CTRIA3 Element Checks and Default Bound Values

CTRIA3 Element Check

The following qualities of the CTRIA3 element are checked:
Aspect Ratio
The aspect ratio of a CTRIA3 element is defined as the ratio of the maximum side length to the minimum side length.
Skew Angle
The skew angle of a CTRIA3 element is the difference between 90 degrees and the minimum of three angles: a1, a2 and a3. These angles are defined, for the CTRIA3 element, as the smallest of the angles created when a line drawn from a node to the midpoint of the opposing side intersects a line connecting the midpoints of the adjacent two sides. The skew angle has a range from 0 degrees for a perfect triangle to 90 degrees for a collapsed triangle.
SKEW = 90 - MIN(a1, a2, a2)

Figure 1.
Vertex Angle
For each vertex, the angle is measured between its two adjacent edges. The minimum and maximum values of the three nodes are reported for the element.

CTRIA3 Default Bounds

Information Default values for warning message Default values for error message Default values for validity check
Lower Limit Upper Limit Lower Limit Upper Limit Lower Limit Upper Limit
Aspect Ratio - 50.0 - 500.0 - 1.0E5
Skew Angle - 75.0 - 85.0 - 90.0
Vertex Angle 15.0 165.0 3.0 177.0 0.0 180.0

The values used for warning and error checks may be adjusted by the ELEMQUAL Bulk Data Entry, but validity checks are hard-coded.