Microplasticity Predictions of r-Values and Yield Loci of Low Carbon Sheet Steels Deforming by <111> Pencil Glide

Abstract

The plastic deformation of low carbon sheet steels has been analyzed using microplasticity models and Hill's theory of anisotropic continuum plasticity. The analytical methods used to determine the crystallite stress states which must be generated for the isostress (lower-bound) and isostrain (upper-bound) cases are briefly discussed and then applied to predict yield loci for three cold-rolled, annealed low-carbon steels (enameling iron, aluminum-killed steel, and interstitial-free steel) whose textures were characterized by crystallite orientation distribution functions. While measured r-values correlate best with upper-bound yield loci predictions for enameling iron, those for the aluminum-killed steels show better agreement with lower-bound yield loci predictions. In the case of the interstitial-free steel, measured r-values could not be accounted for by either upper- or lower-bound predictions. The yield loci measurements and predictions are reviewed in the context of Hill's continuum theory.