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System Reliability-Based Design Optimization (RBDO) considers a single system failure probability constraint. The formulation allows different failure modes to compete with each other. Very few methods and benchmark examples involving optimal design considering system behaviour with progressive failure can be found in the literature. In this article, the conventional System RBDO formulation is compared with a risk-based formulation. A benchmark example involving progressive failure of hyper-static truss is addressed. It is demonstrated that typical System RBDO formulations always lead to isostatic structures, since the formulation does not offer any incentive for the permanence of hyper-static members. In the risk-based formulation, failure costs are differentiated with respect to primary member failure, in hyper-static structures (existence of warning before eventual collapse), and failure of isostatic members (no warning). In this formulation, optimal designs also include hyper-static structures. Results presented herein are relevant in the modern context of robust design considering progressive collapse. 相似文献
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首次利用水平基物质分布函数推出域内积分与边界积分泛函的形状导数 , 建立了复合材料刚性连续结构拓扑优化设计理论的新模型。通过将形状导数和增广的 Lagrangian 乘子法相结合 , 提出了复合材料结构拓扑优化敏度分析的新方法。设计边界的进化是通过人为掌握目标函数下降的速度来控制。水平基函数的曲面在不改变拓扑结构的前提下上下运动 , 从而通过边界的合并与分离改变嵌入其中的零水平基面上设计构件的拓扑结果。广泛的 2D复合材料悬臂梁研究验证了本文中方法的有效性。 相似文献
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In this paper, the most conservative Tsai–Wu failure envelopes are obtained for laminated composite considering material as well as ply angle uncertainty. The uncertainty analysis is performed using Monte Carlo simulation (MCS). The obtained failure envelopes are then used as the constraint functions to perform the minimum weight design optimization problem using particle swarm optimization (PSO). Results show increase in weight of the laminate from the deterministic results and it varies from 4% to 50% depending upon the stacking sequence and loading condition. Substantial effects of uncertainty on the failure envelope and optimal design are quantified. 相似文献
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基于一阶剪切变形理论的新型复合材料层合板单元 总被引：1，自引：2，他引：1
基于一阶剪切变形理论(FSDT),本文构造一种新型的20自由度(每结点5个自由度),四边形复合材料层合板单元,适合于任意铺设情形的层合板的计算。它是按如下方式构造的:(1) 单元每边的转角和剪应变由Timoshenko层合厚梁理论来确定;(2) 对单元域内的转角场和剪应变场进行合理的插值;(3) 引入平面内双线性位移场来体现层合板面内与弯曲的耦合作用。本文单元,记为TMQ20,不存在剪切闭锁现象,在计算单层的各向同性板时可以退化为文[1]中优质的中厚板单元TMQ。在文[2]中将给出本文单元对于层合板问题的详细数值算例。 相似文献
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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。 相似文献
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基于能综合考虑温度效应以及横向线应变和剪切应变的高阶计算模型 ,研究受热复合材料层合板的非线性热振动 ,推导了非线性有限元方程并给出了相应的数值分析方法 ,通过数值算例与已有文献相比较 ,证明了本文理论和算法的精确有效性。文中还以大量数值算例研究了温度效应对幅频曲线的影响。 相似文献
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受热复合材料层合板的非线性热振动——Part Ι: 理论及数值分析 总被引：3，自引：1，他引：2
基于能综合考虑温度效应以及横向线应变和剪切应变的高阶计算模型, 研究受热复合材料层合板的非线性热振动, 推导了非线性有限元方程并给出了相应的数值分析方法, 通过数值算例与已有文献相比较, 证明了本文理论和算法的精确有效性。文中还以大量数值算例研究了温度效应对幅频曲线的影响。 相似文献
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The multi-objective gravitational search algorithm (MOGSA) technique is applied to hybrid laminates to achieve minimum weight and cost. The investigated laminate is made of glass–epoxy and carbon–epoxy plies to combine the economical attributes of the first with the light weight and high-stiffness properties of the second in order to make the trade-off between the cost and weight as the objective functions. The first natural flexural frequency was considered as a constraint. The results obtained using the MOGSA, including the Pareto set, optimum stacking sequences and number of plies made of either glass or carbon fibres, were compared with those using the genetic algorithm (GA) and ant colony optimization (ACO) reported in the literature. The comparisons confirmed the advantages of hybridization and showed that the MOGSA outperformed the GA and ACO in terms of the functions’ value and constraint accuracy. 相似文献
