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Behrooz Farshi Ali Alinia-ziazi 《International Journal of Solids and Structures》2010,47(18-19):2508-2524
This paper describes a new approach to optimum weight design of truss structures. The force method is incorporated in an optimization algorithm based on the method of center points. Design variables are the member cross-sectional areas and the redundant forces evaluated for each independent loading condition acting on the structure. The optimization method utilizes the largest hyperspheres inscribed within the feasible space. The method of hyperspheres has been enhanced here to handle the compatibility equality constraints as well. By including the analysis step in the optimization cycle there is no longer the need to perform separate structural analyses thus saving computation time. The viability and efficiency of the proposed method are demonstrated for truss structures subject to multiple loading conditions and constraints on member stresses, nodal displacement and minimum gage. Numerical results are compared with those reported in the literature. 相似文献
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提出基于节点独立变量的连续体结构动态拓扑优化方法.以动态结构响应量最小或最大为目标,体积比为约束,建立了动态结构拓扑优化模型.基于数字图像处理过滤技术得到清晰、边界光滑和体现网格无关性的优化结果.通过二维结构数值算例对理论方法进行验证.结果表明,该方法在连续体结构动态拓扑优化设计中具有可行性和有效性. 相似文献
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In this paper, an adaptive refinement strategy based on a node‐moving technique is proposed and used for the efficient solution of the steady‐state incompressible Navier–Stokes equations. The value of a least squares functional of the residual of the governing differential equation and its boundary conditions at nodal points is regarded as a measure of error and used to predict the areas of poor solutions. A node‐moving technique is then used to move the nodal points to the zones of higher numerical errors. The problem is then resolved on the refined distribution of nodes for higher accuracy. A spring analogy is used for the node‐moving methodology in which nodal points are connected to their neighbors by virtual springs. The stiffness of each spring is assumed to be proportional to the errors of its two end points and its initial length. The new positions of the nodal points are found such that the spring system attains its equilibrium state. Some numerical examples are used to illustrate the ability of the proposed scheme for the adaptive solution of the steady‐state incompressible Navier–Stokes equations. The results demonstrate a considerable improvement of the results with a reasonable computational effort by using the proposed adaptive strategy. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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In this study, a first attempt has been made to introduce mesh adaptivity into the ensemble Kalman fiter (EnKF) method. The EnKF data assimilation system was established for an unstructured adaptive mesh ocean model (Fluidity, Imperial College London). The mesh adaptivity involved using high resolution mesh at the regions of large flow gradients and around the observation points in order to reduce the representativeness errors of the observations. The use of adaptive meshes unavoidably introduces difficulties in the implementation of EnKF. The ensembles are defined at different meshes. To overcome the difficulties, a supermesh technique is employed for generating a reference mesh. The ensembles are then interpolated from their own mesh onto the reference mesh. The performance of the new EnKF data assimilation system has been tested in the Munk gyre flow test case. The discussion of this paper will focus on (a) the development of the EnKF data assimilation system within an adaptive mesh model and (b) the advantages of mesh adaptivity in the ocean data assimilation model. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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与传统的金属材料相比, 纤维增强复合材料在强度、刚度、抗断裂等诸多方面具备更优良的性能, 目前纤维增强复合材料已在汽车、航空航天等工业领域得到了广泛应用. 本文提出一种求解连续纤维增强复合材料结构无阻尼自由振动下的基频最大化问题的拓扑优化方法. 为了实现结构拓扑构型与纤维角度的同步优化, 建立了以准许的材料用量体积分数为约束、以结构的一阶特征值为目标函数的动力学拓扑优化模型, 该模型包括表征结构拓扑构型的密度设计变量和表征纤维方向的角度设计变量. 详细推导了特征值目标函数关于密度设计变量和角度设计变量的解析灵敏度列式, 并采用移动渐进线方法 (method of moving asymptotes, MMA) 进行了优化求解; 最后通过3个数值算例验证本文方法的有效性, 其中包括一个以刚度最大化为目标的静力学优化算例, 和两个以一阶特征值为目标的动力学优化算例. 结果表明, 所提方法优化迭代过程稳健, 收敛快, 能够在实现结构拓扑构型与纤维角度的一体化优化的同时, 有效提高结构的频率. 相似文献
