有限元计算结果的可视化处理

有限元计算结果的可视化是分析有限元计算结果的重要手段. 提出了一种适用于任意形状单元的彩色云图的通用生成方法,并给出了四节点四边形单元彩色云图的生成算例.该算法简洁,高效,易于推广.     

基于剖面的三维有限元可视化方法研究

提出了一种三维不规则数据场的任意形状截面快速剖切算法。该算法利用有限元网格共边的特点实现相交的单元体快速查找并有效减少求交计算次数。讨论了任意剖切面上的彩色云图生成方法。研究了在多剖切面的基础上,实了不规则数据场的体绘制。实践证明,该方法快速有效,效果良好。     

全三维气辅成型数值模拟结果的任意剖切显示

任意剖切显示是全三维气辅成型过程数值模拟后处理的重要技术。通过研究四 面体单元与剖切平面的空间位置关系,提出了一种基于纯空间几何解析的任意剖切面求取以 及在剖切面上高质量绘制场数据分布彩色云图的方法,即通过遍历确定“有效单元”、类过滤 交点求解,以及物理量插值与颜色映射求得剖切面上的物理场量,然后采用OpenGL 技术实 现任意剖切面上场数据分布彩色云图的绘制与显示。实例验证表明,该方法能准确、清晰地 绘制出气辅成型过程中任意剖切平面上物理量的分布,有助于工程技术人员更加有效地理解 和分析模拟结果。     

一种有限元科学计算可视化方法

通过线性插值和关联网格追踪建立了有限元二维基本单元的等值线生成算法;建立了平面局部坐标和三维整体坐标的转换关系式,并结合分体为面的思想将二维单元可视化算法推广到三维空间;构建了结构变形图比例放大因子计算公式;以三维有限元可视化算法构建了轴承座强度分析的等效应力云图和铁路货运罐车前六阶模态振型图。结果表明,该算法能够准确有效地描述有限元分析结果,具有工程应用价值。     

DirectX在有限元分析结果三维彩色云图生成方法中的应用

本文采用扫描线法,将DirectX技术应用到有限元分析结果三维彩色云图的生成方法中,利用DirectX的实体填充模式和高洛德着色模式完成云图渲染绘制。通过实例验证,本文给出的云图生成方法不仅效果好、速度快,而且方法简单、实用。该方法适用于各类场值三维彩色云图的生成,具有很好的通用性和扩展性。     

基于任意六面体单元数据场的可视化研究

任意８节点六面体单元是有限元分析中常见、且有效的体单元。为了有效地实现对任意六面体剖分结构的结果可视化,提出了基于体单元节点相关性的等值面构造算法,可简捷地确定出等值面的位置,进而得出任意剖面上的等值线,该等值面构造算法突破了以往算法中受规则立方体单元的限制,而且简单可行、实用可靠。     

平面任意区域四边形网格自动生成的一种方法

在改进节点连接法的基础上，提出了一种平面任意区域的有限元网格全自动剖分方法，既能快速生成四边形单元网格，也能生成三角形单元网格；     

一个基于网格前沿技术的三维实体四面体有限元网格剖分算法

在三维实体有限元网格自动生成过程中,其主要问题是如何生成均匀的网格结点。本文用网格前沿技术逐层生成网格结点,并采用Ｄｅｌａｕｎａｙ 三角剖分技术生成四面体网格单元。最后给出了两个剖分实例。     

三维实体的四面体有限元网格自动生成

针对三维实体有限元网格自动剖分的困难，本文提出了一种改进的结点连接法，将传统结点连接法中的结点生成和单元形成两大彼此独立步骤合二为一，使得结点和单元的产生相互依存，彼此影响、交替进行，实现了三维实体Ｄｅｌａｕｎａｙ剖分的自动化，一体化。     

一种应力图生成方法

介绍可视化有限元系统VSES中采用的一种应力图生成方法。首先用扫描线转换填充算法判断各象素是否在单元内,根据单元类型用不同插值方法计算单元内各点应力,最后设置颜色函数,计算各模型中各象素点颜色。由颜色函数的不同设置,可得到应力云图和色带图,用轮廓线追踪法获得应力等值线。方法具有速度快、适应性强、显示效果好等特点。     

A general isoparametric finite element program SDRC SUPERB

SDRC SUPERB is a general purpose finite element program that performs linear static, dynamic and steady state heat conduction analyses of structures made of isotropic and/or orthotropic elastic materials having temperature dependent properties. The finite element library of SUPERB contains isoparametric plane stress, plane strain, flat plate, curved shell, solid type curved shell and solid elements in addition to conventional beam and spring elements. Linear, quadratic and cubic interpolation functions are available for all isoparametric elements. Independent parameters such as displacements and temperatures are obtained from SUPERB using the stiffness method of analysis. The remaining dependent parameters, such as stresses and strains, are evaluated at element gauss points and extrapolated to nodal locations. Averaged values are given as final output. The graphic capabilities of SUPERB consists of geometry and distorted geometry plotting, and stress, strain and temperature contouring. Contours are plotted at user defined cutting planes for solids and at top, middle or bottom surfaces for plate and shell types of structures.In the first part of this paper, the program capabilities of SUPERB are summarized. Extrapolation techniques used for determining dependent nodal parameters and for contour plotting are explained in the second part of the paper. Behavior of standard, wedge and transition type isoparametric elements and the effect of interpolation function orders on accuracy are discussed in the third part. The results of several illustrative problems are included.     

