Chapter 60 Long-Range internal stresses in deformed single-phase materials: The composite model and its consequences

Abstract

Publisher Summary This chapter presents the experimental observations that proved the existence of deformation-induced long-range internal stresses in deformed metals and that lead to the formulation of the so-called composite model of crystal plasticity, and the consequences. The composite model takes into account the fact that dislocations are usually distributed heterogeneously—for example, in a cell structure. The model therefore considers the local spatial variation of the dislocation density and of the flow stress. In its simplest form, the model treats a deformed crystal as a two-component material consisting of hard cell walls of high local dislocation density, separated by soft cell interiors of low local dislocation density. The most important consequence of the composite model is that, the development of deformation-induced long-range internal stresses (whose magnitude and wavelength correspond closely to observation) follows in a straightforward manner because of the compatibility requirements, when the soft and the hard regions are deformed in parallel. Thus, the model predicts the evolution of an internal back stress in the soft regions and an internal forward stress in the hard regions without requiring the existence of classical dislocation pile-ups as sources of the internal stresses.