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与传统的金属材料相比, 纤维增强复合材料在强度、刚度、抗断裂等诸多方面具备更优良的性能, 目前纤维增强复合材料已在汽车、航空航天等工业领域得到了广泛应用. 本文提出一种求解连续纤维增强复合材料结构无阻尼自由振动下的基频最大化问题的拓扑优化方法. 为了实现结构拓扑构型与纤维角度的同步优化, 建立了以准许的材料用量体积分数为约束、以结构的一阶特征值为目标函数的动力学拓扑优化模型, 该模型包括表征结构拓扑构型的密度设计变量和表征纤维方向的角度设计变量. 详细推导了特征值目标函数关于密度设计变量和角度设计变量的解析灵敏度列式, 并采用移动渐进线方法 (method of moving asymptotes, MMA) 进行了优化求解; 最后通过3个数值算例验证本文方法的有效性, 其中包括一个以刚度最大化为目标的静力学优化算例, 和两个以一阶特征值为目标的动力学优化算例. 结果表明, 所提方法优化迭代过程稳健, 收敛快, 能够在实现结构拓扑构型与纤维角度的一体化优化的同时, 有效提高结构的频率. 相似文献
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从材料-结构协同设计的角度研究了热-固耦合结构的优化设计问题,将决定结构材料性质的细观参数与结构宏观几何参数作为设计变量,利用均匀化方法推导了细观设计变量灵敏度显式计算式,并结合耦合场有限元方程构造了耦合场设计变量灵敏度计算式;提出了材料-结构协同设计的三种优化设计模型.利用结构响应最小优化模型对算例进行了计算,比较了宏观设计变量优化和材料-结构协同设计优化的效果.计算结果显示,材料-结构协同优化设计可以取得较单一宏观设计变量更好的优化效果. 相似文献
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桁架拓扑优化的多点逼近遗传算法 总被引:4,自引:0,他引:4
提出一种基于多点逼近函数和遗传算法的桁架拓扑优化方法。该方法建立了包含连续尺寸和离散拓扑两类变量的优化模型,并通过构造多点逼近函数建立了结构优化问题的第一级序列显式近似,然后采用分层优化方法:在外层对拓扑变量采用遗传算法进行优化;在内层对尺寸变量通过可由对偶法求解的第二级序列近似问题进行优化。几个经典的桁架拓扑优化算例表明该方法能以较少的结构分析次数获得比较理想的概率意义上的最优解。 相似文献
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压电桁架作动器/传感器优化配置算法研究 总被引:2,自引:1,他引:1
针对自适应压电桁架结构振动控制,建立了作动器/传感器优化配置数学模型,并提出一种优化配置的新方法。为了减少结构分析次数,该方法将近似概念、对偶法和遗传算法相结合,首先采用多点近似技术建立原问题的序列近似问题,再对近似问题中的作动器/传感器位置离散变量和控制增益连续变量采用遗传算法和对偶方法分别寻优的分层优化策略。为了提高近似问题对原问题的逼近程度,本文提出一种适于离散变量结构优化的分段多点近似函数。算例表明本文方法能够以很少的结构分析次数得到最优解。 相似文献
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The nominal force method for truss geometry and topology optimization incorporating stability considerations 总被引:1,自引:0,他引:1
This paper presents a computationally efficient method for truss layout optimization with stability constraints. Previously proposed approaches that ensure stability of optimal frameworks are first reviewed, showing that existing studies are generally restricted to topology optimization. The present contribution aims to generalize the approach to simultaneous geometry and topology optimization. A lower-bound plastic design formulation under multiple loading will serve as basis for this purpose. The numerical difficulties associated with geometrical variations are identified and the parametrization is adapted accordingly. To avoid nodal instability, the nominal force method is adopted, which introduces artificial loading cases to simulate the effect of geometric imperfections. Hence, the truss systems with unstable nodes are eliminated from the set of optimal solutions. At the same time, the local stability of structural members is ensured via a consistent local buckling criterion. This novel formulation leads to optimal configurations that can be practically used for the preliminary design of structural frameworks. Four applications illustrate the impact of stability constraints on the solution. The importance of geometry optimization is also pointed out by comparing with results that would be unattainable by topology optimization only. 相似文献
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探索将结构优化可行域的极点选取作为初始迭代点 ,从而解决了结构优化的全局最优解问题。文中给出三个算例均得到满意解决 ,并显示了解题时的巨大优越性。 相似文献
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LIU Xiaochen 《力学与实践》1979,42(5):571
从工程数学求解和有限元分析角度对复合材料结构的稳定性分析方法进行研究,基于这两个方面分别建立了同时考虑壁板稳定性约束和气动弹性约 束的气动弹性优化技术,并以大展弦比复合材料机翼为对象,进行气动弹性综合优化设计。研究表明,机翼气动弹性优化中若不考虑稳定性约束条件,虽然可以获得较小结构重量,但往往不满足稳定性要求;相比从有限元角度考虑结构失稳特征的气动弹性综合优化设计方法,通过工程数学方法对机翼结构进行分区失稳分析优化可以更加精准地控制变量,在满足各项性能指标,特别是稳定性约束的同时,进一步减轻了结构重量,提高了结构失稳因子。 相似文献