共查询到20条相似文献,搜索用时 15 毫秒
1.
三维实体的体几何模型 总被引:8,自引:0,他引:8
在科学可视化,体图形学及有限元等许多应用问题中,都需要处理三维实体的内部、从点集拓扑体模型的思想出发,实体内部的属性及结构可看作三维实体占据的空间位置的函数,该文 体几何模型描述三维形体占据的空间位置,并给出构造体几何模型的一些简单方法,体几何模型是三参量模型,容易离散化所需计算量及存储量皆很少,体几何模型可用于三维实体的有限元剖分,实体内部的可视化与体图形学等领域中。 相似文献
2.
B. Wördenweber 《Computer aided design》1984,16(5):285-291
The capabilities of a geometric modeller are extended towards finite element analysis by a mesh generator which extracts all its geometric and topological information from the model. A coarse mesh is created and subsequently refined to a suitable finite element mesh, which accomodates material properties, loadcase and analysis requirements. The mesh may be optimized by adaptive refinement, ie according to estimates of the discretization errors.A survey of research and development in geometric modelling and finite element analysis is presented, then an implementation of a mesh generator for 3D curvilinear and solid objects is described in detail. 相似文献
3.
三维实体有限元自适应网格规划生成 总被引:2,自引:0,他引:2
为实现三维实体有限元网格自适应生成,设计了中心点、沿指定曲线和基于实体表面等网格加密生成方式;并根据分析对象几何特征和物理特性经验估计,以规划的方式构造自适应网格单元尺寸信息场.在此基础上,提出基于Delaunay剖分的动态节点单元一体化算法,生成几何特征和物理特性整体自适应的有限元网格. 相似文献
4.
An algorithm is developed for identifying interior nodes and edges in finite element meshes of three-dimensional solids. The algorithm is extremely simple and quite fast. The interior nodes are identified by assembling the normals to all surfaces of the model according to the usual finite element assembly procedure. Comparison with a sort-search algorithm shows a tenfold reduction in running time; running time is a linear function of the number of nodes or elements. 相似文献
5.
以Delaunay三角剖分为基础,构造几何特征自适应有限元网格单元尺寸信息场,给出动态节点一单元一体化生成算法,实现二维形体几何特征自适应有限元网格的自动生成,并使分析对象力学特性得到一定程度的自适应. 相似文献
6.
7.
In some previous geometric nonlinear finite element formulations, due to the use of axial displacement, the contribution of
all the elements lying between the reference node of zero axial displacement and the element to the foreshortening effect
should be taken into account. In this paper, a finite element formulation is proposed based on geometric nonlinear elastic
theory and finite element technique. The coupling deformation terms of an arbitrary point only relate to the nodal coordinates
of the element at which the point is located. Based on Hamilton principle, dynamic equations of elastic beams undergoing large
overall motions are derived. To investigate the effect of coupling deformation terms on system dynamic characters and reduce
the dynamic equations, a complete dynamic model and three reduced models of hub-beam are prospected. When the Cartesian deformation
coordinates are adopted, the results indicate that the terms related to the coupling deformation in the inertia forces of
dynamic equations have small effect on system dynamic behavior and may be neglected, whereas the terms related to coupling
deformation in the elastic forces are important for system dynamic behavior and should be considered in dynamic equation.
Numerical examples of the rotating beam and flexible beam system are carried out to demonstrate the accuracy and validity
of this dynamic model. Furthermore, it is shown that a small number of finite elements are needed to obtain a stable solution
using the present coupling finite element formulation. 相似文献
8.
The tools available to the mechanical engineer—for example, geometric modeling and computer-aided analysis—are individually quite powerful, but they are based on different geometric representations. Hence, they do not always work well together. In this paper an analysis method is presented that operates directly on the geometric modeling representation. Therefore, the time-consuming and error-prone procedure of generating a mesh is skipped. The method is based on boundary integral equations, but unlike previously published methods, the boundary elements aren-sided trimmed patches, the same patches that are used by modern geometric modelers to represent complex solids. The method is made practical by defining shape functions over the trimmed patches in such a way that the number of degrees of freedom can be controlled. This is done by using a concept called virtual nodes. The paper begins by deriving the trimmed patch boundary element. Then its properties are discussed in comparison with existing boundary element and finite element methods, and several examples are given. 相似文献
9.
