共查询到19条相似文献,搜索用时 202 毫秒
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基于涡轮叶片有限元分析离散数据点的NURBS曲面重构 总被引:3,自引:0,他引:3
为解决有限元方法产生的三角网格数据不利于进行后续的曲面编辑和加工的问题,提出了一套算法将有限元网格逼近为造型和加工常用的NURBS曲面。首先对有限元网格进行预处理,提取出边界曲线并构造出初始曲面;通过基于曲率的自由曲面抽样网格规划方法,将海量离散数据点进行压缩及建立四边域网格,方法具有自组织和压缩比率用户可控等特点;采用迭代逼近的方法进行NURBS曲面拟合,在保证拟合精度的前提下提高了曲面光顺性。对真实叶片数据的处理证明了算法的实用性。 相似文献
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复杂的曲面需要将面拆分成多块,然后再将曲面搭接成需要的连续性级别即可.基于NURBS标准4边结构与特殊状态的3边曲面结构、周期曲面、封闭曲面、修剪面等非4边结构,提出复杂造型NURBS曲面拆分为基础曲面与混合曲面的分面策略及分面时应注意的问题.并结合实际案例,分析同一造型的曲面的2种不同分面思路. 相似文献
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细分曲面由于没有整体解析表达式,与参数、隐式曲面相比求交更加困难。针对基于平面四边形网格的Catmull-Clark细分曲面,在给定精度条件下,把对细分曲面的求交转化为对一定细分层次控制网格的求交:首先构造两张控制网格上相交四边形网格带及其1-邻域网格带,然后不断细分相交四边形网格带及其1-邻域网格带,提高求交精度,其次求解出相交四边形网格的交点,并根据拓扑关系将其顺序连接起来既得到两细分曲面之间的相交曲线,实现了细分曲面的求交。 相似文献
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针对飞机零部件模具设计过程中遇到的曲面延拓困难问题,提出了以B样条双向蒙皮造型技术对曲面进行重构,进而实现曲面快速延拓的新方法,并基于CATIA开发了钣金模具型面辅助设计工具,实现了复杂曲面的快速延拓,可提高航空钣金件模具的设计效率。 相似文献
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基于NURBS直纹面拟合敏感点的空间凸轮侧铣刀轨算法优化原理,提出了拟合误差敏感点的选择方法,根据NURBS曲面重构的原理,将曲面曲率最值点和拟合误差最大点定义为理论加工刀轨曲面误差敏感点。利用曲率敏感点,在理论非等径刀轨曲面规划离散网格,得到初始数据点。通过最小二乘优化方法重构NURBS刀轨直纹面,再根据误差敏感点定义的等参数曲线来调整刀轨直纹面形状。构建了理论加工误差模型,并通过实例的仿真计算和数值模拟说明了该算法的有效性。 相似文献
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An automatic mesh generation scheme with unstructured quadrilateral elements on trimmed NURBS surfaces has been developed. In this paper NURBS surface geometries in the IGES format have been employed to represent geometric models. For unstructured mesh generation with quadrilateral elements, a domain decomposition algorithm employing loop operators has been modified. As for the surface meshing, an indirect 2D approach is proposed in which both quasi-expanded planes and projection planes are employed. Sample meshes for complex models are presented to demonstrate the robustness of the algorithm. 相似文献
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Xue-Feng Zhu Ping Hu Zheng-Dong Ma Xiangkui Zhang Weidong Li Jingru Bao Mingzeng Liu 《The International Journal of Advanced Manufacturing Technology》2013,65(9-12):1215-1227
In an attempt to construct an isogeometric analysis-suited geometry for isogeometric analysis, a new surface parameterization method using the one-step inverse forming (SPIA) is proposed. Initial generation of watertight analysis-suitable geometry (NURBS surfaces) with complex shapes can be a significant bottleneck for isogeometric analysis because computer-aided design models often include ambiguities such as gaps and overlaps. Most of traditional surface parameterization techniques are based on geometric method and limited to finite meshes, while SPIA is a physics-based method using sheet metal forming technique with large elastic–plastic deformation and robust enough and rapid to deal with the finite elements mesh with over 100,000 nodes within 2 min without the necessity to simplify the meshes. Using Coons surface parameterization, global mesh parameterization, and NURBS reconstruction, we can rebuild new computer-aided design models with errors under any tolerance to which isogeometric analysis can be applied. The NURBS surfaces after reconstruction are also used for computer-aided manufacturing. 相似文献
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Sripati Sah Robert X. Gao 《The International Journal of Advanced Manufacturing Technology》2011,55(1-4):121-132
This paper presents an analysis of the dynamic contact pressure distribution at the sheet metal-tooling interface in normal and defective panel stamping operations. Specifically, the stamping of a 1.27?×?20?×?15?cm rectangular aluminum alloy panel has been simulated using finite-element modeling methods. The modeling results are leveraged to determine the forces acting on sensors embedded in the die structure. Based on these results, a customized stamping test bed has been designed, which incorporates an array of force sensors embedded into the stamping die to enable online measurement of the forces in the die. The force measurements are processed by the thin plate spline numeric surface interpolation method to evaluate a continuous contact pressure distribution map of the die cavity. The pressure distribution in the die cavity in normal and defective scenarios has been presented along with a suggested volume thresholding method for automated defect detection. By leveraging the numeric surface generation method to analyze experimental data, the present study establishes the basis for intelligent tooling and in-process monitoring for improved observability in sheet metal stamping. 相似文献
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复杂型面板料件冲压仿真有限元建模技术研究 总被引:1,自引:1,他引:0
