constant normal load condition, the failure transition can be indicated by the peak tangential shear force. Essentially, the failure mode transition is controlled by subsurface contact stress evolution through the dependence of R and contact configuration. Finally, the results also reveal that the total wear volume of fractured asperities scales linearly with the total tangential shear work. These findings provide deeper insights into the wear failure mechanisms of nanoscale rock asperities during friction, which also help shed light on microscopic fault friction mechanisms.