黏弹性复合材料结构的遗传算法优化设计研究

发布时间：2018-05-17 06:29

本文选题：复合材料层合板 + 黏弹性阻尼材料　；参考：《南昌航空大学》2015年硕士论文

【摘要】：复合材料的一些突出优点,如比刚度、比强度高,自由设计性好,这种“轻而强、轻而坚”的材料在先进飞行器结构中应用广泛。复合材料结构在复杂的工作环境下会引发振动和噪声,其结构的一些力学性能会严重受到影响。然而,复合材料在航空航天中的使用已然不可阻挡。为了改善结构产生的振动、噪声,以阻尼耗能成为复合材料夹层结构减振降噪的有效措施。由于阻尼材料的加入,原有结构的强度、刚度会有所变化。充分利用复合材料性能的方向性、结构性能的自由设计性是复合材料结构设计的关键。论文对黏弹性复合材料结构进行优化设计,以权衡该结构在实际应用中的力学性能和阻尼特性。遗传算法,模仿生物遗传和进化开发出的一种计算机模拟的概率搜索算法。相比其他优化算法,有其独特的优势,能较好地应用于复合材料结构的优化设计。针对遗传算法早熟、局部搜索效率低和寻优时间较长等缺陷,论文第2章结合采样选择和保优策略,对基本遗传算法的适应度函数进行改进,提出了一种改进的乘幂适应度函数自适应遗传算法。性能测试表明,改进的自适应遗传算法在优化速度、优化稳定性和优化精度都有显著的提高。分别利用经典板壳理论、剪切变形理论,论文第3章对复合材料层合板做动态非线性分析及优化设计。基于虚位移原理及求变分推导出相应的振动控制方程,建立复合材料板的固有频率计算模型。讨论分析跨厚比、弹性模量比、纤维铺设角等因素的影响。以纤维铺设角为设计参数,基频最大为优化目标,以改进的自适应遗传算法对复合材料板进行优化设计。优化后,复合材料板的基频增大,可以有效地降低其共振的概率。基于黏弹性复合材料结构的层与层之间没有相互错动的假设,且是小挠度形变,可用复合材料层位移表示黏弹性阻尼层位移。论文第4章利用Hamilton原理及求变分推导出结构的振动控制方程,建立固有频率和结构损耗因子的计算模型。将结构损耗因子最大作为优化目标,以改进的自适应遗传算法进行优化设计。优化结果表明,通过对纤维铺设角、黏弹性阻尼材料与复合材料的剪切模量比以及黏弹性阻尼层与复合材料层的厚度比的设计,增大了黏弹性复合材料结构的损耗因子,从而提高了结构阻尼减振降噪的性能。论文第5章简要介绍了多目标优化问题,利用Tsai-Hill强度理论建立黏弹性复合材料结构的强度计算模型。显然,合理地权衡黏弹性复合材料结构的力学性能与阻尼特性才符合实际应用的需求。该章通过遗传算法中的权重系数变换法建立黏弹性复合材料结构的阻尼与强度双目标优化模型,以改进的自适应遗传算法对结构的阻尼-强度进行双目标优化设计,优化结果令人满意。
[Abstract]:Some outstanding advantages of composite materials, such as specific stiffness, high specific strength, good free design, this kind of "light and strong, light and solid" materials are widely used in advanced aircraft structures. Composite structures can cause vibration and noise in complex working environment, and some mechanical properties of composite structures will be seriously affected. However, the use of composite materials in aerospace is unstoppable. In order to improve the vibration and noise caused by the structure, damping energy dissipation has become an effective measure to reduce vibration and noise of composite sandwich structure. With the addition of damping material, the strength and stiffness of the original structure will change. Making full use of the directionality of composite properties and the free design of structural properties is the key to the structural design of composite materials. In order to balance the mechanical properties and damping characteristics of viscoelastic composite structure in practical application, the optimization design of viscoelastic composite structure is carried out in this paper. Genetic algorithm, a computer simulated probabilistic search algorithm developed to mimic biological genetics and evolution. Compared with other optimization algorithms, it has its unique advantages and can be applied to the optimization design of composite structures. Aiming at the defects of genetic algorithm, such as precocity, low local search efficiency and long searching time, chapter 2 improves the fitness function of basic genetic algorithm by combining sampling selection and optimal preservation strategy. An improved adaptive genetic algorithm for power fitness function is proposed. The performance tests show that the improved adaptive genetic algorithm can improve the speed, stability and precision of optimization. Using classical plate and shell theory and shear deformation theory, the dynamic nonlinear analysis and optimization design of composite laminated plates are made in chapter 3. Based on the principle of virtual displacement and variation, the corresponding vibration control equation is derived, and the natural frequency calculation model of composite plate is established. The effects of span thickness ratio, elastic modulus ratio and fiber laying angle are discussed. With the fiber laying angle as the design parameter and the maximum fundamental frequency as the optimization objective, the improved adaptive genetic algorithm is used to optimize the design of composite plate. After optimization, the fundamental frequency of composite plate increases, which can effectively reduce the probability of resonance. Based on the assumption that there is no interaction between layers and layers of viscoelastic composite structures, and the deformation is small deflection, the displacement of viscoelastic damping layer can be expressed by the displacement of composite layer. In chapter 4, the vibration control equation of the structure is derived by using the Hamilton principle and the variational method, and the calculation model of the natural frequency and the loss factor of the structure is established. The maximum loss factor of the structure is taken as the optimization objective, and the improved adaptive genetic algorithm is used to optimize the design. The optimized results show that the loss factor of viscoelastic composite structure is increased by the design of fiber laying angle, shear modulus ratio of viscoelastic damping material to composite material and thickness ratio of viscoelastic damping layer to composite layer. Thus, the performance of damping vibration and noise reduction is improved. In chapter 5, the multi-objective optimization problem is briefly introduced, and the strength calculation model of viscoelastic composite structures is established by using Tsai-Hill strength theory. It is obvious that the mechanical properties and damping properties of viscoelastic composite structures can meet the requirements of practical application. In this chapter, the double objective optimization model of damping and strength of viscoelastic composite structures is established by the weight coefficient transformation method of genetic algorithm, and the modified adaptive genetic algorithm is used to optimize the damping strength of structures. The optimization results are satisfactory.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：V214.8

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