共查询到20条相似文献,搜索用时 31 毫秒
1.
In this paper, an automated digital-image-processing system is developed for the measurement of deformed grids with respect to sheet-metal forming (circular grids imprinted). The proposed system can be used in industry or laboratory to evaluate process design and die design. It can also be used to determine the forming limit and to verify the accuracy of numerical modeling. The application of the system will improve productivity and product quality for the sheet-metal-forming industry. 相似文献
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For aerodynamic shape optimization, the approximation management framework (AMF) method is used to organize and manage the variable-fidelity models. The method can take full advantage of the low-fidelity, cheaper models to concentrate the main workload on the low-fidelity models in optimization iterative procedure. Furthermore, it can take high-fidelity, more expensive models to monitor the procedure to make the method globally convergent to a solution of high-fidelity problem. Finally, zero order variable-fidelity aerodynamic optimization management framework and search algorithm are demonstrated on an airfoil optimization of UAV with a flying wing. Compared to the original shape, the aerodynamic performance of the optimal shape is improved. The results show the method has good feasibility and applicability. 相似文献
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结构等几何分析是计算固体力学领域一种新兴的数值方法,致力于将CAD(计算机辅助设计)和CAE(计算机辅助工程)纳入到统一的数学表达框架。等几何分析紧密联系几何信息,采用相同的数学表达将几何精确建模、结构分析和设计过程结合,为结构优化设计提供了新的选择和机会。相比基于有限元的结构优化方法,等几何优化设计方法可在一定程度上提高结构优化的精度、效率和便利性。本文针对具有代表性的结构等几何优化设计,包括形状优化、尺寸优化和拓扑优化等问题,系统梳理和综述了主要的等几何优化方法及其在结构优化设计中的应用。比较分析和评述了结构等几何优化设计方法的算法特点及计算优势与劣势,探讨了基于等几何分析的结构优化研究的前沿问题,并展望了未来的发展方向,包括:基于复杂剪裁CAD几何的高效等几何分析与优化设计、基于实体几何构造的结构等几何分析和优化设计、等几何分析与其他力学分析方法结合的结构优化、基于等几何分析的壳体优化设计、基于等几何分析的材料和结构一体化优化设计以及考虑不确定性的结构等几何优化设计等。 相似文献
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《International Journal of Solids and Structures》2006,43(9):2631-2645
The preliminary design of most buildings is based on equivalent static forces specified by the governing building code. The height wise distribution of these static forces seems to be based implicitly on the elastic vibration modes. Therefore, the employment of such a load pattern in seismic design of normal structures does not guarantee the optimum use of materials. This paper presents a new method for optimization of dynamic response of structures subjected to seismic excitation. This method is based on the concept of uniform distribution of deformation. In order to obtain the optimum distribution of structural properties, an iterative optimization procedure has been adopted. In this approach, the structural properties are modified so that inefficient material is gradually shifted from strong to weak areas of a structure. This process is continued until a state of uniform deformation is achieved. It is shown that the seismic performance of such a structure is optimal, and behaves generally better than those designed by conventional methods. By conducting this algorithm on shear-building models with various dynamic characteristics subjected to 20 earthquake ground motions, more adequate load patterns are introduced with respect to the period of the structure and the target ductility demand. 相似文献
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在传统拓扑优化设计中,随着结构单元增加,迭代计算过程消耗了大量的时间.本文提出了一种基于深度学习的方法来加速拓扑优化设计过程,缩短了结构拓扑优化设计的迭代过程,并生成了高分辨率拓扑优化结构.利用深度学习方法,在低分辨率中间构型与高分辨率拓扑构型之间创建高维映射关系,利用独立、连续和映射(ICM)方法建立深度学习网络所需要的数据集,训练神经网络以实现加速过程,将结构拓扑优化设计问题转化为图像处理中的风格迁移问题.通过引入条件生成对抗式神经网络CGAN (Conditional Generative and Adversar-ial Network)解决了跨分辨率拓扑优化问题,实验验证了优化过程效率的提高,该方法具有良好的泛化性能,研究模型在其他结构优化设计中具有可推广性. 相似文献
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A complete three-dimensional FEM model of the Bar-Bar Tensile Impact Apparatus (BTIA) is constructed, in which the slots in
the bars and the glue layers between the bars and the flat-shaped specimen are included. For elastic-plastic specimen material,
Ly12cz aluminum alloy, the process of tensile impact experiments is simulated and the matching relation between the specimen
geometry and the bars is investigated. Based on the FEM analysis, an iterative method is proposed to design a reasonable specimen
geometry for obtaining the true dynamic stress-strain relation for a certain specimen material.
