### 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
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Richard L. Weaver
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*Dept. Theoret. and Appl. Mech., Univ. of Illinois, Urbana, IL 61801
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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.]