Tetra Meshing Criteria (Batch Mesh)

Hi all,

I started with 2nd order tetra meshing (Tetra10 or configuration 210) in batch mode i.e. writing tcl script employing Tcl commands for meshing a CATIA solid geometry.

Unfortunately, it seems that it is not possible to set criteria and parameters for 3D meshing (e.g. tetra meshing), and even if the criteria file and parameter file is used (which only provides options for tria and quad elements), it doesn't affect the Tetra mesh quality /emoticons/default_blink.png' alt=':blink:'> and only the surface mesh is monitored by criteria and parameter files.

I am creating Tetra elements by two methods:

1. Directly meshing the solids with Tetra10 elements

2. First creating a skin of Tria6 elements and then creating Tetra10 elements from this skin mesh.

I used the *tetmesh command with suitably selected parameters, so that I can get a nice mesh (with minimum distortion) but finally NASTRAN found that there are some tetra elements with very low internal angles and it marks these elements as 'FAILED' elements and stops the analysis.

I checked the quality parameters for 3D elements (short key: F10), and found that many elements simply fail, and are well far away from the limits e.g. max. size, min size, entered in the tcl script.

Is there any proper way to force HM to respect the limits of 3D mesh properties??

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Altair Forum User

Hi Mubeen,

I think, Most of the elements are failing in tet collapse,.

I think you can try by re-meshing locally by using the option 'TETRA REMESH' in 3D -> Tetra mesh.

It is better you divide the total volume into Sub-Volumes, It will definitely help you to reduce the tet collapse.

Altair Forum User

Thanks Ravi,

the main restriction is that I have to do everything in batch mode (i.e. all tasks should run through Tcl commands). In case of very large/intricate components, the number of elements created, is certainly very huge. So for that case I need to check the elements who fail the tet collapse/aspect ratio and would like to move them to another collector 'failed_elem', so for this purpose I tried to use the following commands (from examples in HyperMesh documentation):

*createmark elements 1 'all'
*createmark elements 2
*elementtesttetracollapse elements 1 $collapse_val 2 2 'Tetra Collapse'
*collectorcreateforpartiallycontained elems 2 failed_elem 0 0 0

BUT: the last command is not available in HyperMesh 11.xx, and I found it only in HM 12.xx documentation. Is there any command/s which could serve the same purpose (i.e. moving the failed elements to another collector??**

Secondly, when I used 'tet remesh' for the failed components, it again issues/uses the command '*tetmesh . . . . ' which was infact used for the previously generated mesh, and nothing is updated/improved (neither in interactive sessions, not in batch mode). What could be the possible alternative?

I thank you again for the response.

** P.S: I found the following alternative command structure for this purpose, in the HM 11.xx documentation example:

To move all elements from comp1 to comp2:

*createmark elems 1 'by collector name' comp1

*movemark elems 1 comp2