Critical-like Features of Stress Response in Frictional Packings

TL;DR

This study investigates the stress response in granular packings, revealing a critical-like transition between anisotropic and isotropic behaviors characterized by a diverging length scale, using large-scale simulations across various friction and force conditions.

Contribution

It uncovers critical-like features in stress response transitions in granular materials and constructs a phase diagram based on friction and force parameters.

Findings

Identification of a diverging length scale at the transition

Crossover from anisotropic to isotropic stress response

Construction of a multidimensional phase diagram

Abstract

The mechanical response of static, unconfined, overcompressed face centred cubic, granular arrays is studied using large-scale, discrete element method simulations. Specifically, the stress response due to the application of a localised force perturbation - the Green function technique - is obtained in granular packings generated over several orders of magnitude in both the particle friction coefficient and the applied forcing. We observe crossover behaviour in the mechanical state of the system characterised by the changing nature of the resulting stress response. The transition between anisotropic and isotropic stress response exhibits critical-like features through the identification of a diverging length scale that distinguishes the spatial extent of anisotropic regions from those that display isotropic behaviour. A multidimensional phase diagram is constructed that parameterises the response of the system due to changing friction and force perturbations.