磁気粘性流体中の圧力波伝播挙動に及ぼす微視的構造の影響

抄録

Magnetorheological (MR) fluids are categorized as smart fluids, which are made of ferromagnetic particles suspended in carrier fluids such as silicone oil. On application of an external magnetic field, the ferromagnetic particles are arranged along the magnetic flux line. It is called a cluster. The flow characteristic changes according to the cluster. It has already been used for the automobile damper by taking advantage of this unique property. In the previous study, the authors have conducted high-speed impact experiment on MR fluids and examined the propagation behavior of pressure waves induced by impacts. The results suggest that clusters affect pressure waves propagation behavior. Therefore, in this study, microscopic structures were observed by laser microscope and X-ray Computed Tomography (CT). We also conducted an experiment to incident a plane wave, and investigated the pressure wave propagation behavior using pressure sensors. In this experiment, by using plane waves, it is possible to clarify the relationship between the micro structure and pressure wave propagation behavior in more detail than in previous impact experiments. Three types of MR fluids were prepared with the ferromagnetic particle concentration of 6 vol%, 15 vol% and 30 vol%. In addition, the experiment was conducted with different magnetic field strengths and directions. As a result of the experiments, the increase of ferromagnetic particle concentration enhanced the wave propagation rate. It was elucidated that the effect of magnetic field strength on pressure wave propagation behavior. It was also confirmed that the anisotropy of MR fluids.