Topics covering the following general categories of nonlinear material models are available:
8.4.1.1. Plasticity
8.4.1.2. Hyperelasticity Material Model
8.4.1.3. Bergstrom-Boyce Hyperviscoelastic Material Model
8.4.1.4. Mullins Effect Material Model
8.4.1.5. Anisotropic Hyperelasticity Material Model
8.4.1.6. Creep Material Model
8.4.1.7. Shape Memory Alloy Material Model
8.4.1.8. Viscoplasticity
8.4.1.9. Viscoelasticity
8.4.1.10. Swelling
8.4.1.11. User-Defined Material Model8.4.1.1. Plasticity
To learn about the material model options for describing plasticity behavior, see Rate-Independent
Plasticity in the Material Reference.
8.4.1.2. Hyperelasticity Material Model
A material is said to be hyperelastic (TB,HYPER) if there exists an elastic potential function (or strain
energy density function), which is a scalar function of one of the strain or deformation tensors, whose
derivative with respect to a strain component determines the corresponding stress component.
Hyperelasticity can be used to analyze rubber-like materials (elastomers) that undergo large strains and
displacements with small volume changes (nearly incompressible materials). Large strain theory is required
(NLGEOM,ON). A representative hyperelastic structure (a balloon seal) is shown in Figure 8.9: Hypere-
lastic Structure (p. 202).
Figure 8.9: Hyperelastic Structure
All current-technology elements except for link and beam elements are suitable for simulating hypere-
lastic materials.
The material response in hyperelastic models can be either isotropic or anisotropic, and it is assumed
to be isothermal. Because of this assumption, the strain energy potentials are expressed in terms of
strain invariants. Unless indicat ed otherwise, the hyperelastic materials are also assumed to be nearly
or purely incompressible. Material thermal expansion is also assumed to be isotropic.
Support is available for several options of strain energy potentials for simulating of incompressible or
nearly incompressible hyperelastic materials. All options apply to the elements listed in Material Model
Element Support for hyperelasticity.
The Mooney-Rivlin hyperelasticity option (TB,MOONEY) also applies to explicit dynamic elements.
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