Dynamic analysis of rotor-bearing systems considering cage-guiding surface contact with a modified conformal model

The accurate simulation of vibration for rotor-bearing systems is vital for the prediction of bearing useful life. However, for large-diameter bearings with small cage guiding clearance, dynamic models considering the conformal contact between the cage and guiding surface are still lacking. This paper proposes a roller bearing model with a 6 DOFs cage by introducing a modified conformal contact model to describe the stress distribution of cage-guiding surface contact. On this basis, a prediction method for rotor-bearing vibration is established to consider the cage-guiding surface contact due to the angular deflection of the rotor shaft. Then, a scaled rotor system with a large-diameter bearing of a turbofan engine is studied numerically and experimentally. The motion of the tested bearing is captured with the high-speed camera to study the cage-guiding surface contact. Experimental results show good agreement with the numerical solutions. Results show that when the bearing cage contacts severely with the guiding surface, the bearing fundamental train frequency and its modulation frequencies with rotor spinning frequency would occur in the rotor vibration spectrum, which could be an effective indicator to identify bearing cage wear.