Phenomenological Modeling and Spectral Analysis of Spalling Planetary Gearboxes: A Theoretical and Experimental Study

As a common failure mode of gears, tooth spall can be easily arisen due to face fatigue. The occurrence of tooth spall can lead to a series of complex properties on the vibration spectrum and brings difficulty to the fault diagnosis of planetary gearboxes. However, the spectral analysis of planetary gearboxes due to a tooth spall has not been yet deeply conducted. Aiming at this issue, a phenomenological model is established to investigate the vibration induced by a spalling fault in planetary gearboxes. In the model, the detailed engagement process of the spalling tooth is considered, and two kinds of fault induced signals due to the entry and exit of the spalling tooth zone are simulated through a step-like and an impulse-like response function. Then vibration signals and their spectra of planetary gearboxes with a spalling sun and a spalling planet gear are obtained, respectively. Finally, the proposed phenomenological models are validated using experimental data collected from a planetary gearbox test rig. The validation results showed that the proposed phenomenological model is effective to exhibit the spectral structures of planetary gearboxes with a spalling tooth.