ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

2aSA9. Experimental investigation of backscatter from an internally loaded cylindrical shell with a constrained layer damping treatment.

Michael Klausbruckner

Matthew Conti

Ira Dyer

J. Robert Fricke

Dept. of Ocean Eng., MIT, Cambridge, MA 02139

Previous investigations have examined the backscatter from empty and internally loaded shells with no damping treatment, demonstrating the primary importance of helical shear waves. The helical waves contribute to large backscatter for aspect angles within 30 deg of normal for the empty shell. The region increases to 45 deg of normal for the internally loaded shells. A constrained layer was applied to the cylindrical section of an internally loaded shell to damp the helical waves while decoupling them from the internal structures. The intended effect was to lower the backscatter levels and reduce the angular width of strong backscatter to within 30 deg of normal. This preliminary investigation demonstrates the achievement of each of these goals. In addition, the importance of direct acoustic backscatter from the attachment locations of the internal rings was highlighted. The bistatic measurements were conducted over a frequency range of 2.5