Investigation of ultrasonic properties of MR fluid under various sweep rates of magnetic field

A. Isnikurniawan, - Y. Fujita - S. Tanimoto - T. Sawada

Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan

Abstract
We report on our investigation of the ultrasonic properties of magnetorheological (MR) fluid under various magnetic field sweep rates. When a magnetic field is applied to a MR fluid, the ultrasonic properties of the fluid change because of cluster formation in the fluid. In this study, the ultrasonic propagation velocity of MR fluid under various magnetic field sweep rates was measured. A magnetic flux density was applied from 0 to 400~mT over different periods of time. On the basis of the experimental results, the effect of the magnetic field sweep rates on the cluster formation of MR fluid was analyzed.We have demonstrated the capabilities to catch the signals of induced electromotive force (EMF). The characteristics of EMF signals are analyzed systematically. Influences of volumes, sizes and travelling velocities of ferrofluids on the magnitudes and wave spans of the signals are presented. In addition, simulations of the induction fields are carried out to provide the physical insights of the induced EMF signals. The signals can be potentially applied as diagnostic characteristics in the measurements of travelling velocities or sizes of moving ferrofluid drops or slugs. Tables 2, Figs 3, Refs 7.