探讨了具有复杂型面的大型板料件冲压仿真有限元建模过程中的一些关键技术问题。针对此类零件具有几何形状复杂的特点 ,利用造型功能强大的三维造型软件对由扫描测量机测到的离散数据进行拟合和光顺处理 ,得到零件的精确曲面 CAD模型 ,然后通过标准数据转换接口 ,将 CAD模型转入仿真软件的前处理器中 ,再利用软件的曲面网格划分功能对其进行网格划分 ,最终建立起冲压仿真所需的有限元模型。以轿车门内板冲压仿真有限元模型建模为例 ,说明了复杂型面板料件冲压仿真有限元建模技术的实际应用。 相似文献
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X. Luo K. Cheng Professor R. Ward 《The International Journal of Advanced Manufacturing Technology》2005,25(11-12):1089-1097
The paper presents a novel approach for modelling and simulation of the surface generation in the machining process. The approach, by integrating a dynamic cutting force model, regenerative vibration model, machining system response model and tool profile model, models the complex surface generation process. Matlab Simulink is used to interactively perform the simulation in a user-friendly, effective and efficient manner. The effects of machining variables and tooling characteristics on the surface generation are investigated through simulations. CNC turning trials have been carried out to evaluate and validate the approach and simulations presented. The proposed approach contributes to comprehensive and better understanding of the machining system, and is promising for industrial applications with particular reference to the optimisation of the machining process based on the product/component surface functionality requirements. 相似文献
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首先叙述了钣金冲压过程中出现缺陷的影响因素,以G180型柴油机油箱为例,具体介绍了其选材、模具设计、工艺等设计制造过程,并着重分析了其在冲压制造过程中所存在的问题及解决办法,为其他板料冲压制造提供了设计素材和处理出现缺陷的经验。 相似文献
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Pralay Pal 《The International Journal of Advanced Manufacturing Technology》2012,63(9-12):1205-1215
In this paper, we presented a method for fitting large B-spline topological surfaces on freeform polygon mesh generated from cloud data of objects. The mesh has been manually segmented and large surfaces are fitted on segments in a hybrid approach, i.e., combination of geometric subdivision and non-uniform rational B-spline (NURBS) interpolation which is an emerging research space. An interpolation method has been proposed to parameterize dense cloud data of any complexity level with capability of handling occluded regions. All junctions are treated with trimming of NURBS surfaces with C 0 and C 1 continuities between adjacent patches. This scheme amalgamated process knowledge of reconstruction on segmented and subdivided point cloud data, various NURBS geometry options and junction treatment resulting in faster high-quality reconstruction. Apart from manual segmentation, almost the entire process is automatic which generated superior quality surface models. Pawn, Stanford Bunny, and human head clouds with occluded surface zones are used for tryout and resulting shapes are recorded in initial graphics exchange specification (IGES) files. 相似文献
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Zezhong C. Chen Maqsood A. Khan 《The International Journal of Advanced Manufacturing Technology》2014,70(5-8):1355-1368
With the development of a new function of computer numerical control controllers, nonuniform rational B-spline (NURBS) interpolation, NURBS tool path generation for sculptured surface machining is under extensive research. The common procedures of the current NURBS tool path planning methods are as follows: first, to find a group of cutter contact points on a sculptured surface; second, to calculate their corresponding cutter locations (CLs); then, to fit a NURBS tool path to the CLs within a prescribed tolerance; and finally, to inspect the tool path for possible gouge by the tool and delete the invalid path segments, if any. However, the NURBS tool path has the following problems: (a) although it passes through the discrete CLs of the theoretical CL path, the deviation along the two paths could be larger than the tolerance; (b) its parameter is not the arc length of the path; and (c) it is difficult to detect gouge along the NURBS path and to remove the invalid segments from it. Consequently, NURBS tool paths generated with the current methods of commercial computer-aided design/computer-aided manufacturing (CAD/CAM) software cannot be used to make smooth and accurate surfaces. To address these problems, this work proposes a new approach to generating arc length parameterized NURBS tool paths with high accuracy in terms of the theoretical CL paths and without gouge and interference. Two practical examples in this work clearly demonstrate the feasibility of this approach and the advantages of the generated NURBS tool paths. Therefore, this approach can be implemented into the CAD/CAM software to promote NURBS machining in industry. 相似文献