Insights on the local dynamics induced by thermal cycling in granular matter

TL;DR

This study uses molecular dynamics simulations to explore how thermal cycling affects granular materials, revealing a threshold amplitude that determines whether the system exhibits localized intermittent dynamics or continuous flow.

Contribution

It introduces a minimal thermal cycling amplitude based on grain properties that predicts the transition from localized to global dynamics in granular assemblies.

Findings

Below threshold cycling amplitude, dynamics are intermittent and localized.

Above threshold, the entire column flows with a range of grain dynamics.

Grain properties like roughness and elastic modulus influence the critical cycling amplitude.

Abstract

In this letter, we report results on the effect of temperature variations on a granular assembly through Molecular Dynamic simulations of a 2D granular column. Periodic dilation of the grains are shown to perfectly mimic such thermal cycling, and allows to rationalize the link between the compaction process, the local grains dynamics and finite size effects. Here we show that the individual grain properties, namely their roughness and elastic modulus define a minimal cycling amplitude of temperature \Delta Tc below which the dynamics is intermittent and spatially heterogeneous while confined into localized regions recently coined "hot spot" [Amon et al., Phys. Rev. Lett. 108, 135502 (2012)]. Above \Delta Tc, the whole column flows while the grains dynamics ranges continuously from cage-like at the bottom of the column to purely diffusive at the top. Our results provide a solid framework for the futur use of thermal cycling as an alternate driving method for soft glassy materials.