Onset and impact of plastic deformation in granular compaction

TL;DR

This study uses simulations to explore how plastic deformation influences the pressure and elastic properties during granular material compaction, revealing simplified models and microscopic strain behaviors.

Contribution

It introduces a bonded particle model with yield behavior to analyze plasticity effects in granular compaction, providing new insights into pressure softening and local strain evolution.

Findings

Plasticity softens pressure increase during compaction.

Data collapses suggest simple models can describe plastic effects.

Microscopic strain evolution correlates with macroscopic behavior.

Abstract

The role of plastic deformation in the high-pressure compaction of granular material is investigated using bonded particle model simulations. Grains are discretized into a set of computational particles connected by pairwise bonds. Bonds are harmonic up to a plastic onset strain $\epsilon_p$ above which they yield, capping out at a maximum force and producing an elastic-perfectly-plastic-like mechanical response in grains. Packings containing over one thousand monodisperse spherical grains are isotropically compacted to different packing fractions to quantify how decreasing $\epsilon_p$ softens the rise in pressure and impacts effective elastic properties of the confined system. By isolating the relative decrease in pressure due to plasticity, we find data can be collapsed across a wide range of values of $\epsilon_p$ suggesting that relatively simple mathematical descriptions may capture plasticity's effect in granular compaction. Lastly, we study the microscopic statistics of local strains in grains and connect their evolution to the observed macroscopic behavior.