碳纤维复合材料控制臂多尺度多目标优化

为实现悬架控制臂轻量化设计,采用碳纤维复合材料(CFRP)对钢制控制臂进行材料替换,并利用多层次优化方法对CFRP控制臂进行铺层优化。基于多尺度分析方法,考虑碳纤维复合材料细观结构参数及铺层角度对控制臂宏观性能的影响,选取细观尺度下纤维束截面高度、宽度、纱线曲折度、单位长度经纬纱数量及四个经典铺层角度作为设计变量,以控制臂的质量最小、一阶模态频率最高为优化目标,以刚度和强度为约束条件,结合响应面近似模型和NSGA-Ⅱ优化算法对碳纤维复合材料控制臂进行多尺度多目标优化,得到Pareto解集。优化结果表明,在刚度满足使用性能要求下,CFRP控制臂的质量较钢制控制臂下降了65%,且强度、振动特性等性能得到大幅提升,轻量化效果显著,可为碳纤维复合材料结构件的轻量化设计提供参考。     

基于灰色关联分析的碳纤维增强树脂复合材料控制臂铺层优化

采用碳纤维增强树脂复合材料(CFRP)对悬架控制臂进行轻量化设计,为了充分发挥CFRP优异的力学性能,对CFRP控制臂进行多目标铺层优化。基于CFRP力学性能试验结果构建控制臂有限元模型,并通过有限元仿真对比分析钢质控制臂和CFRP控制臂结构性能。综合考虑质量、模态频率、刚度和强度等性能,基于正交试验设计方法,并结合灰色关联分析和主成分分析,对CFRP控制臂铺层参数进行多目标优化,确定最优铺层方案。结果表明,相比于原钢质控制臂,除纵向刚度略有下降外,CFRP控制臂其余结构性能指标均有所改善,并且质量降低40.23%,减重效果显著。     

基于几何因子的复合材料气动弹性剪裁设计

实现了基于几何因子的复合材料层合板建模,解决了几何因子与Natran的参数输入问题,并根据工艺约束中的最小铺层比例对几何因子可行空间进行了推导补充。在此基础上,提出了一种基于几何因子和Nastran的复合材料气动弹性剪裁优化设计方法。首先以总厚度和几何因子作为设计变量以及以Nastran作为求解器,以强度、刚度、颤振和发散速度以及几何因子相关性约束作为约束条件进行结构寻优,得到最优的铺层总厚度和几何因子。其次,以最优几何因子作为目标,进行铺层结构逆问题求解,约束条件为复合材料铺层工艺约束。因几何因子为铺层厚度和铺层顺序的表达式,与传统的多级优化相比,以几何因子作为设计变量可以避免铺层厚度和铺层顺序的解耦,进而获得更大的设计空间,且得到的铺层结构可以满足工艺约束。最后,对一矩形悬臂复合材料层合板进行剪裁设计,使得铺层结构满足气动弹性约束且质量最小。结果显示,运用该优化方法可以得到质量更小且满足工艺约束的铺层结构。     

复合结构减振优化设计模型

复合材料由于具有低密度、高阻尼和良好的比强度、比刚度等特性而被工程结构设计广泛采用。复合材料结构设计的特点在于力学性能设计和结构设计相结合,设计变量多,影响因素更为复杂,优化设计工作显得尤为重要。基于不同减振评价指标,结构动力学优化设计可以采用不同优化模型,减振效果也相差很大。以钢 -复合材料复合基座结构为例,研究采用功率流落差与振级落差进行减振效果评价,以结构总重量或评价点输出功率流等为目标函数,以钢板厚度、复合材料铺层数和铺层角度为设计变量,考虑应力约束时各种结构动力学优化数学模型,并采用多岛遗传算法进行求解,比较减振效果。研究表明,采用复合结构功率流优化模型能获得更佳减振效果。     

复合结构减振优化设计模型研究

复合材料由于具有低密度、高阻尼和良好的比强度比刚度等特性而被工程结构设计广泛采用。复合材料结构设计的特点在于力学性能设计和结构设计相结合,设计变量多,影响因素更为复杂,优化设计工作显得尤为重要。基于不同减振评价指标,结构动力学优化设计可以采用不同优化模型,减振效果也相差很大。本文以钢-复合材料复合基座结构为例,研究采用功率流落差与振级落差进行减振效果评价,以结构总重量或评价点输出功率流等为目标函数,以钢板厚度、复合材料铺层数和铺层角度为设计变量,考虑应力约束时各种结构动力学优化数学模型,并采用多岛遗传算法进行求解,比较减振效果。研究表明,采用复合结构功率流优化模型能获得更佳减振效果。     

