A Viscoelastic-Plastic Constitutive Model with a Finite Element Solution Methodology

Abstract

Abstract : A textbook style development of viscoplasticity is presented. For completeness, the report also includes a detailed review of plasticity and viscoelasticity. The combination of plasticity and viscoelasticity is the basis for the so-called viscoelastic-plastic model developed herein. Other combo- viscoplastic models are also introduced. Each constitutive model is introduced with conceptual one-dimensional stress-strain models and then generalized for multidimensional stress space. Furthermore, each model is cast in an incremental form appropriate for numerical solution techniques. Finite element algorithms are outlined for incorporating these nonlinear constitutive models into boundary value problems. In particular, tangent stiffness and initial strain methods are discussed. The viscoelastic-plastic model is compared to experimental data for plexiglas and sea-ice to illustrate the versatility of the model in replicating nonlinear creep and flow of these materials. Moreover, the identification of the model parameters are shown to be no more difficult than the identification of parameters for the classical theories of plasticity and viscoelasticity.