Constitutive flow law for hydrogel granular rafts near the brittle-ductile transition

TL;DR

This paper proposes a universal flow law for hydrogel granular rafts that captures the transition from brittle to ductile behavior, integrating dry granular rheology with nonlocal and viscous effects based on rotary shear experiments.

Contribution

It introduces a constitutive flow law that unifies the behavior of granular rafts near the brittle-ductile transition, combining multiple rheological effects.

Findings

Flow decays from the interface in the quasistatic regime

Particles remain mobile below the yield stress

Universal flow law across jammed and unjammed regimes

Abstract

Spatially varying flow laws have been identified in dry granular flow, yet their applicability to unjammed suspensions remains unclear. This study demonstrates that the quasistatic suspension flow combines dry granular rheology with nonlocal effects in the shear band and damped viscous flow in the outer creep region. Through rotary shear experiments on a hydrogel granular raft, we observe that the flow decays from the interface in the quasistatic regime, where the particles remain mobile even below the yield stress. These findings suggest the universal flow law across the transition between jammed/brittle granular behavior and unjammed/ductile viscous flow.