Insights into the interface dynamic evolution and associated macroscopic tribological response of dry contacts: A numerical investigation

To date, the relationship between contact-scale dynamics and macroscopic frictional response of shear interfaces remains poorly understood. Using a finite element model displaying two contrasting elastic materials sheared along a rough interface, we investigate how local contact dynamics govern macroscopic frictional response, from the nucleation of seismic-like waves through the transition to stick-slip or continuous motion, thereby elucidating the mechanisms that control overall frictional evolution. Our analysis reveals that the origin of the slow propagation front is fundamentally driven by the contact stress distributions resulting from the macroscopic quasistatic boundary conditions, while the rupture of the entire interface arises from the creation of energetic waves associated with local slips, that travel along the interface and through the volume. Remarkably, what appears as smooth macroscopic sliding is not characterized by uniform simultaneous contact motion, but rather by continuous nucleation and dissipation of local slip events that drive portions of the interface through transient slipping phases, sustaining the overall motion of the system.