ORIGIN OF RATE DEPENDENCE IN FRICTIONAL SLIDING

Experiments indicate that frictional resistance to sliding between macroscopic, clean, dry surfaces depends on the average rate V at which the surfaces are translated relative to each other. Using a new lattice automaton, we obtain results suggesting that rate-dependent macroscopic dynamics may arise from microscopic interactions between contact points which decay from a metastable state with a finite lifetime-GAMMA. Sliding is accommodated by clusters, or avalanches, of failed lattice contact points, and corresponds to successive quenches into the metastable state by an electromechanical loading system with a finite response time-DELTA. Under the quasistatic assumption DELTA >> GAMMA, rate dependence is a consequence of the increase in correlation length zeta-d of clusters of failed lattice points as quench rate increases. Special cases of the model are isomorphic to the self-organized criticality model for sandpiles, and to block-spring models of the type first studied by Burridge and Knopoff for earthquakes.