Size effects in dislocation depinning models for plastic yield

Abstract

Typically, the plastic yield stress of a sample is determined from a stress-strain curve by defining a yield strain and reading off the stress required to attain it. However, it is not a priori clear that yield strengths of microscale samples measured this way should display the correct finite size scaling. Here we study plastic yield as a depinning transition of a 1+1 dimensional interface, and consider how finite size effects depend on the choice of yield strain, as well as the presence of hardening and the strength of elastic coupling. Our results indicate that in sufficiently large systems, the choice of yield strain is unimportant, but in smaller systems one must take care to avoid spurious effects.