共查询到20条相似文献,搜索用时 15 毫秒
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This paper presents an integrated approach that supports the topology optimization and CAD-based shape optimization. The main
contribution of the paper is using the geometric reconstruction technique that is mathematically sound and error bounded for
creating solid models of the topologically optimized structures with smooth geometric boundary. This geometric reconstruction
method extends the integration to 3-D applications. In addition, commercial Computer-Aided Design (CAD), finite element analysis
(FEA), optimization, and application software tools are incorporated to support the integrated optimization process. The integration
is carried out by first converting the geometry of the topologically optimized structure into smooth and parametric B-spline
curves and surfaces. The B-spline curves and surfaces are then imported into a parametric CAD environment to build solid models
of the structure. The control point movements of the B-spline curves or surfaces are defined as design variables for shape
optimization, in which CAD-based design velocity field computations, design sensitivity analysis (DSA), and nonlinear programming
are performed. Both 2-D plane stress and 3-D solid examples are presented to demonstrate the proposed approach.
Received January 27, 2000
Communicated by J. Sobieski 相似文献
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《Advances in Engineering Software》2001,32(7):555-567
This paper presents an integrated design and manufacturing approach that supports shape optimization of structural components. The approach starts from a primitive concept stage, where boundary and loading conditions of the structural component are given to the designer. Topology optimization is conducted for an initial structural layout. The discretized structural layout is smoothed using parametric B-Spline surfaces. The B-Spline surfaces are imported into a CAD system to construct parametric solid models for shape optimization. Virtual manufacturing (VM) techniques are employed to ensure that the optimized shape can be manufactured at a reasonable cost. The solid freeform fabrication (SFF) system fabricates physical prototypes of the structure for design verification. Finally, a computer numerical control (CNC) machine is employed to fabricate functional parts as well as mold or die for mass production of the structural component. The main contribution of the paper is incorporating manufacturing into the design process, where manufacturing cost is considered for design. In addition, the overall design process starts from a primitive stage and ends with functional parts. A 3D tracked vehicle roadarm is employed throughout this paper to illustrate the overall design process and various techniques involved. 相似文献
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基于KBE与ActiveX的产品参数化设计研究 总被引:1,自引:1,他引:0
针对目前尺寸驱动参数化建模方法存在的不足,提出了程序外驱动参数化建模思想,利用面向对象方法开发了基于知识工程(KBE)的机械产品参数化设计平台.该平台以三维CAD系统API模块为接口,采用ActiveX Automation技术,通过消息数据通信,将.NET开发的设计系统与CAD/CAE软件进行无缝集成.以桥式起重机设计为例,在知识重用和产品信息共享的基础上快速实现三维建模与虚拟装配,为数字化设计与制造提供了高效,准确、实用的方法. 相似文献
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《Advanced Engineering Informatics》2014,28(2):111-126
An efficient computational methodology for shape acquisition, processing and representation is developed. It includes 3D computer vision by applying triangulation and stereo-photogrammetry for high-accuracy 3D shape acquisition. Resulting huge 3D point clouds are successively parameterized into mathematical surfaces to provide for compact data-set representation, yet capturing local details sufficiently. B-spline surfaces are employed as parametric entities in fitting to point clouds resulting from optical 3D scanning. Beyond the linear best-fitting algorithm with control points as fitting variables, an enhanced non-linear procedure is developed. The set of best fitting variables in minimizing the approximation error norm between the parametric surface and the 3D cloud includes the control points coordinates. However, they are augmented by the set of position parameter values which identify the respectively closest matching points on the surface for the points in the cloud. The developed algorithm is demonstrated to be efficient on demanding test cases which encompass sharp edges and slope discontinuities originating from physical damage of the 3D objects or shape complexity. 相似文献
