共查询到20条相似文献,搜索用时 203 毫秒
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基于外载荷的B样条曲面变形 总被引:1,自引:0,他引:1
针对B样条曲面变形过程中存在变形区域不能自由选择、变形距离不能精确计算和操作效率低等问题,运用能量优化的思想,提出一种B样条曲面变形的算法,用于B样条曲面的变形.给出B样条曲面按节点矢量划分成曲面片的方法,将曲面片类比为有限单元法中薄壁面单元,并将作用在B样条曲面片上的外载荷分解成曲面片四个端点力的双线性插值.分别建立B样条曲面内部能量方程和外载荷能量方程,外载荷的改变引起B样条曲面内部能量的变化,通过求解一个使B样条曲面内部能量变化量为最小的优化问题,得到变形后B样条曲面控制顶点的变化量.给出一种求解B样条曲面变形距离的计算方法,提高B样条曲面变形的精度和变形效率.最后的实例验证所提算法的有效性和实用性. 相似文献
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曲面重构造型技术是整个RE技术的核心。传统的方法是通过对离散的点云进行拟合形成曲面,通过曲面裁减、延伸、拼接得到原始的CAD模型。对曲面的重构技术研究发现,对于具有过渡几何特征的点云,单纯的曲面拟合拼接并不能得到理想的CAD模型。该文针对反求工程中过渡曲面的建模方法,提出了按过渡几何特征分类,以光滑连续为曲面的过渡曲面方法。实践运用表明,运用过渡曲面造型技术得到的CAD模型光顺,更能体现造型设计意图。 相似文献
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结构形状优化已经在工程应用中得到重视,将无网格法与形状优化相结合能够从根本上解决优化过程中出现的有限单元扭曲或畸变问题。为此在无网格Galerkin法的基础上,利用离散导数法,提出一种基于离散型的节点位移灵敏度分析方法,其中采用了拉格朗日乘子法来施加本质边界条件。该方法的最大优势是求解过程与无网格Galerkin法的求解过程相似,容易实现。另外对形状优化的数学模型和节点位移的设计速度域进行了讨论。采用具有解析解的实例,对所提出的灵敏度分析方法进行了验证,所得结果显示两者非常吻合。利用上述所建立的形状优化算法,完成了两个工程实例的形状优化设计。 相似文献
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HE Yaohua RONG Hui SU Chuqi LI Yujie 《机械工程学报(英文版)》2008,21(1):106-110
To many industrial products such as cell phone, family appliance, vehicle, a pretty shape of nice visual effect is indispensable. To fulfill this target, designers are endeavoring to make the curve and surface of the products smooth and continuous during the shape design. Through the analysis and generalization of the present smoothing methods, the energy optimization method which combines the merits of energy method and least squares method together is studied, the target function of energy optimization method is derived, the solution to the target function and steps of curve fairing is introduced, the skills and methods building A-class surface which are based on cloud data measured from 3D scanning are studied, the validity of energy optimization method is verified with the example of the shape design ofa mini-EV as well. 相似文献
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基于多幅图像的逆向造型方法初步研究 总被引:7,自引:1,他引:6
提出了一种由多幅图像初步恢复三维物体形状的方法。在共线光源(光源位于或接近摄像机的光轴上,并且照射方向平行于光轴)照射下,对置于旋转平台上的物体摄像;综合考虑所摄图像序列中包含的几何轮廓信息与光亮度信息,采用立体相交技术和剥离技术,逐步求精地得到三维物体的八叉树表示。这种初步的造型结果可作为其他更精确方法的基础。 相似文献
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考虑到传统生物生长法只能对简单形状进行优化的局限性,结合复杂结构的三维形状优化设计,对生物生长法提出三点改进:①不直接采用修正后节点坐标来调整网格,利用B样条函数描述修改后结构的外边界。②构造出在满足应力和几何条件下可使结构重量最轻的目标函数,进而大大增强了生物生长法在处理复杂结构形状优化设计方面的能力。③在生物生长法形状优化过程中,采用罚方法对违反约束条件的个体给予惩罚。作为工程实例,该方法被用于某三维离心叶轮的结构形状优化设计。计算结果表明,该方法可在较短时间内得到满足各种应力和几何约束的重量最轻解。 相似文献
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PENALTYFUNCTIONMETHODOFCONTINUUMSHAPEOPTIMIZAIONGuoTaiyong;WangXinrong;LiangYingchun(HarbinInstituteofTechnology)Abstract:The... 相似文献
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HuXinXi JuntongJin YeInstitute of Computer Integrated Manufacturing Shanghai Jiaotong University Shanghai ChinaGu Dongyun Dai KerongDepartment of Orthopaedics Shanghai th People''''s Hospital Shanghai Second Medical UniversityShanghai China 《机械工程学报(英文版)》2003,16(3):309-312
Former research work about the modeling of hip joint focus on the upper segment of femoral, and assumes the acetabulum cup is sphere concave, and the acetabulum prostheses is semisphere. A method of acquiring the point data on the surface of the hipbone using the reverse engineering technology is presented. After analyzing the acetabulum surface fitting error, a rotation ellipsoid CAD model is applied to fit the acetabulum surface, and then optimization technique is used to find the geometric parameters of the model. The fitting error between the sphere and rotation ellipsoid is compared and gets the result that the fitting error of rotation ellipsoid is smaller than sphere, and the rotation ellipsoid can describe the shape of the acetabulum better. 相似文献
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ZHU Weidong KE Yinglin College of Mechanical Energy Engineering Zhejiang University Hangzhou China 《机械工程学报(英文版)》2007,20(4):112-116
A method to reconstruct symmetric B-spline curves and surfaces is presented.The symme- try property is realized by using symmetric knot vector and symmetric control points.Firstly,data points are divided into two parts based on the symmetry axis or symmetry plane extracted from data points.Then the divided data points are pararaeterized and a symmetric knot vector is selected in order to get symmetric B-spline basis functions.Constraint equations regarding the control points are deduced to keep the control points of the B-spline curve or surface to be symmetric with respect to the extracted symmetry axis or symmetry plane.Lastly,the constrained least squares fitting problem is solved with the Lagrange multiplier method.Two examples from industry are given to show that the proposed method is efficient,robust and able to meet the general engineering requirements. 相似文献