Diagnosis of gear faults by cyclostationarity

Gearbox maintenance is not an easy task and conventional diagnostic techniques do not always provide suitable indication about failures. In this paper, tooth crack failures have been experimentally investigated. The mechanical system is composed of a two-stage gearbox with spur gears. Two depths of gear cracks are treated. Cyclostationnarity analysis of order 2 has been conducted to some experimental signals delivered by a test bench under two loads by using an electromagnetic brake. The information has been extracted by using the squared envelope of the signal. The results show that the cyclostationarity approach is advisable for extracting the amplitude variation at the characteristic fault frequencies related to the defect. Experimental applications for diagnosis of tooth crack demonstrate that this technique is powerful and effective in feature extracting and fault detection for gearboxes. The crack signature was shown very sensitive to the crack severity whatever the applied load.