Absence of `fragility' and mechanical response of jammed granular materials

TL;DR

This study uses molecular dynamics simulations to investigate the mechanical response of jammed granular materials, revealing they respond elastically and isotropically, indicating an absence of fragility, and identifies a crossover from visco-elastic to plastic behavior with increasing stress.

Contribution

It demonstrates that jammed granular materials do not exhibit fragility and characterizes their elastic and plastic responses under shear stress.

Findings

Materials respond elastically and isotropically to small perturbations.

No evidence of fragility in the jammed state.

Crossover from visco-elastic to plastic behavior with increasing stress.

Abstract

We perform molecular dynamic (MD) simulations of frictional non-thermal particles driven by an externally applied shear stress. After the system jams following a transient flow, we probe its mechanical response in order to clarify whether the resulting solid is 'fragile'. We find the system to respond elastically and isotropically to small perturbations of the shear stress, suggesting absence of fragility. These results are interpreted in terms of the energy landscape of dissipative systems. For the same values of the control parameters, we check the behaviour of the system during a stress cycle. Increasing the maximum stress value, a crossover from a visco-elastic to a plastic regime is observed.