含损伤加筋结构的振动与声辐射特性研究

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

采用有限元/边界元方法针对加筋结构,研究了损伤对振动与声辐射特性的变异特性。将损伤模型引入结构有限元分析中,针对各向同性损伤单元模型中,采取刚度各向整体弱化的方法分析;对于各向异性损伤单元模型中,采用Kachanov理论,分别引入了x和y两个方向的弹性损伤折减系数。基于Mindlin板理论,建立描述健康和损伤的4结点有限壳单元模型,采用有限元方法计算结构振动特性与表面动力响应。基于4结点二维线性边界元模型,根据Rayleigh积分可以计算结构振动向外辐射的声压,进而可以得到辐射声功率和辐射指向性。为了研究损伤结构处于空气或水中不同损伤位置和大小对结构振动及声特性的影响,文章建立了含损伤结构的动力与声辐射分析方法,就各种损伤对结构振动频率、振动模态与声辐射模态、辐射阻尼、辐射功率与指向性的影响进行了数值模拟。通过对典型算例分析,得出了相应的结论,在评价损伤对船舶与海洋结构物常用的加筋结构声辐射特性影响方面做出了一定的探索。

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 influences of the damages present in a stiffened panel on its acoustic radiation properties.