DESIGN OF A HIGH-POWER STEEPED PLATE ULTRASSONIC TRANSDUCER

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.