Amorphous Systems in Athermal, Quasistatic Shear

TL;DR

This study uses 2D atomistic simulations to analyze plastic deformation in amorphous materials under athermal, quasistatic shear, revealing localized shear transformations, slip lines, and the insensitivity of plastic behavior to interaction details.

Contribution

It provides a detailed characterization of plastic events, their organization, and scaling, demonstrating the universality of plastic behavior across different interaction potentials.

Findings

Plastic events involve localized shear transformations.

Slip lines span the entire simulation cell.

Plastic behavior is insensitive to interaction potential details.

Abstract

We present results on a series of 2D atomistic computer simulations of amorphous systems subjected to simple shear in the athermal, quasistatic limit. The athermal quasistatic trajectories are shown to separate into smooth, reversible elastic branches which are intermittently broken by discrete catastrophic plastic events. The onset of a typical plastic event is studied with precision, and it is shown that the mode of the system which is responsible for the loss of stability has structure in real space which is consistent with a quadrupolar source acting on an elastic matrix. The plastic events themselves are shown to be composed of localized shear transformations which organize into lines of slip which span the length of the simulation cell, and a mechanism for the organization is discussed. Although within a single event there are strong spatial correlations in the deformation, we find little correlation from one event to the next, and these transient lines of slip are not to be confounded with the persistent regions of localized shear -- so-called "shear bands" -- found in related studies. The slip lines gives rise to particular scalings with system length of various measures of event size. Strikingly, data obtained using three differing interaction potentials can be brought into quantitative agreement after a simple rescaling, emphasizing the insensitivity of the emergent plastic behavior in these disordered systems to the precise details of the underlying interactions. The results should be relevant to understanding plastic deformation in systems such as metallic glasses well below their glass temperature, soft glassy systems (such as dense emulsions), or compressed granular materials.