limiting number of elements

[kris222]

Hi,
I have been using Nastran to analyse plates.
It seems to work below 11000 elements,
When I use mesh sizes where I reach 11000 elements and I have single subcase, Nastran does not show in output file all supports results, and internal forces seem also to be wrong.
If I have two subcases, then Nastran does not show any results.
I am assuming this is related to number of elements or size for output file.
Is there any flag or way I can change max elements number limit ?
The same plate with eg. 10000 elements works fine (the same size, loads, supports)
Regards,
Kris

[JuanP74]

Hi, maybe a bit late...I do not know if you found a solution but I think I got a workaround. If you send all output requests to the punch file (DISP (PUNCH) = ALL in case control deck for example) then it works. I attach an example for 14800 QUAD4 shells and 2 static subcases (not yet checked modes or buckling solutions). Output can as well be requested using alter and sent to .op2 file which is very convenient if you use pyNASTRAN or other software. Please, try to further test it with more elements and element types and more subcases.
I believe the issue is with the OFP (Output File Processor, in file .../mis/ofp.f

pp01.bdf.txt

BR,
JP.

PS: How do you deal with drilling degrees of freedom in flat plates modeled with QUAD4 shells in COSMIC/NASTRAN?

[JuanP74]

I checked that the output produced, even if it does not lead to error messages it is wrong. This does not happen for small problems like the following.

pp01_medium.bdf.txt

pp01.bdf.txt

It reads another file which is missing.

READFILE COSOUT2

[JuanP74]

Hi, the file is available in op2 file thread, issue #6 here: #6 (comment)

Hi, the file is available in op2 file thread, issue #6 here: #6 (comment)

So, it only useful if you want to output OP2 file. Which one is it? The F12?

[JuanP74]

yes, in fact COSOUT2 is only useful to output op2 for SOL 1. For other SOLs I have created similar alters also in that thread (alters are incomplete, they only request the outputs I was most interested when created them).
I used Fortran unit 12 since it's the usual in MSC Nastran but I think COSMIC user's considered FTN11. It does not matter at all. If you have the wrong assingment in nastran script op2 file will be created with the name "none" in Ubuntu installations.
I attach my modified script (remove .txt extension).

nastran.txt

I used Fortran unit 12 since it's the usual in MSC Nastran

I am under Windows. I got a F12 file. It is binary, but I tried to load it with pyNASTRAN, the program crashed.

I changed to ECHO = SORT, the program stopped very quickly after printing out the GRID info.
If ECHO = NONE, the program will do the solving process for a while and has the result.
Strange.

[JuanP74]

add MAXLINES = 999999 in case control deck, by default printed output is limited to 20000 lines.

[JuanP74]

I used Fortran unit 12 since it's the usual in MSC Nastran

I am under Windows. I got a F12 file. It is binary, but I tried to load it with pyNASTRAN, the program crashed.

check here and if not found report a new issue https://github.com/SteveDoyle2/pynastran/issues

otherwise you can try http://www.m3dfea.com/nastran-support.html, however I think m3d has some issues with QUAD4 elements even if cosmic nastran op2 was written with MSC format

That line 'MAXLINES = 999999' was comment out before.
After remove $, I got GRID & Result. Why you think the result is wrong?

[JuanP74]

check the pp01 example, pp01.bdf is a flat panel (very fine mesh) with a reinforced hole and compression along the 2 vertical edges. It is in equilibrium and SPCFORCES should be zero (almost, in real world) but they are not. Look at results: grids 478 and 576; however if you look at pp01_medium.bdf (exactly same problem with a coarser mesh) the results are as expected (grids 193 and 231).
for the 1/8 hollow sphere just look at the deformation, it does not have physical sense. Also you can check the results with mystran: https://www.mystran.com/

Here is my result. Looks all right.
`pp01_medium
193 G 4.545096E-13 -6.405712E-09 1.346937E-19 0.0 0.0 0.0
231 G 0.0 6.405960E-09 -2.271464E-17 0.0 0.0 0.0

pp01
478 G 0.0 0.0 1.180063E-15 0.0 0.0 0.0
576 G 0.0 0.0 2.409683E-15 0.0 0.0 0.0 `

[JuanP74]

well, this is what I got. I am using the nastran version in ubuntu, which one are you using?

pp01.f06.txt