Reflections on frequently used viscoplastic constitutive models

Abstract

The constitutive problems of plasticity and viscoplasticity are considered in detail via an internal variable formulation. The treatment is set within the framework of the generalized standard material model and exploits the appropriate mathematical tools of convex analysis and subdifferential calculus. Furthermore two frequently used viscoplastic constitutive models are analyzed, the Perzyna viscoplastic model and the Duvaut-Lions viscoplastic model. In the existing literature these two models are frequently used as alternatives. In the sequel interesting relations between them are outlined and it is shown that, under particular hypotheses, the Duvaut-Lions model may be regarded as derived from the Perzyna model.