# Solid elements for incompressible constitutive laws

This branch adds a new family of solid elements and constitutive laws based on a displacement/pressure (u/p-c) formulation.

- hexahedron8upc
- hexahedron20upc
- hexahedron20upcr
- pentahedron15upc
- tetrahedron10upc

Those elements are preferred for Poisson ratios within 0.48 < nu <= 0.5.

Right now, the following constitutive laws are supported:

- incompressible linear elastic isotropic
- incompressible mooney rivlin elastic
- incompressible bilinear isotropic hardening

The following pictures are showing the maximum principal stress of a plain strain example from Klaus Jürgen Bathe with almost incompressible material. Those results were obtained with linear eight node hexahedral elements.