  A novel, concurrent multiscale approach to meso/macroscale plasticity is
demonstrated. It utilizes a carefully designed coupling of a partial
differential equation (pde) based theory of dislocation mediated crystal
plasticity with time-averaged inputs from microscopic Dislocation Dynamics
(DD), adapting a state-of-the-art mathematical coarse-graining scheme. The
stress-strain response of mesoscopic samples at realistic, slow, loading rates
up to appreciable values of strain is obtained, with significant speed-up in
compute time compared to conventional DD. Effects of crystal orientation,
loading rate, and the ratio of the initial mobile to sessile dislocation
density on the macroscopic response, for both load and displacement controlled
simulations are demonstrated. These results are obtained without using any
phenomenological constitutive assumption, except for thermal activation which
is not a part of microscopic DD. The results also demonstrate the effect of the
internal stresses on the collective behavior of dislocations, manifesting, in a
set of examples, as a Stage I to Stage II hardening transition.
