On the Relation between Two Constitutive Models Frequently Adopted in Viscoplasticity

The constitutive models of plasticity and viscoplasticity are formulated in a unified framework by taking advantage of the appropriate mathematical tools of convex analysis and subdifferential calculus. Two viscoplastic constitutive models frequently adopted in viscoplasticity are analyzed, the Duvaut and Lions viscoplastic constitutive model and the Perzyna viscoplastic constitutive model. In literature these two models are frequently adopted as alternatives. In the present paper it is discussed on the relation between the two models and it is shown that, under certain conditions and assumptions, the Duvaut-Lions model may be considered as derived from the Perzyna model.