group_materi_membrane index switch

If switch is set to -yes the $zz$ stress becomes zero in 2D and the $yy$ and $zz$ stress become zero in 1D (in combination with axi-symmetry in 1D, only the $yy$ stress becomes zero since $zz$ is the axi-symmetric direction). If group_materi_membrane is not used the plane strain conditions are used. Always the $z$-thickness is 1. in 3D, and the $y$, and $z$-thickness are 1. in 2D; see however also volume_factor.

The group_materi_membrane option cannot be used in combination with group_materi_elasti_compressibility, group_materi_hyperelasticity and group_materi_viscosity.

The index specifies the element_group, see element_group.