车用CFRP油底壳的结构与制造工艺并行优化设计

为实现碳纤维增强复合材料（carbon fiber reinforced polymer,CFRP）油底壳的替代与制造,结合复合材料铺层可制造性分析软件FiberSim与铺层结构优化模块Optistruct,对CFRP油底壳开展了结构与制造工艺并行优化设计。参照CFRP壳体类零件的成型过程,采用FiberSim软件制定了满足制造工艺要求的CFRP油底壳铺覆方案。并在此基础上,分别以CFRP油底壳刚度最大、质量最小为优化目标,以振动模态、制造工艺要求为约束,采用Optistruct模块对CFRP油底壳的铺层结构进行优化设计。经仿真分析验证,制造工艺调整后的CFRP油底壳满足各项替代要求,且CFRP油底壳的质量较原金属油底壳减小了56.7%。所提出的结构与制造工艺并行优化设计方法可较好地兼顾结构特征、复合材料设计及制造工艺要求,为复合材料产品的优化设计提供了参考。     

一种自适应抽样的代理模型构建及其在复材结构优化中的应用

提出了基于一种自适应抽样和增强径向基插值的自适应代理模型方法，这种自适应抽样方法以确定适量的样本点数量和提高代理模型自适应能力为目的，使新增样本点位于设计空间的稀疏区域并确保所有的样本点均匀分布于设计空间以提高代理模型精度。标准误差用来判断代理模型的精度大小并决定是否对代理模型进行更新。一种条件随机抽样被用来对比本文的自适应抽样方法。经过对比验证发现，采用自适应抽样方法的代理模型精度比条件随机抽样方法的代理模型精度高。这种自适应代理模型结合多岛遗传算法被用来优化旋翼臂的碳纤维增强环氧树脂复合材料铺层角度使得旋翼臂的一阶模态频率最大。优化结果表明，不同的碳纤维增强环氧树脂复合材料铺层角度对旋翼臂的一阶模态频率值影响较大，优化结果获取了最优铺层角度，旋翼臂的一阶模态频率值被提高以远离激励频率而避免旋翼飞机的共振。     

基于遗传算法的复合材料结构-声辐射优化研究

研究了外载荷作用下的复合材料结构振动响应和声辐射问题。在此基础上, 分析了复合材料的结构-声辐射优化设计模型, 基于遗传算法进行了对称型复合材料板结构的结构-声辐射铺层几何优化分析。数值算例表明, 复合材料板结构的铺层数、 铺层厚度和铺层角度等参数优化, 可以有效降低结构的振动和声辐射。数值算例结果验证了优化方法的有效性。     

基于灵敏度分析的复合材料层合板优化设计

工程结构中的复合材料层合板的几何参数往往具有随机性质.如何研究随机参数层合板的灵敏度,并对参数进行优化分析,这对正确估计结构设计的可靠性有着非常重要的意义.根据层合板的一阶剪切理论,采用样条有限元法,推导并建立了层合板的振动方程,刚度矩阵,质量矩阵,比例阻尼矩阵以及求解反对称层合板响应灵敏度的计算公式,在基于灵敏度分析的基础上,进行了复合材料层合板的基频分析和优化设计,并用网格法计算最佳铺层角.数值算例验证了算法的有效性.     

基于密度分布曲线法的复合材料变刚度铺层优化

基于梯度的优化方法对复合材料层合板进行了变刚度铺层优化设计。在优化过程中需确定铺层中各单元的密度以及角度。为了使优化结果具有可制造性,优化结果需满足制造工艺约束并且铺层角度需从预定角度中选取。为了避免在优化问题中引入过多的约束并减少设计变量的数目,提出密度分布曲线法(DDCM)对层合板中各单元的密度进行参数化。根据各单元的密度以及角度设计变量并基于Bi-value Coding Parameterization(BCP)方法中的插值公式确定各单元的弹性矩阵。优化过程中以结构柔顺度作为优化目标,结构体积作为约束,优化算法采用凸规划对偶算法。对碳纤维复合材料的算例结果表明:采用DDCM可得到较理想的优化结果,并且收敛速率较快。     

