PSD Output Envelope

[sarclee]

Hi, I extracted PSD output from ANSYS with 2.5% and 3% damping ratio. I would like to check if the envelope I make is reasonable?

I notice the amplitude of 2.5% is very high, up to 5 G2/Hz. If the envelope covers the peak, does the shaker able to take so high energy?

PSD Input is as below. The PSD output is at one of the critical payload of the structure which its mass contribute 15% of the total mass but the critical payload's peak g RMS 100x more (5/ 0.042 > 100).

Hz G2/ Hz
20 0.01
100 0.015
800 0.042
900 0.042
2000 0.001

 

[IRstuff]

The shaker will do whatever its spec says it can do; it's up to you to keep the shaker from exceeding its spec.

There is an alternate option, which is to envelope the peaks separately. MIL-STD-810 has such constructions for helicopter vibration, where the blade frequencies are added to the overall amplitude envelope, or just put more breaks in the envelope; I see no reason to constrain yourself to only 3 or 4 breaks

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[GregLocock]

Might be worth looking at Tom Irvine's excellent website, he does a lot of envelope stuff

https://www.vibrationdata.com/

Cheers

Greg Locock


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[sarclee]

Thanks IRstuff and GregLocock. I had a quick look of Tom Irvine's blog and website. He does mention that it is too harsh to cover the peak.

The PSD response was extracted before further sizing. I wonder would the peak (up to 5G^2/Hz) also another criteria other than mass requirement for further sizing.