Time varying bearing stiffness and vibration response analysis of high speed rolling bearing-rotor systems

High speed rolling bearings are widely used in the machine tool spindle, aircraft engines and any other systems. Under the complex operating conditions, bearing stiffness shows the characters of strong nonlinearity and time variation, which are often the primary sources of nonlinearity of system. With the consideration of the centrifugal force, gyroscopic moment, inner ring centrifugal expansion and thermal deformation, a high speed rolling bearing nonlinear model is proposed, which can be used to calculate the stiffness matrix. Rotor-bearing coupling finite element model is obtained by assembling rolling bearing nonlinear model and rotor finite element model. Take FAG bearing (HCB7012E) for example, axial and radial relative displacements of inner ring and outer ring are calculated under the condition of static loads, respectively. The calculated results are compared with the results of FAG's online tool (BearinX^®) to validate the model. Moreover, vibration responses due to unbalanced excitation of the bearing-rotor system are simulated and compared with experiments under different bearing preloads. The variations of bearing stiffness under static and dynamic loads are studied with a back-to-back angular contact ball bearing-rotor system, meanwhile, the time vibration response caused by time varying stiffness and its frequency features are calculated, which provide guidance for the design of high speed rolling bearing- rotor system, dynamic analysis and fault diagnosis.