Bulk modulus of soft particle assemblies under compression

TL;DR

This study investigates how the bulk modulus of soft particle assemblies changes under compression, revealing non-linear behaviors and proposing a predictive model that accounts for particle-scale properties and interparticle friction effects.

Contribution

The paper introduces a new numerical model that predicts the evolution of bulk modulus in soft particle assemblies considering non-linearities and friction effects, validated by simulations.

Findings

Bulk modulus deviates from linear predictions under high compression.

The proposed model accurately predicts bulk modulus evolution.

Interparticle friction influences the bulk modulus behavior.

Abstract

Using a numerical approach based on the coupling of the discrete and finite element methods, we explore the variation of the bulk modulus K of soft particle assemblies undergoing isotropic compression. As the assemblies densify under pressure-controlled boundary conditions, we show that the non-linearities of K rapidly deviate from predictions standing on a small-strain framework or the Equivalent Medium Theory (EMT). Using the granular stress tensor and extracting the bulk properties of single representative grains under compression, we propose a model to predict the evolution of K as a function of the sample's solid fraction and a reference state as the applied pressure P tends to zero. The model closely reproduces the trends observed in our numerical experiments confirming the behavior scalability of soft particle assemblies from the individual particle scale. Finally, we present the effect of the interparticle friction on K's evolution and how our model easily adapts to such a mechanical constraint.