Onset of Irreversibility in Cyclic Shear of Granular Packings

TL;DR

This study explores how dense granular materials transition from reversible to irreversible behavior under cyclic shear, revealing a critical amplitude where contact network topology becomes diffusive and irreversible.

Contribution

It provides detailed 3D imaging of bead trajectories showing the micro and mesoscale mechanisms behind irreversibility in cyclically sheared granular packings.

Findings

Reversible contact network topology at small amplitudes

Transition to diffusive, irreversible regime at larger amplitudes

Identification of a critical shear amplitude for irreversibility onset

Abstract

We investigate the onset of irreversibility in a dense granular medium subjected to cyclic shear in a split-bottom geometry. To probe the micro and mesoscale we image bead trajectories in 3D throughout a series of shear strain oscillations. Though beads lose and regain contact with neighbors during a cycle, the topology of the contact network exhibits reversible properties for small oscillation amplitudes. With increasing reversal amplitude a transition to an irreversible diffusive regime occurs.