Module viscoelastic

Viscoelastic constitutive models.

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Viscoelastic constitutive models cannot be defined by a Helmholtz free energy density function and viscous dissipation function. These constitutive models are therefore defined by a relation for the stress as a function of the deformation gradient and rate. Consequently, the rate tangent stiffness associated with the first Piola-Kirchhoff stress is not symmetric for viscoelastic models.

\mathcal{U}_{iJkL} \neq \mathcal{U}_{kLiJ}

Traits

• Viscoelastic
  Required methods for viscoelastic constitutive models.