Dynamic performance of a novel integral magnetorheological damper-rotor system

Magnetorheological dampers (MRDs), as active damping devices, show superior performances in vibration control in rotor systems. However, MRDs tend to cause nonlinear behaviors of rotor systems under a large eccentricity, and the direction of the output damping force cannot be controlled. To overcome these deficiencies of MRDs, this paper proposes an integral magnetorheological damper (IMRD). In the proposed IMRD, the damper combines the elastic support and the squeeze film as a whole, where both magnitude and direction of oil film force are adjustable. Firstly, by employing bilinear constitutive equations to represent the magnetorheological fluid (MRF), the implicit form Reynolds equations of IMRD are established. Then, by implementing the proposed IMRD model into a flexible rotor system, the nonlinear dynamic model of a flexible rotor system with IMRD is developed by finite element (FE) method. The mechanical characteristics of IMRD are revealed from the view of oil film pressure and dynamic coefficients, and the nonlinear dynamic responses of the rotor system with IMRD are investigated and compared with those of rotor system with traditional MRD. The results indicate that oil film pressure in each bearing region can be adjusted independently with the current, which can lead to changes in both the direction and magnitude of the oil film force. Moreover, different oil film bearing regions have different contributions to the stiffness and damping of IMRD. Under certain situations, IMRD can provide pure damping with negligible stiffness. Besides, the over-squeezed MRF with large journal eccentricity ratio tends to produce strong nonlinearity; whereas, the IMRD proposed here can significantly reduce the level of nonlinearity compared with traditional MRDs.