Abstract
New magnetic functional fluids containing both of nanometer-size needle-like magnetic particles and micrometer-size spherical magnetic particles are produced and its damping properties are investigated experimentally by using a simple prototype damper. Damping force is variable by changing intensity of applied magnetic field. Damping property of the damper depends on mixture ratio of nanometer-size magnetic particles to micrometer-size magnetic particles. Higher ratio of volume fraction of needle-like magnetic particles against that of all particles increases the damping force; in contrast higher ratio of volume fraction of nanometer-size magnetic particles against the total volume fraction of particles in a magnetic compound fluid decreases the damping force. In the absence of magnetic field, the fluid behaves like a Bingham fluid, while the fluid can be treated as a pseudoplastic fluid in the presence of magnetic field.
