The null material model allows equations of state to be considered without computing deviatoric stresses.

This material model is useful for modeling contact surfaces via shell elements which are not part of the structure, but are necessary to define areas of contact within nodal rigid bodies or between nodal rigid bodies. Shells that use this material type are bypassed in the element processing.

The mass of the shell elements is computed and added to the nodal points that define the connectivity. The Young's modulus and the Poisson's ratio are used only for setting the contact interface stiffness.