Mesh errors

[george_mcfarlane]

Hi guys,

I am trying to perform some simulations on a part I have been redesigning for my final year project at university, but am having trouble with the meshing of the part. My the original part seems to mesh up fine, but when i try to do a simulation on my new designs the mesh is really chunky and changes the shape of some of the features. I have used the same settings on both mesh's, but they come out different. Have you come across this before? I have attached photos below for reference.

We do not have an FEA simulation paper at my university so I have been trying to teach myself how to do it with tutorials and the videos on autodesk university. I assume this will change the results of the simulation?

The parts were created in Inventor and then imported into fusion.

Any help would be greatly appreciated.

[dsouzasujay]

Hi @george_mcfarlane,

I can clearly see a bad mesh output in the first image, But i cant see the number of nodes and elements created in the both images.

Can you please share the .f3d file (Original and Modified) so that I can see what is happening.

If this model is confidential then you can send this to : sujay.dsouza @ autodesk.com

[george_mcfarlane]

Hi @dsouzasujay

I have attached the .f3d files to look at. I have attached 3. The original file and the bad mesh files are the ones I posted a screenshot of. The 3rd file, v3 good mesh, is another version I imported from inventor this afternoon. For some reason the mesh came out fine on this one. I didn't change anything when I did it. Just imported and ran a simulation with the same constraint and force as the other two.

Any help would be greatly appreciated.

George

[dsouzasujay]

Hi George,

I took the second file (Gearbox plate - production v1 bad mesh v3.f3d ‏4501 KB), and the mesh output was good.

Please find below image.

I tried several times but every time the mesh generated was fine for me.

I don't know why your mesh was bad at the first try.

[Andrew.Sartorelli]

Hi @george_mcfarlane,

I also took a look at the model you uploaded, and I was able to get the same mesh that you had shown. For some reason it is meshing with a voxel mesh instead of a standard mesh. I still haven't determined the cause of this however. One thing you could try would be to remove some of the features from the model. As you can imagine tiny features have a minimal impact on the results generated, so removing some of the fillets and really small extrudes and cuts could help make it easier for meshing.

Regards,

Andrew

[Andrew.Sartorelli · Accepted solution]

Hi @george_mcfarlane,

I had a chance to compare the good mesh part and the bad mesh part. As I had suspected, the poor quality mesh was being caused by small features and faces/surfaces in the model. I put together a quick comparison of the same spot on both models to highlight the difference.

The small surfaces you see present problems for meshing, typically each surface/face will be meshed before being joined together. If you have a really tiny surface that necessitates much smaller elements then the adjacent surface, then forming the transition between the two can cause a poor quality mesh. This becomes especially evident when going to form a volume mesh from the surface mesh. Often times you can get a surface mesh to generate albeit with poor quality, but it's the crucial volume mesh that fails to be generated based on the poor quality surface mesh.

Often times in the simulation world we talk about making a model sim-ready. This is because the CAD model built for producing a production part will have unnecessary details for simulation. Things like fillets, small bodies or extrudes, and other CAD necessities aren't needed to get valid results from a simulation. Taking the time to remove some of these features will often lead to faster simulation run times and better quality meshes.

Best Regards,

Andrew

 
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