Local Plasticity as the Source of Creep and Slow Dynamics in Granular Materials

TL;DR

This study uses numerical simulations to reveal that local plasticity at the grain level drives creep and slow dynamics in frictionless granular materials, showing universal behavior independent of friction.

Contribution

It introduces a micromechanical framework linking grain-scale deformations and plastic dissipation to creep in granular solids without friction.

Findings

Creep involves logarithmic slow dilation after rapid compression.

Localized large strain regions grow over time during creep.

Non-affine displacements correlate linearly with local strain.

Abstract

Creep mechanisms in uniaxially compressed 3D granular solids comprised of faceted frictionless grains are studied numerically using a constant pressure and constant stress simulation method. Rapid uniaxial compression followed by slow dilation is predicted on the basis of a logarithmic creep phenomenon. Micromechanical analysis indicates the existence of a correlation between granular creep and grain-scale deformations. Localized regions of large strain appear during creep and grow in magnitude and size with time. Furthermore, the accumulation of non-affine granular displacements increases linearly with local strain, thereby providing insights into the origins of plastic dissipation during stress-driven creep evolution. The prediction of slow logarithmic dynamics in the absence of friction indicates a universality in the role of plastic dissipation during the creep of granular solids.