Detection of gearbox failures by combined acoustic emission and vibration sensing in rotating machinery

摘要

The wind energy industry continuously demands significant improvements in wind turbine maintenance strategies through the use of condition monitoring systems (CMS). Regardless of their design, wind turbines have rotating parts which need to be monitored during operation in order to avoid unpredicted failures. In this document an experiment conducted in the University of Newcastle is described and initial data analysis is presented. The experiment was performed in a gear test rig of the Design Unit department, where gearbox contact fatigue tests are frequently performed. The testing procedure involves the running of the gears to destruction, starting with 'fresh' gears and operating for a period of time until they fail. In this experiment, the gear monitored is periodically checked to give an indication of the tooth's cross section loss. A combination of vibration analysis and Acoustic Emission (AE) analysis is utilised in this experiment as it is believed that for reliable diagnosis of rotating machinery, multi-sensing technology should be used. Accelerometers and acoustic emission sensors were deployed throughout the tests, conducted in 5 stages over 7 weeks. For the vibration data processing calculation of the data, the Root Mean Square (RMS) and Crest Factor values are calculated and frequency spectrum analysis is performed. For the acoustic emission data processing RMS and energy parameters are calculated. These parameters are shown giving information about the potential gear deterioration over time. The results of the experiment are finally presented and show minimal changes in the vibration and acoustic emission parameters in the first 2 stages of the tests, indicating a reliable baseline reading. However, in the later stages of the tests, data showed very clear indication of possible gear deterioration, with an increase in the values of RMS for both acoustic emission and vibration data and a modal shift in the vibration spectrum. Visual inspection performed afterwards confirmed the onset of severe macro-pitting failures in the gears.