【作者】 邹平；

【导师】 文桂林；

【作者基本信息】 湖南大学 ， 机械工程， 2009， 硕士

【摘要】 薄板作为一种常用的结构件在军民领域中发挥了很大的作用,然而薄板有其自身的不足。薄板通过加厚或其上加筋可以改善力学和声学性能,但是薄板增厚会使其自重增大,且没有充分利用材料;而对薄板加筋在一定条件可使薄板自重不增加且又能改善其性能,因而加筋成为改善薄板性能的最佳选择之一。加筋板结构比较容易通过调节板上加强筋的尺寸和间距等来满足工程设计中的强度、刚度、稳定性和声学特性等多方面的要求,所以比薄板更广泛地使用在军民用领域中。加筋板的振动与声辐射问题很早就受到了人们的高度关注。国内外学者对加筋板的承载性、极限强度、稳定性和声辐射进行了大量的研究。本文从加筋板的拓扑形状着手,具体研究了加筋板的拓扑变化和其边界条件的变动对加筋板的刚性及声辐射性能的影响。本文以常见的“井”字型加筋板结构为研究对象,基于Mindlin板理论和空间梁元理论,根据加筋板物理模型计算简化方法,建立了以四节点壳单元和二节点偏心梁单元组合的加筋板模型并对该模型进行了验算,为后面加筋板拓扑结构与声辐射特性研究提供准确的有限元分析模型。同时基于结构声辐射机理和薄板结构振动声辐射理论,本文设计了空气介质中结构振动声辐射的分析流程。为了研究加筋板的拓扑形状变化在不同边界条件下对其刚性的影响,本文运用有限元方法,以加筋板的第一阶固有频率为参考目标,具体分析了加强筋的结构参数、分布和类型及板的结构参数在不同边界约束条件下对加筋板一阶固有频率的影响。本文根据其一阶固有频率值的大小来评价加筋板的刚性特性,并从中得出了一些有用的结论,为后面的加筋板结构声辐射特性分析提供一定理论依据。同时本文以板、加强筋结构参数为设计变量,分析了加筋板的特征值灵敏度和振动响应灵敏度,为加筋板的结构优化指导了方向。基于弹性结构振动方程和辐射声场的边界元理论,本文设计了空气中无限大刚性障板内加筋板结构声辐射的计算模型。结合有限元和边界元方法,根据第3章的结构声辐射分析流程,详细研究了加强筋的结构参数和分布、激励力作用位置、板长宽比、板厚与结构阻尼等对加筋板的辐射效率、辐射声功率及声辐射指向性的影响,并从中得到了一些有用的结论,为加筋板的声振优化研究提供一定的指导作用。更多还原

【Abstract】 Thin plate is a commonly used structural part and play an important role in military and civil fields, but characteristics of the thin plate is not good enough. Adding thickness or applying stiffener may improve mechanical and acoustic performance of the thin plate. However,the thin plate increases selfweight by adding its thickness and has not high utilization of materials. So adding stiffener on the thin plate is a optimum method because of not increasing its weight. The stiffened plate structure can meet the requirements of structural strength,structural stiffness,structural stability and acoustic characteristics by adjusting size and distance of stiffener in engineering design, so it is widely used in military and civil fields. Mechanical performances and acoustic radiation problems of the stiffened plate caused researchers great interest early. Many scholars reseached its bearing capacity, maximum intensity, stability and acoustic radiation performances at home and abroad. Based on topology and shape of stiffener plate, a specific study on stiffness and acoustic radiation of the stiffened plate which may alter as the topology/shape and boundary conditions changed was completed in this paper.This paper took commonly used stiffened plate as the research object. Based on Mindlin plate theory, spatial beam theory and methods of physical model simplify, a accurate finite element model of the stiffened plate was set up by four nodes shell element and two nodes beam element. Then the model was checked calculation for back-analysis of topology/shape and acoustic radiation of structure. In the end,a analysis process about sound radiation of vibrating structure was designed according to mechanism of sound radiation and theory of acoustic radiation from the thin plate in this paper.By taking first-order natural frequency of the stiffened plate as target, a specific discussion was finished by changing structure parameter,types or distribution of stiffeners and boundary conditions for effects of first-order natural frequency of the stiffened plate. Then according to natural frequency value evaluated the stiffness characteristics of the stiffend plate. This discussion drawed useful conclusions and provided theoretical basis for back-analysis of acoustic radiation of the vibrating stiffened plate. This paper also designed a example of structural sensitivity analysis. By taking structure parameters of the plate and the beam as design variables, the paper studied the eigenvalue sensitivity and displacement sensitivity of the stiffened plate. This pointed out the direction for structural topology optimization of the stiffened plate. This paper designed a calculation model about acoustic radiation of vibrating structure in infinite baffle on the basis of the flexible structure vibration equation and boundary element coupling calculation equation. Then combination of finite and boundry element methods, it discussed structure parameters of plate and stiffener, types or distribution of the stiffener, location of the force incentive, length to wide ratio and structure damping and so on for influence of sound radiation efficiency, acoustic power and radiation directivity. This discussion drawed some useful conclusions and provided theoretical basis for structural-acoustic optimization of the stiffened plate.更多还原