曲轴疲劳寿命的三维有限元分析

针对影响曲轴疲劳寿命的众多复杂因素以及准确估计曲轴疲劳寿命难度大的问题,以某型柴油机组成的动力装置为原始模型,运用三维有限元模态分析计算柴油机曲轴的动态应力,应用动应力载荷谱疲劳计算方法分析曲轴疲劳寿命.实验比较不同情况的曲轴疲劳寿命,比较后的相对值非常可靠.     

考虑多种影响因素的导线舞动三维有限元分析

利用三维有限元方法,分析了风速、攻角、导线分裂、磁场力和防舞装置等各种因素对导线舞动的影响．结果表明：风速、攻角和导线分裂等对导线舞动的影响很大;磁场力的影响很小．为减轻和防止导线舞动,在导线距离杆塔1／3和2／3处施加压重,可以获得明显的防舞效果．     

2D and 3D finite element analysis of central incisor generated by computerized tomography

The purpose of this study was to compare the results of different hierarchical models in engineering analysis applied to dentistry with 2D and 3D models of a tooth and its supporting structures under 100 N occlusal loading at 45° and examine the reliability of simplified 2D models in dental research. Five models were built from computed-tomography scans: four 2D models with Plane Strain and Plane Stress State with linear triangular and quadratic quadrilateral elements and one 3D model. The finite element results indicated that the stress distribution was similar qualitatively in all models but the stress magnitude was quite different. It was concluded that 2D models are acceptable when investigating the biomechanical behavior of upper central incisor qualitatively. However, quantitative stress analysis is less reliable in 2D-finite element analysis, because 2D models overestimate the results and do not represent the complex anatomical configuration of dental structures. Therefore 3D finite element analyses of dental biomechanics cannot be simplified.     

柴油机负荷对曲轴疲劳寿命影响的三维有限元分析

为评估超载运行对柴油机的不利影响,以某型柴油机组成的动力装置为原始模型,设定柴油机发火顺序﹑活塞所受气体力﹑转速和输出扭矩等边界条件,用三维有限元动应力分析和疲劳寿命计算技术计算曲轴在420°缸排插入角下75%负荷、100%负荷、110%负荷和120%负荷时的疲劳寿命.结果表明在420°缸排插入角下,柴油机负荷越高,曲轴单拐的疲劳寿命区域扩大就越明显.     

An efficient method for fully automatic 3D digitization of unknown objects

Our goal is to develop a complete and automatic scanning strategy with minimum prior information about the object shape. We aim to establish a methodology for the automation of the 3D digitization process. The paper presents a novel approach to determine the Next Best View (NBV) for an efficient reconstruction of highly accurate 3D models. Our method is based on the classification of the acquired surfaces into Well Visible and Barely Visible combined with a best view selection algorithm based on mean shift, which avoids unreachable positions. Our approach is applicable to all kinds of range sensors. To prove the efficiency and the robustness of our method, test objects are first scanned manually by experts in 3D digitization from the VECTEO company. The comparison of results between manual and automatic scanning shows that our method is very efficient and faster than trained experts. The 3D models of the different objects are obtained with a strongly reduced number of acquisitions while moving efficiently the ranging device. The obtained results prove the effectiveness and the versatility of our 3D reconstruction approach for industrial applications.     

锥齿轮齿根应力有限元模型和分析

从齿轮加工原理出发,利用渐开线和齿根过渡曲线方程生成轮齿的精确齿形,建立2种等效直齿锥齿轮三维轮齿几何模型,研究渐开线直齿锥齿轮的精确建模方法.分别使用h-单元和p-单元分析计算直齿锥齿轮齿根应力,建立直齿锥齿轮三维轮齿齿根应力有限元计算模型和计算基准.计算结果与ISO国标公式比较,证明模型的正确性、精确性和可靠性.     

三维渗流有限元软件GWSS开发与应用

针对复杂地质条件的三维地质建模、复杂建筑物的几何建模和复杂防渗排水系统作用下渗流场精细模拟等三维渗流场有限元分析的难点问题,采用IDL开发面向水工结构和岩土工程的渗流有限元分析软件GWSS（Ground Water Simulation System）.该软件包括系统控制模块、数据管理模块、前处理模块、计算模块、后处理模块和制图输出模块等六大模块.前处理模块具有基于钻孔和钻孔剖面的三维地质建模、几何建模与有限元网格生成等功能;计算模块主要用于各种闸坝、堤防、隧道和地下洞室等渗流问题的计算分析等;后处理模块可显示各渗流要素的三维云图和任意截面的二维云图等.GWSS已经在国内四十多个工程的渗流计算中得到应用和检验.     

An efficient and robust algorithm for 3D mesh segmentation

This paper presents an efficient and robust algorithm for 3D mesh segmentation. Segmentation is one of the main areas of 3D object modeling. Most segmentation methods decompose 3D objects into parts based on curvature analysis. Most of the existing curvature estimation algorithms are computationally costly. The proposed algorithm extracts features using Gaussian curvature and concaveness estimation to partition a 3D model into meaningful parts. More importantly, this algorithm can process highly detailed objects using an eXtended Multi-Ring (XMR) neighborhood based feature extraction. After feature extraction, we also developed a fast marching watershed-based segmentation algorithm followed by an efficient region merging scheme. Experimental results show that this segmentation algorithm is efficient and robust.     

