RHEOLOGICAL BEHAVIOR OF MILD-STEEL UNDER MONOTONIC LOADING CONDITIONSAND CROSS-LOADING

The rheological behaviour under large strains of mild steel is analyse d for monotonic deformation and after a change of strain path obtained by combining tensile and planar simple shear tests. For monotonic def ormation conventional hardening is obtained and modelled through the e volutionary law of a single parameter identified as the total dislocat ion density. By contrast, for cross-loading the sample exhibits at rel oading a transient softening owing to the development of microbands. T hese microlocalizations of the deformation correspond to the activity of a unique slip system. The instability is attributed to the disappea rance of the dislocation structure generated during the prestrain. The evolutionary laws of structural parameters are used to describe the s oftening process.