Index of content:
Volume 109, Issue 1, January 2001
- STRUCTURAL ACOUSTICS AND VIBRATION 
109(2001); http://dx.doi.org/10.1121/1.1310669View Description Hide Description
The dynamic and static characteristics of asymmetric bimorphic disk transducers that consist of a piezoelectric layer laminated with an unequal radius elastic disks are optimized. An electroelastic laminated plate theory is developed to analyze the mechanical, electrical and electromechanical behaviors. Close form solutions are obtained for the mechanical displacement and electric potential in terms of Bessel functions. Special focus is on the electromechanical coupling coefficients (EMCC) that are shown sensitive to geometric variables, such as thickness and radius ratios of the piezoelectric and elasticmaterials. Optimum configurations to reach the maximum values of the EMCC or static displacement sensitivity and influence of material and geometric properties are presented. Experiments are conducted to verify the theoretical results with good agreement.
109(2001); http://dx.doi.org/10.1121/1.1323236View Description Hide Description
The use of a modal representation for the exterior acoustic field of a structure has received increasing attention in recent years. This modal approach generally seeks a set of orthogonal functions, representing independent surfacevelocity distributions, termed acoustic radiation modes, which diagonalize a radiation operator in the exterior domain of the structure. These orthogonal acoustic radiation modes may be found, among other methods, through an eigenvalueanalysis of a radiation operator and possess a corresponding set of eigenvalues that are proportional to the radiation efficiencies of the acoustic radiation modes. In free space, the acoustic radiation modes of a sphere display a grouping characteristic in their radiation efficiencies, where each acoustic radiation mode’s radiation efficiency within a group has the same frequency dependency. This is a consequence of the fact that the acoustic radiation modes of a sphere are the spherical harmonics. Further, the acoustic radiation modes of an arbitrary three-dimensional structure exhibit the same frequency grouping as those for the sphere. The basis for the arbitrary structure’s grouping follows from the sphere’s grouping. The observation that the acoustic radiation modes of an arbitrary body are dominated by spherical harmonics provides insight on the behavior of such modes. These results have significance for various applications of acoustic radiation modes, including active noise control design, radiation modeling, etc.