Abstract
Damping force of a damper utilizing MR fluids containing needle-like particles is investigated experimentally. In this paper, μm-size carbonyl iron particles (average diameter is about 1.2 μm), and needle-like iron particles (long axis is 100 nm and aspect ratio is 4.0) or non-magnetic needle-like hematite particles (long axis is 194 nm and aspect ratio is 8.3) were mixed in the base fluid. The damping force becomes larger with the mixing ratio of the needle-like particles (iron and hematite) larger even in the absence of the magnetic field. If magnetic field is applied, the damping force becomes larger and the flow characteristic of fluids is changed.
