  We present a new framework to quantify the effect of hydrogen on dislocations
using large scale three-dimensional (3D) discrete dislocation dynamics (DDD)
simulations. In this model, the first order elastic interaction energy
associated with the hydrogen-induced volume change is accounted for. The
three-dimensional stress tensor induced by hydrogen concentration, which is in
equilibrium with respect to the dislocation stress field, is derived using the
Eshelby inclusion model, while the hydrogen diffusion is treated as a continuum
process. This newly developed framework is utilized to quantify the effect of
different hydrogen concentrations on the dynamics of a glide dislocation in the
absence of an applied stress field as well as on the spacing between
dislocations in an array of parallel edge dislocations. A shielding effect is
observed for materials having a large hydrogen diffusion coefficient, with the
shield effect leading to the homogenization of the shrinkage process leading to
the glide loop maintaining its circular shape, as well as resulting in a
decrease in dislocation separation distances in the array of parallel edge
dislocations. On the other hand, for materials having a small hydrogen
diffusion coefficient, the high hydrogen concentrations around the edge
characters of the dislocations act to pin them. Higher stresses are required to
be able to unpin the dislocations from the hydrogen clouds surrounding them.
Finally, this new framework can open the door for further large scale studies
on the effect of hydrogen on the different aspects of dislocation-mediated
plasticity in metals. With minor modifications of the current formulations, the
framework can also be extended to account for general inclusion-induced stress
field in discrete dislocation dynamics simulations.
