  The importance of accurate simulation of the plastic deformation of ductile
metals to the design of structures and components is well-known. Many
techniques exist that address the length scales relevant to deformation pro-
cesses, including dislocation dynamics (DD), which models the interaction and
evolution of discrete dislocation line segments, and crystal plasticity (CP),
which incorporates the crystalline nature and restricted motion of dis-
locations into a higher scale continuous field framework. While these two
methods are conceptually related, there have been only nominal efforts focused
on the system-level material response that use DD-generated information to
enhance the fidelity of plasticity models. To ascertain to what degree the
predictions of CP are consistent with those of DD, we compare their global and
microstructural response in a number of deformation modes. After using
nominally homogeneous compression and shear deformation dislocation dynamics
simulations to calibrate crystal plasticity flow rule parameters, we compare
not only the system-level stress-strain response of prismatic wires in torsion
but also the resulting geometrically necessary dislocation density fields. To
establish a connection between explicit description of dislocations and the
continuum assumed with crystal plasticity simulations, we ascertain the minimum
length-scale at which meaningful dislocation density fields appear. Our results
show that, for the case of torsion, the two material models can produce
comparable spatial dislocation density distributions.
