A Hybrid Model for Characterizing Pre-Yield Properties of MR Fluids

This study aims to present a field dependent phenomenological model to characterize the Magneto-Rheological (MR) fluid in the pre-yield region under varying frequency and applied magnetic field. Systematic analytical and experimental studies are proposed to formulate a hybrid model for representing complex shear modulus of a typical MR fluid (MR 122EG from Lord Corporation) as a function of both applied magnetic field and frequency. Two fully treated MR based sandwich beams with aluminum and copper face layers and MR fluid as the core layer are designed and fabricated. Uniform magnetic flux across the sandwich beam is provided using two permanent magnets. The fabricated MR based sandwich beams are then tested on an electrodynamic shaker under sweep sine excitation and different applied magnetic field to realize the effect of external excitation frequency and applied magnetic field on the stiffness and damping properties of the structure. The finite element model based on classical plate theory is also developed to analyze vibration response of the designed MR based sandwich beams incorporated with MR fluid. Then, by correlating the finite element results with those of the experiment, the frequency and field dependent complex shear modulus of the MR fluid is identified.