How to understand geometry warnings (G30xx) in Nastran analysis

Autodesk Support

Oct 23, 2024

Products and versions covered

Issue:

During an analysis with Nastran, geometry warnings are given in the log, such as the following:

WARNING G3012: type ELEMENT id HAS A SKEW ANGLE GREATER THAN 65.0
WARNING G3013: type ELEMENT id HAS A TAPER RATIO GREATER THAN 0.8
WARNING G3015: type ELEMENT id HAS AN INTERIOR ANGLE LESS THAN 10.0

where "type" is the element type (tet, tri, quad, etc.) and "id" is the element number.

Solution:

For a description of the geometry checks and the consequences, see the documentation for GEOMCHECK.

The elements causing the problem can be highlighted using one of these methods in Inventor Nastran. Note that locating one highlighted element in a complex mesh can be a challenge. Display the model as a wireframe ("View > Appearance > Visual Style > Wireframe") and hide the mesh ("Autodesk Nastran > Display > Object Visibility > Mesh") to see a highlighted element.
 

Use Check Quality for Mesh

  1. Right-click on "Mesh Model" in model tree, then choose "Check Quality For Mesh".
  2. Select the Quality Parameters based on the warning message.
  3. Click "Check" to generate a list of elements that match the criteria.
  4. Highlight a row or multiple rows in the table, and then click the "Highlight" button. The selected elements will be highlighted in the model.
See Also Check Quality for All Meshes in the Help documentation.
 

Highlight Specified Element

  1. Right-click on "Elements" in model tree, then choose "Highlight". 
  2. Enter one or more element numbers (separated by comma) into the "Entity ID List" box.
  3. Click the "Add" button. Repeat as necessary.
  4. The elements listed in the "Selected Entities" box are highlighted on the model.
See Also Elements in the Help documentation.
 

Locate Element from Node Numbers

In some cases, the element may be too small to see the highlight. In such cases,

  1. Use the element number and the Nastran file to determine which nodes are on the element. See Figure 1.
  2. From the node numbers, locate the coordinates of one (or more) node.
  3. From the coordinates, locate the node on the model. See How to get node coordinates in Nastran In-CAD or Inventor Nastran.

Example commands in the Nastran file

Figure 1: The "C" command for the element type lists the nodes that are on the corners (and other details). These are the most common commands:

  • For solid elements, CTETRA command gives the element number (in column 2) and four corner node numbers (in columns 4-7.)
  • For shell elements, the CTRIA3, CQUAD4, CTRIA6, and CQUAD8 commands give the element number (in column 2) and the 3 or 4 corner nodes (in column 4-6 or 4-7, respectively) depending on whether the element is triangular or quadrilateral and is linear or parabolic element.
 

Products:

Nastran; Inventor Nastran;

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