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

5pSA2. Measurement of evanescent waves on a cylindrical shell.

H.-G. Kil

J. Jarzynski

Y. H. Berthelot

School of Mech. Eng., Georgia Inst. of Technol., Atlanta, GA 30332

Calculations are made of the reflection coefficient matrix at the end of a cylindrical shell for various end boundary conditions. The calculations show mode conversion on reflection at the end of the shell, including conversion from propagating to evanescent waves. The evanescent waves are studied experimentally using the laser Doppler vibrometer (LDV) described previously [H.-G. Kil et al., J. Acoust. Soc. Am. 93, 2389(A) (1993)]. The LDV system is used to measure the amplitude and phase of the particle velocity at a large number of points on the shell surface. The data are analyzed in the frequency-wave number domain using Prony decomposition. Data will be presented for a shell 0.94 m long and 1.6 mm thick, freely suspended in air and excited radially by a shaker at approximately twice the ring frequency. [Work supported by ONR.]