Joint time-frequency distribution of rolling bearings with multiple faults on outer raceway based on asymptotic model

At present, the majority of the research on dynamic model of rolling bearings with multiple faults is conducted on the assumption that the displacement deviation between raceway and rolling element changes instantaneously. However, the deviation should vary gradually. As a result, an asymptotic model of rolling bearings with multiple faults on outer raceway is established, considering the interaction of multiple faults. Synchroextracting transformation method is employed to describe the joint time-frequency distribution of the faulty rolling bearings. The discrepancies between the asymptotic model and the traditional model are contrasted and analyzed via simulation modeling. Simultaneously, the effects of fault number and fault interval on the joint time-frequency distribution are investigated. Finally, experiments are performed to verify the rationality of the established model. Simulation results demonstrate that the joint time-frequency distribution derived by the asymptotic model includes not only the fault characteristic frequency but also the rotating frequency. The central frequency increases in a multiple of the fault characteristic frequency as the fault number increase, as does its energy amplitude. Only when multiple faults are uniformly distributed among the interval range of rolling elements, the energy amplitude of the central frequency can reach the maximum. The energy amplitude of the rotating frequency scarcely changes as the fault interval and fault number vary.