Dynamic modeling and vibration analysis for the gear-rotor-bearing system with localized failures

Accurate identification of faults in gearbox requires a clear understanding of its vibration response. In this study, through establishing dynamic model and experimental observation, the vibration characteristics of gear-rotor-bearing systems with localized failures are investigated and discussed. Firstly, the models of the gear pair, rotor and bearing are integrated, a comprehensive model for gear-rotor-bearing systems is developed. Then the model for describing localized failures is established and supplemented to the system equations. By using the model, the influence of the spalling defect and bearing raceway failures on the dynamic response are analyzed. Moreover, multiple sets of experiments are conducted for verifying the model and analysis results. The paper explains that periodic shock will be generated due to the presence of localized failures, the vibration intensity of the faulty part at specific frequencies is greatly enhanced, and a series of harmonic frequency components will be generated. Additionally, due to the pulse force transmission, the operation state of other components is also seriously affected, and frequency modulation phenomenon between different components can be observed. The defect frequency of bearing outer raceway is commonly modulated with meshing frequency and cage frequency, while the inner raceway defect frequency and meshing frequency are modulated with shaft frequency, and the amplitude of harmonics caused by modulation is obviously increased under the excitation of localized failure.