Geared System Condition Diagnostics Via Torsional Vibration Measurement

Gears as important mechanisms for transmitting power or rotation, are widely used in machinery. The smooth operation and high efficiency of gears are necessary for normal running of machinery. Therefore, gear crack damage detection is a main topic in the field of condition monitoring and fault diagnosis. Due to the intrinsic dynamic characteristics and complicated ambient excitations, the on-site measured gear torsional vibration signals are frequently characterized by complexity and non-stationary. For example, the tooth meshing effect, amplitude and phase modulation phenomena inherent with gear pair transmission; the multiple signal components originated from different excitations, complicated propagation, and dynamic coupling between mechanical components, the time averaging characteristics due to operation and conditions; and especially the transient impulses induced by gear crack damage. This paper presents an experimental technique by which the geared system torsional vibration responses can be monitored and used with the high order statistics of RMS averages and Kurtosis value for fault diagnosis. A single-stage gearbox with helical gears is used, where the vibration signal is considered stationary waveform. The results indicate that significant diagnostic information can be gained from this study, which allow the diagnostic information be controlled and consequently used for Condition-Based Maintenance (CBM) regime.