Mechanical annealing and memories in a disordered solid

TL;DR

This paper explores how mechanical annealing in disordered solids can be optimized to minimize memory content, using novel protocols and characterization methods to understand the underlying rearrangements and stability.

Contribution

It introduces a 'ring-down' protocol for mechanical annealing that reduces memory effects and develops techniques to analyze rearrangement populations in disordered solids.

Findings

Ring-down protocol achieves minimal memory content

Characterization method links rearrangements to response and annealing

Techniques applicable to various glassy and disordered materials

Abstract

Shearing a disordered or amorphous solid for many cycles with a constant strain amplitude can anneal it, relaxing a sample to a steady state that encodes a memory of that amplitude. This steady state also features a remarkable stability to amplitude variations that allows one to read the memory. Here we shed new light on both annealing and memory, by considering how to mechanically anneal a sample to have as little memory content as possible. In experiments, we show that a "ring-down" protocol reaches a comparable steady state, but with no discernible memories and minimal structural anisotropy. We introduce a method to characterize the population of rearrangements within a sample, and show how it connects with the response to amplitude variation and the size of annealing steps. These techniques can be generalized to other forms of glassy matter and a wide array of disordered solids, especially those that yield by flowing homogeneously.