Finite element modeling of the ARE low‐frequency flextensional transducer

Abstract

A requirement for underwater acoustic sources with higher source level and wider bandwidth at lower frequencies has, in the past 5 years, lead to interest in flextensional transducers. A low‐frequency prototype, which consists of a GRP shell and convention ceramic stacks, has been developed, manufactured, and tested at ARE(Portland); the technology is the subject of a license agreement with industry. In this paper, finite element (FE) analyses performed in support of the prototype development using PAFEC software are described. PAFEC is a commercially available FE package with the facility to model piezoelectric materials, and exterior fluid loading by the doubly asymptotic approximation. In‐air and in‐water resonant frequencies are well predicted, as is the effect of hydrostatic pressure on stack prestress. The shell is subjected to large interlaminar shear stresses during stack insertion, and predictions for these have also been obtained. Work is in hand at PAFEC to add the capability to couple a Helmholtz integral equation representation for the exterior fluid to the existing finite element package for the structure. This will enable source level and bandwidth calculations to be made, which, at present, cannot be accurately predicted.