Meshing Issues using Tet elements

[grnlan03]

I have been having trouble getting two annular parts to mesh. I am trying to produce a mesh using tet- elements which will be used in a thermal-mechanical analysis. I can mesh the model when the seed size is large but when I lower it to around 0.005 the model will not mesh and I get an error message that says there was a problem with the boundary triangles in the model. I believe theat it has something to do with the partitions I have applied to several surfaces and cells in the parts.
My questions are:
1. Is there something I am missing in the model that will not allow it to mesh? I.e. a control or setting that I should be changed?
2. I need to apply a surface heat flux to only part of the model which is why I have done the partitioning. Is there a different way to do this without partitioning that will allow me to still only apply a heat flux to part of a surface?
I have attached the .cae file with the seeds and partitions that will not mesh.
Thanks

 

[rstupplebeen]

If you mesh with a smaller seed it can create the mesh. With 0.005 the mesh is very coarse and would probably yield poor results. I tried 0.004 which was still coarse but could mesh.

Since this is basically coaxial cable I would suggest partitioning with the X and Y planes and then you can mesh with a structured hex mesh.

I hope this helps.

Rob Stupplebeen

 

[grnlan03]

Ohh I was actually using 0.0005 not 0.005. That was my mistake in the post. The .cae file should be 0.0005 unless I messed that up as well. Could you maybe look at with the 0.0005 seed value?

I'll also look into the Hex mesh.

Thanks for the help.

 

[rstupplebeen]

I meshed it at 0.0005 with the section cuts I recommended for Hex meshing and it did mesh. 2 million elements sounds like overkill though. What are you trying to model? Continuum shells might me a good option for you. I hope this helps.

http://files.engineering.com/downlo...6-4667-b042-069d16e25e34&file=CoaxialTube.JPG

Rob Stupplebeen

 

[corus]

I can't open the file as it's 6.9.EF-1 or something. Not knowing the boundary conditions though, isn't this a plane strain problem? At the very least, using a hex mesh will halve the number of elements.

Tata

 

[grnlan03]

Rob,
When you partitioned the model on the X and Y plane did you partition the cells in the models or the surfaces? I assume it’s the cells but just want to make sure.

I know the seed size is a bit of an over kill but I'm trying to get mesh independence so I'm just taking it down to explore the numbers. In the final model I should be using something more course.

Will the structured hex mesh have problems with the curved nature of the cylinders? I know there is a curvature control in the seed part dialogue box and I believe this is what controls that. Do you know if that is correct or not?

Corus,
Sorry you could not open the model but sounds like I need to try hex elements.

Thank you all for your help

 

[rstupplebeen]

I partitioned the cells.

I usually start coarse and then refine once everything is working.

I did not see any issues with the hex mesh. I believe the curvature control is to add more elements were curvature is changing rapidly.

I hope this helps.

Rob Stupplebeen

 

[grnlan03]

Partitioning it along the X and Y plane helped a lot, I was able to use a structured Hex-mesh.

I was wondering how you knew to use that approach? I have only been using Abaqus since the beginning of the year and my experience is a little limited. I would like to know for future models.

I am starting a new thread related to convergence issues I am having in a model. It would be great if either one of you could take a look at it.

Thanks for all of the help.

 

[rstupplebeen]

Meshing is one of the 'art' areas of FEA. Basically you are trying to help the auto mesher recognize prismatic shapes. By cutting the tube it created topology with 6 sides similar to a cube. I hope this helps.

Rob Stupplebeen

 

[grnlan03]

Here is another thread I started don't know if any of you would have experiance in this or not.

http://www.eng-tips.com/viewthread.cfm?qid=277382&page=1

Thanks