Manufacturing and testing of an optimized Magneto-Rheological (MR) fluid and modelling of a Twin tube MR damper using a modified non-Newtonian model using analytical quasi-static, analytical unsteady, numerical and experimental methods

Magneto-Rheological Fluids (MRF) are one of the intelligent fluids which have been extensively used in engineering application including Magneto-Rheological Dampers (MRD). Having yield stress in a magnetic field and ability to control and increase their viscosity is their most important characteristics. . In this study and after three different carbonyl iron powders were subjected to SEM and EDX analysis, five different MRFs were synthesized and were tested for stability. Effect of iron powder weight percentage in the fluid and preservative on level of sedimentation in the MRFs were investigated and the optimized fluid in terms of stability and concertation was selected for rheological characterization in various magnetic fields. The results obtained from the optimized MRF with 85% (weight %) iron powder was similar to that of LORD MRF-140CG oil. Also, a modified non-Newtonian rheological model was developed to predict the behavior of the optimized MR fluid which is more accurate than Bingham and Herschel-Bulkley models and could be implemented in CFD modelling. The modelling of the MR damper was conducted by implementing modified non-Newtonian and Bingham models using analytical quasi-static, unsteady and CFD methods and the results were validated with experimental data. The results show that neglecting factors including fluid shear thinning, wall shear stress and inertia term effects and effect of magnetic field on plastic viscosity in conventional modelling methods results in considerable error that will increase as magnetic field, Reynolds number and gap are increasing. Consequently presented model and methods, could be used for improved MR damper design.