ASA 124th Meeting New Orleans 1992 October

2pSA10. Scattering from infinite coated cylindrical shells by a new shell theory.

J. Gregory McDaniel

Jerry H. Ginsberg

School of Mech. Eng., Georgia Inst. of Technol., Atlanta, GA 30332

Acoustic coatings have very low sound speeds in comparison to the underlying shell, and therefore tend to respond in higher-order thickness modes not contained in most shell theories. Previously, a variationally based, arbitrary order shell theory has been formulated in order to describe vibration of viscoelastically coated cylindrical shells. In this approach the dependence of all displacement components on the thickness coordinate are represented by a series of Legendre polynomials. Coated shells are modeled by independent expansions in the shell and coating, with displacement compatibility conditions between the shell and coating enforced explicitly. The formulation is extended in the present work to model plane wave scattering from an infinite cylindrical shell with a coating attached to its exterior surface. Numerical results include the backscattered form function, which is compared to published results, and detailed plots of displacement variations through the thickness. A focus of the present work is to assess the effect of higher-order thickness variations on the vibroacoustic response. [Work supported by ONR.]