Many of the hexahedral and quadrilateral elements in ANSYS allow for degenerate forms. While all of these elements may be defined under a single element type, a user may wish to select only certain types of element shapes (for example, the figure below shows only pyramid elements selected).

This can be quite straightforward to do with an APDL macro. The basic idea is to use *VGET to get the nodes in the I-J-K-L-etc. position. Degenerate elements have duplicate node numbers in certain slots, so by checking against this, one can determine which elements are degenerate. Use of *VMASK allows doing this very quickly with vectors. There is an undocumented *VPUT to use an array as a selection vector to ‘select’ only the desired element shapes with a single command.

Although very simple, the SELECT_HEXPYRA macro demonstrates this technique and how easy it is to implement. This is an example that a user can build upon. Note that the undocumented *VPUT method is not used in the referenced macro, but a *DO loop is used instead.

Pyramids

Pyramids