Size and boundary effects in discrete dislocation dynamics: coupling with continuum finite element

In this work, we develop a framework coupling continuum elasto-viscoplastic ity with three-dimensional discrete dislocation dynamics (micro3d). The mai n problem is to carry out rigorous analyses to simulate the deformation of single crystal metals (fcc and bcc) of finite domains. While the overall ma croscopic response of the crystal is based on the continuum theory, the con stitutive response is determined by discrete dislocation dynamics analyses using micro3d. Size effects are investigated by considering two boundary va lue problems: (1) uniaxial loading of a single crystal cube, and (2) bendin g of a single crystal micro-beam. It is shown that boundary conditions and the size of the computational cell have significant effect on the results d ue to image stresses from free-boundaries. The investigation shows that sur face effects cannot be ignored regardless of the cell size, and may result in errors as much as 10%. Preliminary results pertaining to dislocation str uctures under bending conditions are also given. Published by Elsevier Scie nce B.V.