The collective motion of defects and their interaction are the basic building blocks for plastic deformation and
corresponding mechanical behaviors of crystalline metals. Especially, dislocations among various defects are the
“carrier” of plastic deformation in many crystalline materials, particularly ductile materials. To get a funda–
mental understanding of plastic deformation mechanisms, it calls for an integrated computational platform to
simultaneously capture detailed defects characteristics across several length scales together with corresponding
macroscopic mechanical response. In this paper, we present a three-dimensional mesoscale defect dynamics
model to directly couple the three dimensional discrete dislocation dynamics model with continuum finite
element method, aiming at capturing both size dependent plasticity at micron-, and submicron scale and
constitutive behaviors at larger scales where such size-dependence disappear. Using non-singular dislocation
theories, our model could accurately consider both short- and long-range elastic interactions between multiple
dislocation segments with even higher computational efficiency than traditional dislocation dynamics simula–
tions, together with the careful consideration of crystal/material rotation in the coupled framework. In addition,
our model could directly model dislocation nucleation from stress concentrators such as a void, crack and
indentor tip, which could allow us to investigate various defects’ motion and their mutual interactions, pre–
dicting macroscopic mechanical response of complex structures. The developed concurrently coupled model
could also consider multiphysical phenomena by solving coupled governing equations in finite element frame–
work, which could shed light on complex defect behaviors under various physical environments.