The Hyperelastic Material subnode adds the equations for hyperelasticity at large strains. Hyperelastic materials can be suitable for modeling rubber and other polymers, biological tissue, and also for applications in acoustoelasticity. The Hyperelastic Material is available in the Solid Mechanics and Membrane interfaces. This material model requires the Nonlinear Structural Materials Module.

When a hyperelastic material is included in your model, all studies are geometrically nonlinear. The Include geometric nonlinearity check box in the study settings is selected and cannot be cleared.

Select a hyperelastic Material model from the list and then go to the applicable section for more information.

All hyperelastic material models have density as an input. The default Density ρ uses values From material. For User defined enter another value or expression.

For Neo-Hookean you can use a mixed formulation by adding the negative mean pressure as an extra dependent variable. For this case, select the Nearly incompressible material check box. Then if the check box is selected, enter a value for the Initial bulk modulus κ.

The default values for both Lamé parameter λ and Lamé parameter μ use values From material.

For St Venant-Kirchhoff you can use a mixed formulation by adding the negative mean pressure as an extra dependent variable. For this case, select the Nearly incompressible material check box.

The default values for both Lamé parameter λ and Lamé parameter μ use values From material.

For Mooney-Rivlin, two-parameters the Model parameters C10 and C01 both use values From material. Enter the Initial bulk modulus κ.

For Mooney-Rivlin, five-parameters the Model parameters C10, C01, C20, C02, and C11 all use values From material. Enter the Initial bulk modulus κ.

For Mooney-Rivlin, nine-parameters the Model parameters C10, C01, C20, C02, C11, C30, C03, C21, and C12 all use values From material. Enter the Initial bulk modulus κ.

For Yeoh the Model parameters c1, c2, and c3 all use values From material. Enter the Initial bulk modulus κ.

For Ogden you can use a mixed formulation by adding the negative mean pressure as an extra dependent variable. For this case, select the Nearly incompressible material check box.

In the table for the Ogden parameters, enter values or expressions in each column: p, Shear modulus (Pa), and Alpha parameter.

If the Nearly incompressible material check box is selected, also enter the Initial bulk modulus κ.

For Storakers, in the table for the Storakers parameters, enter values or expressions in each column: p, Shear modulus (Pa), Alpha parameter, and Beta parameter.

For Varga the Model parameters c1, c2, and c3 all use values From material. Enter the Initial bulk modulus κ.

For Arruda-Boyce you can use a mixed formulation by adding the negative mean pressure as an extra dependent variable. For this case, select the Nearly incompressible material check box.

The default values for the Macroscopic shear modulus μ0 and the Number of segments N use values From material.

If the Nearly incompressible material check box is selected, also enter the Initial bulk modulus κ.

For Gent the default values for the Macroscopic shear modulus μ and the model parameter jm is to use values From material. Enter the Initial bulk modulus κ.

For Blatz-Ko the Shear modulus μ and the Model parameters β and φ all use values From material.

For Gao the Model parameters a and n all use values From material.

For Murnaghan the Murnaghan third-order elastic moduli constants l, m, and n and the Lamé parameters λ and μ use values From material.

For User defined you can use a mixed formulation by adding the negative mean pressure as an extra dependent variable. In this case, select the Nearly incompressible material check box.

If the Nearly incompressible material check box is selected, enter the Isochoric strain energy density Wsiso and the Volumetric strain energy density Wsvol.

If the Nearly incompressible material check box is not selected, enter an expression for the Strain energy density Ws.

Select the Calculate dissipated energy check box to compute the energy dissipated by Plasticity.

 Solid Mechanics>Material Models>Hyperelastic Material
 Membrane>Material Models>Hyperelastic Material

Physics tab with Solid Mechanics selected:
Domains>Material Models>Hyperelastic Material

Physics tab with Membrane selected:
Boundaries>Material Models>Hyperelastic Material