  Micropillar compression experiments probing size effects in confined
plasticity of metal thin films, including the indirect imposition of
'canonical' simple shearing boundary conditions, show dramatically different
responses in compression and shear of the film. The Mesoscale Field Dislocation
Mechanics (MFDM) model is confronted with this set of experimental observations
and shown to be capable of modeling such behavior, without any ad-hoc
modification to the basic structure of the theory (including boundary
conditions), or the use of extra fitting parameters. This is a required
theoretical advance in the current state-of-the art of strain gradient
plasticity models. It is also shown that significantly different inhomogeneous
fields can display qualitatively similar size effect trends in overall
agreement with the experimental results. The (plastic) Swift and (elastic)
Poynting finite deformation effects are also demonstrated.
