Meshing Problem 2D shellelement and offset surface

[Anonymous]

Hello there,

once again i have a problem with nastran in cad.

I want to do a linear static analysis with shell elements. I have loaded my geometry as 3D solid in nastran. Then I used the offset surface command to create a surface model, which I then want to mesh.(In the 3D model I made previously defined surfaces with the Separate command). After idealizing and the first meshing, strange things happen. For example, when I remesh, individual surfaces or idealizations are not meshed.This is only possible again when I completely redefine the idealization again!

With every new definition the surface numbers seem to change... In the meantime I have reached high surface numbers. Also the defined boundary conditions and forces must be redefined, or lose their assignment. Additionally I get many different error messages... I can't reproduce all of them right now. It seems to me that nastran is constantly redefining or renaming the previously defined offset surfaces.

I use Nastran in CAD 2018
If necessary I can upload the model.

Thanks a lot!
Alex

[Anonymous]

Edit: Model attached

[benoit.neu-faber]

Hallo Alexander,

It's not clear for me when you say that you use the separate command.

I also almost never use offset surfaces. Why do you use this ?

Best would be to upload a model.

Best Regards

Benoit Neu-Faber

INNOSIM https://servicesmarketplace.autodesk.com/provider/public/innosim

Autodesk Service Provider / NASTRAN Trainer

https://www.linkedin.com/in/benoit-neu-faber/

[Anonymous]

Hello @benoit.neu-faber ,

I uploaded the modell. (see first answer)

I have a solid geometry as a reference. I wanted to use the outer contour as surfaces to create my model. In the 3D model I have divided surfaces (inventor command) to be able to define different entities afterwards.

[Anonymous · Accepted solution]

Update:

i created a surfacemodel. Everything works so far...
i found out: If you touch the Surface offset entity in the modellbrowser nastran loses (some) surfaces whitch result in broken idealisations.

For me this means: never use surface offset, instead create surface models!
It's a shame, since this tool worked very well up to then.

[benoit.neu-faber · Accepted solution]

Hi Alexander,

I didn't had the time to have a look to your model so far.

Creting a surface model is a way of dealing with welded sheetmetal construction.

But using midsurface without offset is probably the fastest. The gap created due to the thikness can be closed by contact solver that is very powerfull.

Please accept solution and give likes if applicable

Benoit Neu-Faber

INNOSIM https://servicesmarketplace.autodesk.com/provider/public/innosim

Autodesk Service Provider / CFD Trainer

https://www.linkedin.com/in/benoit-neu-faber/