Browsing by Subject "Transducers."

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    Barrel-stave flextensional transducer design
    (2009) Şahin, Aykut
    This thesis describes the design of low frequency, high power capability class-I flextensional, otherwise known as the barrel-stave, flextensional transducer. Piezoelectric ceramic rings are inserted inside the shell. Under an electric drive, ceramic rings vibrate in the thickness mode in the longitudinal axis. The longitudinal vibration of the rings is transmitted to the shell and converted into a flexural motion. Low amplitude displacements on its axis create high total displacement on the shell, acting as a mechanical transformer. Equivalent circuit analysis of transducer is performed in MATLAB and the effects of structural variables on the resonance frequency are investigated. Critical analysis of the transducer is performed using finite element modeling (FEM). Three dimensional transducer structure is modeled in ANSYS, and underwater acoustical performance is investigated. Acoustical analysis is performed by applying a voltage on piezoelectric material both in vacuum and in water for the convex shape barrel-stave transducer. Effects of transducer structural variables, such as transducer dimensions, shell thickness, shell curvature and shell material, on the electrical input impedance, electroacoustical transfer function, resonance frequency and quality factor are investigated. Thermal analysis of designed transducer is performed in finite element analysis. Measured results of the transducer are compared with the theoretical results.
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    The design of a wideband and widebeam piston transducer in a finite closed circular baffle
    (2008) Şahin, Zekeriyya
    The design of a high power piezoelectric underwater transducer operating at frequency range 42 kHz-78 kHz with acoustic power capability in excess of 250W is described. The transducer consists of two back-to-back elements. Each element is formed by stacked PZT-4 ceramic rings, a matching and a steel backing layer, and placed in a finite rigid circular baffle. We investigate the dependence of bandwidth and beamwidth to the combination of piston and baffle radii, a and b, respectively. With ka of 2.45 (k is the wave number) at resonance and a b/a ratio of 2, the transducer resonates at 60kHz with 60% bandwidth and has a beamwidth of 60º at each half space. We show that when two transducers are placed at right angles spatially and driven in parallel, we can obtain an omnidirectional beam pattern in the lower frequency band. The beam pattern exhibits two dips in each quadrant at the higher end of the frequency band, which are within 8 dB. We also investigate power handling capability of the transducer from thermal point of view using finite element analysis. The input impedance measurements agree well with the numerical results within the pass band.