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Dynamic Performance of a Disk-type Magnetorheological Fluid Damper under AC Excitation

It is shown that the dynamic behavior of a disk-type magnetorheological (MR) fluid damper based on shear mode operation for rotational machinery can be controlled by the application of an external DC magnetic field produced by a low-voltage electromagnetic coil and that the disk-type MR fluid damper can effectively attenuate the rotor vibration. In this article, the dynamic behavior of the disk-type MR fluid damper for attenuating rotor vibration under AC sinusoidal magnetic fields is experimentally studied on a flexible rotor. It is shown that as the frequency of AC sinusoidal magnetic field increases, the capability of the disk-type MR fluid damper to attenuate rotor vibration significantly reduces. There is a maximum frequency of AC sinusoidal magnetic field for a given magnetic field strength, and a minimum strength of AC sinusoidal magnetic field for a given frequency of AC sinusoidal magnetic field to realize the MR effect. When the frequency of AC sinusoidal magnetic field is over the maximum frequency or the applied strength of AC sinusoidal magnetic field is less than the minimum strength of AC sinusoidal magnetic field, the MR activity almost completely disappears and the dynamic behavior of the disk-type MR fluid dampers under AC magnetic field is the same as that without magnetic field. Since the AC sinusoidal magnetic field applied in the disk-type MR fluid damper results in the amplitude-modulated phenomenon in the rotor motion, it is better to use the DC magnetic field than to use the AC sinusoidal magnetic field to control the dynamic behavior of the disk-type MR fluid dampers in the rotor vibration control of view.