Compression of smart materials: Squeeze flow of electrorheological and magnetorheological fluids

Squeeze flow behavior was experimentally tested for Newtonian fluids. The results show that the squeezing force as a function of the gap gives force ∝ gap-2.5 and gap-4 for constant area and constant volume respectively. These results were compared with the Stefan, perfect slip, and Rady-Laun partial slip equations and found not to match exactly, but best approximated the Stefan equation. The results also show that squeezing force as a function of squeezing speed matched predictions by Stefan, perfect slip, and Rady-Laun equations, while force as a function of viscosity for these equations overestimates the force at high viscosities.;Squeeze flow behavior of zeolite suspensions was also considered. The results matched the force vs. gap of the Newtonian fluids tested. The relative viscosities of the suspensions determined by squeeze flow matched the shear viscosity measurements at less than 15% vol concentrations. Likewise at less than 15% vol concentrations the data was shown to match the Maron-Pierce equation.;Electrorheological (ER) fluids were then examined under electric field in squeeze flow using constant volume conditions to eliminate the "sealing effect" that prevented knowing the concentration of particles in the fluid. The results show that increasing the concentration significantly increases the gap at which the fluid takes on large (>100 lbs) loads. Increasing the carrier oil viscosity decreased the steepness of the force vs. gap curves.;Filtration was assessed in squeeze flow of ER fluids using the Pe number as a predictor. Decreasing squeezing speed and viscosity were both shown to encourage filtration in electrorheological squeeze flow. Similarly increasing squeezing speed and viscosity were both shown to encourage convection in squeeze flow for ER fluids.;Squeeze flow of magnetorheological (MR) fluids showed similar behavior as ER fluids in the effects of concentration of particles. For MR the results on the effect of the viscosity of the suspending oil was done at a lower---5% vol---concentration, and showed similar behavior to the results seen for filtration in ER fluids.