Effect of hybrid structure (1-3 composite and ceramic) on the performance of sandwich transducers

By using 1-3 composite rings to replace the ceramic rings in a Langevin sandwich transducer, the non-axial and many other spurious resonances in the transducer are suppressed, and only the axial resonance modes are retained. In this study, a combination of ceramic and 1-3 composite rings, referred to as a hybrid structure, was used as the driving element to improve the performance of the transducer. Sixty-kilohertz pre-stressed sandwich transducers with hybrid structures were constructed. Various relative placements of the ceramic and composite rings in the transducers were studied in order to optimize the transducer performance and the results are discussed. The damping effects in the composite rings were evaluated from the axial vibration displacements measured by a laser vibrometer. Characteristics of hybrid transducers were compared with the full ceramic and full composite transducers. A symmetric structure in the hybrid transducer is found to be most effective for the fundamental and harmonic mode operations. (C) 2002 Elsevier Science B.V. All rights reserved.