Quantifying the Features of an Amorphous Solid's Local Yield Surface

TL;DR

This study characterizes local yield surfaces in Lennard-Jones glasses, linking features to shear transformation zones and describing their behavior with a combined Schmid-Mohr-Coulomb criterion, enhancing understanding of plastic flow initiation.

Contribution

It introduces a detailed analysis of local yield surface features in amorphous solids and models them with a combined criterion, providing new insights into plasticity mechanisms.

Findings

Local yield surfaces are dominated by regions with positive second derivatives of yield stress.

Features correspond to shear transformation zones with characteristic displacement fields.

A combined Schmid-Mohr-Coulomb criterion effectively describes most features.

Abstract

In two-dimensional Lennard-Jones glasses, mechanical probing reveals that local yield surfaces are dominated by regions with a positive second derivative of the yield stress with respect to the loading angle. Each feature corresponds to a shear transformation zone and a characteristic non-affine displacement field at yield. Most features are well described by a combined Schmid-Mohr-Coulomb criterion parameterized by a weak-plane orientation, a critical stress, and a pressure sensitivity. The resulting parameter statistics clarify how the onset of plastic flow is governed by the population of discrete yielding features encoded in the amorphous structure.