共查询到20条相似文献,搜索用时 714 毫秒
1.
连续体结构综合优化设计 总被引:1,自引:0,他引:1
以连续体为对象的优化解法所求得的优化结果,经常只是反映最佳传力途径的具有锯齿状边界的某个区域。基于此,将拓扑优化、形状优化、有限元分析和计算机辅助几何设计有机地集成在一起,提出一种基于隐含边界描述的水平集连续体结构拓扑和形状渐进综合优化设计方法,将形状导数与拉格朗日乘子法引入到优化敏度分析中,控制水平集函数的动态运动,从而间接地实现结构边界的动态演化;用B样条曲线曲面逼近拓扑优化后的结构体边界,将前一优化过程所得到的反映传力途径的概念解上升为具有光顺边界,并被参数化了的物理解;在形状优化中,设计变量定义为B样条曲线或曲面的控制顶点的运动,建立边界节点移动速度场计算方法和边界形状调整方法,寻求较快的搜索方向,以合理速度分布,使结构变为最佳。通过一个典型算例证明所研究方法的有效性。 相似文献
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研究基于灵敏度的电磁结构形状优化设计方法。针对以往用磁位作为状态变量不方便的情况,文中直接采用磁通密度为状态变量。在用直接法求解矢量磁位灵敏度方程的基础上,给出适合形状优化的磁通密度灵敏度分析的两种方法——半解析法和局部差分法。前者在磁通密度灵敏度计算中对形函数导数采用了差分近似,后者用一阶近似方法得到设计变量扰动后的矢量磁位和磁通密度,然后用差分法计算磁通密度灵敏度。两种方法简单且计算效率高,精度能够满足要求。优化问题求解采用序列线性规划算法。应用本文方法对电磁铁和同步电机磁极进行形状优化,取得了满意的结果。 相似文献
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Minjin Oh Moon Kyu Lee Naksoo Kim 《Journal of Mechanical Science and Technology》2010,24(12):2545-2553
Roll-formed slide rail used as a linear guide in the smooth movement of drawers and electric home appliances requires geometric
accuracy because of a high slenderness ratio and repetitive usage. The slide rail members are generally manufactured by the
roll forming process. The members need to be improved through optimization of the roll forming process instead of the designer’s
experience. The aim of this study is to determine the optimal roll forming parameters by using robust optimization technique
which simultaneously satisfies three criteria such as the shape difference factor, bowing factor and modified inverse safety
factor. In analyzing the roll forming process of a slide rail, the pass in which the largest deformation occurred is designated
as the target pass. The positions and the curvature of rolls are set as the design variables in the target pass. The cost
function, which is comprised of the shape difference factor, the bowing factor, and the modified inverse safety factor, is
obtained using design-of-experiments of the response surface method. The cost function is minimized by using robust optimization
techniques and showed the improved the straightness and the durability value. Using robust design methodology, it is able
to be constructed a multi-objective function, and optimized three criteria, simultaneously. 相似文献
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Cam profile optimization for a new cam drive 总被引:2,自引:0,他引:2
A complex cam shape optimization problem is studied to optimize a unique cam mechanism for a new cam drive engine. First,
the optimization problem is defined through analyzing the unique cam mechanism. Multiple design specifications are included
in the optimization problem by defining the output torque of the engine as the objective function and the contact stress,
radius of curvature, and pressure angle as the constraints. Second, an analytical scenario is designed to find the best ever
cam profiles through manipulating the different combinations of cam profile representations and optimization methods. Two
types of curve representations, including general polynomial spline and B-spline, are employed in cam profile synthesis. In
addition, both a classical optimization technique and a genetic algorithm (GA) based method are applied to solve the complex
optimization problem. Finally, comparative studies are performed among the initial profile and the optimal profiles to demonstrate
the effectiveness of these proposed design approaches on solving the cam profile optimization problem. Results show that the
best profiles are obtained from a combination of the B-spline representation and the GA-based method. In addition, compared
to the initial design, the engine performance is improved greatly by the proposed optimization approaches. 相似文献
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Fengbei Cheng Zhenyu Liu Guifang Duan Chan Qiu Bing Yi Jianrong Tan 《Journal of Mechanical Science and Technology》2014,28(7):2715-2722
