ASA 127th Meeting M.I.T. 1994 June 6-10

1pSA4. Plate volume probing in manufacturing (or, extension modes in thin plates excited by broad normal sound beams).

Dov Hazony

Dept. of Elec. Eng. and Appl. Phys., Case Western Reserve Univ., Cleveland, OH 44106

A thin plate is excited by a normal acoustic beam of a finite area. The beam forms a propagation channel across the plate. This propagation mode is analyzed when the driving signals are sharp pulses. But, the main emphasis is on leaks that radiate off the main channel. These contain extension modes that travel along the off-channel axis in a coherent manner. Further, it will be seen that these may be singled out to monitor volumes of plates, walls of tubes, and inspection of welds; especially when access is restricted to a single surface. Experimental results will be presented and discussed. [Work supported by ONR and TecSonics, Inc.]