ATLAS

IEqua8

The IEqua8 element defines a 8-noded quadrilateral interface element (IE).

This IE can be used as interface between two hex8 or hex8sr elements that share a quadrilateral face.

Stiffness Matrix

See [Franceschini,2020] for details.

Input Notes

In the input file interf_topol must be set for each IE : the element index IE_IND, the element type IE_TYPE = 2, the fault index IE_FAULT, the material index IE_MAT and the nodal connections IE_CON[8].
The nodal connections must have a specific sorting (n1,n2,n3,n4,n5,n6,n7,n8):

             n5 ----------- n8
            /               /
           /     Top       /
          /               /
         n6 ----------- n7


             n1 ----------- n4
            /               /
           /    Bottom     /
          /               /
         n2 ----------- n3

where (n1,n2,n3,n4) are the nodes on the bottom face and (n5,n6,n7,n8) are the nodes on the top face. Defined with \(\mathbf{X}_{i}\) the coordinates of the i-th node, the following equivalences must hold: \(\mathbf{X}_{n1}\) = \(\mathbf{X}_{n5}\), \(\mathbf{X}_{n2}\) = \(\mathbf{X}_{n6}\), \(\mathbf{X}_{n3}\) = \(\mathbf{X}_{n7}\) and \(\mathbf{X}_{n4}\) = \(\mathbf{X}_{n8}\). The bottom face (n1,n2,n3,n4) must have a counterclockwise sorting.

The interface behaviour is defined by the material related to IEMAT_TYPE[IE_MAT] index (see interf_topol and interf_materials input files).

Output Notes

The output in terms of stress and displacements is given in the local reference system:

local_ref