Elastic-plastic intermittent re-arrangements of frictionless, soft granular matter under very slow isotropic deformations

How do soft granular materials (or dense amorphous systems) respond to externally applied deformations at different rates and for different system sizes? This long-standing question was intensively studied for shear deformations but only more recently for isotropic deformations, like compression-decompression cycles. For moderate strain rates, in the solid-like state, above jamming, the system appears to evolve more or less smoothly in time/strain, whereas for slow enough deformations, the material flips intermittently between the elastic, reversible base state and plastic, dynamic events. Only during the latter events, the microstructure re-arranges irreversibly. The reversible base state involves both affine and non-affine deformations, while the events are purely non-affine. The system size and rate dependence of the events are studied, providing reference data for comparison in future studies evaluating materials like hydrogel particles.

Automated summary

Soft granular materials exhibit different responses to externally applied deformations at different strain rates and system sizes. At moderate strain rates, the material evolves smoothly, while at slow strain rates, it toggles between an elastic reversible state and plastic dynamic events, causing irreversible rearrangement of the microstructure.