Element Degeneration

Element degeneration is the collapsing of an element by one or more edges. For example: making an eight node element into a seven node element by giving nodes 7 and 8 the same node number.

The use of degenerated elements for fluid applications is not recommended. The use of degenerated elements for assumed strain formulation is not recommended. If they cannot be avoided, any two nodes belonging to a same edge can be collapsed, with examples shown below.

For solid elements, it is recommended that element symmetry be maintained.

For 4 node elements, it is recommended that the special tetrahedron element be used.

Brick elements can be degenerated into other 3D solid elements by repeating nodes numbers in the node_ID input to combine brick corners to together to form another shape. The most common example is a triangular prism pentahedra element, as shown in the next two images but other shapes are shown if needed to connect a complex mesh.

Figure 1. Degenerated 3D Solid Element Examples