How to obtain planar stress of specific GRIDPOINT- NASTRAN

[pmn_dv]

Hi everyone, I have been working on NASTRAN for a few months and I have a problem that I would like to bring to your attention. I'm working on a model composed by shell elements and want to obtain the planar stress (in the xy plane of the elements) of some GRIDPOINT that I've specified in a SET. The problem is that I don't know how to manage the STRESS card in the BDF file in order to output what I specified above. I specify that I would like to obtain a numerical output (in the f06 file) and not just a graphical output on the post-processor. Thanks in advance

 

[rb1957]

so you've got a node at the location you want, and you want the stress there ? what am I missing ??

you want to include stress output, maybe you can specify the node ? I'd maybe pull stresses for all the elements that share that node.

maybe Grid Point Force Balance (another output option) would help ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[pmn_dv]

thanks for the answer. I will try to explain more clearly with the following simple model I've built.

https://files.engineering.com/getfile.aspx?folder=53ce754c-e7d0-4dcb-bfdd-7eb5037cde29&file=TEST.bdf

I his example model I've defined a SET of points and I want to obtain the planar stress at these. However I'm not able to set the STRESS card in order to get this result. In the example you can se that the STRESS card is set to obtain the von mises stress of all the model and i know I have to modify the card but I don't know how.
I don't think that the GPFORCE card can help me because it is about forces while I'm looking for stress.
Thanks for your attention

 

[rb1957]

you're using NASTRAN cards I've never (directly) encountered.

you've created Grid Points, right ?
and Elements ?

(I wasn't able to open you bdf, no NASTRAN on my home PC, maybe attach a txt file ?)

have you tried YT ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[pmn_dv]

yes I've searched also in the documentation but i wasn't able to build the right combination for the STRESS card.
If you suggest me to plot the elements stress instead of the grid points one I could try, but my problem with the stress card would persist.
(I've attached the txt file in this reply). Thanks

https://files.engineering.com/getfi...7-824d-4747-9f9e-8a3ee8e3fa73&file=TEST-1.txt

 

[rb1957]

ok, wouldn't that be "STRESS(...) = 1" (not "ALL") ? I've never used SETs or "STRESS". You're not using a pre-processor (like FeMap or SolidWorks) ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[pmn_dv]

yes that ("wouldn't that be "STRESS(...) = 1" (not "ALL")") could work, but the problem is that I want the planar stress, not the one calculated with the von mises criterion.
I use MSC Apex as pre-processor, but it allows only to set the general stress as request. Than I modify the bdf generated by Apex.

 

[rb1957]

what is "planar stress" ? "normal stress" ?

so the issue is with the options you have under this "STRESS" command ? never used it myself.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[pmn_dv]

yes, I'm looking for the y and x components, and I say planar stress because these components lie on the xy plane.

yes I've issues with the command STRESS because I think it's the right card to use but I don't know how

 

[SWComposites]

have you looked at the STRESS case control documentation here:

https://help-be.hexagonmi.com/bundl.../MSC_Nastran_2022.1_Quick_Reference_Guide.pdf

 

[rb1957]

these are normally called "normal stresses" (at least for the direct x- and y- stress), or in-plane stress, or in the case of a 2D element (like a CQUAD) ... stresses.

I'd thought there'd be an "ALL" option ... ie the direct FE results (your "planar stresses"), principal stresses and von mises ?

but yeah like SWC above, look into the manual. I've never used/defined such a card ... my pre-processor (FeMap) handles that drudgery for me.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[pmn_dv]

Thanks everyone for your time, I'll try to read more carefully the Nastran Reference Guide and to do more more attempts with the STRESS card

 

[rb1957]

let us know how you get on.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.