Nucleation and propagation of self-healing cracks at an elastic adhesive interface

Slip between two bodies in frictional contact is mediated by rupture fronts, which can propagate as either crack-like or pulse-like modes. While crack-like fronts resemble a growing crack, pulse-like fronts involve reattachment at the trailing edge of the propagating front. When and why these fronts occurs remains an open question, actively explored through both theory and experiments. In this work, we investigate the role of boundary conditions in the existence of pulse-like fronts under shear-driven sliding using a two-dimensional elastic network-based numerical model consisting of load-bearing bonds. The interface bonds are capable of attachment and reattachment under specific conditions. We show that in the same system, under shear loading, crack-like fronts are precursors to pulse-like events, and transition to them under increasing remote normal load. The pulse speed in all cases never exceeds the Rayleigh wave speed. To explain this limiting speed, we present an analytical model of moving pulses comprising stick and slip regions, based solely on kinematic boundary conditions, independent of specific friction laws.