Scaling of relaxation and excess entropy in plastically deformed amorphous solids

TL;DR

This study explores how microscopic structure and relaxation dynamics in plastically deformed amorphous solids are interconnected, revealing power-law shear-thinning behavior and exponential scaling with excess entropy, through experimental analysis of colloidal monolayers under shear.

Contribution

It demonstrates the correlation between relaxation rates, strain rates, and microscopic structure in amorphous solids, highlighting the role of excess entropy in non-stationary plastic deformation.

Findings

Relaxation rate correlates with strain rate and structure at different times.

Relaxation exhibits power-law shear-thinning behavior.

Relaxation rate scales exponentially with excess entropy.

Abstract

When stressed sufficiently, solid materials yield and deform plastically via reorganization of microscopic constituents. Indeed, it is possible to alter the micro-structure of materials by judicious application of stress, an empirical pro- cess utilized in practice to enhance the mechanical properties of metals. Un- derstanding the interdependence of plastic flow and microscopic structure in these non-equilibrium states, however, remains a major challenge. Here, we ex- perimentally investigate this relationship, between the relaxation dynamics and microscopic structure of disordered colloidal solids during plastic deformation. We apply oscillatory shear to solid colloidal monolayers and study their particle trajectories as a function of shear rate in the plastic regime. Under these cir- cumstances, the strain rate, the relaxation rate associated with plastic flow, and the sample microscopic structure oscillate together but with different phases. Interestingly, the experiments reveal that the relaxation rate associated with plastic flow at time t is correlated with the strain rate and sample microscopic structure measured at earlier and later times, respectively. The relaxation rate, in this non-stationary condition, exhibits power-law shear-thinning behavior and scales exponentially with sample excess entropy. Thus, measurement of sample static structure (excess entropy) provides insight about both strain-rate and constituent rearrangement dynamics in the sample at earlier times.