共查询到20条相似文献,搜索用时 15 毫秒
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N. El‐Abbasi S. A. Meguid A. Czekanski 《International journal for numerical methods in engineering》2001,50(4):953-967
In this paper, a new strategy for the smooth representation of 2D contact surfaces is developed and implemented. The contact surfaces are modelled using cubic splines which interpolate the finite element nodes. These splines provide a unique surface normal vector and do not require prior knowledge of surface tangents and normals. C2‐continuous cubic splines are suitable for representing rigid contact surfaces, while C1‐continuous Overhauser splines are shown to be most suitable for representing flexible contact surfaces. A consistent linearization of the kinematic contact constraints, based on the spline interpolation, is derived. The new spline‐based contact surface interpolation scheme does not influence the element calculations. Consequently, it can be easily implemented in standard FE codes. Several numerical examples are used to illustrate the advantages of the proposed smooth representation of contact surfaces. The results show a significantimprovement in accuracy compared to traditional piecewise element‐based surface interpolation. The predicted contact stresses are also less sensitive to the mismatch in the meshes of the different contacting bodies. This property is useful for problems where the contact area is unknown a priori and when there is significant tangential slip. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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散乱数据点三角剖分方法综述 总被引:25,自引:2,他引:25
构造散乱数据插值曲面首先必须对散乱数据点实行三角剖分。本文简要阐述三角剖分的基本概念。并按优化准则将现有的各种三角剖分方法进行分类比较,为建立更好的凸域三角剖分算法提供依据,并为解决复杂多边形区域散乱数据点三角剖分奠定基础。 相似文献
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给出了一类可以保持几何与拓扑信息一致性的裁剪面的参数变换定理及其算法。首先,确定了参数变换对裁剪面表示信息的影响。然后,根据参数变换后几何与拓扑信息的一致性要求,给出了对裁剪面表示信息进行调整的方法。最后,通过建立参数变换的关系,以裁剪球面为例阐述了这类参数变换的具体实现方法。 相似文献
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Frdric Noël 《International journal for numerical methods in engineering》2002,54(7):965-986
We describe a new geometric algorithm to map surfaces into a plane convex area. The mapping transformation is bijective; it redefines the whole surface as a unique bi‐parametric patch. Thus this mapping provides a global parametrization of the surface. The surfaces are issued from industrial CAD software; they are usually described by a large number of patches and there are many shortcomings. Indeed, the decomposition into patches depends on the algorithm of the geometric modelling system used for design and usually has no meaning for any technological application. Moreover, in many cases, the surface definition is not compatible, i.e. patches are not well connected, some patches are self‐intersecting or intersect each other. Many applications are hard to address because of these defects. In this paper we show how patch‐independent meshing techniques may be easily automated using a unique metric in a plane parametric space. Thus we provide an automatic procedure to build valid meshes over free‐form surfaces issued from industrial CAD software (Computer Aided Design: this terminology should refer to a large amount of software. For the scope of this paper we only refer to geometric modelling systems. Indeed geometric modelling systems remain the kernel of many CAD software). Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Abdelhamid Adouani 《Dynamical Systems: An International Journal》2012,27(2):169-186
We give a characterization of piecewise C 1 class P-homeomorphism f of the circle with irrational rotation number and finitely many break points which is piecewise C 1 conjugate to a C 1-diffeomorphism. The following properties are equivalent:
?(i)?f is conjugate to a C 1-diffeomorphism of the circle by a piecewise C 1-homeomorphism. (ii)?The product of jumps of f in the break points contained in a same orbit is trivial. (iii)?f is conjugate to a C 1-diffeomorphism of the circle by a piecewise linear (PL)-homeomorphism or a piecewise quadratic homeomorphism.
For a PL-homeomorphism f having the property (ii): f is conjugate to a rotation either by a PL-homeomorphism or by a piecewise analytic homeomorphism. 相似文献
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Finding optimum conditions for process factors in an engineering optimization problem with response surface functions requires structured data collection using experimental design. When the experimental design space is constrained owing to external factors, its design space may form an asymmetrical and irregular shape and thus standard experimental design methods become ineffective. Computer-generated optimal designs, such as D-optimal designs, provide alternatives. While several iterative exchange algorithms for D-optimal designs are available for a linearly constrained irregular design space, it has not been clearly understood how D-optimal design points need to be generated when the design space is nonlinearly constrained and how response surface models are optimized. This article proposes an algorithm for generating the D-optimal design points that satisfy both feasibility and optimality conditions by using piecewise linear functions on the design space. The D-optimality-based response surface design models are proposed and optimization procedures are then analysed. 相似文献
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M. Stadler G. A. Holzapfel 《International journal for numerical methods in engineering》2004,60(7):1161-1195
