Raymond Porzio
Peter G. Harvey
Charles P. Wason
Gerald L. Bernier
Lockheed Sanders, Antisubmarine Warfare Directorate, P. O. Box 868, Nashua, NH 03061-0868
Inverse barrel stave or class III flextensional projectors provide the designer of flexural low frequency projectors with an alternative high efficiency, high power density, broadband source which is less sensitive to service life limitations due to long term creep associated with ceramic stacks in other flextensional types. Other benefits arise from the stress-biased concave stave shell which undergoes a reversal in the sign of static stresses as the projector descends in depth resulting in greater shell strength margins allocated to dynamics. Results from combined electroacoustic modeling, finite element analysis and measurements show that, unlike convex shell flextensionals, shell wall thickness has only a very weak influence on resonance frequency and coupling. Instead, the R/L ratio (defined as the radius of curvature of the stave shell normalized by the ceramic stack length) exerts a surprisingly strong influence on the projector's frequency response and performance metrics. [Work supported by SPAWAR and NCCOSC, San Diego.]