Mechanical noise dependent Aging and Shear Banding behavior of a mesoscopic model of amorphous plasticity

TL;DR

This paper investigates how aging influences shear band formation and localization in a mesoscopic amorphous plasticity model, revealing that older systems tend to form more localized shear bands with longer stress correlations.

Contribution

It introduces a model incorporating aging effects into amorphous plasticity, demonstrating how initial high yield stress states lead to spontaneous shear band formation and increased localization.

Findings

Older systems form more localized shear bands.

Stress correlation time diverges with aging.

Lower slip increments increase localization and decorrelation time.

Abstract

We discuss aging and localization in a simple "Eshelby" mesoscopic model of amorphous plasticity. Plastic deformation is assumed to occur through a series of local reorganizations. Using a discretization of the mechanical fields on a discrete lattice, local reorganizations are modeled as local slip events. Local yield stresses are randomly distributed in space and invariant in time. Each plastic slip event induces a long-ranged elastic stress redistribution. Mimicking the effect of aging, we focus on the behavior of the model when the initial state is characterized by a distribution of high local yield stress values. A dramatic effect on the localization behavior is obtained: the system first spontaneously self-traps to form a shear band which then only slowly widens. The higher the "age" parameter the more localized the plastic strain field. Two-time correlation computed on the stress field show a divergent correlation time with the age parameter. The amplitude of a local slip event (the prefactor of the Eshelby singularity) as compared to the yield stress distribution width acts here as an effective temperature-like parameter: the lower the slip increment, the higher the localization and the decorrelation time.