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SIMULTANEOUS SHAPE AND TOPOLOGY OPTIMIZATION OF TRUSS UNDER LOCAL AND GLOBAL STABILITY CONSTRAINTS 总被引:5,自引:0,他引:5
GuoXu LiuWei LiHongyan 《Acta Mechanica Solida Sinica》2003,16(2):95-101
A new approach for the solution of truss shape and topology optimization problem sunder local and global stability constraints is proposed. By employing the cross sectional areas of each bar and some shape parameters as topology design variables, the difficulty arising from the jumping of buckling length phenomenon can be easily overcome without the necessity of introducing the overlapping bars into the initial ground structure. Therefore computational efforts can be saved for the solution of this kind of problem. By modifying the elements of the stiffness matrix using Sigmoid function, the continuity of the objective and constraint functions with respect to shape design parameters can be restored to some extent. Some numerical examples demonstrate the effectiveness of the proposed method. 相似文献
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A continuous variable optimization method and a topological optimization method are proposed for the vibration control of piezoelectric truss structures by means of the optimal placements of active bars. In this optimization model, a zero-one discrete variable is defined in order to solve the optimal placement of piezoelectric active bars. At the same time, the feedback gains are also optimized as continuous design variables. A two-phase procedure is proposed to solve the optimization problem. The sequential linear programming algorithm is used to solve optimization problem and the sensitivity analysis is carried out for objective and constraint functions to make linear approximations. On the basis of the Newmark time integration of structural transient dynamic responses, a new sensitivity analysis method is developed in this paper for the vibration control problem of piezoelectric truss structures with respect to various kinds of design variables. Numerical examples are given in the paper to demonstrate the effectiveness of the methods. 相似文献
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Liu Tao Deng Zichen 《Acta Mechanica Solida Sinica》2006,19(3):264-274
In this paper, a method for the design optimization of elasto-plastic truss structures is proposed based on parametric variational principles (PVPs). The optimization aims to find the minimum weight/volume solution under the constraints of allowable node displacements. The design optimization is a formulation of mathematical programming with equilibrium constraints (MPECs). To overcome the numerical difficulties of the complementary constraints in optimization, an iteration process, comprising a quadratic programming (QP) and an updating process, is employed as the optimization method. Furthermore, the elasto-plastic buckling of truss members is considered as a constraint in design optimization. A combinational optimization strategy is proposed for the displacement constraints and the buckling constraint, which comprises the method mentioned above and an optimal criterion. Three numerical examples are presented to show the validity of the methods proposed. 相似文献
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Pan Jin Wang De-yu 《Acta Mechanica Solida Sinica》2006,19(3):231-240
In this paper, adaptive genetic algorithm (AGA) is applied to topology optimization of truss structure with frequency domain excitations. The optimization constraints include fundamental frequency, displacement responses under force excitations and acceleration responses under foundation acceleration excitations. The roulette wheel selection operator, adaptive crossover and mutation operators are used as genetic operators. Some heuristic strategies are put forward to direct the deletion of the extra bars and nodes on truss structures. Three examples demonstrate that the proposed method can yield the optimum structure form and the lightest weight of the given ground structure while satisfying dynamic response constraints. 相似文献
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The optimal topology design of truss structures concerning stress and frictionless unilateral contact displacement constraints
is investigated. The existence of ununique optimal solution under contact gaps is found. This shows that the contact conditions
have an effect on structural topology, and different initial contact gaps may lead to different structural topologies. To
avoid the singular optima in structural topology optimization in multiple loading cases, an ε-relaxed method is adopted to
establish the relaxing topology optimization formulations. The problem is solved by means of a two-level optimization method.
In the first sublevel, the solution of the frictionless unilateral contact problem is obtained by solving an equivalent quadratic
programming. In the second sublevel, topology optimization of truss is carried out by an ε-relaxed method. The validity of
the method proposed is verified by computational results.
