Computer simulation of high temperature deformation

Abstract

A computer simulation of high temperature creep is made by considering the properties of an array of positive and negative edge dislocations with a common slip system. The dislocations are permitted to glide and climb in response to both the applied stress and the internal stresses which arise from all the other dislocations in the solid. The dislocations can both multiply and annihilate. It is shown that the apparent internal stress, defined as the reduced applied stress for which the creep rate is zero, is closely related to the average value of the internal stresses evaluated at the dislocations. The phenomenon of dislocation annealing is also studied. It is found that the rate of dislocation annihilation depends strongly on the dislocation density. The principal effect of applied stress on dislocation annealing is to increase the rate of annihilation, owing to the greater probability of dislocation-dislocation collisions for moving dislocations. The transient and steady state creep properties have also been studied. We find the dislocation density reaches a steady state value that is proportional to the square of the applied stress. When the dislocations are assumed to have a fixed mobility, the dislocation density changes monotonically from the initial value to the steady state value. It is shown that the dislocation density can be made to rise abruptly with strain and then decrease to the steady state value if the dislocations mobility is assumed to decrease with creep strain.