Simple natural frequency calculation
Simple natural frequency calculation
(OP)
It's been a while for me to do a vib calculation. I was trying to determine the resonance frequency of the structure. The structure is basically a beam hanging vertically down from the ceiling. The lower end of the beam is attached with a mass. I found a simple equation from Steinberg, natural frequency (fn) = [1/(2 pi)]* sqrt(K/m) or alternatively fn = [1/(2 pi)]* sqrt(g/deflection)
My question is whether this equation is applicable to any mounting orientation of the beam.
Note: Steinberg has an example of using this equation to calculate the natural frequency of the beam which is mounted horizontally. For my case where the beam is mounted vertically, would this equation still applicable? Also how should the deflection be calculated if the equation can be used for vertical orientation.
Thanks for any help.
My question is whether this equation is applicable to any mounting orientation of the beam.
Note: Steinberg has an example of using this equation to calculate the natural frequency of the beam which is mounted horizontally. For my case where the beam is mounted vertically, would this equation still applicable? Also how should the deflection be calculated if the equation can be used for vertical orientation.
Thanks for any help.





RE: Simple natural frequency calculation
RE: Simple natural frequency calculation
Thanks
RE: Simple natural frequency calculation
I think it make sense. The deflection was only used to determine the stiffness, which is what the fn depends on. It sounds like if I know the stiffness and the mass of the system, I would know the fn. This is independent of orientation...or g field.
Thanks a lot.
RE: Simple natural frequency calculation
g appears in your second equation as a sort of scaling factor.
I suppose it is obvious that for that to work you have to know the beam deflection when horizontal?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Simple natural frequency calculation
Do you expect the motion to be pivoting about the ceiling? If so this sounds like a pendulum with a stiffness at the support.
If it is cantelevered and the beam acts flexibly the standard beam equations should work.
It could be a combination of the two, depending upon the circumstances.
Regards,
Bill
RE: Simple natural frequency calculation
http://www.vibrationdata.com/tutorials2/beam.pdf
Tom Irvine
http://www.vibrationdata.com
RE: Simple natural frequency calculation
It is what I am going to do next, determine the stiffness of the mounting bracket (which support the cylinder to the ceiling).
Thanks.