Study on the Characteristics of Vibration and Acoustic Radiation of Damaged Stiffened Panels

The characteristics of dynamic and acoustic radiation of a damaged stiffened panel are investigated by FEM/BEM. The modes of damages are introduced into the finite element analysis. Isotropic damage modes are modeled by softening the stiffness globally and isotropically. Anisotropic damage modes are modeled by using reduction coefficients for elastic damages in x and y directions according to Kachanov theory. Based on Mindlin theory, a 4-node shell element model is built to analyze the healthy and damaged structures, and calculate the dynamic characteristics and response of a structure surface. With the 4-node, linear boundary element, the sound pressure of structure radiation can be calculated through the Rayleigh＇ s integral formula and the radiated power and directivity can then be obtained. An analysis method has been established to analyze acoustic characteristics of a damaged structure. Conclusions have been drawn from the analyses of some typical examples. Panels are widely used in ship and ocean structures. The proposed method is useful for assessing the influen ces of the damages present in a stiffened panel on its acoustic radiation properties.