How does static granular matter re-arrange for different isotropic strain rate?

Multi-Scale Mechanics (MSM), Department of Thermal and Fluids Engineering (TFE), Faculty of Engineering Technology (ET), MESA+ Institute for Nanotechnology, University of Twente, POBox 217, 7500AE Enschede, NL

^* e-mail: s.luding@utwente.nl

Published online: 7 June 2021

Abstract

The question of how soft granular matter, or dense amorphous systems, re-arrange their microstructure under isotropic compression and de-compression, at different strain rates, will be answered by particle simulations of frictionless model systems in a periodic three-dimensional cuboid. Starting compression below jamming, the systems experience the well known jamming transition, with characteristic evolutions of the state variables elastic energy, elastic stress, coordination number, and elastic moduli. For large strain rates, kinetic energy comes into play and the evolution is more dynamic. In contrast, at extremely slow deformation, the system relaxes to hyper-elastic states, with well-defined elastic moduli, in static equilibrium between irreversible (plastic) re-arrangement events, discrete in time. Small, finite strains explore those reversible (elastic) states, before larger strains push the system into new states, by irreversible, sudden re-arrangements of the micro-structure.