Magnetorheological fluid characterization using ultrasound measurements

In this work the variations of velocity of sound and attenuation in magnetorheological (MR) suspensions have been studied when the temperature and the intensity of magnetic field have been varied and, also, when the suspension is observed for a long period of time. It has been shown that the behaviour of the MR fluids depends strongly on the fluid used as solvent when temperature is varied. Regarding the sedimentation process, it has been proved that the application of an external magnetic field enhances the stabilization process. Analyzing the hysteretic behaviour it is seen that the system does not recover its initial state when the magnetic field is removed, because the ordered microstructure does not disappear completely. As ultrasound parameters are sensitive to changes in the temperature, in the structure and also in the volume fraction, they are a promising tool to characterize MR fluids in order to improve its performances.