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Robust uniform triangulation algorithm for computer aided design 总被引:2,自引:0,他引:2
This paper presents a new robust uniform triangulation algorithm that can be used in CAD/CAM systems to generate and visualize geometry of 3D models. Typically, in CAD/CAM systems 3D geometry consists of 3D surfaces presented by the parametric equations (e.g. surface of revolution, NURBS surfaces) which are defined on a two dimensional domain. Conventional triangulation algorithms (e.g. ear clipping, Voronoi-Delaunay triangulation) do not provide desired quality and high level of accuracy (challenging tasks) for 3D geometry. The approach developed in this paper combines lattice tessellation and conventional triangulation techniques and allows CAD/CAM systems to obtain the required surface quality and accuracy. The algorithm uses a Cartesian lattice to divide the parametric domain into adjacent rectangular cells. These cells are used to generate polygons that are further triangulated to obtain accurate surface representation. The algorithm allows users to control the triangle distribution intensity by adjusting the lattice density. Once triangulated, the 3D model can be used not only for rendering but also in various manufacturing and design applications. The approach presented in this paper can be used to triangulate any parametric surface given in S(u,v) form, e.g. NURBS surfaces, surfaces of revolution, and produces good quality triangulation which can be used in CAD/CAM and computer graphics applications. 相似文献
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参数化设计是几何体建模的重要手段,而桥梁的三维可视化是当今桥梁信
息化的发展趋势。论文针对桥梁外观参数化模型可视化的需要,对几何体参数化建模的原理
和方法进行了深入探讨。结合桥梁结构特点,分析了主要桥梁组件结构(如T 梁、盖梁柱
式墩、轻型桥台等)构件图的几何和拓扑关系,对组件进行了参数化设计,实现组件的三维
建模;并对组件中特殊图元(如圆弧倒角形墩柱、桥台近似锥面护坡)的绘制算法进行详细
研究;根据各组件间空间位置的拓扑关系,利用参数化变量驱动计算各组件空间位置坐标,
进行桥梁的快速拼接。完成的桥梁三维参数化建模以参数为驱动,用户可以对设计结果进行
可视化修改。所实现的三维参数桥梁可视化系统具有模型构建精致,参数化建模彻底、建模
速度快,参数分类清晰,可视化效果好的特点。 相似文献
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In order to take advantage of trends such as genetic-design students need to be familiar, and comfortable, with the concept of parametric computer models and how their parameters relate to physical-forms. Virtual learning software can aid in creating that understanding and help support studies at all undergraduate levels in engineering design disciplines. As an example, hydropower rotors are complex and largely rely on computational analysis of geometries for single rotor types. That problem can be significantly overcome using a parametric algorithm capable of creating an almost-infinite variety of computer models. Therefore, this paper investigates the shared parametric properties of common crossflow hydropower rotor geometries, resulting in a generic model that is then used to illustrate application in real-time interactive virtual learning software capable of producing accurate stereoscopic images and stereolithography files for 3D printing, as well as linking to constructive solid geometry software for slower, but more detailed, analysis. A pilot survey of student attitudes to the virtual learning prototype and resulting geometries is then discussed, illustrating the potential for 3D graphics as an effective addition to virtual learning of parametric design methods, and giving initial direction for future work. 相似文献
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符号方案三维实体化的自动化方法研究 总被引:1,自引:0,他引:1
如何将创新设计过程中得到的符号方案生成直观的图形方案,是机械概念设计中的关键技术问题,通过对符号方案的邻接矩阵元素进行分析,得到机构的结构组成、构件连接关系等信息;运用符号方案的尺度矩阵确定各装配构件的二维几何尺度,在面向对象二次开发的环境下,基于三维参数化平台,实现构件的三维实体化;根据构件所处空间位置,按后台预置装配方法得到三维虚拟实体装配图。上述过程基于面向对象的环境,输入/读入概念设计得到符号方案后,系统自动地将符号方案生成三维虚拟实体方案。 相似文献
