ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06
2aUW3. Appearance of elastic wave contributions in high resolution
acoustic images.
Gregory Kaduchak
Chad M. Wassmuth
Charles M. Loeffler
Appl. Res. Labs., Univ. of Texas, P.O. Box 8029, Austin, TX 78713-8029
Studies involving plane wave scattering by finite cylindrical shells at
oblique incidence display monostatic echo contributions from surface elastic
waves. These waves follow helical paths along the shell's surface and are
guided back in the source direction after reflection from the cylinder
truncation [X.-L. Bao, 1461--1465 (1993)]. The present research
examines such effects viewed in the time record of a high resolution sonar
system. The target consists of a finite cylindrical shell with a radius to
thickness ratio of 5%. The shell is immersed in water and is subject to both
exterior and interior fluid loading. It is ensonified with short tone bursts of
narrow beam width over a range of incidence angles 90(greater than or equal
to)(phi)(greater than or equal to)50, where (phi) is measured relative to the
cylinder axis. The backscattered echo signature exhibits prominent artifacts as
a result of scattering processes involving the s[sub 0] and a[sub 0] Lamb waves
interacting with the cylinder truncation. The echo contributions are extremely
sensitive to the angle of incidence and interior fluid loading which may assist
in target classification schemes.