基于复合材料层板稳定性的铺层参数优化设计方法

提出一种基于复合材料层板稳定性的铺层参数优化设计方法,首先利用最大应变能准则优化分层厚度,利用库塔条件推导出层合板单元厚度迭代公式优化单元厚度,两步交替进行,完成层板厚度与铺层比例优化;在此基础上采用遗传算法优化层合板铺层顺序,最终设计出满足稳定性要求的最佳层合板铺层.通过算例分析表明,文中方法与传统方法相比收敛速度明显提高.同时,最佳的厚度分布也为层合板加筋设计提供理论参考.     

基于改进自适应遗传算法的层合板铺层设计

针对复合材料结构设计中层合板铺层角度多变、难以确定最优设计方案的问题,应用遗传算法对复合材料层合板进行以铺层角度为变量、以层合板强度最大为目标的优化设计。采用MALTAB语言编写改进的自适应遗传算法主程序,在寻优过程中,调用APDL编写应力计算程序,并将输出的计算结果返回MALTAB进行优化计算。以对称层合板为算例进行计算验证,其安全裕度提高了21.5%;通过对比传统遗传算法,证明改进的遗传算法具有快速收敛性。     

纤维复合材料的可靠性优化研究

采用遗传算法分析有初始缺陷的层合板的可靠性优化问题.初始缺陷、强度参数为随机变量,采用一阶矩法分析单元层的可靠性,每个单层板考虑基体破坏和纤维断裂两种失效模式,系统失效概率的计算基于最终层失效理论.以纤维方向角和层合板厚度为设计变量,系统可靠度最小为目标,采用遗传算法计算优化问题.数值算例说明方法的有效性,分析不同失效理论时的最优解.     

基于改进遗传算法的复合材料层合板自振频率优化设计

针对复合材料层合板设计的特点,应用改进的遗传算法研究了复合材料层合板 自振频率的优化设计问题。算例分析结果表明,本文方法具有较高的计算效率。     

基于自适应遗传算法的层合板铺层优化设计

针对复合材料层合板结构设计中因铺层角度多变、难以确定最优铺层方案的问题,提出一种基于自适应遗传算法的铺层优化设计方案。该方案以层合板铺层角度为变量,以层合板最大形变量为优化目标,采用整数编码策略,运用MATLAB平台进行遗传算法设计。在寻优过程中调用ABAQUS对层合板进行有限元分析并将分析结果返回至MATLAB进行优化计算。通过对比经典遗传算法表明,该算法收敛快,更易达到优化设计的目的。     

基于最终失效强度的层合板结构的鲁棒优化分析

采用有限元方法分析复合材料层合板结构的最终失效强度，并以此对结构进行优化和鲁棒优化分析。层合板结构同时承受面内和面外载荷，每个单层板考虑基体失效和纤维断裂两种失效模式。当某一单层失效后采用比率退化法计算结构新的刚度，然后重新进行结构分析，直到求得结构的最终失效强度。以纤维方向角和层合板厚度作为设计变量，最终失效强度为目标，对结构进行优化。在此基础上，考虑了层合板结构的鲁棒优化分析。     

复合材料层合板的极限强度分析与可靠性优化设计

研究层合板结构基于最终层失效准则的可靠性分析方法,在此基础上,对复合材料层合板可靠性优化设计的方法和算法进行讨论.层合板作为一个系统考虑,其可靠性分析含以下几个步骤:(1)随机载荷和强度参数作为随机变量,利用一次二阶矩法(first order reliability method, FORM)分析单层板的失效概率.(2)假定失效概率最大的单层板首先破坏,然后通过修改刚度矩阵对结构进行再分析,得到剩余结构各单层板的失效概率,从而建立主要失效序列.(3)计算系统的可靠度.在确立复合材料基于最终层失效准则的可靠性分析方法的基础上,以系统可靠度指标最大为目标,研究层合板的可靠性优化问题.建立和发展基于最终层失效准则的复合材料层合板可靠性优化方法以及相应的算法,并对比讨论单变量和多变量优化设计问题.     

基于整数编码并行遗传算法的复合材料螺旋桨结构优化设计

提出一种针对大型复合材料结构铺层厚度和铺层顺序同时进行优化的整数编码并行遗传算法,并将该优化方法应用于复合材料螺旋桨结构优化问题.首先,在区域划分的基础上,对每一单层设定一个长度控制因子来决定单层的铺设区域,以实现对大型复合材料结构的整体一次性优化.然后对遗传算法进行改进,使之成为一种能同时优化铺层厚度和铺层顺序的高效算法.并采用并行编程语言标准MPI( message passing interface)构建并行编程环境,利用主从式并行遗传算法框架,实现遗传算法在单机多进程上的并行计算.最后针对复合材料螺旋桨结构进行优化设计,以验证该方法的高效性,并分析并行遗传算法的加速效果.     

CFRP汽车防撞梁结构/材料一体化优化设计

针对复合材料汽车防撞梁结构布局和层合板铺层优化问题,提出以防撞梁强度最大为目标,宏观结构与层合板铺层角为变量的结构/材料双尺度优化设计方法。结构层面采用B样条对防撞梁轮廓曲线进行参数化表达,并改变防撞梁截面关键尺寸,构建几何模型;材料层面考虑铺层角对层合板性能带来的影响,采用0°、±45°、90°四种标准铺层角进行铺设。通过自适应遗传算法对结构与材料两个层面的设计变量进行初始化,实现了适用于复合材料汽车防撞梁的结构/材料一体化优化设计。结果表明:防撞梁结构的强度较优化之前升幅为81.41%,且最大等效应力下降至64.885MPa,小于CFRP材料的极限强度,优化结果达到预期效果。     

