2. Measurements and analysis of diagnostic signals.
Why do you not recommend to use the enveloping method
for diagnostics on the bearing unit resonance frequency?
The question was asked by a post graduate student of the Alabama University.
The question is answered by
There are two main reasons of it:
The first one - is the instability of the vibration level, measured on the
resonance, and the possibility of its frequency deviation from one measurement
to another because of the changes in the mechanical properties of the object,
the method of the sensor mounting and other reasons.
The second - the losses in the accuracy of the defect type identification
because this identification depends on the combination of harmonic components in
the vibration envelope spectrum. When the measurements are made on the resonance
frequency some of these components do not coincide with the resonance frequency
band. It leads to a deep decrease of the amplitudes of such harmonic components
in the vibration envelope spectrum.