Memory in nonmonotonic stress relaxation of a granular system

TL;DR

This study shows that granular systems can remember multiple strain states during stress relaxation, with interactions between elements influencing the relaxation behavior, relevant for understanding memory in soft matter systems.

Contribution

It introduces a model for memory in granular stress relaxation and reveals the importance of interactions between elements in the relaxation process.

Findings

Granular packings can store multiple strain memories.

Interactions between elements affect relaxation dynamics.

A corrected model better predicts the relaxation behavior.

Abstract

We demonstrate experimentally that a granular packing of glass spheres is capable of storing memory of multiple strain states in the dynamic process of stress relaxation. Modeling the system as a non-interacting population of relaxing elements, we find that the functional form of the predicted relaxation requires a quantitative correction which grows in severity with each additional memory and is suggestive of interactions between elements. Our findings have implications for the broad class of soft matter systems that display memory and anomalous relaxation.