Vibration characteristics of bearing-rotor systems with inner ring dynamic misalignment

The inner ring dynamic misalignment of deep groove ball bearings (DGBBs), as a possible error type in practical engineering, has significant influences on the service performance of the rotor system. A novel dynamic model of the bearing-rotor system with inner ring dynamic misalignment and a model solving method based on the Newton-Raphson and Newmark-β nested iterations are proposed in this paper. This method perfectly integrates the quasi-static model of the ball bearing with the dynamic model of the rotor system. In addition, the proposed model can better consider the nonlinearity caused by the ball-raceway contact and the three-dimensional (3D) clearance inside the bearing. By comparing with the experiment, the accuracy of the proposed model is verified. On this basis, the effects of misalignment angle, radial clearance, and rotational speed on the dynamic characteristics of the system are analyzed. The results show that the inner ring dynamic misalignment introduces additional bearing force excitation and increases the vibration of the system. In addition, the inner ring dynamic misalignment cancels out the radial clearance, enhances the axial restraint of the system, and changes the axial vibration characteristics from soften-type to hardening-type nonlinearity.