ESTIMATION OF VIBRATIONAL POWER IN BUILT-UP SYSTEMS INVOLVING BOX-LIKE STRUCTURES, PART 2: INFINITE TOP-PLATE AND CIRCULAR GEOMETRY

Following on from a previous paper [1], work is presented in which the distributed forces exhibited between a box and its top and recipient are simplified by the introduction of assumed uniform distributions. The box consists of four side-walls, the recipient is a thick infinite plate, and the model is completed with a thin infinite top-plate attached via a roller condition. The introduction of a roller coupled infinite top-plate is motivated by the hypothesis that losses associated with wave propagation into its outlying region equate, approximately, to losses inherent in a fully coupled finite top-plate associated with wave conversion (at the coupled boundaries) and then divergence and dissipation (within the structure). Comparisons with experimental results are presented which corroborate the hypothesis. When uniform force distributions are assumed the study indicates that the transmitted power can be reliably calculated up to the first two or three resonances and, for higher wavenumbers, that the overall trend can be predicted. A constraint to this conclusion is, however, that strongly excited, anti-symmetric modes cannot be predicted. Analytical studies in which the box is reduced to a circular can are also performed and the results indicate that this simplification is valid when the requirement is for a simple estimate of the overall trend of the power. Overall, therefore, the paper proposes several possibilities through which models of built-up systems can be simplified.