The project supported by the National Natural Science Foundation of China (19272061) 相似文献
8.
Self-twisting composite marine propellers, when subject to hydrodynamic loading, will not only automatically bend but also twist due to passive bend–twist (BT) coupling characteristics of anisotropic composites. To exploit the BT coupling effects of self-twisting propellers, a two-level (material and geometry) design methodology is proposed, formulated, and implemented. The material design is formulated as a constrained, discrete, binary optimization problem, which is tackled using an enhanced genetic algorithm equipped with numerical and analytical tools as function evaluators. The geometry design is formulated as an inverse problem to determine the unloaded geometry, which is solved using an over-relaxed, nonlinear, iterative procedure. A sample design is provided to illustrate the design methodology, and the predicted performance is compared to that of a rigid propeller. The results show that the self-twisting propeller produced the same performance as the rigid propeller at the design flow condition, and it produced better performance than the rigid propeller at off-design flow conditions, including behind a spatially varying wake. 相似文献
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相比于单一材料,复合材料具有轻质高强等优点,拓扑优化方法是设计复合材料的方法之一.本文采用改进的参数化水平集方法,更新了水平集迭代格式,并应用水平集带方法在优化过程中引入中间密度,使水平集方法与变密度法无缝结合以改善水平集方法的拓扑寻优能力,降低其初始设计依赖性.本文以最大化体积模量、剪切模量和负泊松比作为材料设计目标,结合均匀化方法预测材料的宏观等效性能,研究了不同体积分数、多种初始设计及水平集带方法的引入对优化结果的影响,并得到了多种满足不同目标函数的微结构拓扑形式.数值算例验证了本文方法在复合材料微结构设计问题中的有效性. 相似文献
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Seigo Imamura Mitsuo Yokokawa 《International Journal of Computational Fluid Dynamics》2016,30(6):395-401
ABSTRACTEnsemble computing, which is an instance of capacity computing, is an effective computing scenario for exascale parallel supercomputers. In ensemble computing, there are multiple linear systems associated with a common coefficient matrix. We improve the performance of iterative solvers for multiple vectors by solving them at the same time, that is, by solving for the product of the matrices. We implemented several iterative methods and compared their performance. The maximum performance on Sparc VIIIfx was 7.6 times higher than that of a naïve implementation. Finally, to deal with the different convergence processes of linear systems, we introduced a control method to eliminate the calculation of already converged vectors. 相似文献
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基于非概率可靠性的结构优化设计研究 总被引:5,自引:1,他引:5
基于不确定参量的凸集合描述,研究了考虑非概率可靠性约束时,结构优化设计模型的求解问题。由于非概率可靠性指标是用一个极小极大模型来定义的,故以该指标作为设计约束,将得到一个嵌套的二级优化模型。为了求解该模型,提出了一种序列线性化的计算方法。利用非概率可靠性分析的拉格朗日乘子,逐步构造可靠性指标的一阶近似,通过序列线性规划法求解二级优化问题。该算法可用于区间变量和超椭球凸集模型并存的情形,具有较好的适用性。论文给出了主要的敏度计算公式,并通过简单算例对所提算法进行了验证。 相似文献
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Wolff法则是指骨骼在外部荷载变化时,骨骼内部小梁骨保持沿主应力方向分布以更好抵抗外部荷载。基于Wolff法则的连续体拓扑优化方法是模仿骨骼重建规律的一种新的连续体优化方法。基本思想是将待优化的结构看成是遵从Wolff法则的“骨骼”,仿照骨骼重建过程,连续体的拓扑优化过程即为“骨骼”重建过程。该方法中利用用于描述材料微结构几何及弹性性质的构造张量作为设计变量,采用参考应变区间确定构造张量特征主值的更新规律。本文通过对仿生过程中各因素的分析,解释了优化模型中各参数的物理意义。通过数值分析,给出了参数选取规律以保证算法稳定和快速收敛,从而使得本文优化方法更具实际应用价值。 相似文献
