Place: MSE 2012, Darmstadt, Germany
The influence of geometrically necessary dislocation density on isotropic and the kinematic hardening during a plastic deformation of crystalline materials have been investigated. It was found that the isotropic hardening amplifies small heterogeneity of the deformation field, whereas the the kinematic hardening tends to smoothen the deformation localization. The observation that grain boundary induced GND density and internal stress are almost independent of grain size implies that the volume fraction of grain boundaries of a polycrystal is a crucial parameter to predict macroscopic mechanical properties such as the yield stress. It was also found that the higher order boundary condition of nonlocal constitutive models is not important for the plastic deformation of a polycrystal when there exists initially a finite density of mobile dislocations in each material point.