General solution procedures in elasto/viscoplasticity Original Research Article

Constitutive relations and numerical integration algorithms for elasto/viscoplastic problems are investigated. A fully implicit integration scheme is adopted and the relevant expression of the consistent tangent operator for yield criteria and flow functions of arbitrary type is derived by suitably generalizing the approach exploited for rate-independent plasticity. This is achieved by replacing the consistency condition of plasticity with a relation between the viscoplastic consistency parameter and the flow function of the constitutive model in use. The methodology adopted simplifies alternative procedures for the evaluation of consistent tangent operators which necessitate the inversion of a viscoplastic compliance operator. The general expression of the consistent tangent operator is then specialized to the von Mises yield criterion endowed with commonly adopted viscoplastic constitutive models. Numerical examples are finally presented.