Hexahedral mesh generation constraints 总被引:4,自引:1,他引:3
For finite element analyses within highly elastic and plastic structural domains, hexahedral meshes have historically offered
some benefits over tetrahedral finite element meshes in terms of reduced error, smaller element counts, and improved reliability.
However, hexahedral finite element mesh generation continues to be difficult to perform and automate, with hexahedral mesh
generation taking several orders of magnitude longer than current tetrahedral mesh generators to complete. Thus, developing
a better understanding of the underlying constraints that make hexahedral meshing difficult could result in dramatic reductions
in the amount of time necessary to prepare a hexahedral finite element model for analysis. In this paper, we present a survey
of constraints associated with hexahedral meshes (i.e., the conditions that must be satisfied to produce a hexahedral mesh).
In presenting our formulation of these constraints, we will utilize the dual of a hexahedral mesh. We also discuss how incorporation
of these constraints into existing hexahedral mesh generation algorithms could be utilized to extend the class of geometries
to which these algorithms apply. We also describe a list of open problems in hexahedral mesh generation and give some context
for future efforts in addressing these problems. 相似文献
10.
André Maués Brabo Pereira Marcos Chataignier de Arruda Ant?nio Carlos de O. Miranda William Wagner M. Lira Luiz Fernando Martha 《Engineering with Computers》2012,28(3):225-239
An algorithm for Boolean operations on non-manifold models is proposed to allow the treatment of solids with multiple regions (internal interfaces) and degenerate portions (shells and wires), in the context of mesh generation. In a solid modeler, one of the most powerful tools to create three-dimensional objects with any level of geometric complexity is the Boolean set operators. They are intuitive and popular ways to combine solids, based on the operations applied to point sets. To assure that the resulting objects have the same dimension as the original objects, without loose or dangling parts, a regularization process is usually applied after a Boolean operation. In practice, the regularization is performed classifying the topological elements and removing internal or lower-dimensional structures. However, in many engineering applications, the adopted geometric model may contain idealized internal parts, as in the case of multi-region models, or lower-dimensional parts, as in the case of solids that contain dangling slabs that are represented as zero-thickness surfaces or wireframes in the model. Therefore, the aim of this work is the development of a generic algorithm that allows the application of the Boolean set operations in a geometric modeling environment applied to finite and boundary element mesh generation. This environment adopts a non-manifold boundary representation that considers an undefined number of topological entities (group concept), and works with objects of different dimensions and with objects not necessarily plane or polyhedral (parametric curved surfaces). Numerical examples are presented to illustrate the proposed methodology. 相似文献
11.
Free-Form Solid Modeling with Trimmed Surface Patches 总被引:3,自引:0,他引:3
Solid modelers store a more complete representation than wireframe or surtace modelers. This completeness permits the automation of such tasks as interference analysis, mass property calculation, and finite element mesh generation. But the denser information content and complex algorithms needed to perform these tasks complicate the support of free-form geometry, especially Boolean operations. Consequently, the high degree of geometric coverage traditionally found in surface modeling systems has not, for the most part, been equaled in modern solid modelers. This article explores some of the difficulties encountered in Boolean combinations of free-from solids and presents a geometric representation designed to circumvent them. 相似文献
12.
Youping Gong Xiangjuan Bian Chen Guojin Lv Yunpeng Zhangming Peng 《Microsystem Technologies》2016,22(5):993-1003
Modeling and simulation of MEMS devices is a very complex task which involve the electrical, mechanical, fluidic and thermal domains, and there are still some uncertainties need to be accounted because of uncertain material and/or geometric parameters factors. According to these problems, we put forward to stochastic model order reduction method under random input conditions to facilitate fast time and frequency domain analyses, the method firstly process model order reduction by Structure Preserving Reduced-order Interconnect Macro Modeling method, then makes use of polynomial chaos expansions in terms of the random input and output variables for the matrices of a finite element model of the system; at last we give the expected values and standard deviations computing method to MEMS stochastic model. The simulation results verify the method is effective in large scale MEMS design process. 相似文献
13.
