Avalanche dynamics in sheared athermal particle packings occurs via localized bursts predicted by unstable linear response. Issue 12 (10th March 2022)

• Record Type: Journal Article
• Authors: Stanifer, Ethan; Manning, M. Lisa
• Is Part Of: Soft matter. Volume 18:Issue 12(2022)
• Page Start: 2394
• Page End: 2406
• Publication Date: 2022-03-10
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/d1sm01451j
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : Under applied strain, granular and glassy materials exhibit system-spanning avalanches. These can be decomposed into localized bursts of deformation, predicted by soft spots derived from an extension of linear response methods to unstable systems. Abstract : Under applied shear strain, granular and amorphous materials deform via particle rearrangements, which can be small and localized or organized into system-spanning avalanches. While the statistical properties of avalanches under quasi-static shear are well-studied, the dynamics during avalanches is not. In numerical simulations of sheared soft spheres, we find that avalanches can be decomposed into bursts of localized deformations, which we identify using an extension of persistent homology methods. We also study the linear response of unstable systems during an avalanche, demonstrating that eigenvalue dynamics are highly complex during such events, and that the most unstable eigenvector is a poor predictor of avalanche dynamics. Instead, we modify existing tools that identify localized excitations in stable systems, and apply them to these unstable systems with non-positive definite Hessians, quantifying the evolution of such excitations during avalanches. We find that bursts of localized deformations in the avalanche almost always occur at localized excitations identified using the linear spectrum. These new tools will provide an improved framework for validating and extending mesoscale elastoplastic models that are commonly used to explain avalanche statistics in glasses and granular matter.