Random Analysis in Nastran

NastranQ · Feb 8, 2019

Hi All,

I am running a random vibration analysis on some structure and I am interested in the RMS stress.
I am able to obtain it in the .op2 file by using STRESS(PLOT,CRMS,NORPRINT)=ALL, but the problem is that it also stores the stress results for the preceding frequency response analysis for each frequency increment which makes the file size huge.
Is there any way of retaining only the RMS results in the .op2 file?

Thanks in advance!

NastranQ · Feb 8, 2019

Below is the relevant part of the deck which I am using:

SOL 111

CEND

ECHO = NONE
SPC = 1
METHOD = 1
DLOAD = 10
RANDOM = 30
SDAMPING = 20
FREQ = 40
RESVEC = YES

STRESS(PLOT,CRMS,NORPRINT)=ALL

dfreire · Feb 11, 2019

Hello NastranQ,

I do not know if it is possible to obtain only the RMS in the op2 file. Possibly it can be done, but I will explain what I do int these cases.

What I usually do is to reduce the output RMS using a smaller set that contains all the critical components. If you do not know which ones will be critical, take a look at the FRF and it will give you some clue.

If that is not possible or something else, if you have Altair software there is a tool, called Hvtrans, that reads the op2 file and extracts only the subcases and stresses that you select. It could be the solution.

I hope it helps.

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