Granular dynamics in compaction and stress relaxation

TL;DR

This paper investigates the elastic and dissipative behavior of granular materials under compression, revealing exponential and logarithmic stress relaxation, and identifies a glass-like transition with aging phenomena.

Contribution

It introduces a novel compaction method and combines experiments with simulations to elucidate relaxation dynamics and a glass transition in granular assemblies.

Findings

Stress relaxation exhibits exponential followed by logarithmic decay.

Logarithmic decay is linked to damping and sliding interactions.

A glass transition-like behavior is observed with aging in grain dynamics.

Abstract

Elastic and dissipative properties of granular assemblies under uniaxial compression are studied both experimentally and by numerical simulations. Following a novel compaction procedure at varying oscillatory pressures, the stress response to a step-strain reveals an exponential relaxation followed by a slow logarithmic decay. Simulations indicate that the latter arises from the coupling between damping and collective grain motion predominantly through sliding. We characterize an analogous "glass transition" for packed grains, below which the system shows aging in time-dependent sliding correlation functions.