Contact analyse, NeNastran / Femap 1

[AndyLake]

We use NeNastran V9.0 and Femap V9.1. Does not Femap really show the contact pressure distribution/values? Almost all of our calculation includes the contact surfaces.

 

[fkmeyers]

You should have these in V9. Look for SSHL NORMAL STRESS for the stress and SSHL NORMAL FORCE for the contact force

 

[AndyLake]

-> NeNastran + Femap V9.1 and V9.2 are useless as regards to contact. It is very bad thing because the contact stress and contact distributions are significant part of our calculation.

 

[SWComposites]

Have you talked to Noran technical support? I have found them to be very helpful.

 

[fkmeyers]

We have found the surface contact in NEiNastran to be very helpful. We use it often but it does require some interaction sometimes. There is contact pressure or stress output as I mentioned before. I guess I am not seeing what your issue is specifically. Does the model not complete? Have you tried contacting Noran support directly?

 

[AndyLake]

The analysis is completed successfully without any significant warning. The problem is that Femap does not show the contact pressure. If I run the model by Abaqus or NX/Nastran I can select Contact Pressure from the Contour menu (F5 -> Deformed and Contour Data -> Contour -> Contact Pressure). If I run the model by NE/Nastran there is no Contact Pressure option in Contour menu.

There is a SQUAD MAX NORMAL STRESS in Contour menu but it does not show the contact pressure either.

Of course, I can check the maximum contact pressure from LOG-file (It was LOG-file, if I remember right…), but I should know the contact pressure distribution too.

Is anyone able to look the contact pressure at Femap V9.1 or V9.2 when the model has been calculated by using NE/Nastran?


We took contact to Noran’s dealer, but they have not given an answer yet.

 

[fkmeyers]

SQUAD MAX NORMAL STRESS is useless. You are looking for SSHL NORMAL STRESS. It is in the tree around the displacements and grid forces. Look for id number 305 SSHL NORMAL STRESS. It is there if you have V9 because that is what I am using and I can see it now. This will allow you do either contour the pressure values or do a vector plot of them. The forces normal and shear forces are around there as well.

I would complain to the main tech support (tech@noraneng.com) if their dealer is not helping you.

 

[AndyLake]

We had earlier Femap V9.0. There was SSHL NORMAL STRESS. Now we have V9.2 -> there is no SSHL NORMAL STRESS. That option is removed, why?

I have to complain to the Noran.

 

[NoranTech]

Dear Andy,

There haven't been any changes to FEMAP in regards to displaying SSHL results in going from V9.0 to V9.2. We have confirmed that SSHL results are visible in FEMAP V9.2 with NEiNastran V9.0.

What I would recommend is opening the .nas example problem 6 from our examples folder (C:\Program Files\NEiNastran Engine V9\Example Files\Tutorial Problems\Example Problem 6) into the Editor and running it. Then bring in the model and results into FEMAP and see if you can display the SSHL results. If you can, then the issue you are having is most likely due to your specific model (perhaps you are running it as a linear static solution, or the contact pair is missing, etc).

If you don't see the SSHL results in Example Problem 6, then something is different with your setup (version, etc), since I tested it and found it to work fine.

Thank you,

Noran Support

http://www.nenastran.com

 

[AndyLake]

NoranTech,

I ran the Example Problem 6 with NeiNastran V8.4 and V9.0 and I brought the results into Femap V9.2.

When I ran the problem 6 with V8.4, SSHL results were visible.
When I ran the problem 6 with V9.0, SSHL results were not visible?!

The Analysis Options were same for both version (there were some differences in analysis options between V8.4 and V9.0). You said that maybe something is different with our setup (version, etc). Our NEiNastran version is 9.0.5.475 so we have quite new version (the newest?). I have tried to check all setups and everything should be ok. Some setups have to still be wrong.

Regards,

Andy

 

[fkmeyers]

I suggest you get the latest maintenance update from Noran. I checked my version 9.0 as well and I have SSHL labels appearing.

 

[AndyLake]

I downloaded the newest version of NeiNastran. Now the version is 9.0.2.275. SSHL is visible! Thanks for the hint! I downloaded about two weeks ago too and then the version was 9.0.5.475 and SSHL was not visible.

Now I can look the contact pressure at Femap.

I detect one oddity in Example problem 6. I dare say that the maximum contact stress would be at the contact point of the balls (nodes 8 and 488). When I ran the model, the maximum contact stress was not at the contact point of the balls. Is there one option, which “lightens” the contact at the edge of the model?

I made a few tests and at all of those, the contact stress was low at the edge of the contact area. The contact stress at the edge of the contact area should have been at least as big as the contact stress at the middle of the contact area. Is the purpose to suppress the edge pressure?