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      Please click here for a short but important announcement   03/26/17

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francois.B

Random Fatigue Analysis

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Hello guys,

I'm trying to do a Random fatigue analysis thanks to Optistruct. So first of all, I know that 2017 version has its own module which does this kind of analysis, and I already did it. 
I'm now trying to compare Optistruct results with a VBA code I did.
So here are the step I did:

- FRF and Random Subcases (with RANDPS, TABLED1 etc)
- I ask for STRESS PSDF .Peak files for X to Z1, X to Z2, Y to Z1, Y to Z2, XY to Z1 and XY to Z2
 Here, I can already see the number of positive crossing (which allow me to calculate life). First Question, do I have to divide this number by 2PI?

My second question is, is it okay to create a derivated results on Hyperview, which does : RMS VELOCITY / (2*PI RMS DISPLACEMENT) in order to obtain the number of positive zero crossing directly on HyperView?
This whole zero crossing things is kind of getting me crazy, a lot of people use it but I do'nt really understand how it works.
(By the way, I can give you the files I have on my simple model if it is needed)


Thanks for your answers!

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Hi,

Please forgive me I'm kind of new to this and I don't really know how to be sure to look at equivalent PSD stress.

here are My files, please tell me if anything is correct. By the way I did one different subcase for direction.

NB : I limited the study to one element, ID = 14 (the one taking most damage according to Optistruct).
 

PLAQUE_T.fem

RUN_PLAQUE_T_ELEM_14.fem

RUN_PLAQUE_T_ELEM_14.peak

RUN_PLAQUE_T_MODAL.1.eigv

SET_ETUDE.fem

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