Servocontrol Vibration Analysis

[Freemesh]

Hi. I'm performing dynamic analysis on a servocontrol. There are three positions (three different lengths) : mini, middle, maxi. Structure is excited in one direction (sine wave). I have got results for each position : resonance frequencies and their amplification factors. I have to choose the most critical position (mini, middle ou maxi). Is there a methodology to determine this position?

 

[FrenchCAD]

I know people working on this field, they might be able to help you.

Send me an email at cyril.guichard@wanadoo.fr with your question and I'll forward it to them if you wish.

Hope this helps,

Cyril Guichard
Mechanical Engineer

 

[andyfe]

The most critical position depends on the vibration spectrum of the service environment, first of all: is it airplane or helicopter environment?
Typical spectrums can be found in RTCA/DO160 section 8 or MIL-STD-810. Typically, you have to ensure the resonance frequencies of your item are never within +/- 5% of the forcing frequencies for any position.
If you find a position for which one of the natural frequencies is equal to the forcing frequency, you have to ensure that the amplification factor is low enough for the part to attain its required life (depending of what sizing loads were considered during structural design).
In many cases, a narrowband sinusoidal or a dwelling test @resonant frequency is required to prove the item can resist the service environment.