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A crack in the tooth root, which is the least desirable damage caused to gear units,
often leads to failure of gear unit operation. A possible damage can be identified
by monitoring vibrations. Time signals were obtained by experiments.
Amplitudes of time signal vibration are, by frequency analysis, presented above
all as a function of frequencies in spectrum using hybrid procedure for
determining the level of non-stationarity of operating conditions primarily of
rotational frequency. A non-stationary signal was analysed as well, using the
family of Time Frequency Analysis tools, including Wavelets and Joint Time
Frequency Analyses. Wavelet analysis is suitable primarily for non-stationary
phenomena with local changes. The purpose was to obtain the location of the
crack, i.e. to identify the tooth. Typical spectrogram and scalogram patterns result
from reactions to faults or damages; they indicate the presence of faults or
damages in a very reliable way.