Origin of low-velocity restitution-coefficient dependence

Determine the physical origin of the weaker dependence of the steady stress ratio on the restitution coefficient at low scaled dislocation velocities $v_d/v_s$ in a granular crystal containing a single dislocation.

Background

The paper investigates how contact damping, controlled through the restitution coefficient $e$, affects the steady rheology of a granular crystal containing a single edge dislocation. The simulations show that damping has its clearest influence in the intermediate-velocity regime, where stronger damping produces a larger stress ratio and an approximately linear rate-dependent increase.

The results also indicate a weaker dependence on $e$ at low $v_d/v_s$, but the paper does not identify the mechanism responsible for this residual dependence. This leaves unresolved the physical explanation of how restitution-dependent contact dissipation affects the low-velocity stress plateau, beyond the better-understood contributions from the elastic lattice barrier and interparticle friction.