Phenomenological study of acoustic emissions generated by gear meshing in planetary gearboxes

Abstract This study explores the frequency content of the envelope spectrum of acoustic emission (AE) signals from planetary gearboxes. Since AE signals contain continuous AE and burst-type AE, it is important to determine how different types of amplitude modulation affect these components. Phenomenological simulations of the AE signals were conducted to analyze the influence of the modulations. This approach quantitatively determines how the different harmonics in the envelope spectrum change depending on the level and type of modulation. The modulations under analysis are sinusoidal and single square wave. The simulations indicate that sidebands at the planet gear pass frequency around the gear mesh components are mainly attributed to the modulation of AE bursts, while harmonics at the planet gear pass frequency are primarily attributed to the modulation of the continuous AE. An application case to a wind turbine gearbox is also presented. The study highlights the influence of normal modulations or fault-related modulations in the AE envelope spectra from planetary gearboxes. It provides meaningful insights for establishing AE technology as a consistent condition monitoring technique for planetary gearboxes. The main practical value of the research is providing guidelines for the correct interpretation of AE envelope spectra in planetary gearboxes, which is crucial for avoiding gear failures.