Abstract:

In this paper a study on the characterization of the acoustic beam pattern for two PZT-5H, 3.5-MHz transducers using both experimental and FEA methods is reported. To obtain actual pressure-field measurements, a three-axis positioning system was constructed. The transducers were submerged in an acoustic test tank and the positioning system was used to maneuver a 200-micron PVDF hydrophone within the pressure field. At each location the output voltage of the hydrophone was measured along with the corresponding location. Using SPYGLASS[sup (registered)], these data were plotted to yield a two-dimensional ``slice'' of the actual pressure field. A finite-element model of the water-loaded ultrasonic transducer was created using ANSYS[sup (registered)]. Material properties that were needed to model the piezoceramic and polymers properly in the transducer were measured via pulse--echo technique. To validate the FEM results the electrical impedance of the transducers was calculated and compared to the actual measured values. The frequency-dependence of the impedance curves match closely. Using harmonic analysis, the pressure field in the water generated by the transducer was calculated and compared to the measured pressure-field data. Excellent agreement was obtained.