USE OF THE MOVING CEPSTRUM INTEGRAL TO DETECT AND LOCALISE TOOTH SPALLS IN GEARS

The objective of this paper is to propose a new indicator for the vibratory diagnosis of gear systems. This indicator is deduced from the power cepstrum of the accelerometer signal. A model aimed at simulating the contributions of local tooth defects such as spalls to the gear dynamic behaviour is set-up. The pinion and the gear of a pair are modelled as two rigid cylinders with all six degrees of freedom connected by a series of springs which represent gear body and gear tooth compliances on the base plane. It permits us to foresee the shape of the excitation induced by the presence of spalls. From an analytical analysis of the equations of motion, a detection technique based upon the acceleration power cepstrum is proposed. The identification of the spalls is provided by the fact that the power cepstrum of the excitation that it generates is strictly negative, in contrast to that of a normal excitation. A tool of detection and localisation, using this property, has been defined. It is first tested on acceleration signals simulated by numeric integration of the model, then on real signals.

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