Tips & Tricks: Optistruct axisymmetric model definition
Altair EmployeeOptistruct – 2D axisymmetric model definition
Product Version: Optistruct 2019 or above
Topic description: In Optistruct 2019 a new 4 or 8 nodes axi-symmetric element, CQAXI has been introduced. This element can be used together with 3 or 6 nodes CTAXI element to create models for 2d axisymmetric analysis.
Before running this type of analysis extra attention should be taken to check that mesh is properly defined. A list of actions is described below.
- Check for elements normal, all elements must be oriented in the same way. Model in Figure 1 has wrong normal orientation.
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Figure 1: Wrong elements normal orientation |
Figure 2: Correct elements normal orientation |
This will produce a warning message #2501:” # elements had incorrect node numbering sequence and had their nodes renumbered. This will affect the orientation of respective element coordinate systems” that in turn can cause error messages in contact definition.
- Add SYSETTING, AXEGORD card to control numbering sequence of your elements. Depending on card value, node numbering sequence should follow order shown in Figure 3.
Figure 3: CQAXI node numbering
Figure 4: element node numbering sequence with AXEGORD card
- Remember that all the grid points must be in the x-y plane or in the x-z plane of the basic coordinate system with x = r ≥ 0.