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Mesh Quality

Creator
Creator

Experts,

 

I have a 2D mesh which has 0 element quality error but everytime I mesh it with tet4 and change to tet 10 and run the analysis I get an AR more than 100 error! I then manually clean up these elements before running the analysis again. Is there any way to adjust the mesh quality for the 3D mesh before meshing so that this quality error can be elemenated? 

 

Thank you!

4 REPLIES

Re: Mesh Quality

Siemens Phenom Siemens Phenom
Siemens Phenom

The 2-D surface mesh could be fine, i.e. if they're triangles, they can all be well shaped, but when you go to tetras, if the triangles are close to crossing, the resulting tetrahedrons can be poorly shaped.  If you'd like to send me the 2-D mesh, I'll take a look at it -

 

sherman dot mark at siemens dot com

 

Mark.

Re: Mesh Quality

Creator
Creator

I am sorry, I cannot share the model due to my company's confedentiality. I have all my elements above min size of 0.5mm. My mesh size is 2.5mm and my AR is 5. I meshed it in HyperMesh and imported the mesh into Femap to do the tetrameshing. 

Re: Mesh Quality

Phenom
Phenom
If you mesh with Tet4 and change to Tet10, then you have the option to move midside nodes onto geometry. If you chose that, you might need to not do that. But perhaps if it came from Hypermesh, I assume there is no geometry? Also, what format did you use to transfer from Hypermesh? If just a text format like Nastran .dat, is it small field (8 character field width). If so, is the model quite a long way from the origin (ie. small numbers at large distances)? If so, you may need to use large field (16 character field width) format.
You can use the Locator in the Meshing Toolbox (dropdown in the 2nd icon on the Meshing Toolbox menu) to locate Elements of poor quality (eg. via Aspect Ratio or Jacobian). As mentioned above, you could have excellent triangle elements, but very poor solid elements without too much trouble. For example, a triangular surface mesh of a sharp knife blade could have perfect surface elements, while the tet mesh would be poor due to very thin elements. If you use the Locator in the Meshing Toolbox, you should be able to identify why the problem is occurring.

Re: Mesh Quality

Creator
Creator

Thats right. I don't have geometry once I import the small size 8 character .dat file into Femap. Yes the model is long away from the origin too as out CAD guys do the design modeling that way. I will try the locator option like you said, but I have never used the meshing toolbox before in Femap. I am trying to learn your tool better as it gives us better results. Can you please break down the steps on how do I use the locator in the meshing toolbox?