Theoretical and experimental studies of an electro-rheological grease shock absorber

One method of achieving fail-safe, semi-active damping is to utilize a cont rollable fluid with a high zero-field damping capacity. To this end, this p aper introduces a prototype electrorheological grease (ERG) as anew concept in electro-rheological fluids (ERF's). The general properties of grease-li ke fluids imply a non-Newtonian post yield viscosity. The fluid model devel oped in this paper considers the influence of a non-Newtonian post yield vi scosity by using a power law model to account for shear thinning behavior. This model can be applied to all controllable fluids since it reduces to a Newtonian viscosity as a special case. The theoretical study includes a lum ped parameter dynamic system model to predict the behavior of an actual dam per, which takes into consideration inertial and compressibility effects. T o validate the proposed models, a prototype damper was designed and used to collect data for a known ERF and the new ERG. Results from the ERG test da ta indicate that a good match between experimental and theoretical data was achieved. A sensitivity analysis shows that the model was insensitive to t he mass of the fluid, but sensitive to the bulk modulus of the fluid. Compa risons are also made between the performance of the ERG and the existing ER E The ERG demonstrates higher zero-electric field damping capacities than t hose of the ERF, yet produces an increase in damping when an electric field is applied.