To a large extent, the success of the product shape design depends on whether the geometric modeling systems can satisfy more and more complicated design demands in the engineering field. This paper proposes a shape design method based on semantic features for complex CAD surface. By the proposed method, we can easily meet the complicated design requirements, since the semantic can effectively represent the design intent. We discussed three aspects in shape design using semantic features, which are semantic design demands of the target surface, geometric constraints in accordance with semantic features, and surface shape deformation under the geometric constraints, respectively. The basic semantic features of geometric models drive the deformation of the target surface shape by changing the related constraint, and the desirable features are added to the CAD surface shape. The examples of the car shape design are presented to verify the effectives of our method. 相似文献
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DIRECT MANIPULATION OF B-SPLINE SURFACES 总被引:6,自引:0,他引:6
Wang Zhiguo Zhou Laishui Wang Xiaoping College of Mechanical Electrical Engineering CAD/CAM Research Center Nanjing University of Aeronautics Astronautics Nanjng China 《机械工程学报(英文版)》2005,18(1):103-108
Engineering design and geometric modeling often require the ability to modify the shape of parametric curves and surfaces so that their shape satisfy some given geometric constraints, including point, normal vector, curve and surface. Two approaches are presented to directly manipulate the shape of B-spline surface. The former is based on the least-square, whereas the latter is based on minimizing the bending energy of surface. For each method, since unified and explicit formulae are derived to compute new control points of modified surface, these methods are simple, fast and applicable for CAD systems. Algebraic technique is used to simplify the computation of B-spline composition and multiplication. Comparisons and examples are also given. 相似文献
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JM Zheng KW Chan I Gibson 《The International Journal of Advanced Manufacturing Technology》2003,22(1-2):54-67
There is an increasing demand in conceptual design for more intuitive methods for creating and modifying freeform curves and surfaces in CAD modeling systems. The methods should be based not only on the change of the mathematical parameters but also on the user's specified constraints and shapes. This paper presents a new surface representation model for freeform surface deformation representation. The model is a combination of two functions: a displacement function and a function for representing an existing NURBS surface called a parent surface. Based on the surface model, the authors develop several novel deformation methods which are named SingleDef (Single-point constraint based deformation method), MultiDef (Multiple-points constraints based deformation method), CurDef (Curve constraints based deformation method) and FeatDef (Feature constraint based deformation method). The techniques for freeform surface deformation allow conceptual designers to modify a parent surface by directly applying point constraints, curve constraint or a surface constraint to the parent surface. The deformation methods are implemented in an experimental CAD system. The results show that designers can easily and intuitively control the surface shape. 相似文献
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针对现有铣削工艺参数优化方法未考虑设计参数不确定性,导致优化结果难以满足实际产品性能要求的问题,引入近似模型对铣削工艺参数进行可靠性设计优化。以铣削加工表面粗糙度为目标函数,以最大铣削力小于给定值的可靠度作为约束,综合考虑铣削加工过程中铣削速度和每齿进给量的变动,建立了铣削工艺参数可靠性优化模型,并分别采用Kriging近似和径向基函数近似对铣削表面粗糙度、铣削力与设计变量之间的隐式关系进行近似替代,最后采用Monte Carlo仿真-序列近似规划对模型进行了寻优求解,通过试验对可靠性优化的结果进行了验证。结果表明,该方法可有效地降低铣削加工表面粗糙度,并且可保证加工过程中最大铣削力的可靠度要求。 相似文献
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《机械工程学报(英文版)》2020,33(1):65-72
