The Interplay Between Forces, Particle Rearrangements, and Macroscopic Stress Fluctuations in Sheared 2D Granular Media

TL;DR

This study uses simulations to explore how particle rearrangements, force fluctuations, and stress changes are interconnected in sheared 2D granular materials, emphasizing the regional nature of plastic events during slip.

Contribution

It provides new insights into the regional behavior of plastic events and their correlation with force and stress fluctuations in sheared granular media.

Findings

Large slip events involve particle clusters with high non-affine motion.

These clusters coincide with regions of force reduction.

Non-affine motion correlates strongly with stress fluctuations.

Abstract

Recent studies have established correlations between non-affine motion and macroscopic stress fluctuations in sheared granular media. However, a comprehensive examination of the relationship between non-affine motion, macroscopic stress fluctuations, and inter-particle forces remains lacking. We investigated this interplay in simulations of 2D granular media during stick-slip events under plane shear. We found that, during most large slip events, particles with the greatest non-affine motion, as quantified by D2min, initially coalesce into one or two dominant connected clusters. These clusters coincide with the region exhibiting the greatest instantaneous reduction in inter-particle forces, indicating a significant correlation between inter-particle force fluctuations and particle rearrangements. Furthermore, the magnitude of the greatest non-affine motion within these clusters correlates strongly with the magnitude of macroscopic stress fluctuations during slip events. This correlation increased when the non-affine motion of particles in a neighborhood around the point of greatest non-affine motion was included in the analysis, suggesting that plastic events are best understood as regional rather than point-like occurrences. Our results held for various inter-particle friction coefficients. Our findings suggest that elastoplastic models should consider plastic events as regional rather than point-like and highlight the importance of studying the propagation of particle rearrangements.