Higher order models on the eigenfrequency analysis and optimal design of laminated composite structures

This paper deals with the structural optimization of multilaminated composite plate structures of arbitrary geometry and lay up, using single layer higher order shear deformation theory discrete models. The structural and sensitivity analysis formulation is developed for a family of C⁰ Lagrangian elements. The design sensitivities of free vibration response for objective and/or constraint functions with respect to ply angles and ply thickness are presented. The objectives of the design are the maximization of natural frequencies of specified modes and/or the minimization of the structure weight or volume. The accuracy and relative performance of the proposed discrete models are compared and discussed among developed elements and alternative models. Several test designs are optimized to show the applicability of the proposed refined discrete models.     

Optimum weight design of fiber composite plates in flexure based on a two level strategy

This paper offers a method for weight optimization of multilayer fiber composite plates under the action of lateral loadings. The objective is to design a fiber composite plate of minimum thickness which can sustain multiple static loadings applied normal to its surface without exhibiting failure based on Tsai-Hill criterion in any of its layers. In this investigation, fiber orientation angles are treated as discrete variables, which can vary only by pre-assigned increments, while thicknesses of layers are treated as continuous variables. The optimization procedure is based on a two stage strategy; in the first of which only the fiber orientation angles for the layers are treated as variables, and in the second, only the layer thicknesses. A powerful criterion based on a load factor has been defined to find the best angle for a new layer in the first stage, and the method of center points has been used for thickness optimization in the second stage. After any angle and thickness optimization has been done, a new layer is added to the thickness and the procedure is repeated for other new layers. The end of the two stage procedure is signaled whenever the thickness of the new layer in the optimization process approaches zero; meaning that no new layers would improve the set of layers already found. In this way at the end of the optimization procedure the plate thickness would be made of a minimum number of layers whose fibers are optimally oriented, and whose thicknesses are minimal. A poor choice of layers in the stack produce near zero thickness for the respective layer, and are thus deleted from the set. A repeat process is performed after each cycle, to modify layer angles in order to compensate for errors due to approximations involved. The priorities exercised in the choice of new layers for inclusion in the set and exclusion of all the un-necessary ones, allow an optimal state of stacking sequence to be achieved. Several examples are given to demonstrate the operation of the algorithm.     

Composite robot end effector for manipulating large LCD glass panels

Recently, the design and the manufacture of light robot end effectors with high stiffness have become important in order to reduce the deflection due to the self-weight and weight of glass panel, a part of LCD, as the size of glass panels as well as robot end effectors increases. The best way to reduce the deflection and vibration of end effectors without sacrificing the stiffness of end effectors is to employ fiber reinforced composite materials for main structural materials because composite materials have high specific stiffness and high damping. In this work, the end effector for loading and unloading large glass panels were designed and manufactured using carbon fiber epoxy composite honeycomb sandwich structures. Finite element analysis was used along with an optimization routine to design the composite end effector. A box type sandwich structure was employed to reduce the shear effect arising from the low modulus of honeycomb structure. The carbon fiber epoxy prepreg was hand-laid up on the honeycomb structure and cured in an autoclave. A special process was used to reinforce the two sidewalls of the box type sandwich structure. The weight reduction of the composite end effector was more than 50% compared to the weight of a comparable aluminum end effector. From the experiments, it was also found that the static and dynamic characteristics of the composite end effector were much improved compared to those of the aluminum end effector.     

基于改进模拟退火算法的复合材料层合板频率优化

针对复合材料层合板频率优化问题,结合可行规则法和直接搜索模拟退化算法,提出了一种自适应模拟退火(SA)改进算法。层合板优化目标是基频、频率带隙以及给定基频和带隙约束的层合板厚度。设计变量包括铺层角度和铺层数两种离散变量。改进算法的自适应新点产生模块采用依赖温度的动态调整搜索半径,改善了直接搜索模拟退化(DSA)算法易陷入局部极值的缺陷,而可行规则法的引入提高了SA算法求解约束问题的效率和简易性。采用Ritz法进行频率响应分析以考虑弯扭耦合影响。不同铺层数、角度增量和长宽比时的层合板3类算例结果显示:改进算法能有效求解层合板频率优化,可获得更多或更好的铺层顺序全局优化解。     

