Dynamic characteristics of rotor system with initial bending induced by the misaligned four-point contact ball bearing

Abstract

Previous studies on bearing misalignment mainly focused on abnormal bearing loads, assuming a healthy rotor, which overlooked the initial bending induced by misalignment. This could cause inaccurate vibration predictions. To bridge the gap, a developed dynamic model incorporating rotor initial bending induced by bearing misalignment is proposed and validated through vibration tests. The model includes a quasi-static analysis of misaligned four-point contact bearings to calculate abnormal loads and rotor deformation. Results show that bearing nonlinearity generates harmonic and combined frequencies. The bearing outer ring tilt significantly alters the contact stress between balls and raceways, while rotational speed and rotor bending have minimal impact at large tilt angles. Due to the tilt of the bearing outer ring around the vertical, during the revolution of balls, when the azimuth angle of balls is within the range of -90° to 90°, the ball is always in contact with the left inner raceway; when the azimuth angle of balls is within the range of 90° to 270°, the ball is always in contact with the right inner raceway. In radar maps, the contact loads in these two regions show symmetry. The phase difference and magnitude of initial bending mainly affect rotor vibration.