Multi-parameter optimization of magnetorheological fluid with high on-state yield stress and viscosity

Magnetorheological fluids belong to a class of smart materials, whose rheological characteristics such as yield stress, viscosity, etc. change in the presence of applied magnetic field. In this paper, multi-response optimization of MR fluid constituents is obtained. For this, 18 samples of MR fluids are prepared using L-18 Orthogonal Array. These samples are experimentally tested on the in-house developed and fabricated electromagnet setup. The setup has been validated using a reference fluid. Yield stress of MR fluid mainly depends on the volume fraction of the iron particles and type of carrier fluid used in its preparation. An optimal combination of these input parameters with mineral oil as a carrier fluid and Fe 300 mesh (32% by volume) as an iron particle, oleic acid (0.5% by volume), and tetra-methyl-ammonium-hydroxide (0.7% by volume) has given the largest numerical values of on-state yield stress and viscosity of the MR fluid sample as 48.197 kPa and 573.0944 kPa-s, respectively, within the range of the input parameters. The yield stress of optimized MR fluid is higher than Lord MRF-122-EG fluid. Furthermore, a confirmation test on the optimized MR fluid sample has been carried out and the response parameters thus obtained are found to be matching quite well (with error less than 1%) with the statistically obtained values. This high value of the yield stress and viscosity can be used more effectively in the formulation and designing of MR devices requiring larger variation in the damping.