Introduction to Mesh Based Generated Lumped Parameter Models for Electromagnetic Problems using Triangular Elements

This paper is an introduction to mesh based generated reluctance network modeling using triangular elements.Many contributions on mesh based generated reluctance networks using rectangular shaped elements have been published,but very few on those generated from a mesh using triangular elements.The use of triangular elements is aimed at extending the application of the approach to any shape of modeled devices.Basic concepts of the approach are presented in the case of electromagnetic devices.The procedure for coding the approach in the case of a flat linear permanent magnet machine is presented.Codes developed under MATLAB environment are also included.

Compression of finite element hybrid mesh

A method for encoding and compressing finite element models is proposed. Themodel may be various non-simple topological structures and contain any combinations of beams,triangular elements and quadrilateral elements. First the model is subdivided into simple meshesthat are orientable and manifold. Based on the Edgebreaker algorithm, 13 labelled pairs areintroduced for quadrilateral meshes and five other labelled pairs are introduced for triangles. Thenthe connectivity information of mixed triangle/quadrilateral meshes is coded in a direct manner.Two other bits are used to record the wireframe information. For the pure wireframe model, Taubin'smethod is extended to compress it. The compression algorithm is implemented and evaluated.Experiments with several models show that the method achieves excellent compression ratios.

AUTOMATIC FINIT EELEMENT MODELING OF A WING

This paper is concerned about the automatic finite element modeling of a wing structure. The row and column method is used to identify the structure parts(ribs, spars, skins and pillars). A customization module of PCL(PATRAN Command Language under PATRAN 6.0) code from constructing airfoil curves to creating the entire wing FEM model is designed and developed. The geome tric, mesh density, material, load and boundary parameters can be easily and correctly input with the friendly interactive interface. A VFW614 wing is analyzed from creating airfoil curves to the show of stresses calculated by using NASTRAN 68 as an example. The results show that this customization module is very effective and efficient.

Introduction to Mesh Based Generated Lumped Parameter Models for Electromagnetic Problems

This paper is an introduction to mesh based generated reluctance network modeling.An overview of scientific works which led to the development of this approach is first presented.Basic concepts of the approach are then presented in the case of electromagnetic devices.A step-by-step procedure for coding the approach in the case of a flat linear permanent magnet machine is presented.Codes developed under MATLAB and Scilab environments are also included.

A modified discrete element method for concave granular materials based on energy-conserving contact model

The development of a general discrete element method for irregularly shaped particles is the core issue of the simulation of the dynamic behavior of granular materials.The general energy-conserving contact theory is used to establish a universal discrete element method suitable for particle contact of arbitrary shape.In this study,three dimentional(3D)modeling and scanning techniques are used to obtain a triangular mesh representation of the true particles containing typical concave particles.The contact volumebased energy-conserving model is used to realize the contact detection between irregularly shaped particles,and the contact force model is refined and modified to describe the contact under real conditions.The inelastic collision processes between the particles and boundaries are simulated to verify the robustness of the modified contact force model and its applicability to the multi-point contact mode.In addition,the packing process and the flow process of a large number of irregular particles are simulated with the modified discrete element method(DEM)to illustrate the applicability of the method of complex problems.

基于Hypermesh的有限元前置优化设计

网格质量是指网格几何形状的合理性,网格质量不好将影响计算精度,甚至会中止计算。因此,工程师往往在CAE分析工程中要花费大量的时间来建立有限元模型和修改模型。作为一个高性能的有限元前后处理器,Hypermesh有效地解决了有限元软件存在的前后置处理的问题,大大提高了生产率。文中给出了Moldflow模流分析前处理实例。

应用HyperMesh和Ansys WorkBench分析阀体应力

介绍了应用Hyper Mesh网格划分软件建立阀体的有限元模型,并使用Ansys Work Bench软件对阀体进行应力分析,阐述了两种软件在阀门网格划分及应力分析中的使用技巧及分析方法。

Fifty years of finite elements——a solid mechanics perspective

The finite element method has been considered as one of the most significant engineering advances of the twentieth century. This computational methodology has made substantial impact on many fields in science and also has profoundly changed engineering design procedures and practice. This paper, mainly froln a solid mechanics perspective, and the Swansea viewpoint in particular, describes very briefly the origin of the methodology, then summaries selected milestones of the technical developments that have taken place over the last fifty years and illustrates their application to some practical engineering problems.

