Acoustic Emission Source Localization in Ring Gears from Wind Turbine Planetary Gearboxes

Condition monitoring and fault diagnosis are methods to achieve ahigher reliability for complex mechanical systems. Due to the ability of acoustic emission (AE) technology to detect damages during at an early stage, AE has high potential to be considered in novel machine condition monitoring systems. Since AE waves are generated due to rapid releases of strain energy, such as crack propagation, roughness contact and mechanical impacts, it is possible to use multiple AE sensors to track down the AE source location. This paper presents an accurate and easy-to-use methodology to locate AE sources in ring gears from planetary gearboxes. The methodology uses AE wave's time of arrival calculated from three signal differential envelopes. The time of arrival is subsequently used to analytically determine the angular position of the AE source. The proposed methodology was tested in two different real-sized wind turbine gearboxes using Hsu-Nielsen sources. The results showed that, with the correct selection of filter cut-off frequencies, the localization could be carried out with an error equivalent to only two teeth from the correct position, indicating the good performance of the approach.