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特征向量导数计算各种模态法的比较和发展 总被引:14,自引:0,他引:14
在结构动力学修改以及结构动态设计中,灵敏度分析是十分重要的一环,往往也是主要工作量所在。如何在保证精度前提下减少灵敏度分析工作量和计算时间,具有重要意义。本文对特征向量灵敏度分析中计算特征向量导数的模态法作了综合评述,除了经典模态法和修正模态法之外,还对新近发展的迭代模态法和移位模态法进行了介绍。最后通过典型结构实例的计算仿真,对各种模态法作了比较。 相似文献
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基于一种新型的数值计算技术—无网格伽辽金法,提出了一种整体式柔性机构拓扑优化设计的新方法.利用移动最小二乘形函数和伽辽金的弱变分形式建立弹性问题的控制方程,用Lagrange乘子法增强本质边界条件.在优化问题中,同时综合考虑机构的柔性和结构的刚度要求,用折衷规划法建立了柔性机构拓扑优化的多准则优化模型,这样对于非凸的优化问题也能保证搜索到Pareto解集所有的有效解.基于SIMP密度函数惩罚模型和优化准则法,建立了一种设计变量的显式迭代格式.运用经典算例证明了文中方法的正确性和有效性. 相似文献
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A new procedure for the optimum layup design of composite laminates is described in this paper. In this method the global optimum search and local relaxing constraints are adequately combined together. The design variables are divided and applied in separate processes. A 16-node hybrid semi-Loof element model is used in the global structure analysis. The iterative complex method is adopted in the optimization. The method is suitable for the minimum weight design of a laminate subjected to the strength and stiffness constraints under multiple loading. The numerical results demonstrate the high efficiency and reliability of the present method.The project was supported by National Natural Science Foundation of China 相似文献
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This work deals with a reliability assessment of springback problem during the sheet metal forming process. The effects of operative parameters and material properties, blank holder force and plastic prestrain, on springback are investigated. A generic reliability approach was developed to control springback. Subsequently, the Monte Carlo simulation technique in conjunction with the Latin hypercube sampling method was adopted to study the probabilistic springback. Finite element method based on implicit/explicit algorithms was used to model the springback problem. The proposed constitutive law for sheet metal takes into account the adaptation of plastic parameters of the hardening law for each prestrain level considered. Rackwitz-Fiessler algorithm is used to find reliability properties from response surfaces of chosen springback geometrical parameters. The obtained results were analyzed using a multi-state limit reliability functions based on geometry compensations. 相似文献
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In this paper, the proposed is a quasi-flow constitutive model with strain-rate sensitivity for elastic plastic large deformation.
The model is based on the Quasi-flow Corner theory, and is suitable for the sheet metal forming process simulation with a
variable punch machine velocity. Uniaxial tensile tests and deep-drawing tests of a circular blank with square punch are carried
out and numerically simulated. The consistency between the experimental and the numerically simulated results shows the validity
of the present new constitutive model.
The project supported by the Scientific Foundation of National Outstanding Youth of China (10125208), the National Natural
Science Foundation of China (19832020), and the National Education Committee of China 相似文献