| This thesis describes the design, fabrication, modeling, and calibration of cymbal-type flextensional transducers for use as underwater electroacoustic projectors and receivers. The cymbal-type transducel-consists of a piezoelectric (PZT) disk poled in the thickness direction which is coupled to two thin metal caps on each of its electroded faces. Each cap is shaped such that a shallow air pocket exists between the cap and ceramic after they are attached. These caps serve as mechanical transformers for converting and amplifying the small radial displacement of the disk into a large axial displacement normal to the caps. The standard size cymbal transducer is 13.7 mm in diameter with a PZT thickness of 1.00 mm. The caps are 0.35 mm thick containing a cavity 9 mm in diameter and 300 {dollar}rmmu m{dollar} in height at the apex.; The in-air performance of these transducers was tested by examining the effect of the cap material and geometry as well as the PZT type on the resonance frequency, admittance spectra, coupling coefficient, and permittivity. One of the distinct advantages of the cymbal transducer, aside from its cheap cost and easy manufacturability, is the ability to readily tailor its properties by simply changing the cap material or the cap shape. The in-air fundamental resonance frequency for a 12.7 mm diameter cymbal can be set anywhere from 10 kHz to 50 kHz. Single element transducers were then evaluated under hydrostatic pressures up to 7 MPa to ascertain both performance capability and means of failure. It was found that the cap material and cap geometry both strongly influence the pressures the device is able to withstand before failure.; Using an anechoic underwater test chamber, the hydrophone and projector performance of these transducers (both as single elements and as small arrays) was evaluated. The effect of different cap materials, cap shapes, PZT types, and potting on electroacoustic performance was examined.; Computer modeling was also performed using finite element analysis {dollar}rm (ANSYSspcircler).{dollar} The calculated data was correlated with that measured experimentally. Both air and water loads were applied to the model. Resonance frequencies, mode shapes, and admittance spectra were calculated. |
