Title: Time dependent rearrangements in an amorphous solid

Author (Table Talk): Zhicheng Wang, Pennsylvania State University

Abstract:

In an amorphous solid undergoing oscillatory shear, particles may rearrange in localized, reversible plastic events. Recent studies of memory and yielding have imposed or assumed the limit of low strain rates, treating each rearrangement as an instantaneous switching event. We explore the much richer dynamics at finite strain rates, in experiments with a monolayer of bidisperse colloidal particles at a decane-water interface. We drive the monolayer at increasing frequencies while observing how particles rearrange. We find that individual rearrangements have a wide distribution of switching timescales at a given driving frequency, and that there are latent rearrangements that occur only at frequencies much lower than in previously-published experiments. Furthermore, the strains at which rearrangements happen seem to depend on driving frequency as well. We show that a generic model of hysteresis with linear damping reproduces these frequency-dependent behaviors.