  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.
