A dislocation-based constitutive description for modeling the behavior of FCC metals within wide ranges of strain rate and temperature

In this work a dislocation-based constitutive description for modeling the thermo-viscoplastic behavior of FCC metals has been developed. The constitutive description, which is founded on the concepts of thermal activation analysis and dislocation dynamics, assumes the plastic flow additively decomposed into internal stress and effective stress. The internal stress represents the applied stress required for the transmission of plastic flow between the polycrystal grains and it is defined by the Hall–Petch relationship. The effective stress formulation, which is the main innovative feature of this work, represents the thermally activated deformation behavior. This is defined taking into account the interrelationship between strain rate and temperature, and gathers structural evolution dependence. This structural evolution is described as a function of dislocations density, which acts as internal state variable in the material deformation behavior. A systematic procedure for identification of the material parameters is developed and the model is applied to define the behavior of annealed OFHC copper. The analytical predictions of the constitutive description are compared with the experimental data reported by Nemat-Nasser and Li (Nemat-Nasser, S., Li, Y., (1998). Flow stress of FCC polycrystals with application to OFHC Copper. Acta Mater. 46, 565–577). Good correlation between experiments and analytical predictions is found within wide ranges of strain rate and temperature.

► A dislocation-based constitutive description for FCC metals has been developed.
► An original formulation to describe the thermally activated deformation mechanisms is proposed.
► A systematic procedure for identification of the material parameters is developed.
► The analytical predictions of the constitutive description are compared with experimental data.
► Good correlation between experiments and model predictions is found.