Abstract
An analysis of the first resonance mode of piezoelectric fibers with metal core is carried out, and a method to estimate their piezoelectric properties is proposed. The modeled structure is first a hollow ceramic cylinder. The importance of radial stresses is investigated. Correlation with Finite Element Modeling is presented to validate the analytical approach. The effect of the insertion of a metal core is then presented through the calculation of the electromechanical coupling factor of the whole fiber after a homogenization of the metal core and the hollow cylinder. It is found that there is an optimal diameter at which the pseudo-lateral (length vibration) coupling factor is maximum. Finally the model is simplified, and a characterization procedure -called upward approach- of actual fibers is given. FEM is used to predict the resonance frequencies of a fiber with platinum core. The upward approach is then applied and the obtained piezoelectric ceramic parameters are found to be quite close to the real parameters, i.e. errors inferior to 7.9% in the worst case.
