Nonmonotonic Aging and Memory Retention in Disordered Mechanical Systems

TL;DR

This paper demonstrates non-monotonic aging and memory effects in disordered mechanical systems like crumpled sheets and foams, showing long-lasting memory and scaling behaviors similar to glassy dynamics.

Contribution

It reveals non-monotonic aging and memory effects in mechanical systems, extending glassy dynamics concepts to a-thermal disordered materials.

Findings

Peak-time scales linearly with waiting time

Systems retain long-lasting memory of previous states

Results agree with a theoretical glassy dynamics model

Abstract

We observe non-monotonic aging and memory effects, two hallmarks of glassy dynamics, in two disordered mechanical systems: crumpled thin sheets and elastic foams. Under fixed compression, both systems exhibit monotonic non-exponential relaxation. However, when after a certain waiting time the compression is partially reduced, both systems exhibit a non-monotonic response: the normal force first increases over many minutes or even hours until reaching a peak value, and only then relaxation is resumed. The peak-time scales linearly with the waiting time, indicating that these systems retain long-lasting memory of previous conditions. Our results and the measured scaling relations are in good agreement with a theoretical model recently used to describe observations of monotonic aging in several glassy systems, suggesting that the non-monotonic behavior may be generic and that a-thermal systems can show genuine glassy behavior.