| The purpose of this study involves the development of an ER fluid and applications for controlling torsional vibrations. These two parts concern the development and characterization of an ER fluid and the application of this ER fluid for semi-active damping of vibrations of rotors.;In the second part, we have designed a new Smart ER Dynamic Absorber (SERDA) in which our ER fluid has been introduced, in order to semi-actively damp the rotor torsional vibrations. The purpose of this study is to evaluate the efficiency of the SERDA absorber. The results show that the SERDA absorber could semi-actively provide various torsional damping and stiffness under the application of an electric field. A general Quasi Bingham model is proposed in order to describe the dynamic behavior of the fluid ER. The measurements of the absorber efficiency have been carried out and the results show that the ER dynamic absorber exhibits very good performances in order to semi actively reduce the torsional vibrations of rotor systems.;This thesis is presented in the published paper form. Three papers (one published and two submitted) and three papers published in proceedings of conferences show the results of this research.;In the first part, we have developed an ER fluid by applying a design of experiments and by analyzing the influence of different parameters of design on rheological efficiency. This new ER fluid, called ETSERF, provides good rheological efficiency. In order to describe the ER behavior of the ER suspension, two empirical models has been developed. Based on ANDVA analysis, a quantitative relationship between the dynamic shear stresses and the independent variables has been developed. A relationship provides a very useful explanation for the contributions of each independent variable to the viscosity and yield stress. In order to improve this relationship, especially at low shear rates, a new empirical model, called the Quasi-Bingham model, is proposed to explain the performance of rheological fluids that have ER shear-thinning behavior, especially when the ER fluid works under the conditions of low speed and near yield stress. This new model may be used for all fluids with a shear-thinning behavior, especially when they work at low shear rates and yield stress conditions. The relationship between the ER effect and permittivity was also deeply studied since the ER effect strongly depends on the dielectric properties of ER fluids. |
