# DESIGN OF A HIGH-POWER STEEPED PLATE ULTRASSONIC TRANSDUCER

## Palavras-chave:

High Power, ultrasound transducer, finite element method, genetic algorithm## Resumo

High-intensity airborne ultrasonic waves have been used to accomplish several phenomena,

such as defoaming, food drying and agglomeration of aerosol fine particles. In those applications,

circular stepped-plates are often chosen to generate continuous waves due to their high efficiency and

directive radiation patterns. In this study, a high-power stepped-plate transducer is designed for future

investigation of the effects of airborne ultrasonic waves on iron ore flotation froth. The acoustic

energy is generated by a piezoelectric Langevin transducer with a mechanical amplifier coupled to the

stepped circular plate. The finite element method is used to simulate the dynamic behavior of the

device through modal and harmonic analysis. Axisymmetric models are used on a parametric

optimization problem formulated to design the transducer. This problem is solved with a meta-

heuristic (genetic algorithm) employed to determine the set of lengths that define the geometry of the

plate. In this approach, the objective function presented assures the proper vibrational behavior of the

device, given a series of practical considerations. To validate the obtained design, a harmonic analysis

of a three-dimensional model for the stepped plate is used to assess the occurrence of undesirable

modal interactions. The Rayleigh Integral is solved to calculate the acoustic pressure field considering

the vibrational displacements of the plate, obtained by the finite element model. The performance of a

similar transducer with a smaller vibrating surface is presented to establish a general comparison.