Effect of adhesive interaction on strain stiffening and dissipation in granular gels undergoing yielding

TL;DR

This study investigates how adhesive interactions influence strain stiffening, energy dissipation, and yielding behavior in granular gels, revealing complex nonlinear flow regimes and the role of inter-particle forces through rheology and imaging.

Contribution

It introduces a comprehensive phase diagram and a normalized energy dissipation measure to understand the effects of adhesion on granular gel rheology and yielding.

Findings

Identification of intra-cycle strain stiffening and plasticity regimes

Development of a normalized energy dissipation parameter ($E_N$)

Revelation of irreversible particle rearrangements during yielding

Abstract

Stress induced yielding/fluidization in disordered solids, characterized by irreversibility and enhanced dissipation, is important for a wide range of industrial and geological processes. Although, such phenomena in thermal systems have been extensively studied, they remain poorly understood for granular solids. Here, using oscillatory shear rheology and in-situ optical imaging, we study energy dissipation in a dense granular suspension of adhesive particles that forms yield stress solids far below the isotropic jamming point obtained in the limit of hard-sphere repulsion. We find interesting non-linear flow regimes including intra-cycle strain stiffening and plasticity that strongly depend on the applied strain amplitude ($\gamma_0$) and particle volume fraction ($\phi$). We demonstrate that such nonlinearity over the entire parameter range can be effectively captured by a dimensionless variable termed as the normalized energy dissipation ($E_N$). Furthermore, in-situ optical imaging reveals irreversible particle rearrangements correlating with the spatiotemporal fluctuations in local velocity, the nature of which strikingly varies across the yielding transition. By directly measuring the critical jamming packing fractions using particle settling experiments, we propose a detailed phase diagram that unravels the role of inter-particle interactions in controlling the flow properties of the system for a wide range of $\gamma_0$ and $\phi$ values.