This paper presents a strategy to parameterize contact surfaces of arbitrary mesh topology in 3D with at least C1‐continuity for both quadrilateral and triangular meshes. In the regular mesh domain, four quadrilaterals or six triangles meet in one node, even C2‐continuity is attained. Therefore, we use subdivision surfaces, for which non‐physical pressure jumps are avoided for contact interactions. They are usually present when the contact kinematics is based on facet elements discretizing the interacting bodies. The properties of subdivision surfaces give rise to basically four different implementation strategies. Each strategy has specific features and requires more or less efforts for an implementation in a finite element program. One strategy is superior with respect to the others in the sense that it does not use nodal degrees of freedom of the finite element mesh at the contact surface. Instead, it directly uses the degrees of freedom of the smooth surface. Thereby, remarkably, it does not require an interpolation. We show how the proposed method can be used to parameterize adaptively refined meshes with hanging nodes. This is essential when dealing with finite element models whose geometry is generated by means of subdivision techniques. Three numerical 3D problems demonstrate the improved accuracy, robustness and performance of the proposed method over facet‐based contact surfaces. In particular, the third problem, adopted from biomechanics, shows the advantages when designing complex contact surfaces by means of subdivision techniques. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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S. Gosselin C. Ollivier‐Gooch 《International journal for numerical methods in engineering》2011,87(8):795-820
This paper studies the practical performance of Delaunay refinement tetrahedral mesh generation algorithms. By using non‐standard quality measures to drive refinement, we show that sliver tetrahedra can be eliminated from constrained Delaunay tetrahedralizations solely by refinement. Despite the fact that quality guarantees cannot be proven, the algorithm can consistently generate meshes with dihedral angles between 18circ and 154°. Using a fairer quality measure targeting every type of bad tetrahedron, dihedral angles between 14° and 154° can be obtained. The number of vertices inserted to achieve quality meshes is comparable to that needed when driving refinement with the standard circumradius‐to‐shortest‐edge ratio. We also study the use of mesh improvement techniques on Delaunay refined meshes and observe that the minimum dihedral angle can generally be pushed above 20°, regardless of the quality measure used to drive refinement. The algorithm presented in this paper can accept geometric domains whose boundaries are piecewise smooth. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Zhenqun Guan Julin Shan Yao Zheng Yuanxian Gu 《International journal for numerical methods in engineering》2008,74(4):642-667
An extended advancing front technique (AFT) with shift operations and Riemann metric named as shifting‐AFT is presented for finite element mesh generation on 3D surfaces, especially 3D closed surfaces. Riemann metric is used to govern the size and shape of the triangles in the parametric space. The shift operators are employed to insert a floating space between real space and parametric space during the 2D parametric space mesh generation. In the previous work of closed surface mesh generation, the virtual boundaries are adopted when mapping the closed surfaces into 2D open parametric domains. However, it may cause the mesh quality‐worsening problem. In order to overcome this problem, the AFT kernel is combined with the shift operator in this paper. The shifting‐AFT can generate high‐quality meshes and guarantee convergence in both open and closed surfaces. For the shifting‐AFT, it is not necessary to introduce virtual boundaries while meshing a closed surface; hence, the boundary discretization procedure is largely simplified, and moreover, better‐shaped triangles will be generated because there are no additional interior constraints yielded by virtual boundaries. Comparing with direct methods, the shifting‐AFT avoids costly and unstable 3D geometrical computations in the real space. Some examples presented in this paper have demonstrated the advantages of shift‐AFT in 3D surface mesh generation, especially for the closed surfaces. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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裁剪曲面的三角化及图形显示 总被引:2,自引:0,他引:2
结合自主版权的超人CAD/CAM系统的开发,本文提出了一种适合于裁剪曲面图形显示的曲面三角化算法,该算法将曲面的三角化转化为曲面参数域的三角化,并将二维图形的集合运算与Delaunay三角剖分应有和于曲面参数域边界的处理,从而使裁剪曲面在边界上的三角形分布均匀。 相似文献
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Guangshun Yi Yuan Yuan Xiukai Li Yugen Zhang 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(14)
ZnO nanopillars coated on various surfaces are able to kill adhered bacteria and fungi due to their physical structure through a rupturing mechanism. Remarkably, zinc foil and galvanized steel surfaces with ZnO nanopillar coatings demonstrate an excellent remote bacteria‐killing property. Their bacterial killing efficacy is several orders higher than ZnO nanopillars coated on other surfaces as well as ZnO nanoparticles themselves. Mechanistic study shows that the nanostructure surface kills adhered microbial cells by rupturing the cell wall, while superoxide (?O2?) released from the ZnO coating with electrons donated from zinc via the Zn/ZnO interface rather than photoirritation is responsible for the superior remote killing. The results of this study represent a novel mechanism of surface disinfection and its application in water disinfection is also demonstrated. 相似文献
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本文对代数曲面的几何连续拼接作了研究,给出了多个代数曲面的几何连续过渡方法,同时给出了一种基于分片的曲面过渡方法。 相似文献
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A. Aimi M. Diligenti G. Monegato 《International journal for numerical methods in engineering》1999,45(12):1807-1830
In this paper we consider singular and hypersingular integral equations associated with 2D boundary value problems defined on domains whose boundaries have piecewise smooth parametric representations. In particular, given any (polynomial) local basis, we show how to compute efficiently all integrals required by the Galerkin method. The proposed numerical schemes require the user to specify only the local polynomial degrees; therefore they are quite suitable for the construction of p‐ and h‐p versions of Galerkin BEM. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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Abstract The Delaunay triangulation is broadly used on flat surfaces to generate well‐shaped elements. But the properties of Delaunay triangulation do not exist on curved surfaces whose Jacobians are different. In this paper we will present a modified algorithm to improve the shape of triangulation for the curved surface. The experiment results show that making use of “mapping factors” in the Delaunay triangulation and Laplacian method can produce better mesh (most aspect ratios≤3) on a curved surface. 相似文献