Vibration analysis of a flexible gearbox system considering a local fault in the outer ring of the supported ball bearing

Ball bearings are key components in the gear transmission system. Supported ball bearings have great influences on the vibrations of the gear transmission system, especially the presence of the local faults. Although some reported works formulated the local fault in the supported bearings of the gear transmission system, the box and shaft were considered as rigid bodies. To overcome this problem, a rigid-flexible coupling dynamic model for a flexible gearbox with the supported ball bearings is developed, which cannot be described by the previous multibody models. The local fault in the supported bearing is described by a time-varying impact force model with a half-sine profile. The bearing clearance, flexible shaft, and box are considered in the rigid-flexible coupling dynamic model. The flexible shaft and box are formulated by a finite element method. The damping and contact stiffness in the bearings and gears are obtained by the previous methods in the listed works. The frictions between the mating components are formulated by the Coulomb friction model. An experimental study is applied to validate the rigid-flexible coupling dynamic model. The effects of the faults on the vibration transmission characteristics are investigated. The results provide that the local fault in the supported bearings will greatly affect the vibrations of the gearbox system. Moreover, it depicts that the vibration collection point for the defective bearings should be located at the same side to obtain better singles. This work can provide a more reasonable method for understanding the vibration transmission characteristics of the gearbox system with the local faults in the supported bearings than the reported multibody models.