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

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.