Abstract:
The aim of this research is to investigate the feasibility of using stress waves for
condition
monitoring of gears. The project involved setting up an experimental rig,
carrying out experimental work, acquiring stress waves signatures, and processing the
signals. It has been shown that stress waves can successfully be employed for early
detection of incipient gear failure.
A
experimental gearbox was employed during the experiments. Miniature ultrasound
transducers, both sensitive and sufficiently small, were manufactured and installed on the
stationary outer race of the rolling element bearing of the gearbox to detect stress waves
from the
meshing gears. The stress waves signals from the transducers were digitised and
digitally processed to extract relevant information.
The
signatures were high-pass filtered at a cut-off frequency of 200 kHz, thus
representing exclusive ultrasonic frequencies. A new statistical parameter, Energy Index,
was
developed and performed on the stress wave signatures which were segmented to
represent individual gear teeth. Along with this new parameter, the classical statistical
parameters, (Peaks, RMS, Standard Deviation, Kurtosis, etc.) were also performed.
Conclusive results are
presented in graphical form in terms of Cumulative Energy
Indices' and
Energy Indices in polar form for individual gear teeth. A new algorithrn was
also
developed and presented for the envelope detection of signal by iterative peak
detection.
Although no direct comparison was made between condition monitoring of gears using
stress waves and methods such as low
frequency vibration analysis and wear debris
analysis, it is apparent that stress waves monitoring offers a much earlier warning of
incipient gear failure because the technique can detect material defonnations which are
precursors to changes in the dynamic properties of gears and the occurrence of wear
debris. The
technique, therefore, can predict incipient failure much earlier, extending the
lead-time before failure, and as a result, minimising sudden failures which may have
catastrophic consequences.
