Modeling of Recovery of State Using the Viscoplasticity Theory Based on Overstress
Unified constitutive models, which do not postulate separate constitutive equations for creep and plasticity but consider all inelastic deformation rate dependent, have been applied to the modeling of transient and cyclic short—term deformation behavior. Their application to modeling long—term creep has been demonstrated in principle and hinges on the introduction of recovery terms in the growth laws for the state variables. After postulating a set of phenomenological indicators of recovery the viscoplasticity theory based on overstress (VBO) for small strain is introduced and the growth law for each of two state variables is augmented by a recovery term. Hypothetical, but realistic material properties are postulated and numerical experiments are performed to simulate the tests which were previously designated as indicators of significant recovery. The results show that each state variable has specific effects and that recovery terms in both state variables are needed to reproduce the significant phenomena.
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