基于hypermesh的汽车车身有限元建模方法研究

基于某汽车车身有限元建模，首先将CATIA建立的汽车车身几何模型导入到hypermesh中，再利用hypermesh强大的前处理功能研究了几何清理、分特征2D网格划分、网格质量调整、不能抽取中面情况下的网格划分等主要问题。重点介绍了汽车车身的几种典型结构特征，根据不同的结构特征布置不同的网格，完成了汽车车身的较高质量的2D网格划分，同时提出一种hypermesh误操作后恢复的方法，为复杂的车身有限元建模思路提供了很好的参考。

Finite element modeling and analysis of planetary gear transmission based on transient meshing properties

Planetary gear trains are widely applied in various transmission units.Whether strengths of all gears are accurately calculated or not can affect reliability of the entire system significantly.Strength calculation method for planetary gear trains usually follows the method for cylindrical gears,in which the worst meshing positions for both contact stress and bending stress cannot be determined precisely,and calculation results tend to be conservative.To overcome these shortcomings,a kinematics analysis for a planetary gear train is firstly performed,in which the influence of relative speed is investigated.Then the finite element strength analysis of a planetary gear train based on its transient meshing properties is carried out in ANSYS.Time–history curves of contact and bending stresses of sun gear,planetary gears and ring gear are respectively obtained.Also the accurate moment and its corresponding position of the maximum stress are precisely determined.Finally,calculation results of finite element method(FEM)and traditional method are compared in order to verify the effectiveness.Simulation and comparison show the stability of the proposed method in this paper.Researches in this paper establish the foundations for fatigue analysis and optimization for a planetary gear train.

嵌于CAD系统的有限元建模方法及其应用

研究目的:当下,多数有限元分析应用的建模功能较为薄弱,导致复杂结构体系的有限元分析既琐碎又麻烦。另一方面,虽然计算机辅助设计(CAD)应用在建模方面十分强大,由CAD应用建立的模型通常无法用作有限元分析。为此,本文提出一种嵌于CAD系统的有限元建模方法,为说明其有效性及实用性,进一步研发了一款名为DirectMesh的Rhinoceros插件并将其应用于武汉站有限元分析中。研究结论:(1)利用CAD系统所提供的交互性环境及各种建模工具可大幅提高有限元建模的效率;(2)本文所提独立网格生成单元可生成代表单个对象的网格;(3)本文所提综合网格生成单元可生成含多个对象的综合网格系统;(4)本文所提有限元模型生成器可通过网格有效生成复杂结构系统的有限元模型;(5)本文所提方法可大幅提高有限元建模的易用性及效率,有助于提高机械工程、土木工程及岩土工程中仿真模拟工作的智能化程度。

大跨度木结构蒙古包的设计与工程实践

在我国“双碳”目标的实现和新时代中国民族建筑复兴的背景下,木结构建筑市场再次兴起。在原民族建筑文化内涵的基础上对结构进行创新,以满足现代市场的需求已成为新的研究方向。本文针对希拉穆仁草原景区设计了一座大跨度蒙古包,在不改变建筑材料的基础上,采用木网壳结构体系对传统建筑结构进行创新与优化,其最大跨度为23.5 m,最大高度为11.5 m,且整体结构稳定。在此基础上,利用有限元软件进行建模,对可能出现的各种工况进行静力计算和屈曲分析,验证了该结构的可靠性。本研究对我国大跨度木结构的发展和传统木结构建筑的创新具有重要的借鉴意义。

基于SBFEM的剪切型裂纹动态开裂模拟

剪切型断裂是岩土工程中常见的破坏模式,了解剪切破坏机理并准确预测剪切型裂纹的萌生、扩展过程对保障工程结构的安全性与稳定性具有重要意义.文章建立了基于比例边界有限元法(scaled boundary finite element methods,SBFEM)和非局部宏-微观损伤模型的剪切型裂纹动态开裂模拟方法,定义了基于偏应变概念的物质点对的正伸长量,可作为预测剪切型裂纹扩展行为的动态开裂准则,一点的损伤定义为该点影响域范围内连接的物质键损伤的加权平均值,而物质键的损伤则与基于偏应变概念的物质点对的正伸长量相关联,并引入能量退化函数建立结构域几何拓扑损伤与能量损失之间的关系,将拓扑损伤与应力应变联系起来,通过能量退化函数修正了SBFEM的刚度系数矩阵,得到了子域在损伤状态下的刚度矩阵,推导了考虑结构损伤的SBFEM动力控制方程,采用Newmark隐式算法对控制方程进行时间离散.最后,通过3个典型算例验证了建议的模型可较好地模拟剪切型断裂问题,能够很好地捕捉剪切型裂纹的扩展路径,并得到较为准确的载荷-位移曲线.