Supported by the Postdoctoral Science and Research Foundation of Shanghai, China. 相似文献
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This paper is concerned with the optimum design and sensitivity analysis methods of piezoelectric intelligent trusses on the
structural stiffness and free-vibration frequency. On the basis of the finite element method and taking into account the mechanical-electric
coupling effect under electric load and mechanical load, the computational formula of sensitivities of structural displacement
and free-vibration frequency with respect to the size and shape design variables are proposed. A new kind of design variable
of the electric voltage and the calculating method of displacement sensitivity with respect to the electric voltage variable
is presented. The new method for structural deformation control by optimizing the voltages of piezoelectric active bars is
given. The numerical methods of optimum design and sensitivity analysis for piezoelectric truss structures are implemented
in JIFEX software. Numerical examples demonstrate the effectiveness of the methods and the program.
Project supported by the Special Funds for National Key Basic Research of China (No. G1999032805) and the Foundation for University
Key Teachers by the Ministry of Education of China. 相似文献
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计算具有区间参数结构的固有频率的优化方法 总被引:7,自引:0,他引:7
基于区间函数的单向包含性质,把具有区间非确定参数结构的固有频率所在区间范围问题
转化成两个全局优化问题,并采用一种实数编码遗传算法求取问题的全局解. 用一种能够求
得剪切型结构和弹簧质量系统特征值范围精确解的单调分析方法进行检验. 在一
些文献中,直接采用区间数运算法则和有限元法得到结构区间刚度阵和区间质量阵,并把关
于该区间刚度阵和区间质量阵的广义区间特征值问题的特征值区间作为待求的非确定性结构
的特征值所在的区间范围,该方法易于扩大问题的解域. 算例表明,可望得到结构
固有频率区间范围的准确解. 相似文献
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《基于设计的结构力学与机械力学》2013,41(2-3):219-236
A method is presented for the optimal layout of material in three-dimensional elastic structures subjected to multiple loads. The problem is solved using a moment formulation to characterize optimal anisotropy of the material at each point of the domain. The method has important practical applications, e.g., in design of cross sections of prismatic bars and in optimal design of laminates. 相似文献
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基于类桁架连续体的结构拓扑优化方法与应用 总被引:1,自引:0,他引:1
以各向异性连续体为基结构,采用类桁架连续体材料模型进行结构拓扑优化。以材料在结点位置的密度和方向作为优化设计变量,使材料在设计域内连续分布。并以此建立材料的弹性矩阵和刚度矩阵。优化过程没有抑制中间密度,这从根本上避免了许多拓扑优化方法普遍存在的单元铰接、棋盘格现象以及单元依赖性等数值不稳定问题。采用满应力准则法,借助有限元结构分析,经过少量迭代,建立优化的材料连续分布场,即类桁架连续体结构。由于首先建立的拓扑优化结构是各向异性连续体,从而得到更大优化空间。然后可以结合工程实际需要将其转化为离散的拓扑优化杆系结构。最后,以1个经典Michell桁架和3种形式的拱桥为数值算例,演示了其结构拓扑优化过程。 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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线弹性幂强化材料平面杆系弹塑性分析的数值解 总被引:4,自引:0,他引:4
各杆任意铰接在一个刚体上的平面杆系是一种比较复杂的杆系结构,某些其它类型的平面杆系常常可以看作是它的特例。本文将材料的本构关系描述为线性幂强化形式,推导出了该类平面杆系结构弹塑性分析的普遍表达式,编制了通用程序,使这一类问题有了一个通用的解题方法。 相似文献
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在结构优化中,拓扑优化相比于尺寸优化和形状优化,设计空间更加广泛,因而能够取得更大的效益.近年来,结构拓扑优化逐渐成为人们研究的热点和难点.随着科学技术的发展,工程结构越来越复杂,材料本身和外部环境的不确定性影响加剧,因此在拓扑优化中需要考虑不确定性的影响.本文研究了桁架结构的非概率可靠性拓扑优化问题,用区间模型来量化... 相似文献