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In this paper, we introduce a novel parametric finite element method for segmentation of three-dimensional images. We consider a piecewise constant version of the Mumford–Shah and the Chan–Vese functionals and perform a region-based segmentation of 3D image data. An evolution law is derived from energy minimization problems which push the surfaces to the boundaries of 3D objects in the image. We propose a parametric scheme which describes the evolution of parametric surfaces. An efficient finite element scheme is proposed for a numerical approximation of the evolution equations. Since standard parametric methods cannot handle topology changes automatically, an efficient method is presented to detect, identify and perform changes in the topology of the surfaces. One main focus of this paper are the algorithmic details to handle topology changes like splitting and merging of surfaces and change of the genus of a surface. Different artificial images are studied to demonstrate the ability to detect the different types of topology changes. Finally, the parametric method is applied to segmentation of medical 3D images. 相似文献
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在分析产品零部件设计重用过程的基础上,借鉴软件重用中组件模型的可重用服务及接口与实现过程相分离等思想,给出一个基于Web服务的零部件参数设计重用框架。该框架由上至下分别为设计接口层、设计服务层、设计结果层。在服务端通过软件集成技术(如iSIGHT等)实现零部件设计过程自动化、参数化及集成化,建立零部件的参数化设计模板。利用Web封装技术(如EASA软件)对参数化设计模板封装、管理,从而实现客户端基于Web服务的零部件参数化设计重用。实例验证表明,通过该方法实现的零部件重用在保证零部件设计质量前提下可有效地提高效率。 相似文献
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介绍了基于AutodeskInventor的部件库的体系结构和实现方法。把部件库系统分为零件库和部件库两层结构,通过部件模型确定组成部件的组成零件及其装配关系,通过数据表和程序确定零件的规格。此方法解决了常用三维CAD软件不直接支持装配件参数驱动的问题,使得基于三维CAD软件创建部件库系统成为可能。文中所述部件库系统是使用VC++对Inventor进行二次开发而得到的。同时,该方法也适用于其他常用三维CAD软件。 相似文献
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介绍了虚拟样机技术和Pro/E 软件,描述了铁路货车轴端电机的结构和功
能特点及其虚拟样机模型的三维设计流程。讲述了模块化理念和并行设计方法在轴端电机总
体设计中的应用,并详细描述了参数化设计方法在轴端电机详细设计中的应用,主要包括零
部件尺寸参数化、装配约束参数化及Pro/E 提供的“外部复制几何”和“使用参照”两种参数化
工具。以永磁体厚度作参数化变量为例,介绍了多学科分析在轴端电机结构设计中的作用。
通过铁路货车轴端电机结构设计的实践表明:先进的三维设计技术和卓越的多学科分析方法
是基于虚拟样机技术的产品结构设计的重要工具和组成部分,能有效缩短设计周期、减少设
计成本,并能保证产品满足使用者的需求。 相似文献
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多裁剪自由曲面生成有限元网格的实现 总被引:1,自引:0,他引:1
论述了多裁剪自由曲面生成有限元曲面网格的几个关键技术.采用了推进波前法生成曲面网格,给出了核心算法;在曲面算法中运用了介于参数法与直接法之间的新方法.针对求解曲面上最优点的参数域反算问题,引入了切矢逆求方法,可使迭代次数大为降低.测试表明,该算法快速、稳定.对大型的多裁剪自由曲面生成的曲面有限元网格,可直接用于有限元计算. 相似文献
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Damir Vucina Zeljan Lozina Igor Pehnec 《Engineering Applications of Artificial Intelligence》2012,25(3):648-667
Optimum design introduces strong emphasis on compact geometry parameterization in order to reduce the dimensionality of the search space and consequently optimization run-time. This paper develops a decision support system for optimum shape which integrates geometric knowledge acquisition using 3D scanning and evolutionary shape re-engineering by applying genetic-algorithm based optimum search within a distributed computing workflow.A shape knowledge representation and compaction method is developed by creating 2D and 3D parameterizations based on adaptive chaining of piecewise Bezier curves and surfaces. Low-degree patches are used with adaptive subdivision of the target domain, thereby preserving locality. C1 inter-segment continuity is accomplished by generating additional control points without increasing the number of design variables. The control points positions are redistributed and compressed towards the sharp edges contained in the data-set for better representation of areas with sharp change in slopes and curvatures. The optimal decomposition of the points cloud or target surface into patches is based on the requested modeling accuracy, which works as lossy geometric data-set compression. The proposed method has advantages in non-recursive evaluation, possibility of chaining patches of different degrees, options of prescribing fixed values at selected intermediate points while maintaining C1 continuity, and uncoupled processing of individual patches.The developed procedure executes external application nodes using mutual communication via native data files and data mining. This adaptive interdisciplinary workflow integrates different algorithms and programs (3D shape acquisition, representation of geometry with data-set compaction using parametric surfaces, geometric modeling, distributed evolutionary optimization) such that optimized shape solutions are synthesized. 2D and 3D test cases encompassing holes and sharp edges are provided to prove the capacity and respective performance of the developed parameterizations, and the resulting optimized shapes for different load cases demonstrate the functionality of the overall distributed workflow. 相似文献