NX 8.5 Advanced Simulation: Hex to Tet

[kyle8888]

I was curious if NX8.5 supported pyramid elements? I would like to transition between a swept hex mesh to a tetrahedral mesh, but can't find any options to do so. From what I've seen on the web it looks like this was an explicit option in 6.5, but that option appears to have gone away. I'm relatively new to meshing in NX so it could be user error.

Thanks,

Kyle Stoker
Structures Engineer
Florida Turbine Technologies, INC.

 

[BlasMolero]

Dear Kyle,
Oh yes!, this is a feature available since a few versions. When you are working with NX Nastran, ANSYS, NX Thermal and Flow, NX Electronic Systems Cooling, or NX Space Systems Thermal as your specified solver, you can use the Transition with Pyramid Elements option in the 3D Tetrahedral Mesh dialog box to create transitional pyramid elements between the tetrahedral mesh and an adjacent hexahedral mesh. Pyramid elements offer several advantages over using rigid elements or multi-point constraint equations to connect dissimilar meses, thus ensuring a conforming mesh.

The key: a Glue Coincident type of mesh mating condition must be defined at the interface between the two bodies to ensure that the nodes on the adjacent hexahedral and tetrahedral meshes match exactly. Then, mesh first one part with TET mesh and the other with HEX, making sure to select the Transition with Pyramid Elements option in the 3D Tetrahedral Mesh dialog box, OK?.

Best regards,
Blas.




~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[kyle8888]

Blas,

The "mesh mating condition" was the step that I was missing. Thank you very much!

Regards,


Kyle Stoker
Structures Engineer
Florida Turbine Technologies, INC.

 

[kyle8888]

Had another question along the same lines as my first post. I have a part which is sliced into a few sweepable areas. I was able to get the pyramid elements to work just fine for this part. I have another, similar part in which I am trying to accomplish the same thing. The problem is when I specify the "mesh mating condition", sweep (with hex mesh) the bodies, and then try and tet mesh the remaining body it fails with an error. When I go back and look at the swept bodies it looks like a face is entirely deleted which causes the tet mesh to fail. I can go back and recreate the body which fixes the missing face, but I am unable to tet mesh the final part. Has anyone seen this?

Thanks,

Kyle Stoker
Structures Engineer
Florida Turbine Technologies, INC.

 

[BlasMolero]

Dear Kyle,
If you add parts to the assembly repeat the meshing sequence from the beginning, the "order" of meshing parts is important, I would mesh first the TET parts and finally the HEX ones.
Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[kyle8888]

Thanks again for the reply Blas, I'll keep that in mind when meshing.

I was able to get around my problem by changing the type of "mesh mating condition". If I use the "glue coincident" option the face on one of the bodies will always be deleted. It's almost like NX is taking the two separate faces from the bodies and combining them into one. If I use the "free coincident" option the faces are retained and I'm able to successfully mesh both bodies with transition pyramid elements.

-Kyle

Kyle Stoker
Structures Engineer
Florida Turbine Technologies, INC.