Dislocations Jam At Any Density

TL;DR

This paper investigates how dislocations in crystalline materials jam at any density, revealing that the critical stress for unjamming increases with the square root of dislocation density, contrasting with granular materials.

Contribution

It demonstrates through dislocation dynamics and scaling that dislocations jam at any density, with critical stress scaling as the square root of density, a novel insight into material deformation.

Findings

Critical stress scales with the square root of dislocation density.

Dislocations jam at any density, unlike granular materials.

Material exhibits plastic response below critical stress.

Abstract

Crystalline materials deform in an intermittent way via dislocation-slip avalanches. Below a critical stress, the dislocations are jammed within their glide plane due to long-range elastic interactions and the material exhibits plastic response, while above this critical stress the dislocations are mobile (the unjammed phase) and the material fails. We use dislocation dynamics and scaling arguments in two dimensions to show that the critical stress grows with the square root of the dislocation density. Consequently, dislocations jam at any density, in contrast to granular materials, which only jam below a critical density.