Magnetorheological (MR) fluids and dampers have wide advances as smart materials because of its unique properties, notably, viscosity increases in the presence when magnetic field applied MR Fluids composed of three key components, including carrier fluid, surfactants and metal particles. The major applications of MR Fluids are in brakes, dampers, journal bearings, fluid clutches, pneumatic artificial muscles, aerospace etc. where electrical energy is converted to mechanical energy (Damping Force) in a controlled manner. Within a few milliseconds the fluid converts from liquid to semi solid state. Over the years, researchers were concerned on the ways to enhance the modelling precision. Though the proposed Dynamic models of MR Dampers represent displacement and force behaviour. In this review paper, the advances of MR Fluids, MR Damper, Damper Models, Energy harvesting and their applications for seismic resistance of structures are briefly discussed in the present study.

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A B S T R A C TThe present study focusses on the damping force control of shear mode magnetorheological (MR) damper for seismic mitigations. Therefore, the semi-active MR damper which can control the vibration is analyzed both experimentally and numerically. Carbonyl iron is used as the magnetic particle and Castrol Magnetec oil as carrier fluid throughout the study. MR damper is designed and fabricated, and its damping force was evaluated experimentally at 2.5 A-10 V. Shear mode MR Damper is tested in universal testing machine using time history loading. The model was numerically analyzed using Newmark's method for nonlinear system in MATLAB to control the three storey model building frame taken from the literature. The result indicates that 49.42% reduction in displacement at the second storey and 48.14% in the third storey, respectively. Maximum reduction was observed when damper was kept in the ground floor. The maximum force observed for the MR Damper is 0.777 kN.

Magnetorheological damper (MR damper) is one of the promising vibration control systems, applicable for damping seismic induced vibrations in structures, because of their ability to be controlled and to adapt their mechanical properties by varying the magnetic field, their high damping force, their low energy input required and their simple use. This paper presents the experimental results carried out to study the use of Nano Fe3O4as component of MR fluid. The Nano Fe3O4particles are obtained by an indigenous process to convert a waste product of chemical industry. The performance of Nano Fe3O4MR fluid is compared with five commercially available samples in the market namely, Mill scale, cast iron (1), cast iron (2), carbonyl iron and white iron oxide. Surface morphology was identified using SEM & the average particle size was analysed using XRD. Viscosity & settling measurements were also performed for all the six samples. Shake table tests were conducted to study the performance of steel frame with MR damper. The model for the study was a single bay three storey steel frame where the response of the structure, in terms of acceleration, velocity and displacement was observed. It was observed that the percentage of reduction in displacement, velocity, acceleration, approximately 40 – 67% for structure with MR damper.

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