Improve Tet mesh quality - Cube with multiple spheres

[Brian Nguyen]

Hi All,

I am working on modelling of a cube with multiple spheres which induces extremely complex geometry.
Using free mesh provided in Abaqus, I am able to generate the tetrahedral mesh (C3D4 element

However, it is very bad quality mesh, there are many distorted elements (~500 element). I think it is impossible to use Mesh Edit to manually edit each element.
I've tried Virtual Topology. It doesn't work well. And the geometry is too complex for Partitioning.
Could you please suggest any solution to obtain a quality mesh for this geometry?
In case you are interested, I upload .sat file of this model.
Thanks.

 

[Mustaine3]

What is your expectation? You will always have elements with warnings when meshing a complex geometry. Especially when it's a very irregular and partially thin walled solid. So if you have no error and 0.1% warnings, then this isn't a major problem. Just make sure, that you have good elements in regions where you expect large distortions and where you want to have a closer look at the stresses. And be careful with linear tets.

 

[Brian Nguyen]

Thanks Mustaine3 for your suggestion.
I did run a test and it seems to be good although with element distortion warning.
Btw, Can you explain more about "be careful with linear tets"?
I still don't understand your warning about C3D4 element?
Thanks.

 

[Mustaine3]

The formulation of linear tets is too stiff. In general - not only in Abaqus.
For realistic results you should use parabolic tets.

 

[Brian Nguyen]

Thanks Mustaine3.
I thought linear tet is only stiff for bending case.
But I did a quick search and linear tet certainly is too stiff as you said.
Thank you.