摘要：The goal of this work is to provide a general framework for constitutive
viscoelastic and viscoplastic models based on the theoretical background
proposed in Ortiz and Stainier, Comput. Meth. App. Mech. Engng., Vol. 171,
419-444 (1999). Thus, the approach is qualified as variational since the
constitutive updates obey a minimum principle within each load increment. The
set of internal variables is strain-based and thus employs, according to the
specific model chosen, multiplicative decomposition of strain in elastic and
irreversible components. Inserted in the same theoretical framework, the present
approach for viscoelasticity shares the same technical procedures used for
analogous models of plasticity or viscoplasticity, say, the solution of a
minimization problem to identify inelastic updates and the use of exponential
mapping for time integration. Spectral decomposition is explored in order to
accommodate, into analytically tractable expressions, a wide set of specific
models. Moreover, it is shown that, through appropriate choices of the
constitutive potentials, the proposed formulation is able to reproduce results
obtained elsewhere in the literature. Finally, different numerical examples are
included to show the characteristics of the present approach and to compare
results with others found in literature when possible.
