CHEXA 1st-order (8-noded) Element Checks

The following qualities of the CHEXA 1st-order element are checked:

The aspect ratio of a CHEXA 1st-order element is defined as the maximum aspect ratio among its six faces; each treated as a CQUAD4 element.

The face skew angle of a CHEXA 1st-order element is defined as the maximum skew angle among its six faces; each treated as a CQUAD4 element.

The same vertex angle check is performed for all of the faces, and each is treated as a quadrilateral (CQUAD4) element. The minimum and maximum values reported for the element.

The face warpage of a CHEXA 1st-order element is defined as the maximum warpage among its six faces; each treated as a CQUAD4 element.

The twist angle of a CHEXA 1st-order element is defined as the maximum rotation of one face with respect to its opposite face. The calculation is done as follows:

For each face, define two diagonal vectors as:

D1 = 0.25 * (PL1 + PL2)
D2 = 0.25 * (PL1 + PL2)

Where, PL1 and PL2 are the place vectors of the face treated as CQUAD4. See the definition of reference plane for quadrilateral element or face.  The diagonal vectors for a planar parallelogram can be show below:

Then, for each pair of opposing faces, a reference plane that is perpendicular to the axis connecting the centroids of the faces is constructed. The diagonal vectors D1 and D2 of each of the two opposite faces are projected onto this reference plane. The angles between the projected and the projected are computed as t1 and t2. The maximum of t1 and t2 is defined as the relative rotation between these two opposite faces (TAF). Finally, the twist angle (TA) of a CHEXA 1st-order is calculated as the maximum relative rotation of its three pairs of opposing faces.

An edge angle is the absolute value of the angle between two faces sharing a common edge, subtracted from 90 degrees. For warped faces, the projected planes are used to compute the face normals used for the angle calculation. The edge angle of a CHEXA 1st-order is defined as the maximum edge angle in the element.

 

CHEXA 1st-order Default Bounds

 

CHEXA 2nd-order (20-noded) Element Checks

The following qualities of the CHEXA 2nd-order element are checked:

This quality is calculated using only the corner nodes. Its definition is the same as that used for the CHEXA 1st-order element.

This quality is calculated using only the corner nodes. Its definition is the same as that used for the CHEXA 1st-order element.

This quality is calculated using only the corner nodes. Its definition is the same as that used for the CHEXA 1st-order element.

This quality is calculated using only the corner nodes. Its definition is the same as that used for the CHEXA 1st-order element.

This quality is calculated using only the corner nodes. Its definition is the same as that used for the CHEXA 1st-order element.

This quality is calculated using only the corner nodes. Its definition is the same as that used for the CHEXA 1st-order element.

The hoe normal offset is the maximum of its edges normal offset values. See the definition of hoe normal offset of 3-node edge.

The hoe tangent offset is the maximum of its edges tangent offset values. See the definition of hoe tangent offset of 3-node edge.

 

CHEXA 2nd-order Default Bounds

The values used for warning and error checks may be adjusted by the ELEMQUAL bulk data entry, but validity checks are hard-coded.

See Also:

Element Quality Check