Characteristics of ultrasonic propagation in a magnetic functional fluid under AC magnetic fields

Abstract

This paper reports experimental studies about anisotropy and attenuation as characteristics of ultrasonic propagation in a magnetorheological fluid (MRF) under AC magnetic fields. Parameters of this studies are magnitude of AC magnetic fields (50 mT), frequencies of AC magnetic fields (1, 2, 3 Hz) and angles between directions of ultrasonic propagation and magnetic field (0, 45, 90°). As results of change rate of sound velocity, MRF has characteristics of time dependence, frequencies dependence and anisotropy under AC magnetic fields. Also, length of clusters in MRF became short with increase of frequencies of AC magnetic fields. The clusters in MRF are formed along the magnetic force under AC magnetic fields. Attenuation decreased with increase of the angles between directions of ultrasonic propagation and magnetic field. But, attenuation did not change with increase of frequencies of AC magnetic fields.