A Finite Element Method on Convex Polyhedra

We present a method for animating deformable objects using a novel finite element discretization on convex polyhedra. Our finite element approach draws upon recently introduced 3D mean value coordinates to define smooth interpolants within the elements. The mathematical properties of our basis functions guarantee convergence. Our method is a natural extension to linear interpolants on tetrahedra: for tetrahedral elements, the methods are identical. For fast and robust computations, we use an elasticity model based on Cauchy strain and stiffness warping. This more flexible discretization is particularly useful for simulations that involve topological changes, such as cutting or fracture. Since splitting convex elements along a plane produces convex elements, remeshing or subdivision schemes used in simulations based on tetrahedra are not necessary, leading to less elements after such operations. We propose various operators for cutting the polyhedral discretization. Our method can handle arbitrary cut trajectories, and there is no limit on how often elements can be split.     

六面体体元网格三维地质模型剖切算法

针对常用的六面体体元网格三维地质模型,提出了一种求剖切面的算法.首先,采用分层投影求交点的方式,将地质体模型与切割面投影到同一平面,三维空间下的地质体模型与切割面的剖切转化为二维平面上的四边形网格与切线段求交点的运算.为减少判交次数,先根据切线走势判断可能存在交点的区域,再对可能区域进行精确判交.其次,找到并求出不能通过投影方式得到的交点.然后,将得到的所有交点按规则组成四边形网格,对每个四边形三角化处理得到TIN形式的剖切面.最后,对该TIN面进行显示.实验证明了对六面体体元网格三维地质模型剖切的可行性.     

Generating contours on FEM/BEM higher-order surfaces using Java 3D textures

An efficient technique to visualize primary and secondary results for combined finite element method/boundary element method models as contours is presented. The technique is based on dividing higher-order surfaces into triangles and on using texture interpolation to produce contour plots. Since results of high accuracy with significant gradients can be obtained using sparse meshes of boundary elements and finite elements, special attention is devoted to element face subdivision. Subdivision density is defined on the basis of both face edge curvature and ranges of result fields over element faces. Java 3D API is employed for code development.     

复杂防雷条件下保护范围及三维模型研究

研究了复杂防雷条件下防雷保护范围模型的重建方法,提出通过保护范围 平面二维轮廓线重建保护范围三维模型的基本思路。通过运用滚球法原理,详细分析了利用 包络原理生成保护范围平面二维轮廓线产生的方法,并给出了相应的数学模型;研究通过二 维轮廓线重建三维模型的方法。由二维轮廓线重建保护范围模型的方案不仅适合于复杂条件 的防雷范围设计,同样也适合简单模型条件下的防雷范围模型,为防雷保护范围设计提供了 一条新的思路。     

The development of a 3D-Navier–Stokes code for the simulation of an airbag inflation

The aim of this work is to develop a stable and fast algorithm for simulation of an airbag deployment. The mechanical structure problem is solved with commercially available finite element software. A 3D Navier–Stokes code for compressible fluids is developed to solve the fluid mechanic problem. For reasons of stability, a fixed rectangular grid is used. The contour adjustment is achieved by blocking off the outer cells, which can be switched on or off as the airbag surface passes by. To provide a conservative system during the contour adjustment, a method for the handling of the boundary was developed.     

基于面翻转三维传感器网络边界节点识别算法

针对三维环境下的传感器网络边界节点识别问题,提出了一种基于面翻转的传感器网络边界节点分布式识别方法。算法在已知三个相邻边界节点的基础上,以三个相邻边界节点构成的三角形的各边为轴,以有限面积的面向网络外侧翻转,扫描到的第一个点为新的边界节点,该节点与翻转轴上的两个节点构建成新三角形,迭代上述过程,最终识别出边界节点,获取边界包络。实验结果表明,与Alpha-shape3D算法相比,所提算法能大大减少冗余边界节点。     

A finite element analysis of deep beams with cutouts considering four supports

Using the finite element method, the biaxial stress distribution has been determined for a wide-flange deep beam, with rectangular cutouts placed at various locations, on four supports. An elastic plane state of stress is assumed for the web of the beam and an elastic uniaxial state of stress is assumed for the flanges. The influence that cutouts indeterminate supports have on the stress distribution in deep beams is illustrated by plotting the stress distribution, at several longitudinal locations, for the homogeneous beam and the beam with cutouts, on both determinate and indeterminate supports. Several convergence studies have been performed to determine the proper mesh sizes for the given problems.     

多裁剪自由曲面生成有限元网格的实现

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.     

一种基于二次等参单元的等值线图生成算法

本文提出了一种基于二次等参单元的等值线图生成算法，该算法根据有限元法将整个区域分割成多个互相连续的二次等参单元，通过生成每个等参单元内的等值线，进而生成整个区域内的等值线。