Characterization of Magneto-Rheological Fluid and Monotube Damper through Experimental and Computational Analysis

Abstract

Magnetorheological fluid belongs to a class of smart materials which exhibit change in their rheological properties, when exposed to an external magnetic field and these properties are completely reversible. By utilizing these special characteristics, the damping force of the MR damper can be controlled and varied in real time applications. The main objective of this research work is to investigate the characteristics of MR fluid and MR damper through experimental as well as computational methods and to evaluate the semi-active suspension with MR dampers performance in terms of ride comfort and road holding of vehicles, when subjected to random road conditions. The rheological characterization of the MR fluid samples under different magnetic fields and fluid gap has been evaluated through experimentation. The measured fluid properties were used for computing the damping force of MR damper. Using single and multi-objective particle swarm optimization techniques, the optimal proportion of iron particles for MR damper application was determined to maximize the shear stress and damping force. The dynamic characterization of MR damper through experimental approach using dynamic test facility at 1.5 Hz and 2 Hz frequencies has been carried out. Also, the influence of material properties of MR damper components on the induced magnetic flux density and geometrical parameters on the damping force was investigated through finite element analysis as well as analytical methods. Multi-objective genetic algorithm and screening optimization techniques were employed to maximize the magnetic flux density and to identify the optimal values of the design variables. Using the analytical method, damping force of the damper was computed for the obtained optimal values of the design variables. It was observed that the damping force of the MR damper whose cylinder is made up of magnetic material was 2.79 times greater than that of MR damper whose cylinder is made up of non-magnetic material. Further, a coupled finite element analysis (FEA) and computational fluid dynamics (CFD) analysis was used for estimating the magnetic flux density and damping force for different input currents. The credibility of the shear mode monotube MR damperanalysis results were validated with experimental results. To overcome certain limitations of shear mode damper, an attempt has been made to realize the mixed mode damper by combining the flow and shear mode operations. The variations in the damping characteristics of flow and mixed mode MR damper under different input were compared with shear mode MR damper. Results showed that combination of two modes of operation could enhance the damping force to a significant level. The damping force of mixed mode MR damper was found to be 3 times greater than that of shear mode MR damper at 2 Hz frequency and 0.4 A current. Based on results obtained from computational analyses, a non-parametric representative model exhibiting the hysteretic behavior of MR damper was developed. The developed nonparametric model was implemented in a quarter car semi-active suspension to determine the dynamic response of the vehicle subjected to random road excitations. Further, this model was implemented in three-wheeler vehicle semi-active suspension system to evaluate its dynamic performance. The outcome showed that the vehicle with non-parametric based MR suspension system provided good vibration isolation for semi-active suspension than passive suspension system in terms of rice comfort and road holding.