Synthesis and Rheological Characterization of Magnetorheological Fluids

Abstract

Magnetorheological (MR) fluids correspond to the kind of smart materials, capable of varying their rheological characteristics i.e., viscosity, yield stress, etc. on varying the magnetic field. In this article, 18 MR fluid samples utilizing various constituents are prepared and optimized with the aid of an L₁₈ orthogonal array. The synthesized samples are experimentally tested on a rotational oscillatory shear rheometer namely MCR-102 (modular compact rheometer) to obtain the shear stress values at various shear rates (0 - 1000 Sec^-1) and different currents (0 - 5 Ampere). This experimentally obtained data is fitted to the Herschel-Bulkley fluid model to estimate the On-state Yield Stress (OYS) for the tested MR fluid samples. An optimal set of the selected parameters i.e., silicon oil (carrier fluid), CI6 as the type of iron particle, 24 (Vol%) of iron particle proportion, and ethylene glycol monostearate (1.0% by volume) has been obtained using Taguchi analysis. An experimental verification test on the MR fluid with the Taguchi predicted optimal set of parameters has been performed and OYS matches well (a marginal error of 1.54%) with its statistically predicted value. The ANOVA results examine the contribution of input parameters and present that the iron particle proportion is the most prominent parameter that impacts the OYS, contributing 76.36%, followed by iron particle type which contributes 19.75%, carrier fluid with a contribution of 3.11% and additive proportion has a contribution of less than 0.1%. The OYS values for the optimal MR fluid are compared with commercially available MR fluids i.e., Lord MRF-122EG and MRF-132DG at various magnetic field intensities (0 - 164 kA/m). The comparison results exhibit that the OYS for the optimal in-house prepared MR fluid follows the same pattern as followed by MRF-122EG and MRF-132DG at all values of applied magnetic fields.