Characteristics analysis of rotor-rolling bearing coupled system with fit looseness fault and its verification

Outer ring of bearing fit looseness fault is a common fault. Scratch often appears in the inner surface of pedestal. The fit looseness fault mechanism is not clear. For rotor-rolling bearing system with fit looseness fault between rotor-bearing outer ring and pedestal, a rotor coupling dynamic model that the interaction of bearing outer ring and pedestal are considered. This model is different from the universal rubbing model, where the directions of relative motion between rotor and stator are not considered. Numerical integration method is used to obtain the response of the system where the rotor is established by FEM and the bearing outer ring and pedestal are established by lumped mass model. Firstly, modal test results and simulation results were used to verify the correctness of this model. Secondly, the role of tightening torque between bearing outer ring and pedestal is considered, and the response characteristics of bearing and rotor are analyzed when fit looseness fault is considered. Finally, comparing the simulation results with test results, the waveform and spectrum are similar, which verifies the correctness of the fit looseness model. The fit looseness fault characteristics are that the acceleration after noise reduction shows periodic impact, up and down asymmetry, multiple frequencies appear. A method by increasing tightening torque is put forward to control the vibration caused by fit looseness fault.