Bellows Vibration

[mark20]

Dear Savior...

I am trying to calculate the natural frequency of a bellows compressed under load.
the best calc i have used is Fn=2Pi x SQROOT(k/m)

My questions are :

1, Does anyone know of a better calc?
2, When I finally come to being able to check the calc through testing, what instrument do I use? (accelerometer?)

Thanks...
Mark.

 

[pjhype]

mark20,

The correct formula for calculating the natural frequency of a single degree-of-freedom oscillator is fn=(1/(2*pi))*sqrt(k/m). That is, (2*pi) is in the denominator.

If you can model your system as a single mass on a single spring this equation is appropriate.

You could use an accelerometer hooked up to a dynamic signal analyzer to verify the natural frequency. Alternately, you can hook up your accelerometer to a strip chart recorder or oscilliscope and measure the period between oscillations.

pj

 

[mark20]

hi PJ;

Sorry, that was the equasion that I used, at least I have a varification of that.

I think I can use an oscilliscope (If the company hasn't dumped it!)...Just need to pursuade them to get an accelerometer!!

Thanks a lot for your help..

Regards,
Mark.

 

[Rob45]

BTW, if you're talking about the natural frequency of the bellows in axial motion, you're going to have to specify the mass that's attached to it. Assuming that is that this bellows is connected to something in use; its' free natural frequency will be rather meaningless.

 

[asking]

Why don'y u try it using FEA? The bellow can be modelled easily using its axi-symmetricity.