Inverse Bauschinger to Bauschinger Crossover under Steady Shear in Amorphous Solids

TL;DR

This study reveals how directional memory in amorphous solids, quantified by the Bauschinger effect, can invert depending on deformation history, strain rate, and temperature, linking microscopic plasticity to macroscopic memory behavior.

Contribution

It introduces a phase diagram connecting memory inversion to deformation parameters and identifies plastic healing as a key mechanism for memory inversion in amorphous solids.

Findings

Memory inversion correlates with shear-band morphology.

A critical deformation amplitude governs memory type.

Plastic healing enables memory inversion.

Abstract

Directional memory in amorphous solids is commonly quantified through the Bauschinger effect, yet the observation of the inverse Bauschinger effect suggests that the sign of memory can invert, pointing to distinct underlying plastic organization. Here, we connect directional memory to the nature of yielding in steadily sheared amorphous solids. Using simulations of two-dimensional polydisperse glasses, we show that the type of directional memory (Bauschinger versus inverse Bauschinger) is jointly controlled by deformation history, strain rate, and parent temperature. We identify a critical history amplitude $\gamma_{N,\mathrm{crit}}(T_p,\dot{\gamma})$ and construct a phase diagram that delineates regimes with memory inversion from those showing only conventional Bauschinger response. Microscopically, memory inversion correlates with network-like shear-band morphology and plastic healing, whereas conventional memory is associated with persistent localization and cumulative damage. These results establish directional memory as an order parameter for a shear-rate and annealing-controlled brittle-ductile crossover and suggest that plastic healing provides a generic route to memory inversion in disordered solids.