Size effects in dislocation depinning models for plastic yield

TL;DR

This paper investigates how finite size effects influence the measurement of plastic yield stress in microscale samples, modeling yield as a depinning transition and analyzing the impact of yield strain choice, hardening, and elastic coupling.

Contribution

It introduces a depinning model for plastic yield and examines finite size effects, highlighting the importance of yield strain selection in small systems.

Findings

In large systems, yield strain choice is negligible.

In small systems, careful selection of yield strain is necessary.

Finite size effects can lead to spurious yield stress measurements.

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.