### ASA 126th Meeting Denver 1993 October 4-8

## 3aSA10. A comparison of structural intensity formulations.

**Yong Zhang
J. Adin Mann, III
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*Dept. of Aerosp. Eng. and Eng. Mech., Iowa State Univ., Ames, IA 50011
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Much past research concerning structural intensity has focused on the
structural intensity formulation and measurement methods. For the structural
intensity in a thin plate, different formulas were derived based on different
assumptions. Pavic's structural intensity formula [G. Pavic, J. Sound Vib.
49(2), 221--230 (1970)] was based on classical plate theory, which is described
by Lagrange's equation of motion. A more general derivation was perfomed by
Romano et al. [Proceedings of the International Congress on Intensity
Techniques, CETIM, 137--142 (1990)], which was based on three-dimensional
elasticity. In this paper, a structural intensity formula is derived by
simplifying Romano's structural intensity formula using Mindlin's assumption
for thin plate theory that considers the rotary inertia and shear effect. The
differences between the formulations will be discussed. From plate velocity
measurements for an aluminum plate at single frequencies, the structural
intensity is calculated based on the above-mentioned intensity formulas. In
addition, the input mechanical force function is estimated. Results show that
the input power from structural intensity and the input mechanical force match
well with the experimental results.