Crackling to periodic dynamics in sheared granular media

TL;DR

This study investigates how sheared granular media transition from crackling to periodic dynamics by varying shear rate and stiffness, revealing a phase diagram and microscopic stress behaviors.

Contribution

It introduces a dynamic phase diagram for granular media, linking macroscopic parameters to the transition between crackling and periodic regimes.

Findings

Transition from crackling to periodic motion with parameter changes

Scaling laws associated with the force signals

Microscopic stress evolution insights from photo-elasticimetry

Abstract

The local and global dynamics of a sheared granular medium are studied in a model experiment as a function of several macroscopic parameters. We observe that by changing the shear rate or the loading stiffness, the system crackles, with intermittent slip avalanches, or exhibits periodic motion. By analyzing the global force, induced while shearing, we capture the transition from the crackling to the periodic regime and associated scaling laws. We deduce a novel dynamic phase diagram as a function of the shear rate and the system's stiffness. Using photo-elasticimetry, we also capture the grain-scale stress evolution, and investigate the microscopic behavior in the different regimes.