ASA 126th Meeting Denver 1993 October 4-8

3aSA10. A comparison of structural intensity formulations.

Yong Zhang J. Adin Mann, III

Dept. of Aerosp. Eng. and Eng. Mech., Iowa State Univ., Ames, IA 50011

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.