An Improved Model for Magnetorheological Fluid-Based Actuators and Sensors

Abstract

The resistance to flow of magnetorheological (MR) fluids is greatly increased by the application of a magnetic field. At present, most devices exploiting this MR fluid behavior are pistons executing straight-line motion. The MR fluids in these devices are subjected to shear flow, and are modeled by either the Bingham plastic or Herschel-Buckley models, both 1D, phenomenological continuum-level forms relating strain rate, magnetic field magnitude, and stress magnitude, and fit to continuum-level empirical measurements. We employ a multiscale model of the MR fluid introduced in an earlier paper, which integrates nanoscale behavior over a mesoscale volume to deduce continuum properties. This approach replaces many of the phenomenological features of the Bingham plastic and Herschel-Buckley models with first principles, and isolates those few phenomenological features that remain into a single scalar term. The model is compared to the Bingham plastic and Herschel-Buckley models, assessing each model’s ability to capture the experimentally measured mechanical response of a particular MR fluid-based damper to specified magnetic fields. The result of this comparison is that, our model possesses the flexibility to best match the measured behavior of the MR fluid device observed in our experiments, with fewer required experimental measurements.