Patran solid mesh :(

[rm447]

Hello, I have some geometries in STL and IGES format that were created using a medical image procesing program from MRI scans. Patran does not recognize them as solids so I can not do a solid mesh. How do you get around this problem?
Thanks!

 

[Onda]

1- Use mesh on mesh to recreate a good tria mesh of your stl file.
2- Verify that your boundary is perfectly closed. Else, modify your mesh until You see any free edge.
3- Change the topology of your mesh from tria3 to tria6.(under Modify> Element> Edit> Type
4- Create the solid mesh using: Creat>Mesh>Solid;
Element shape>Tet; Mesher>TetMesh; Topology>Tet10;
Select all the shell elements previus created and mesh them!

For the Iges file, You could use the same procedure or You can try to close the surface onto a solid using Geometry>Create>Solid>B-Rep and then mesh the solid.

Regards

Onda

 

[rm447]

Hi Onda, thanks for your response

 

[fl11]

Hi,

I would like to add to that thread. I have a very complexe 3D geometry with a lot of surfaces. Actually, only few of those surfaces are really of some interest to me.

I want to do a 3D FEA. I would like to know if there is any easy way to refine the 3D solid mesh on those specific surfaces without having to mesh each surface individually which would take forever and then mesh with TET10 elements.

Also, the surfaces on the solid are usually not biparametric so an isomesh is impossible and then controlling the mesh is harder.

I have heard that Patran was pretty good in terms of 3D meshing, but so far, I can't see why one would think that. Unless I am missing something.

Any advices?

Thank you very much.

 

[Onda]

Hi, could you post an image of your geometry to better understand?

Onda

 

[fl11]

Here is a pictures of the geometry, hope this helps.

 

[Onda]

Hi Francois,

If you have your solid model in Catia (isn't it?), you should remove all unnecessary fillet and radius and try to import a easier model to Patran.

Try to change the tolerance (Preference>Global) when importing to Patran in way to obtain all edges coincident. Then Patran should recognize as solid and mesh it without problems.

If Patran do not recognize as solid and You don't have any way to do it then:

Mesh the model with the sheetbody option (using Tria3).
Using sheetbody you could mesh many surface as only one.
Seed the mesh where edges are non coincident in way to obtain a closed shell mesh.
Then use the previous posted procedure to obtain a solid Tet10 mesh from the shell Tria3 mesh.
I'm afraid that with Patran You couldn't mesh your model with Isomesh.

Regards

Onda

 

[fl11]

Onda

Thanks for the answer. The problem with that model is not that Patran do not recognize the solid. It does and I can mesh it using TET elements without too much problems.

What I am trying to do, is to refine that TET10 mesh on specific surfaces or portion of the geometry since high stresses are found only at some few specific locations. For now, I haven't found any possibility to refine localle a 3D mesh. Is it at all possible?

I will try the sheet body option see what I can do with it.

 

[Onda]

Hi Francois,

Sorry, I misunderstood your point. . .

You could try, if you have a solid, to make a mesh seed on borders of surface that you want to refine. In this way you could force the dimensions of elements close to the borders.
You should also reduce the Minimum edge length to 0.1* global edge length.
If this is not enough you should go for the long way. .
Mesh using tri elements and then convert to solids.
Using shell elements you are able to refine any location you want but for sure it take a lot more time!