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.

An Overview

“…This tutorial has outlined the F.E. method [1], discussed aspects of programming the algorithm [2] and given some transducer design applications [3][4]. We see that the F.E.…”

“…An extensive account of F.E. methods applied to a flextensional design including fluid loading effects has also been presented [4]. Reduction in stack pre-stress that occurs while the flextensional transducer is lowered to operational depths is well described.…”

Measuring Flextensional Transducer Mode Shapes Underwater Using Laser Speckle Intrferometry

“…They are not readily amenable to traditional equivalent circuit analysis methods, but Finite Element (FE) techniques [3] have been shown to be successful. More recently, FE analysis has been extended to three dimensional modelling of transducers [4], the results suggesting that the modal structure is not necessarily consistent across the surfaces ofthe transducers. As in many cases where a modelling technique such as FE is used, experimental veri cation is generally required for model validation.…”