New aspects concerning the generation of acoustic emissions in spur gears, the influence of operating conditions and gear defects in planetary gearboxes

In this study, alternative hypotheses for AE generation in gears are presented and compared to the commonly accepted hypothesis of asperity contact. The effects of load, speed and lubricant viscosity on film thickness and pressure distribution are discussed, and AE from a non-faulty planetary gearbox are analysed. Results are compared to the behaviour expected from EHL theory and asperity contact hypothesis. Additionally, AE signals obtained with faulty gears are analysed. Planet and sun gear defects are evidenced in the AE envelope spectrum and the signals' behaviour is in agreement with the conclusions derived from the first set of measurements.