Learning Forum

[solaplusplus]

Hello

Please can someone help me?

I am having mesh failure on the model shown below due to self- intersecting surface. But in design modeler fault detection, I can't find any faults with the model.

 

Thanks,

Simi

[peteroznewman]

Hello,

Please create a Workbench Project Archive .wbpz file by using File > Archive.  Attach that .wbpz file to your post above using the Attach button.

Regards, Peter

[solaplusplus]

Hello Peter,

I have now attached the file.

Thanks,

Simi

[peteroznewman]

Hello Simi,

I see you have a thin walled body with at least 3 different wall thicknesses: 15, 25 and 50 mm, and you have some extra bodies that are different thickness such as 55 mm.

Filling a thin walled solid body with tetrahedral elements is a poor way to make a model. It requires too many elements and might lack accuracy in the results.

It would be much better to replace the the solid body with a collection of surfaces. Each surface is meshed with shell elements that can be assigned the correct thickness. 

Here are the 50 mm walls

Here are the 25 mm walls

Here are the 15 mm walls

The 55 mm wall that joins a 15 mm and 25 mm wall could be left solid or you can just lose the tapered section in this simplified model.

[solaplusplus]

Hi Peter,

Thank you for your response. Please could you advise on creating the surface element on ANSYS, as the 3d model was created using a cad package?  Also is using a thin sweep mesh an alternative option for this?

Thanks.

Simi

[peteroznewman]

Hi Simi,

You make surfaces by creating a plane on the center of the thickness of each wall, and slicing the body. That will create a new face that is the surface to keep. You can do that in the original CAD package that made the solid, or in DM or SpaceClaim. The images in my post above were from the Midsurface tool in the Prepare tab of SpaceClaim, which finds all face pairs in a body that have the same wall thickness. It automatically creates the surfaces needed, though there is some manual trimming needed at the end due to there being multiple thicknesses.

Yes, you could slice and dice each body until there are sweepable bodies. You need to make twice as many planes to do that, one for each side of the wall, but you need to sweep at least two elements through the thickness, so this approach will take longer to solve.

Regards, Peter

[peteroznewman]

Hi Simi,

I looked at your geometry again. If you delete all the operations you made to the imported geometry and set Shared Topology to None on all the parts, then you get almost all the bodies being sweepable.  Therefore, you don't need to do a lot of slicing and dicing. With this approach, you will need to add Bonded Contact to connect the meshes together.

Attached is an ANSYS 19.2 archive that changed the Mesh to force 2 elements by using the Proximity set to Yes and 2 elements across the gap. That makes a more dense mesh than shown below that was created with the Proximity set to No.

[solaplusplus]

Hi Peter,

Thank you very much for your help!

Simi