Characterization and modeling of the behavior of magnetorheological fluids at high shear rates in rotational systems

The behavior of magnetorheological fluids in rotational systems for torque transmission such as brakes and clutches offering a drum-shaped shear gap design is investigated for high-speed operation up to 6000 rpm or respectively high shear rates up to 34,000 s⁻¹. The occurrence of a Taylor vortex flow is described and experimentally proven for the operation without and with an applied magnetic field. By measurements it is shown that a mixing effect due to the vortex flow avoid a disadvantageous particle centrifugation. In further measurements a weakening of the magnetorheological effect with increasing rotational speeds is observed. Utilizing a magnetic dipole model for calculating the yield stress with a common parameterization based on measurements, a prediction of the achievable torque as a function of the rotational speed is possible. This modeling approach provides an important tool for the design process of magnetorheological-fluid-based actuators for high rotational speed application.