Element Quality Calculation: Medina

Additional element checks not listed here are not part of the solver’s normal set of checks, and therefore use HyperMesh check methods.

Checks used for both 2D and 3D elements

These checks apply to both types of elements, but when applied to 3D elements they are generally applied to each face of the element. The value of the worst face is reported as the 3D element’s overall quality value.

Check

Description

Aspect Ratio

(Edge Ratio)

The Edge Ratio is calculated as the ratio between an element’s shortest edge and its longest edge; For the sake of consistency, HyperMesh inverts this result (effectively making it the ratio of longest to shortest) and reports the result as the element’s aspect ratio.

Interior Angles

These maximum and minimum values are evaluated independently for triangles and quadrilaterals.

Jacobian

This measures the deviation of an element from its ideal or "perfect" shape, such as a triangle’s deviation from equilateral. The Jacobian value ranges from 0.0 to 1.0, where 1.0 represents a perfectly shaped element. The determinant of the Jacobian relates the local stretching of the parametric space which is required to fit it onto the global coordinate space.

HyperMesh evaluates the determinant of the Jacobian matrix at each of the element’s integration points (also called Gauss points) or at the element’s corner nodes, and reports the ratio between the smallest and the largest. In the case of Jacobian evaluation at the Gauss points, values of 0.7 and above are generally acceptable. You can select which method of evaluation to use (Gauss point or corner node) from the Check Element Settings window.

Length (min.)

Minimum element lengths are calculated using one of two methods:

•	The shortest edge of the element. This method is used for non-tetrahedral 3D elements.

•	The shortest distance from a corner node to its opposing edge (or face, in the case of tetra elements); referred to as "minimal normalized height".

height2closenode

Maximum Angle

The largest angle between adjacent edges of the element is reported.

Minimum Angle

The smallest angle between adjacent edges of the element is reported.

Skew

The element’s interior corner angles are compared to 90 degrees (for quads) or 60 degrees (for trias). The absolute values of these deviations are summed and reported.

Taper

Quadrilateral elements are split into two triangles.

taper_medina

The area of the smaller of the two triangles is compared to the total area of the quadrilateral. In the example above,

Note:

To improve consistency with other taper checks, HyperMesh displays a value of 0.5 minus this value so that 0 implies no taper. However, this is not completely consistent with other taper checks, because in this case taper ranges from 0 (no taper) to 0.5 (full taper), whereas HyperMesh’s own taper check reports a 1.0 for full taper.

Warpage

Elements with more than three nodes are split into triangles. The largest angle between the normals of triangle pairs is reported as the warpage.

Checks Used Only for 3D Elements

Medina does not use any 3D specific checks. HyperMesh uses its own checks instead.