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受热复合材料层合板的非线性热振动--Part Ⅱ:实验研究 总被引：4，自引：1，他引：3
对不同铺层方式和铺设角度的复合材料层合板的热振动进行实验研究, 实验结果给出了一些有益的结论, 并有力证明了作者提出的非线性高阶层合理论和非线性热振动分析有限元算法(Part Ι) [1]的正确性。 相似文献
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The optimal lay-up design for the maximum fundamental frequency of variable stiffness laminated composite plates is investigated using a layer-wise optimization technique. The design variables are two fibre orientation angles per ply. Thin plate theory is used in conjunction with a p-element to calculate the fundamental frequencies of symmetrically and antisymmetrically laminated composite plates. Comparisons with existing optimal solutions for constant stiffness symmetrically laminated composite plates show excellent agreement. It is observed that the maximum fundamental frequency can be increased considerably using variable stiffness design as compared to constant stiffness design. In addition, optimal lay-ups for the maximum fundamental frequency of variable stiffness symmetrically and antisymmetrically laminated composite plates with different aspect ratios and various combinations of free, simply supported and clamped edge conditions are presented. These should prove a useful benchmark for optimal lay-ups of variable stiffness laminated composite plates. 相似文献
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以人为本地开展施工企业的安全教育工作,针对施工企业施工人员安全教育的现状,从人因工程的角度探究改善安全教育效果不佳的措施。统计工作人员在接受安全教育后15 d内产生不安全行为的类别及次数,并对记录的实验数据进行分析处理,确定保护他人安全意识及规范习惯性不安全行为的安全教育效果不佳。利用得出的结论对工人进行反馈调查,结果表明问题产生的原因主要是人际关系和有针对性的安全操作技术培训强度不够。结合人因工程理论的作业活动分解理论,从安全教育培训方式、工人接受意愿和安全教育效果的保持性等方面提出了相应的改善措施,为施工企业提升施工人员安全教育培训效果提供了新途径。 相似文献
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文中分析了复合材料单层板的弹性主方向及非弹性主方向的弹性特性，进而分析了一般层合板的弹性特性及多层壳的弹性特性，以及导得具有普遍性的多层壳的稳定方程。 相似文献
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介绍了包装用复合薄膜的综合性能、组成、层压方法和食品包装复合薄膜用粘合剂的条件,以及我国对薄膜复合工艺的研制及其应用。 相似文献
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文中分析了复合材料单层板的弹性主方向及非弹性主方向的弹性特性,进而分析了一般层合板的弹性特性及多层壳的弹性特性,以及导得具有普遍性的多层壳的稳定方程. 相似文献
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Optimization leads to specialized structures which are not robust to disturbance events like unanticipated abnormal loading or human errors. Typical reliability-based and robust optimization mainly address objective aleatory uncertainties. To date, the impact of subjective epistemic uncertainties in optimal design has not been comprehensively investigated. In this paper, we use an independent parameter to investigate the effects of epistemic uncertainties in optimal design: the latent failure probability. Reliability-based and risk-based truss topology optimization are addressed. It is shown that optimal risk-based designs can be divided in three groups: (A) when epistemic uncertainty is small (in comparison to aleatory uncertainty), the optimal design is indifferent to it and yields isostatic structures; (B) when aleatory and epistemic uncertainties are relevant, optimal design is controlled by epistemic uncertainty and yields hyperstatic but nonredundant structures, for which expected costs of direct collapse are controlled; (C) when epistemic uncertainty becomes too large, the optimal design becomes redundant, as a way to control increasing expected costs of collapse. The three regions above are divided by hyperstatic and redundancy thresholds. The redundancy threshold is the point where the structure needs to become redundant so that its reliability becomes larger than the latent reliability of the simplest isostatic system. Simple truss topology optimization is considered herein, but the conclusions have immediate relevance to the optimal design of realistic structures subject to aleatory and epistemic uncertainties. 相似文献
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采用ABAQUS软件建立了圆锥头弹体正冲击复合材料层合板的有限元模型,并与已有文献结果进行对比验证了模型的可靠性,进而研究圆锥头弹体以不同的入射角度冲击复合材料层合板时初始速度与剩余速度的关系、复合材料层合板的破坏形态及弹体发生跳弹的规律。结果表明：弹体以90°入射角冲击复合材料层合板,在距离临界速度较大时,弹体的剩余速度与初始速度呈线性关系;不同的初始速度对复合材料层合板的损伤面积和破坏机制也不相同;弹体的入射角度越小、复合材料层合板越厚,越容易产生跳弹现象,并给出了入射角度和铺陈层数对跳弹现象的影响规律。该研究可为各种防护装备的设计和优化提供参考。 相似文献
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