基于材料-结构协同设计的层合板多级优化方法

提出一种以材料参数与结构参数为变量的复合材料层合板多级优化设计新方法。以单层纤维含量、层厚和铺层角为设计参数,建立了刚度和强度约束下的结构减重设计模型,基于有限元分析,运用所提出的三级优化策略完成结构轻量化设计。本文给出了不同载荷类型和位移边界条件下层合板优化算例,设计结果验证了方法的有效性。     

Finite element analysis of stress concentrations and failure criteria in composite plates with circular holes

In this study, the stress concentration factors (SCF) in cross-and-angle-ply laminated composite plates as well as in isotropic plates with single circular holes subjected to uniaxial loading is studied. A quadrilateral finite element of four-node with 32 degrees of freedom at each node, previously developed for the bending and mechanical buckling of laminated composite plates, is used to evaluate the stress distribution in laminated composite plates with central circular holes. Based up on the classical plate theory, the present finite element is a combination of a linear isoparametric membrane element and a high precision rectangular Hermitian element. The numerical results obtained by the present element compare favorably with those obtained by the analytic approaches published in literature. It is observed that the obtained results are very close to the reference results, which demonstrates the accuracy of the present element. Additionally, to determine the first ply failure (FPF) of laminated plate, several failure criterions are employed. Finally, to show the effect of E ₁/E ₂ ratio on the failure of plates, a number of figures are given for different fiber orientation angles.     

飞机复合材料蒙皮的优化设计

从工程实际出发,提出了一种针对连续纤维增强复合材料蒙皮的三级优化设计方案。能够从铺设角、铺层比例、铺层厚度、铺层块形状及位置以及铺层次序等多个方面给出层合板的设计参数。在设计过程中．加入了一系列与实际加工制造非常吻合的制造性约束,使复合材料层合板构件的优化设计结果具有非常好的可制造性。运用该方法对某型飞机复合材料机翼前缘蒙皮进行了优化设计,取得了良好的设计结果。     

Optimum design of composite laminated plates via a multi-objective function

This paper deals with the optimum design of composite laminated plates under stiffness and gauge constraints. A multi-objective function which combines the plate weight and the strain energy stored in the plate by weighting parameters is introduced. This objective function is minimized while satisfying constraints such as the structural deformation and the limits on design variables. Both ply orientation angles and ply thicknesses of the composite plate are used as the design variables. The stiffness analysis is performed by the finite element method in which a triangular element is used that is suitable for the analysis of thin to thick plates and includes the transverse shear effects. Analyses of the derivatives of the objective function and the constraint functions with respect to the design variables is performed analytically. The mathematical programming method called the constrained variable metric is used to solve this optimum problem. An example is provided for the optimal design of a rectangular laminated plate.     

A methodology for synthesizing symmetric laminated beams with optimal elastodynamic response characteristics

A methodology is presented herein for synthesizing symmetric laminated beams with optimal elastodynamic response characteristics by generalizing a previous publication of the first two authors [Liao et al., J. Composite Mater. 21, 485–501 (1986)] in order to include the percentage of fiber and matrix in each ply, and to also accommodate fibers with transversely isotropic properties. Constitutive models are developed for the stiffness and damping properties of laminated beams as a function of the ply fiber volume fraction, the fiber orientation in each ply, the ply thickness and the stacking sequence prior to incorporating these models into an optimal design formulation. This formulation is then employed in illustrative transient response studies of cantilever beams in order to demonstrate the significance of incorporating these micromechanical parameters into design algorithms for optimally tailoring the properties of these laminated beams. A generalized reduced gradient algorithm is employed in this optimal design endeavor.     

Effect of loading and lamination parameters on the optimum design of laminated plates

This paper illustrates the effect of loading conditions and lamination parameters on the optimum design of the laminated composite plates. Optimum design procedure based on the flexibility criterion is presented in this paper. The objective is to determine the optimum thickness of the laminate layers and its optimum orientations without exhibiting any failure. The finite element method based on Mindlin plate theory is used in conjunction with an optimization method in order to determine the optimum design. Newmark implicit time integration scheme is used to discretize the time domain and calculate the transient response of the laminated plate. Exterior penalty method is exploited as a constrained minimization technique. For this purpose, four numerical examples are presented to figure out the effects of dynamic loading profile, boundary conditions, number of layers, and degree of orthotropy on the optimum weight design.     

Design optimization of hip prosthesis of thick laminated composites by developing finite element method and sensitivity analysis

An investigation has been performed to develop a finite element method for the analysis of the behavior of complicated three-dimensional thick laminated composite structure, and the method has been applied to the design of hip prosthesis with nonuniform cross-sections. The developed method can accomodate the varying material properties layered within the element and allow the ply-drop-off along the element edges. The numerical results are compared with the analytical solution, and the results show that the number of elements can be reduced up to 80% within 5% error bounds by using the ply-drop-off element. A method of design sensitivity analysis has also been developed to find the optimal ply angles minimizing the deflection of thick laminated composite structures. The developed finited element method together with the design sensitivity analysis has been applied to design of hip stem, and a procedure for calculating the optimum ply angle is proposed to minimize the rotational micromotion which is one of causes of patients’ pain.     

遗传算法在齿轮减速机优化设计中的应用

从理论上探讨了基因遗传算法 (GA)与传统约束优化设计方法相结合的可能性 ,并从中发现“基因遗传算法+惩罚函数法”非常适合求解复杂的非线性约束优化问题 ,且成功地采用了“基因遗传算法 +惩罚函数法”对一个通用的二级斜齿圆柱齿轮减速机的概率可靠性优化设计的数学模型进行求解 ,与传统的优化方法相比 ,得到了一个较为理想的全域最优解 ;同时该方法也改善了基因遗传算法的局限性