Layerwise theory in modeling of magnetorheological laminated beams and identification of magnetorheological fluid

In recent years, structures integrated with magnetorheological (MR) fluid have been considered for their tunable dynamic characteristics. Shear modulus of MR layer in composite structure is dramatically lower than the elastic layers, leading to high shear deformation inside the MR layer, thus classical theories are not accurate enough to predict the dynamic behavior of such structures. In present study a layerwise displacement theory has been utilized to predict a more accurate deformation for MR-composite beam and equation of motions derived using finite element model (FEM). ASTM E756-98 was employed to evaluate the complex shear modulus of MR fluid. By experimental test a practical formulation for complex shear modulus of MR fluid was extracted. In this formulation shear modulus of MR fluid was presented as function of magnetic flux density and also driving frequency. Based on switched-stiffness vibration control concept a control algorithm was designed and effect of this control strategy on force and free vibration was examined.