Cohesion-induced hysteresis and breakdown of marginal stability in jammed granular materials

TL;DR

This study investigates how cohesive forces influence the mechanical response and hysteresis in jammed granular materials, revealing that cohesion causes persistent hysteresis and deviations from marginal stability.

Contribution

It extends effective medium theory to include cohesive interactions, demonstrating how cohesion affects stability and hysteresis in jammed granular systems.

Findings

Hysteresis in shear modulus persists in cohesive packings.

Cohesion causes deviations from marginal stability.

Numerical simulations verify the theoretical predictions.

Abstract

The dependence of mechanical properties on microscopic interactions remains a central problem in the physics of disordered solids near the jamming transition. We numerically and theoretically investigate the mechanical response of jammed cohesive granular materials using discrete element simulations and effective medium theory (EMT). We find that the shear modulus exhibits pronounced hysteresis under compression and decompression, even though the interparticle force law itself is strictly history-independent. While such hysteresis disappears for purely repulsive particles when mechanical properties are characterized in terms of pressure, it persists in cohesive packings, indicating that pressure is not a unique state variable for cohesive particles. Extending EMT to cohesive interactions, we show that the functional form of the shear modulus remains the same for both repulsive and cohesive particles, but that attractive interactions violate marginal stability. The resulting deviation from marginal stability generates excess rigidity, as predicted by a scaling relation. This prediction is quantitatively verified by numerical simulations and explains the persistent hysteresis in cohesive packings.