Measurement of Magnetorheological Fluid Properties at Shear Rates of up to 25 000 s$^{-1}$

Abstract

Magnetorheological energy absorbers (MREAs) have been successfully deployed in occupant protection systems to protect against potentially injurious shock, crash and blast loads. These MREAs operate at shear rates upwards of 25 000 s , but magnetorheological fluids (MRFs) are typically characterized for shear rates up to 1000 s in commercially available parallel counter-rotating disk rheometers. Because of the lack of availability of data at the required high shear rates, a Searle-type magnetorheometer (essentially a concentric cylinder rotating in a cup) was designed and fabricated at the University of Maryland. Using this magnetorheometer, two commercial MRFs were characterized over the shear rate range of 0-25 000 s . It is shown that the rheometer was successful in replicating available characterization data at low shear rate, as well as quantifying high shear rate behavior as a function of applied field. In addition, it was shown that the Herschel-Bulkley constitutive model is appropriate and successfully characterized the apparent viscosity vs. shear rate behavior of the MRFs over this shear rate range. Experimental data demonstrate that an increase in field dependent yield stress can be realized over this entire shear rate range, so that MREAs can be designed using data taken with the magnetorheometer. Finally, the Mason number, which has been shown to be a useful non-dimensional number at low shear rates, also provides a useful physical interpretation at high shear rates.

Load and stiffness of a hydrostatic bearing lubricated with a Bingham plastic fluid

“…It showed that the internal pressure generated in an FF subjected to a magnetic field is not strong enough to be relevant for use as an active lubricant in most journal bearing applications. The work of Becnel et al (2012) showed that the magnetoviscous effect is still present at shear rates up to 25,000 s 21 , a value that is regularly observed in bearing system applications. However, Urreta et al (2010) showed that the gain of using an MR fluid at high shear rates diminishes due to the large viscous stresses at higher speeds.…”

Nondimensional scaling of magnetorheological rotary shear mode devices using the Mason number

“…Originally validated using low shear rate γ̇< − ( 1000 s ) 1 measurements, it was later shown to hold true in high shear rate operation [6] in carefully controlled laboratory experiments. It is proposed here that this nondimensional analysis can be effectively extended to model practical MREA devices under real-world conditions.…”

“…Both MR yield stress and fluid viscosity have been shown to vary with temperature [4,5]. Furthermore, MRFs are highly shear thinning materials, so they exhibit a significant reduction in viscosity as shear rate increases [6]. For these reasons, a wide variety of fluid characterization tests, which vary temperature, shear rate, and applied magnetic field are currently required to adequately determine the performance of a given MR fluid utilized in certain devices and environments, and consequently, predictive models such as the Herschel-Bulkley (HB) constitutive model typically employed to characterize measured rheological behavior must rely on a huge data set of characterization tests to be useful across the entire range of expected operating conditions.…”

Numerical analysis of multiphysical field for independent three-stage magnetorheological damper of double rod during recoil process of artillery

“…Based on the above discussion, the flow characteristics of MRG-70 can be described by the Herschel–Bulkley model (equation (1)), which is slightly modified from the Bingham fluid model (equation (2)) 27–29 where τ is the shear stress, τ y , is the shear yield stress, r· is the shear rate, η is the viscosity, k is the consistency coefficient, and n is the non-Newtonian exponent. Different values of n represent different characteristics, as follows …”