Investigation on the dynamic characteristics of a magnetorheological squeeze-film damper for the design of a classical rotor control strategy

In the last decades there has been an increasing attention towards magnetorheological fluids (MR), which react to magnetic fields undergoing variations of viscosity and stiffness, due to their possible application in semiactive devices also in the field of vibration control. A lab magnetorheological squeeze-film damper for the control of the vibrations of a rotating shaft was designed and constructed. In order to implement a classical control the dynamic model of the damper must be completely known and validated. Therefore a suitable apparatus aimed at the identification of the parameters of the devised model as function of the excitation frequency and of the electric current generating the magnetic field was set up and interfaced to a modified Bently-Nevada Rotor-Kit. Eddy current displacement sensors measured the dynamic response of the shaft to the synchronous rotating unbalance force while a triaxial load cell placed between the damper and the Rotor-Kit pedestal measured directly the forces transmitted by the shaft to the damper. On the basis of such measurements the dynamic stiffness, damping and adjoint mass coefficients, related to a linear model of the MR fluid were determined by means of a parametric identification technique. The non-linear response was also investigated