铺设角度与铺层顺序对层合板稳定性的影响

以层合板结构的临界屈曲载荷系数最大化为优化目标,基于改进型模拟退火算法对层合板结构铺设角度和铺层顺序进行优化。由于层合板结构的铺层角度是离散变量,模拟退火算法适合求解离散变量的优化问题。利用模拟退火算法优化层合板铺层,在算法内采用并行计算、引入记忆功能同时设置双阈值终止准则,有效地提高了优化过程的收敛速度,同时避免优化过程中出现局部最优解。以临界屈曲载荷系数作为目标函数,选取复合材料层合板的铺设角度顺序为设计变量,采用改进的模拟退火算法得出复合材料层合板的最优铺设角度以及铺层顺序。     

基于遗传算法的大型风机复合材料叶片根部强度优化设计

为了提高复合材料叶片承担载荷的能力, 尤其是承受最大弯矩的叶片根部的承载能力, 研究了遗传算法的优化原理并将遗传算法应用到复合材料叶片根部铺层的优化设计中。针对复合材料层压结构遗传算法优化设计中, 层压结构参数具有离散型的特点, 提出了适合复合材料层压结构遗传算法优化设计的整数编码策略, 以整数来表征层压结构参数。在分析层压结构强度的基础上, 针对结构强度优化的目标构造了可用于遗传算法的适应度函数。同时参考了一定的铺层规则, 在铺层角度限制为工程中常用的四种角度的前提下, 应用遗传算法对叶片根部进行了铺层优化设计。结果表明, 由于遗传算法特有的处理离散型问题的优势, 在叶片根部的铺层优化设计中应用遗传算法是可行和可信的。     

Ti-C纤维金属层压板自由振动试验和数值分析

为研究由钛合金和碳纤维增强复合材料交替铺设而成的Ti-C纤维金属层压板(FMLs)的制备及自由振动,首先,使用有限元分析软件MSC.PATRAN/NASTRAN对不同尺寸Ti-C FMLs的自由振动进行了二维有限元建模计算,确定了尺寸效应对FMLs固有频率的影响;然后,采用电磁激振器和非接触式激光扫描仪进行自由振动试验,比较了数值仿真结果和试验结果;最后,计算了相同尺寸的纯碳纤维复合材料层压板和不同钛合金层压板层数的Ti-C FMLs的固有频率,研究了钛合金层压板层数对FMLs固有频率的影响。结果显示:试件的尺寸越小,固有频率的计算误差越大,即当结构面内尺寸相对于厚度的倍数较小时,模型的计算误差大;数值仿真结果和试验结果总体吻合较好,有限元模型有效;FMLs的固有频率随着钛合金层压板层数的增加而减少。所得结论可为提高Ti-C FMLs自由振动的可设计性提供参考。      

玻璃钢/复合材料叶片结构优化设计

本文讨论玻璃钢/复合材料叶片结构动力优化设计。设计变量为截面单向层壁厚,目标函数为叶片最轻重量,约束条件为应力和频率约束,并考虑了工艺和构造对壁厚的要求。应力约束采用满应力准则来处理,频率约束采用非线性规则中的Kuhu—Tucker条件来处理。文中给出了两个算例,表明本文介绍的方法对于叶片结构动力优化设计是有效的。     

Particle swarm-based structural optimization of laminated composite hydrokinetic turbine blades

Composite blade manufacturing for hydrokinetic turbine application is quite complex and requires extensive optimization studies in terms of material selection, number of layers, stacking sequence, ply thickness and orientation. To avoid a repetitive trial-and-error method process, hydrokinetic turbine blade structural optimization using particle swarm optimization was proposed to perform detailed composite lay-up optimization. Layer numbers, ply thickness and ply orientations were optimized using standard particle swarm optimization to minimize the weight of the composite blade while satisfying failure evaluation. To address the discrete combinatorial optimization problem of blade stacking sequence, a novel permutation discrete particle swarm optimization model was also developed to maximize the out-of-plane load-carrying capability of the composite blade. A composite blade design with significant material saving and satisfactory performance was presented. The proposed methodology offers an alternative and efficient design solution to composite structural optimization which involves complex loading and multiple discrete and combinatorial design parameters.