Viscoplasticity is a model for rate-dependent plasticity. Rate dependent plasticity is important for (high-speed) transient plasticity calculations. It should be used in combination with a plasticity law. Viscoplasticity influences the stresses via the plastic strains.

The **group_materi_plasti_visco_exponential** model reads

where and are material fluidity constants and is the pressure. This model was first developed for visco-plastic soil behaviour.

The **group_materi_plasti_visco_power** model reads

where (fluidity constant), (reference value for yield function, e.g. the yield stress for Von-Mises plasticity) and (power) are user specified parameters.

tochnog 2001-09-02