The manual design of addendum surfaces on common CAD platforms is very tedious which requires many trialscorrections, which will certainly a ect the construction e ciency and quality of addendum surfaces, and then a ect the formability and quality of the workpiece in the process of sheet forming. In this paper, an automatic procedure based on parametric design method is proposed for the rapid construction of the addendum surfaces. The kernel of the parametric method is constructing boundary curves based on the shape of surfaces of workpiece and designing guide curves based on Hermite curve interpolation. By some simple parameters, the shape of the addendum surfaces could be controlled and adjusted easily. In addition, a minimum energy optimization method is employed to further optimize the constructed addendum surface. A finite element analysis for the sheet forming process is performed to evaluate the forming quality of constructed addendum surfaces. The instance illustrates that the addendum surface constructed by the proposed method could ensure both the overall smoothing of surfaces and the final forming quality, and it has a good e ect on springback after forming. This research proposes a smoothing parametric design method for addendum surfaces construction which could construct and optimize addendum surfaces rapidly. 相似文献
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Yong Shao Bin Lu Hengan Ou Facai Ren Jun Chen 《The International Journal of Advanced Manufacturing Technology》2014,71(1-4):69-80
Preform design plays an important role in forging design especially for parts with complex shapes. In this paper, an attempt was made to develop a topological optimization approach for the preform design in bulk metal forming processes based on the bidirectional evolutionary structural optimization strategy. In this approach, a new strain-based element addition and removal criterion has been proposed for evaluating and optimizing the material flow in the forging process. To obtain a smooth preform boundary, a closed B-spline curve based on the least square algorithm is employed to approximate the uneven surface of the updated preform profile. A C# program has been developed to integrate the FE simulation, shape optimization, and surface approximation processes. Two 2D forging preform design problems are evaluated by using the developed method. The results suggest that the optimized preform with the strain uniformity criterion has shown better performance in improving the material flow and deformation uniformity during the forging process. The results also demonstrate the robustness and efficiency of the developed preform optimization method. 相似文献
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一种骨架线驱动的产品曲面变形设计方法 总被引:1,自引:0,他引:1
针对复杂产品外形设计中一类由骨架线驱动的曲面变形设计问题,提出基于变分原理和扩散效应控制目标曲面变形的设计方法。通过提取决定产品外形曲面几何特征的骨架线(如脊线、谷线),按照给定的约束条件控制曲面骨架线的几何变形,以变形后的骨架线为几何约束条件控制曲面形状的变化趋势,从而实现产品形状变形设计。此外,利用该方法可以提取原曲面拉普拉斯微分坐标表示的曲面细节,保持曲面变形过程中几何细节特征基本不变。产品曲面变形实例验证了方法的有效性。 相似文献
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基于Internet网络的主从式并行遗传算法及其在叶栅优化中的应用 总被引:3,自引:0,他引:3
为了解决遗传算法在优化中由于适应度评价很费时而导致计算时间过长的问题 ,本文发展了一种基于In ternet网络实现的主从式并行遗传算法。在函数优化的测试实验中 ,通过控制待优化函数适应度评价的时间 ,验证了主从式模型在适应度评价很费时且远远超过通讯时间时将获得接近于线性的加速比 ,讨论了主从式并行遗传算法应用于气动性能优化中的可行性。通过二维叶栅的优化算例 ,证明了本文提出的算法适合于需要大计算资源的叶栅气动优化设计 相似文献
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建立了基于试验设计理论和响应面近似的液力透平叶轮的优化设计方法。以最高效率、高效区范围及转轮所得扭矩-流量曲线在小流量区的稳定性为目标函数。在使用CFturbo软件建立液力透平叶轮的参数化模型后,先用Plackett-Burman试验设计筛选结构参数,并根据结构参数对目标函数的影响将其划分为三个等级:显著因素、次显著因素和不显著因素;再用正交试验法确定次显著因素的设计中心点;最后由中心复合和Box-Behnken设计及响应面分析确定各级结构参数的最优设计点。该方法以计算流体力学(CFD)的计算结果为基础,共进行40次试验,构造了液力透平叶轮的结构参数与多目标函数的响应面近似模型,分析了结构参数间的交互效应。对最优设计点的液力透平进行了实验研究,试验结果及CFD计算值与响应面近似值吻合,且较优化前的模型在性能上有明显改善,表明基于试验设计和响应面的优化设计方法可用于液力透平叶轮的优化设计。 相似文献
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介绍了极限转速为15000r/min,储能量为600wh的空心飞轮转子的优化设计方法,根据飞轮储能系统设计要求利用三维软件SolidWorks对飞轮模型进行建模与有限元软件ansys workbench进行仿真分析与优化,首先进行初步建模,然后通过改变其模型轮辐曲线找到更优的飞轮形状并提取其轮辐曲线的结构参数,再通过多目标遗传算法对飞轮转子进行优化设计及研究,以飞轮质量更轻,极转动惯量更大以及应力应变更小为约束条件,提取其飞轮结构几何尺寸为设计变量进行优化,得出一种更优的飞轮结构形式。结果表明,优化后得到的飞轮转子形状较原模型相比性能更佳。 相似文献
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应力分布均匀程度是衡量精密机电产品装配精度和性能稳定性的重要指标,均匀的应力分布也是当前精密机电产品装配过程所追求的目标之一。形状设计是改善装配界面接触应力分布的重要途径,针对当前基于应力分布的装配界面形状主动设计方法中初始参数取值难以确定,且相关参数对优化过程计算效率、数值计算稳定性影响较大的问题,提出了一种根据优化过程中接触应力分布均匀程度变化信息来调节优化参数的自适应参数计算方法。并以典型单螺栓连接结构为设计对象,对比了采用自适应参数设计方法与采用固定参数设计方法分别进行装配界面形状主动设计后的结果。理论分析结果表明:该方法可以很好地解决基于应力分布的装配界面形状主动设计方法中初始参数难以确定的问题,同时提高了优化效果、计算效率和优化过程中的数值计算稳定性。 相似文献