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Subsubsection 4.1.3.16: Neo-Hookean Up Subsection 4.1.3: Unconstrained Materials Subsubsection 4.1.3.18: Coupled Veronda-Westmann

#### 4.1.3.17 Coupled Mooney-Rivlin

The coupled Mooney-Rivlin material describes an unconstrained formulation of the Mooney-Rivlin material. The material type for this material is coupled Mooney-Rivlin. The following material parameters can be defined.
 Mooney-Rivlin c1 parameter [P] Mooney-Rivlin c2 parameter [P] k “Bulk-modulus” [P]
The strain-energy function is given by the following expression. Here, and are the first and second invariants of the right Cauchy-Green deformation tensor and is the determinant of the deformation gradient tensor.
This material model uses a standard displacement-based element formulation, so care must be taken when modeling materials with nearly-incompressible material behavior to avoid element locking. For (nearly-) incompressible materials, use the Mooney-Rivlin material described in Section 4.1.2.7↑.
Example:
<material id="1" type="coupled Mooney-Rivlin">
<c1>10.0</c1>
<c2>1.0</c2>
<k>100.0</k>
</material>


Subsubsection 4.1.3.16: Neo-Hookean Up Subsection 4.1.3: Unconstrained Materials Subsubsection 4.1.3.18: Coupled Veronda-Westmann