Accession Number:

ADP011289

Title:

Subsonic Rayleigh Wave Resonances on Solid Polymer Spheres in Water and Backscattering Enhancements Associated with Tunneling: Experiments, Models, and the Relative Significance of Material and Radiaton Damping

Descriptive Note:

Corporate Author:

WASHINGTON STATE UNIV PULLMAN

Personal Author(s):

Report Date:

2001-06-04

Pagination or Media Count:

8.0

Abstract:

Rayleigh waves on typical solid plastic polymers have phase velocities which are less than the speed of sound in water. One consequence is that when a solid sphere or shell made of such a material is placed in water, the backscattering mechanisms can differ from the situation for ordinary solids. For example, since the Rayleigh waves on a sphere are subsonic waves instead of leaky waves, the scattering processes need to be modeled as acoustic tunneling through an evanescent region. We have experimentally confirmed the existence of the resulting resonance and backscattering enhancements. Experiments and computations also support the extension of a tunneling model previously developed for quasi-flexural waves on thin metallic shells L. G. Zhang, N. H. Sun, and P. L. Marston, J. Acoust. Soc. Am. 91, 1862-1874 1992. For the case of PMMA spheres studied, the intrinsic material damping can significantly affect the scattering. Some models were tested for the combined effects of material and radiation damping. The material damping was sufficiently small for the quadrupole mode that the observed enhancement may be useful for sonar calibration targets as an alternative to liquid-filled shells. Work support by the Office of Naval Research.

Subject Categories:

  • Acoustics
  • Radiofrequency Wave Propagation

Distribution Statement:

APPROVED FOR PUBLIC RELEASE