Material characterization of MR fluid at high frequencies

Magnetorheological (MR) fluid is made of fine iron powders dispersed in silicon oil, which is utilized in many smart structures and devices because of its significant rheological property changes by the applied magnetic field. The evaluation of high frequency characteristics of MR fluids is necessary in many smart structure applications, for example, noise reduction and shock wave attenuation. The characterization of MR fluid is experimentally performed in the frequency range of 50-100 kHz. An experimental setup based on wave transmission test is made and the storage and loss moduli of MR fluid are found from the measured speed of sound and attenuation data. To investigate the magnetic field effect, the magnetic fields are applied in parallel and orthogonal directions to the wave propagation direction. The storage modulus of MR fluid trends to be linearly increased with the frequency. The direction effect of magnetic field and the loss factor for MR fluid are discussed.