How to use results from natural frequency analysis?
How to use results from natural frequency analysis?
(OP)
G'day everyone!
I have a basic rookie question regarding extracting natural frequencies and mode shapes. So I have 3 different designs of an automotive part for which I have run frequency analysis. The results are in, but how do I use them in the correct way? I have always been told that you pick the stiffest design by choosing the one with the highest (first) natural frequency. Is it really that simple? Or is there more science and art to judging the "best" design based on mode shapes?
Thanks in advance!
Jo
I have a basic rookie question regarding extracting natural frequencies and mode shapes. So I have 3 different designs of an automotive part for which I have run frequency analysis. The results are in, but how do I use them in the correct way? I have always been told that you pick the stiffest design by choosing the one with the highest (first) natural frequency. Is it really that simple? Or is there more science and art to judging the "best" design based on mode shapes?
Thanks in advance!
Jo





RE: How to use results from natural frequency analysis?
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RE: How to use results from natural frequency analysis?
RE: How to use results from natural frequency analysis?
No. That is ridiculous advice. Suppose you had a couple of shaft designs for a machine that runs at 3000 rpm. Do you choose the one with a resonance at 50 Hz? or 30 Hz?
Cheers
Greg Locock
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RE: How to use results from natural frequency analysis?
I would say that if you pick the design with the highest frequency you will have picked the stiffest design.
Since in short: F = SQRT (S/M)
S = Stiffness
M = Mass
But that does not mean that the stiffest design is the best for your particular situation. Basically, I agree with Gregs statement.
I usually say the frequency tells you when in vibrates, the mode shape tells you how it vibrates. But what is really interesting is often how much it vibrates.
Regards
Thomas
RE: How to use results from natural frequency analysis?
I was simply wondering what is the use of viewing mode shapes because so few books and tutorials touch on this.
Much obliged!
cheers
Jo
RE: How to use results from natural frequency analysis?
Within that range, any normal deflections caused by a static load can be amplified by dynamic resonance, bouncing effects, like when you jump on a trampoline. If you jump at intervals corresponding to the trampoline surface's natural frequency, you go higher and higher.
RE: How to use results from natural frequency analysis?
RE: How to use results from natural frequency analysis?
RE: How to use results from natural frequency analysis?
RE: How to use results from natural frequency analysis?
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RE: How to use results from natural frequency analysis?
Hope that makes sense.
Jeff