Magnetorheological fluid composites

An interesting extension in the use of magnetic fluids has resulted from the development of magnetic fluid composites obtained by dispersing micrometre-sized non-magnetic particles in a magnetic fluid. The composites possess a yield stress in a magnetic field which can be described at sufficiently high strain rates by the Bingham relation , where is the shear stress perpendicular to the applied field, the extrapolated yield stress, the strain rate and the plastic viscosity. Thus, a composite, particle concentration , in a field 0.036 T with has a yield stress of 26 Pa. The yield stresses obtained experimentally for different and correspond well to values predicted theoretically by Rosensweig using a determination of based on a continuum concept of unsymmetric stress that develops in the deformed but unyielded anisotropic medium.