In the present study, the shear stress response and the dynamic mechanical properties of an electrorheological fluid are experimentally investigated for small/large shear strain amplitude at moderate range of frequencies and different field intensities. A new efficient constitutive model has also been proposed, which can accurately predict the measured experimental data. Compared with the Fourier transformation rheology, the proposed model requires less number of parameters in order to predict the stress response and the mechanical properties, including storage and loss moduli for different strain amplitudes, frequencies, and field intensities. This leads to simplify the parameter identification in order to predict the material response using the optimization methods.

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Compared with viscoelastic materials, electrorheological fluids can be effectively used to suppress the vibration over a broad frequency and temperature range. In this study, vibration analysis and damping characteristics of sandwich cylindrical panel structures using semiactive electrorheological fluid treatments have been investigated for different boundary conditions. Unconstrained viscoelastic material has been used at boundary and untreated locations to seal electrorheological fluids. First, an efficient finite element method has been formulated to investigate the effect of electric field intensity and thickness of top constrained elastic layer on the vibration and damping performance of the viscoelastic- and electrorheological-based sandwich cylindrical panel. Then, a design optimization methodology has been developed to simultaneously optimize the number of unconstrained viscoelastic and constrained electrorheological fluid patches and their distributions, thickness ratios of the electrorheological core and constrained elastic layers to base layers, and the external electric field intensity. The methodology integrates the finite element model of the sandwich panel with the combined genetic algorithm and sequential quadratic programming to effectively identify the global optimal solutions. The results show that for some boundary conditions, the sandwich panel partially treated with electrorheological fluids provides better damping performance compared with that of fully treated.

Nonlinear vibration analysis of sandwich shell structures with a constrained electrorheological (ER) fluid is investigated for different boundary conditions. To accomplish this, a nonlinear finite element model of a multi-layer shell structure with an ER fluid layer in the core of the sandwich shell has been developed. A new notation referred to as H-notation is presented, in place of the two well known notations referred to as B-and N-notation, in order to represent the nonlinear equations of motion. This notation leads to a considerable reduction in the computational costs caused by the time-consuming integrations in the nonlinear vibration analysis of the structure using a direct iteration technique. In particular, this notation is very useful for solving the nonlinear vibration analysis of sandwich layered shell structures in which large numbers of integrations are required to be repeatedly performed throughout the direct iteration technique. Finally, for different boundary conditions, the effects of small and large displacements, core thickness ratio and electric field intensity on the nonlinear vibration damping behavior of the sandwich shell structure are presented.