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ABSTRACT. THE PIEZOELECTRIC TRANSDUCERS EMPLOYED IN HIGH POWER ULTRASOUND ARE COMPOSED OF PIEZOELECTRIC CERAMICS AND METALLIC PIECES. THESE TRANSDUCERS ARE MECHANICALLY PRE-STRESSED IN ORDER TO AVOID THE CERAMIC FRACTURES WHEN IT IS SUPPLIED WITH HIGH VOLTAGE ON RESONANCE FREQUENCY. IT WAS OBSERVED THE PRE-STRESSING APPLICATION ON COMPOSED TRANSDUCERS YIELDS SHIFTINGS ON RESONANCE AND ANTI-RESONANCE CHARACTERISTICS. SIMILAR EFFECTS WERE OBTAINED FROM ELECTRIC IMPEDANCE CURVE OF TRANSDUCERS SIMULATIONS WHERE THE PIECES CONTACT TRANSVERSAL SECTION WAS VARIED. THESE FEATURES REVEAL THAT THE PRE-STRESSING CONTRIBUTES FOR THE IMPROVEMENT OF EFFECTIVE ACOUSTIC CONTACT BETWEEN THE TRANSDUCERS PARTS.
KEY-WORDS: TRANSDUCERS, PIEZOELECTRICS, PRE-STRESSING, ULTRASOUND
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