This paper proposes an approach for extracting non-manifold mid-surfaces of thin-wall solids using the chordal axis transform
(CAT) (Prasad in CNLS Newsletter—Center for Nonlinear Studies, Los Alamos National Laboratory, vol 139, 1997). There is great
demand for extracting mid-surfaces as it is used in dimension reduction. Quadros and Shimada previously used CAT in extracting
2-manifold mid-surfaces of a particular type of thin-wall solids. The proposed approach is an extension of the previous approach
(Quadros and Shimada in 11th international meshing roundtable, 2002) in order to extract non-manifold mid-surfaces of general
thin-wall solids. The three steps involved in extracting the mid-surface of a thin-wall solid are: (1) generating a tet mesh
of a thin-wall solid without inserting interior nodes; (2) generating a raw mid-surface by smart cutting of tets; and (3)
remeshing the raw mid-surface via smart clean-up. In the proposed approach, a discrete model (i.e., a tet mesh without any
interior nodes) is used instead of working directly on a CAD model. The smart cutting of tets using CAT yields correct topology
at the non-manifold region in the raw mid-surface. As the raw mid-surface is not directly suitable for engineering purposes,
it is trimmed using a smart clean-up procedure and then remeshed. The proposed approach has been implemented using C++ in
commercial ALGOR finite element analysis software. The proposed approach is computationally efficient and has shown effective
results on industrial models. 相似文献
14.
Pseudo-interference stiffness estimation, a highly efficient numerical method for force evaluation in contact problems 总被引:2,自引:0,他引:2
This paper presents a novel method, Pseudo-Interference Stiffness Estimation (PISE), for evaluating the contact compliance and the contact load in the contacting elastic solids. The PISE method is based on the evaluation of the geometric overlap of two assumedly rigid bodies and estimation of the contact force based on this artificial overlap area (or volume). In this paper, an example of the dynamic simulation of two disk collision problem is solved both by PISE method and finite element contact model. The contact force and velocity changes during impact from both methods are shown to be in good agreement. However, PISE method is, computationally, orders of magnitude (about 3000 times in our numerical simulations) faster than finite element contact analysis. The proposed method will be of practical use in contact force approximation of contacting bodies, such as meshing of spur gear teeth, cam analysis and synthesis, robotic grabbing, and numerous other applications. 相似文献
15.
Mohammed Moumnassi Salim Belouettar Éric Béchet Stéphane P.A. Bordas Didier Quoirin Michel Potier-Ferry 《Computer Methods in Applied Mechanics and Engineering》2011,200(5-8):774-796
In this paper, we present some novel results and ideas for robust and accurate implicit representation of geometric surfaces in finite element analysis. The novel contributions of this paper are threefold: (1) describe and validate a method to represent arbitrary parametric surfaces implicitly; (2) represent arbitrary solids implicitly, including sharp features using level sets and boolean operations; (3) impose arbitrary Dirichlet and Neumann boundary conditions on the resulting implicitly defined boundaries. The methods proposed do not require local refinement of the finite element mesh in regions of high curvature, ensure the independence of the domain’s volume on the mesh, do not rely on boundary regularization, and are well suited to methods based on fixed grids such as the extended finite element method (XFEM). Numerical examples are presented to demonstrate the robustness and effectiveness of the proposed approach and show that it is possible to achieve optimal convergence rates using a fully implicit representation of object boundaries. This approach is one step in the desired direction of tying numerical simulations to computer aided design (CAD), similarly to the isogeometric analysis paradigm. 相似文献
16.
