On NonGlide Stresses and Their Influence on the Screw Dislocation Core in BodyCentred Cubic Metals II. The Core Structure
Abstract
The change in core structure of the screw dislocation in a bodycentred cubic lattice subjected to a general applied stress tensor is studied by means of computer simulation. The large variations observed are found not to be correlated with the applied stress, in that the same deformed core structure can be realized by many different combinations of stress components. Instead, the core structure is found to be characterized almost exclusively by the magnitude and orientation of the induced glide strain, with a much smaller dependence on the glide stress. This means that while the force acting on a dislocation is defined by the applied stress, it is the elastic strain within the lattice that determines the resistance to motion. This explains the anomalously large dependence of the Peierls stress upon nonglide components of the applied stress tensor. The Peierls stress varies strongly with the shape of the dislocation core, which depends upon the glide strain. However, the glide strain is in turn dependent on nonglide components of the applied stress by way of anisotropic elastic couplings. Therefore the Peierls stress is itself dependent on the nonglide stresses, to an extent governed by the elastic anisotropy. The possible origin of the straindependence of the core structure in elastic strain multiplet forces (equal and opposite generalized forces acting on the dislocation) is discussed briefly, as are implications for the phenomenon of ductile fracture.
 Publication:

Proceedings of the Royal Society of London Series A
 Pub Date:
 March 1984
 DOI:
 10.1098/rspa.1984.0028
 Bibcode:
 1984RSPSA.392..175D