Development and application of an internal state variable constitutive model for deformation of metals

Fred Kocks dedicated his career to the study of deformation kinetics and the implications for the specification of constitutive relations, primarily relating to dislocation glide and dislocation storage. A major theme of this work was the need to evaluate kinetics at a constant material condition – or state. Motivated by the apparent increase in strain rate sensitivity at very high strain rates, a detailed set of experiments was performed to assess the strain and strain-rate dependence of structure evolution in copper. Conclusions of this study are summarized and the ensuing constitutive relations, introduced by Kocks and coworkers, are reviewed. Considerable experience with the application of this constitutive formalism in over twenty pure metals and alloys is reviewed and the question as to the required number of independent variables is assessed.