ASA 126th Meeting Denver 1993 October 4-8

4pSA5. Traveling wave decomposition of surface displacements on a cylindrical shell: Numerical evaluation displaying guided wave properties.

Gregory Kaduchak Thomas J. Matula Philip L. Marston

Dept. of Phys., Washington State Univ., Pullman, WA 99164-2814

Internal displacements of spherical shells subjected to steady sound waves in water have previously been computed by other researchers [R. Hickling et al., J. Acoust. Soc. Am. 92, 499 (1992)]. Such displacements can be difficult to interpret with a guided wave representation because of the superposition of counterpropagating Lamb waves and the local response to the incident wave. In this research the surface displacements of a cylinder were evaluated since they can be mathematically decomposed into counterpropagating circumferential traveling waves. (Unlike an analogous decomposition for spheres, the amplitudes in the cylinder case are regular at 0 and 180 deg.) By limiting attention to the radial displacements of the outer surface, it was also possible to display the response to short-tone bursts and thereby distinguish between the local response to the incident acoustic wave and Lamb waves launched on the shell. Both the steady-state and burst response situations clearly manifest waves launched on the shell. These can be easily seen for ka as low as 8 for a thin shell. [Work supported by ONR.]