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Date of Publication:2005-01-01

Journal:船舶力学

Issue:4

Page Number:119-129

ISSN No.:1007-7294

Abstract:Panels are widely used in ship and ocean structures. This paper is concerned with assessing the influences of the damages present in a stiffened panel on its acoustic radiation properties. Acoustic radiation power and directivity are two indices, which are able to fully describe the inherence acoustic radiation properties of a linear structure. The sound power and directivity pattern of a stiffened panel under different damaged conditions are thus investigated. Using Mindlin theory, the four-node health and damage shell finite elements were built up, and then the finite element method was applied to calculating the dynamic response of a structure. Isotropic damage elements are built by global and isotropical weakening of the stiffness. Anisotropic damage elements are built by using reduction coefficients for elasticity damages in x and y directions based on Kachanov's theory. Sound pressure of structure radiating outwards can be calculated through Rayleigh's integral formula, by use of which the radiated power and directivity can then be obtained. Influences of various types of damages on natural frequencies, vibration modes, acoustic radiation power and directivity of sound are studied. Finally, a computational method is given to analyze acoustic behavior of a damaged structure, demonstrated by some typical examples.

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