page_title: Viscoplasticity
section_title: Elastoviscoplastic hardening solid
hierarchical_section_title: Viscoplasticity / Rheological models of viscoplasticity / Elastoviscoplastic hardening solid
caption_attribution_description: English: This was done on Power Point Presentation.
context_page_description: 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.
  The elastic response of viscoplastic materials can be represented in one-dimension by Hookean spring elements. Rate-dependence can be represented by nonlinear dashpot elements in a manner similar to viscoelasticity. Plasticity can be accounted for by adding sliding frictional elements as shown in Figure 1.
context_section_description: An elastic-viscoplastic material with strain hardening is described by equations similar to those for an elastic-viscoplastic material with perfect plasticity.  However, in this case the stress depends both on the plastic strain rate and on the plastic strain itself.  For an elastoviscoplastic material the stress, after exceeding the yield stress, continues to increase beyond the initial yielding point.  This implies that the yield stress in the sliding element increases with strain and the model may be expressed in generic terms as
  .
  This model is adopted when metals and alloys are at medium and higher temperatures and wood under high loads. The responses for strain hardening, creep, and relaxation tests of such a material are shown in Figure 9.
caption: Figure 9. The response of elastoviscoplastic hardening solid to hardening, creep and relaxation tests.
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