Identification of piezoelectric complex parameters in rings for power ultrasound applications

Power ultrasonic devices frequently use Langevin type transducers. These types of transducers are essentially constructed using a sandwich of piezoelectric rings and two metal masses at the ends. The whole assembly is tuned to resonate in a desired main frequency and the total length corresponds to a half of the wavelength of that frequency. Finite element simulations (FEM) are used in the design of such complex structures; however the accuracy of the results is limited by the knowledge of the constitutive properties for the materials used in the transducer construction. Metals like aluminum or steel are well characterized, but the complete set of piezoelectric parameters for piezoceramics are difficult to find in the literature. In the few cases where the manufacturer gives the complete set of parameters, strong differences are observed between simulated and experimental data. In this work a novel methodology proposed by our research group is applied in the case of piezoelectric rings made with a hard piezoelectric material. The results are evaluated in rings with internal diameter 8 mm, external diameter 27 mm and thickness 5 mm. Finally the results are validated using an optical interferometer showing a good agreement.