Viscoplasticity is a theory in
continuum mechanics that describes the rate-dependent inelastic behavior of solids. Rate-dependence in this context means that the
deformation of the material depends on the rate at which
loads are applied. The inelastic behavior that is the subject of viscoplasticity is
plastic deformation which means that the material undergoes unrecoverable deformations when a load level is reached. Rate-dependent plasticity is important for transient plasticity calculations. The main difference between rate-independent plastic and viscoplastic material models is that the latter exhibit not only permanent deformations after the application of loads but continue to undergo a
creep flow as a function of time under the influence of the applied load.