249,409 research outputs found
The gauge theory of dislocations: a nonuniformly moving screw dislocation
We investigate the nonuniform motion of a straight screw dislocation in
infinite media in the framework of the translational gauge theory of
dislocations. The equations of motion are derived for an arbitrary moving screw
dislocation. The fields of the elastic velocity, elastic distortion,
dislocation density and dislocation current surrounding the arbitrarily moving
screw dislocation are derived explicitely in the form of integral
representations. We calculate the radiation fields and the fields depending on
the dislocation velocities.Comment: 12 page
Asymptotic analysis of a pile-up of edge dislocation
The idealised problem of a pile-up of dislocation walls (that is, of planes each containing an infinite number of parallel and identical dislocations) was presented by Roy et al. (Mater. Sci. Eng. A 486:653-661, 2008) as a proto-type for understanding the importance of discrete dislocation interactions in dislocation-based plasticity models. They noted that analytic solutions for the dislocation wall density are available for a pile-up of screw dislocation walls, but that numerical methods seem to be necessary for investigating edge dislocation walls. In this paper, we use the techniques of discrete-to-continuum asymptotic analysis to obtain a detailed description of a pile-up of edge dislocation walls. To leading order, we find that the dislocation wall density is governed by a simple differential equation and that boundary layers are present at both ends of the pile-up
Hydrogen-enhanced local plasticity in aluminum: an ab initio study
Dislocation core properties of Al with and without H impurities are studied
using the Peierls-Nabarro model with parameters determined by ab initio
calculations. We find that H not only facilitates dislocation emission from the
crack tip but also enhances dislocation mobility dramatically, leading to
macroscopically softening and thinning of the material ahead of the crack tip.
We observe strong binding between H and dislocation cores, with the binding
energy depending on dislocation character. This dependence can directly affect
the mechanical properties of Al by inhibiting dislocation cross-slip and
developing slip planarity.Comment: 4 pages, 3 figure
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