ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

4pSA2. Diffuse energy propagation on heterogeneous plates: Structural acoustics radiative transfer.

Joseph A. Turner

Richard L. Weaver

Dept. Theoret. and Appl. Mech., Univ. of Illinois, Urbana, IL 61801

The propagation of diffuse energy on an unwetted heterogeneous plate is examined using a diagrammatic approach. The heterogeneities are assumed to lightly couple the membrane and flexural waves. The energy propagation is formulated in terms of the Bethe--Salpeter equation. This equation is further reduced to a radiative transfer equation in limit that the attenuations per wave number are small, i.e., when the heterogeneities are weak. This approach allows the diffuse energy propagation to be calculated as a function of space, time, and propagation direction. Solutions of the derived radiative transfer equation are presented for the simple case of attached heterogeneities in the form of delta-correlated springs excited by an extensional point source launched in a single direction. The results show the evolution and mode conversion of the extensional, shear, and flexural energy densities across the plate as a function of time. A similar approach is expected to apply to the more complicated case of submerged complex structures. [Work supported by ONR.]