Two unlike dislocations gliding in parallel slip planes in a channel of a persistent slip band are considered. Initially they are kept apart in straight screw positions. As the dislocations are pushed by the applied stress between two walls in the opposite directions, they bow out and attract one another forming a dipole. With the increasing stress the dislocations become more and more curved, until they separate. The walls of the channel are represented by elastic fields of rigid edge dipoles. The dislocations are modelled as planar curves approximated by moving polygons. The objective of the simulations is to determine the stress in the channel needed for the dislocations to escape one another. The stress and strain controlled regimes considered provide upper and lower estimates of the escape stress. The results are compared with the studies by Mughrabi and Pschenitzka, and Brown and the recent dislocation dynamics estimates. Problems encountered in the dislocation dynamics evaluation of the escape stress are analyzed.
The aim of the paper is to analyze in detail the glide of interacting dislocations by means of a computational model. The model is based on the numerical solution of the evolution equation providing the arc-length parametric description of the dislocations. The governing equation for the dislocation parametrizations incorporates the line tension, the interaction with other dislocations as well as the external forces. In comparison with previously published approaches, the numerical model is derived in a mathematically rigorous way supporting long-term stable behavior and allowing further generalization. The described approach is demonstrated in evaluation of a dislocation bow-out from the channel walls in a persistent slip band and of their mutual interactions. Two different situations are considered: (i) stress-control where the stress in the channel induced by boundary conditions is assumed to be uniform, (ii) strain-control where the sum of elastic and plastic strains is uniform.
Edge dislocation segments bowing out of dislocation walls of persistent slip bands (PSBs) during cycling are experimentally well documented. Instead of dealing with the problem in its complexity a simplified computer simulation of this process is presented. The bowing out segment interacts with the wall of the PSB. The walls are represented by the elastic field of a cluster of edge dipolar loops. Mutual interactions between the loops in the cluster and an interaction between the loop cluster and the bowing out dislocation segments are incorporated in the simulation procedure. The dislocation segments deposited at the walls are trapped in the elastic potential valleys produced by the dipole loops. Our aim is to determine the local shear stress needed to bow out fully the edge dislocation segment from the PSB wall. The obtained result is in reasonable agreement with the local shear stress at the wall deduced from measurements.
To estimate the fatigue endurance limit at the micro-scale two unlike dislocations
gliding in a channel of a persistent slip bands are considered. The dislocations are modeled as
moving planar flexible curves. The objective of the simulations is to determine the averaged
stress in the channel needed for the dislocations to escape one another using statistics of
encounters of such dislocation pairs. We employed an iso-strain approach, i.e. the assumption
that the total strain everywhere in the channel is the same.
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