基于有限元分析的液压缸密封圈磨损分析

液压缸密封圈磨损原因较多,难以通过肉眼直观观察,很难找到直接原因,提出基于有限元的液压缸密封圈磨损量分析方法。基于液压缸密封圈几何模型、材料模型和物理模型,分析了橡胶密封圈在应力和应变上的非线性,通过定义应变密度函数,构建了液压缸密封圈的有限元模型。根据液压缸活塞的密封结构,分析了液压缸活塞的运动特点,利用Archard模型描述密封圈的外观特征变化,通过计算密封圈接触面上任意一点的磨损深度,分析液压缸密封圈的磨损量。试验结果表明,所研究方法可以对液压缸密封圈的裂纹深度与裂纹扩展角度进行有效分析,两项指标的试验分析与实测结果基本一致,裂纹深度的试验分析误差最大值仅为0.002 mm。方法有助于提高液压缸设计的密封可靠性。

谱元法波场模拟中网格质量影响的量化分析

本文旨在量化分析网格质量对谱元法波场正演模拟精度与收敛性的影响。研究首先通过理论计算,明确了网格歪斜度对拉格朗日多项式插值近似误差的影响,结果显示当网格歪斜度增加时,插值误差显著增大。在此基础上,对六种不同网格歪斜度的地质模型进行了谱元法地震波场正演模拟实验,实验结果显示:当网格剖分的歪斜度大于0.8时,模拟精度不受影响;歪斜度降至0.6时,吸收边界波场模拟开始出现不稳定;而歪斜度进一步降低至0.4及以下时,波场正演模拟出现严重不收敛现象。这些量化结果直接证明了网格质量对谱元法波场正演模拟的重要性,为网格质量评价和波场正演模拟精度、效率稳定性之间建立了可量化分析的桥梁,同时为优化网格剖分策略提供了科学依据。

一种板状结构网格模型破口面积快速算法

论文针对板状网格模型破口面积的快速定量计算问题,设计了一种快速算法,并针对一批某鱼雷对某驱逐舰爆炸毁伤数值仿真结果进行了计算,验证了该算法的有效性。该算法应用主成分分析方法,可实现对各类板状结构产生的不规则破口区域面积的快速计算,可为相关结构物毁伤评估提供支撑。

ANSYS有限元网格划分浅析

为提高有限元数值计算的精度和对复合材料结构及力学分析的准确性 ,结合实例阐述了有限元网格划分复合材料结构件的方法和过程 ,指出了采用ANSYS有限元分析软件在网格划分时应注意的技术问题 ,并对进行ANSYS网格划分采用的方法、工具进行了详细的分析和论述 .研究认为 ,对于单一模型的分析可采用自由网格划分方法 ;对于尺寸变化的系列模型分析 ,则应考虑采用对应网格划分方法 。

复杂岩石块体识别的单元重构–聚合方法

为解决工程岩体开挖中含有复杂开挖边界时的块体识别问题,提出岩石块体识别的单元重构–聚合方法。首先,引入成熟的网格划分技术,通过建立网格模型(如有限元模型),实现对复杂开挖边界的精确模拟;其次,采用基于单元重构技术的结构面建模方法,将分布于岩体内的结构面建入网格模型;然后,提出基于单元聚合技术的块体构建方法和考虑有限性结构面时的单元组处理方法;最终可实现基于网格模型的复杂岩石块体识别。该方法识别所得的块体系统基于网格模型,块体的所有特征信息均可通过模型的单元和节点提取,块体的可视化也可在既有网格模型图形显示平台上实现。算例验证表明,当将结构面分别考虑为无限延伸和有限延展时,该方法的块体识别和稳定分析成果均与通用块体分析软件的结果一致。进一步将该方法应用于水电站大型地下洞室群的块体识别,可证明其应用于复杂岩石块体识别的有效性和优越性。因此,该方法是一种能够考虑复杂工程岩体开挖边界的岩石块体识别的新方法,其实现过程独立于基于拓扑原理的传统块体识别思路,为块体稳定分析提供了新的实现途径。

生物组织有限元建模与分析

组织工程是生物工程中的一个重要部分 ,是多学科交叉而形成的新工程学科 .利用有限单元法进行组织工程中的组织应力分析具有重要意义 .研究了对生物组织采用逆向建模和基于公共界面有限元网格划分技术 。

任意多边形的Delaunay三角剖分

任意多边形的三角剖分是计算机图形学领域中的一个基本算法，其用途非常广泛．本文利用著名的Ｄｅｌａｕｎａｙ三角剖分的优化性质，提出了一种简洁、通用的任意多边形Ｄｅｌａｕｎａｙ三角剖分算法，并给出了该算法在有限元网格自动生成过程中的应用．