TABLE OF CONTENTS Flextensional transducers (see Fig. 1.17) are generally used as low to medium frequency high-power projectors radiating sound by the flexure of a metal or GRP shell excited by a drive stack operated in an extensional mode. The most common design is a Class IV type (see Fig. 1.18) which is an oval or elliptical shell driven by a piezoelectric ceramic stack along the major axis of the shell with amplified motion along the direction of the minor axis. Since the inactive shell makes up a significant portion of the transducer stiffness, it causes a significant reduction in the coupling coefficient, resulting in an effective value of k e ? k 33/2 for a 33-mode driven system.
The first flextensional transducer has been attributed [47] to Hayes [48] (see Fig. 1.25); however, it was the later work and patent of Toulis [49] that led to the Class IV design, which was modeled by Brigham [50] and later encoded for computer design and analysis by Butler [51]. Other early flextensional designs by Merchant [52] and Abbott [53], as well as the modeling by Royster [54], laid the foundation for more recent designs by Jones and McMahon [55] and Nelson and Royster [41b]. Dogan and Newnham [61] developed a very compact design, and Butler [56a, 56b, 63, 64a] extended the flextensional concept in various ways. Since flextensional transducers make use of flexural modes of an elastic shell, the analysis and modeling required to determine equivalent circuit parameters is...
