MAGNETORHEOLOGICAL FLUIDS EMPLOYING SUBSTITUTION OF NONMAGNETIC FOR MAGNETIC PARTICLES TO INCREASE YIELD STRESS

Magnetorheological fluids (MRFs) were characterized in this study to investigate the effect of replacing magnetic particles with nonmagnetic micro-scale glass beads to increase yield stress, while also reducing density and settling rate. Two MRF samples were prepared. MRF-40 had a Fe concentration of 40 vol% while the second fluid had a total Fe concentration of 37 vol% and a glass bead concentration of 3 vol%. A comparative study of MRF characteristics was conducted to determine the impact of the nonmagnetic glass beads on yield force, as well as viscosity, and settling rate. Both MRFs were characterized as follows: 1) magnetorheology as a function of magnetic field, 2) sedimentation analysis conducted with an inductance-based sensor, and 3) cycling of a small-scale damper undergoing sinusoidal excitations at frequencies of 1 Hz for characterization and 4 Hz for fatigue tests. Further investigation of the glass beads was conducted to examine their durability post-cycle. The goal of this study is to analyze the effectiveness and feasibility of replacing magnetic particles with micro-scale glass beads in MR fluids as a means to reduce the specific gravity and increase the yield stress.