may i know how to identify the gear natural frequency.thank you very much

natural_frequency.ppt (141 Kb, 51 downloads)

The gear "natural" frequency is the (resonant)frequency it will vibrate at if it is struck or bumped as opposed to the gear-mesh frequency which is a function of the number of teeth vs the shaft rotational speed.

Three ways:
1. Information provided by the gear’s vendor. Many vendors do not include this information in the data sheet.
2. Finite element analysis on gear. This requires special advance software and a skilled person to model the gear.
3. Impact test. This test can be done using common vibration analyzers but it will have a margin of error depending on the impact test procedure.

Good luck.

Ali M. Al-Shurafa

I agree with the above.

In the context of this chart, I would say that the behavior described is sharp impacting recurring at running speed of the affected gear. In that case, we will expect to see (approximately) a series of harmonics of running speed which peak in a certain frequency range. The frequency which contains the highest magnitudes is roughly the resonant system excited by the impact. That is what they are describing as a "resonant frequency with sidebands". I prefer to call it a series of harmonics which peaks in the neighborhood of a resonant frequency.