Spatial correlation and temporal evolution of plastic heterogeneity in sheared granular materials

Abstract

Granular materials will yield and undergo serrated plastic flow when subjected to loading. The serrated plastic flow is related to the spatial concentration and temporal evolution of the microscopic plastic events. Limited by the temporal resolution of experimental techniques available, the initialization and localization of the plastic events within timescale much less than the structural relaxation time is still poorly understood. We use combined finite and discrete element method to model the simple shearing of an assembly of irregularly shaped particles. At small temporal scales, nonaffine motions originate at particles experiencing large stress fluctuations. The cooperative dynamics and long-ranged dynamic heterogeneity is responsible for the annihilation and merging of plastic zones at the timescale close to the structural relaxation time, and the plasticity is manifested as irreversible rearrangement at large enough strain scales. The spatiotemporal variability of plastic activity is confirmed by the transient nature of the high mobile clusters.