It was recalled that the non-uniform distribution of dislocations in metals caused a material anisotropy that was reflected by a strain-path dependence of the mechanical response. Attention was focussed here upon the micromechanical modelling of face-centred cubic metals with a dislocation cell structure. The objective was to enhance a continuum cell structure model. Modelling of the internal stress in dislocation cell structures, with an improved description of the dislocation density evolution enabling a correct prediction of strain path change effects under complete or partial stress reversal. Therefore, attention was concentrated on the dislocation mechanisms accompanying a stress reversal. Physically based evolution equations for the local density of the statistically stored dislocations were formulated to describe the formation and dissolution of a dislocation structure under deformation. Incorporation of these equations in the cell structure model resulted in improved predictions for the effects of large strain path changes. The simulation results showed a good agreement with experimental data, including the well-known Bauschinger effect. The contributions of the dislocation mechanisms and the internal stresses to the resulting macroscopic strain path change effects were analysed. The dislocation dissolution was concluded to have a significant influence on the macroscopic behaviour of face-centred cubic metals after stress reversals.

Modelling the Evolution of Dislocation Structures upon Stress Reversal. E.M.Viatkina, W.A.M.Brekelmans, M.G.D.Geers: International Journal of Solids and Structures, 2007, 44[18-19], 6030-54