# CTRIA6 Element Checks and Default Bound Values

## CTRIA6 Element Check

The following qualities of the CTRIA6 element
are checked:

- Aspect Ratio
- This quality is calculated using only the corner nodes. It is defined as the ratio of the maximum side length to the minimum side length.
- Skew Angle
- This quality is calculated using only the corner nodes. It is the
difference between 90 degrees and the minimum of three angles:
`a1`,`a2`and`a3`. These angles are defined, for the CTRIA6 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. - Vertex Angle
- This quality is calculated using only the corner nodes. 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.
- Hoe Normal Offset
- The hoe normal offset is the maximum of its edges normal offset values. See Hoe Normal Offset of 3-Node Edge
- Hoe Tangent Offset
- The hoe tangent offset is the maximum of its edges tangent offset values. See Hoe Tangent Offset of 3-Node Edge

## CTRIA6 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 |

Hoe Normal Offset | - | 0.30 | - | 0.60 | - | 1.0E5 |

Hoe Tangent Offset | - | 0.20 | - | 0.24 | - | 0.25 |

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