Inner Race or Rolling Element Faults (Sound and Vibration Measurement Suite)
December 2007
NI Part Number:
372416A-01
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If a bearing fault is on the inner race or rolling elements, the position of the sensor relative to the fault location varies periodically, which causes an additional modulating effect on the vibration signal. The power spectrum of the envelope signal then exhibits some sidebands around the characteristic frequencies or orders of the bearing. However, you can ignore these sidebands and still use the characteristic frequencies or orders to perform bearing fault detection.
The front panel below shows the power spectrum of the envelope signal from a constant-speed bearing with an inner race fault.
The inner race characteristic frequency, fIR, of the bearing is approximately 105 Hz. Notice that the Power spectrum of envelope signal shows some sidebands around fIR and its harmonic, 2fIR.