Mixed Dimensional Coupling in Finite Element Stress Analysis 总被引:4,自引:0,他引:4
Many analysis models utilize finite elements of reduced dimension. However, to capture stress concentrations at local details,
it would be desirable to combine the reduced dimensional element types with higher dimensional elements in a single finite
element model. It is therefore important in such cases to integrate into the analyses some scheme for coupling the element
types that conforms to the governing equations of the problem. In this paper, a novel method that can correctly couple beams
to solids, beams to shells and shells to solids for elastic problems is presented. The approach adopted is to equate the work
done on either side of the interface between dimensions, and this leads to multi-point constraint equations, thus providing
a relationship among nodal degrees of freedom between the differing element types. Example results show that the proposed
technique does not introduce any spurious stresses at the dimensional interfaces.
ID="A1" Correspondence and offprint requests to: C. G. Armstrong, School of Mechanical and Manufacturing Engineering, The Queen's University of Belfast, Ashby Building,
Stranmillis Road, Belfast BT9 5AH, Northern Ireland. E-mail: c.armstrong@qub.ac.uk 相似文献
17.
Machiraju C Phan AV Pearsall AW Madanagopal S 《Computer methods and programs in biomedicine》2006,83(1):29-33
Numerical techniques such as the finite element method employ the material constitutive laws for their analysis. With regards to finite element analysis involving viscoelastic solids, the Generalized Standard Linear Solid (Wiechert) model has been a popular choice among available constitutive laws. Although numerous models have been developed to specifically describe the viscoelastic behavior of tendons and ligaments, most of them have not been implemented in commercial finite element packages. This paper describes a stress relaxation test on the human subscapularis tendon, and then presents an approach for obtaining constitutive parameters of a Wiechert model for the human subscapularis tendon using experimental data from the aforementioned relaxation test. The approach is general and thus, can be applied to other tendons and ligaments, as well as any linear viscoelastic solid materials. The Wiechert model is required if finite element analysis using the commercial finite element package ANSYS is to be performed for a biomechanic structure composed of tendons and/or ligaments. 相似文献
18.
《Computer Methods in Applied Mechanics and Engineering》2005,194(30-33):3291-3314
Conventional shape optimization based on the finite element method uses Lagrangian representation in which the finite element mesh moves according to shape change, while modern topology optimization uses Eulerian representation. In this paper, an approach to shape optimization using Eulerian representation such that the mesh distortion problem in the conventional approach can be resolved is proposed. A continuum geometric model is defined on the fixed grid of finite elements. An active set of finite elements that defines the discrete domain is determined using a procedure similar to topology optimization, in which each element has a unique shape density. The shape design parameter that is defined on the geometric model is transformed into the corresponding shape density variation of the boundary elements. Using this transformation, it has been shown that the shape design problem can be treated as a parameter design problem, which is a much easier method than the former. A detailed derivation of how the shape design velocity field can be converted into the shape density variation is presented along with sensitivity calculation. Very efficient sensitivity coefficients are calculated by integrating only those elements that belong to the structural boundary. The accuracy of the sensitivity information is compared with that derived by the finite difference method with excellent agreement. Two design optimization problems are presented to show the feasibility of the proposed design approach. 相似文献
19.
A finite element model is applied to the non-conservative stability problems of a cracked thick rotating blade. This finite element model can satisfy all the geometric and natural boundary conditions of a rotating blade. The blade is considered to be subjected to follower moments and aerodynamic forces. The effects of crack locations and crack sizes are studied. It is found that the rotation speed and crack can change the stability characteristics of a non-conservative system. 相似文献
20.
There are an extensive number of algorithms available from graph theory, some of which, for problems with geometric content, make graphs an attractive framework in which to model an object from its geometry to its discretization into a finite element mesh. This paper presents a new scheme for finite element mesh generation and mesh refinement using concepts from graph theory. This new technique, which is suitable for an interactive graphical environment, can also be used efficiently for fully automatic remeshing in association with self-adaptive schemes. Problems of mesh refinement around holes and local mesh refinement are treated. The suitability of the algorithms presented in this paper is demonstrated by some examples. 相似文献