strength ratio in a random patran-nastran analysis

[Fra22Pul]

Good morning to all, it is the first time I write in this forum so I introduce myself. I am a student at the last year of aerospace engineering and after following a course on solidworks I am following a course on patran-nastran.

I modeled a frame consisting of a c beam and a pipe made of composite material, I did a random analysis (using the patran random tool) imposing a psd where the frame is bound and I got psd and stress at the points of my interest (I attach an image of the model).

I would kindly ask if someone knows how to view strength ratio. to calculate and display them I added the command param,srcomps,yes to the .bdf file (which allego) but it seems not to work. stength ratio do not appear in the .f06 file. in case they are in the xdb file, how can I view them in patran? until now to view the results of random analysis I have always uploaded the xdb file to patran in the xy-plot and rms-analysis menus in the patran random tool.


If anyone could solve this problem, I'd be grateful, thank you very much.

 

[Onda]

As long as I'm taking you back to a static or a non-linear, I don't know if it's valid for the type of analysis you're doing.
the ratio strength writes it in f06 but not in the file of the graphic results, so you can't plot it.
at most you can plot the failure index, which depending on the type of criterion adopted, is in relation to the strength ratio.

 

[Fra22Pul]

Thanks for the answer, yes indeed with the command I used in a static analysis I could plot even the strength ratio (I attach photo), while with this type of analysis I can not. the f06 file in this case is very short, while the results are contained in the xdb.

 

[Onda]

You probably can't get them out of your analysis. but the deformed you have?

 

[Fra22Pul]

Yes yes I have both accelerations and tensions and deformations, and I can plot them, the result file (xdb) is almost 3gb..

 

[Onda]

you can apply the deformations as a shift imposed on the knots and turn a static from your analysis, remember to leave at least one node without shifting imposed, otherwise nastran has nothing to solve. then post processing as if it was a static.
What are you using? msc? Nx?

 

[Fra22Pul]

I am using nastran msc, I had tried this strategy using tensions and not deformations because the data on failure of my material are in terms of stress, but I had difficulty applying the load conditions. I will try to use deformations thank you so much! basically I have to do a field with fem data and then use it in input on a static analysis right?

 

[Onda]

you have to apply nodes deformations, such as deformations imposed in a static analysis, the model will assume the corresponding tensions, but doing it with a static, you can also get the failure index / strength ratio. In addition, the solution is very rapid, as deformations are already imposed. Remember to leave at least one node without imposed deformation, otherwise you have error.

 

[Fra22Pul]

Thank you very much! by tomorrow I try

 

[Fra22Pul]

I did not succeed in the way you recommended me but solved by changing the output format, in the bdf I forced the writing of the results in the f06 and the creation of the h5 file instead of having the data in the xdb. with the command I used to create the Sr but I couldn't just pull out the data. Thanks anyway!

 

[Onda]

then doing the results in hdf5 format you managed to plot strength ratio?
It's just that nastran allows it, I just updated to 2020 and I didn't know it, first I used 2014 and didn't do it, plotted only failure index. I'll try and thank you.

 

[Fra22Pul]

Yes exactly, happy to have made you discover something new

 

[Onda]

Yes, in fact plotting strength ratio has always been a problem. paran first plotto only failure index and strength ratio put them only in f06. I used an alter, which is a modification of the nastran routine, to write the strength ratio instead of failure index in the output file op2. recently passed to hdf5 as output format and it is seen that with this format they decided to pull out also strength ratio. very useful to know. Thank you.

 

[boraborazz]

I did not succeed in the way you recommended me but solved by changing the output format, in the bdf I forced the writing of the results in the f06 and the creation of the h5 file instead of having the data in the xdb. with the command I used to create the Sr but I couldn't just pull out the data. Thanks anyway!

Hi, could you share your experience? How did you end up? I have your own problem, too.
I can't view strength ratio by doing a random analysis with composite materials. with what command and how did you create the h5 file instead of the xdb? I can't, thank you very much

 

[Onda]

insert into the bulk the following line
mdlprm,hdf5,1