擦窗机悬挂轨道三维结构有限元分析

为探究某擦窗机悬挂结构的合理性,在AIP中创建其悬挂轨道的三维参数化特征模型,并根据轨道的结构、材料和特定工况受力等边界条件,建立悬挂系统的有限元模型,模拟计算2种有代表性的偏栽荷工况受力情况,得到悬挂轨道的三维应力分布、结构变形和安全因数．根据工程设计要求和初步分析结果,在保持边界条件和载荷条件不变的情况下,快速更新轨道结构参数,并通过比较分析确定塔楼悬挂轨道的最佳断面参数．该轨道及其固定间距、滑车滚轮和导向轮等构件均满足设计安全要求．     

Three-dimensional finite element method for the filling simulation of injection molding

With the development of molding techniques, molded parts have more complex and larger geometry with nonuniform thickness. In this case, the velocity and the variation of parameters in the gapwise direction are considerable and cannot be neglected. A three-dimensional (3D) simulation model can predict the filling process more accurately than a 2.5D model based on the Hele–Shaw approximation. This paper gives a mathematical model and numeric method based on 3D model to perform more accurate simulations of a fully flow. The model employs an equal-order velocity–pressure interpolation method. The relation between velocity and pressure is obtained from the discretized momentum equations in order to derive the pressure equation. A 3D control volume scheme is used to track the flow front. During calculating the temperature field, the influence of convection items in three directions is considered. The software based on this 3D model can calculate the pressure field, velocity field and temperature field in filling process. The validity of the model has been tested through the analysis of the flow in cavities.     

Processing of fiber architecture data for finite element modeling of 3D woven composites

An efficient procedure to process the textile simulation data and generate realistic finite element meshes of woven composites is proposed. The textile topology data in point cloud format is used to identify individual yarns, interpolate their cross-sectional contours, and generate smooth yarn surfaces. A robust algorithm to repair possible interpenetrations between yarn surfaces is developed and implemented in MATLAB. A 3D finite element mesh of the unit cell of composite material is generated based on the obtained yarn surfaces. The anisotropic material properties of the constituents are assigned with proper orientations.The procedure is successfully applied to generate four finite element models with 1–10 million degrees of freedom. The models are used to predict effective elastic properties of an orthogonal 3D woven composite. The sensitivity of results to the level of finite element discretization is investigated.     

融合2D/3D摄像机的方法与获取高精度三维视觉信息的装置

三维飞行时间摄像机可实时同步获取场景三维信息和灰度图像信息.虽然它存在图像分辨率和质量较差等问题,但它可作为二维摄像机的互补.本文借鉴立体视觉技术,提出了一种2D/3D摄像机融合的三维视觉信息获取方案.论文首先基于固定空间关系和相近视野原则,设计2D/3D立体摄像机系统对空间场景同步成像.结合三维TOF摄像机成像特性,论文借鉴立体视觉技术完成二维摄像机的高质量二维彩色图像与插补后的三维摄像机深度图像的匹配关联.因此,本方法可实现场景的高精度彩色图像和对应三维空间信息的实时同步获取,同时保留了二维摄像机的高质量彩色二维成像和三维摄像机的快速稠密三维信息获取的优势.2D/3D摄像机图像融合匹配算法复杂度低,匹配精度和准确度取决于二维摄像机和三维摄像机自身性能、摄像机标定参数精度和深度图像插补算法,不会引入新的运算误差.试验结果验证了本文算法的有效性和精确度.     

新型转炉系统整体结构三维有限元分析

为考察大型转炉系统应力和变形对生产安全和结构优化设计的影响,采用三维有限元方法,建立新型转炉的整体结构装配体模型,计算该转炉系统在不同倾动角工况及重力载荷下的应力和位移. 通过详细分析各零部件的应力、变形和位移情况,研究应力和位移随倾动角的变化规律,提出改进设计方案. 结果可为转炉系统的设计和应用提供计算依据.     

A finite element model for the analysis of 3D axisymmetric laminated shells with piezoelectric sensors and actuators: Bending and free vibrations

This paper addresses the bending and free vibrations of multilayered cylindrical shells with piezoelectric properties using a semi-analytical axisymmetric shell finite element model with piezoelectric layers using the 3D linear elasticity theory. In the present 3D axisymmetric model, the equations of motion are expressed by expanding the displacement field using Fourier series in the circumferential direction. Thus, the 3D elasticity equations of motion are reduced to 2D equations involving circumferential harmonics. In the finite element formulation the dependent variables, electric potential and loading are expanded in truncated Fourier series. Special emphasis is given to the coupling between symmetric and anti-symmetric terms for laminated materials with piezoelectric rings. Numerical results obtained with the present model are found to be in good agreement with other finite element solutions.     

三维高速机动目标跟踪交互式多模型算法

对三维机动目标,尤其是高速机动目标的跟踪一直是目标跟踪领域的重点和难点,通过二维或解耦模型扩展并不一定能满足精度要求.提出了一种基于常速模型、"当前"统计模型、带约束的三维常速率协同转弯模型的交互式多模型算法.通过对包括匀加速模型、Singer模型、"当前"统计模型在内的不同模型组合进行Monte-Carlo仿真比较表明本算法对三维高速机动目标跟踪是有效性,并具有很好的实用性.     

Deliverability analysis of greedy routing in the spherical cap 3D sensor networks

For 3D sensor networks to monitor the ocean, forest and aerosphere, etc., sensors can forward their data to the base station by greedy routing. It is critical to quantitatively greedy routing’s deliverability for evaluating network’s functionality and performance. The probability that all sensors can successfully send their data to the base station by greedy routing is usually modeled as the probability of guaranteed delivery. For a typical spherical cap 3D sensor network deployment scenario where nodes follow a homogeneous Poisson point process, the relationship between the sensor transmission radius and the probability of guaranteed delivery is studied, and a tight analytical upper bound on the sensor transmission radius to ensure the designed deliverability probability is derived in this paper. The correctness and tightness of the derived upper bound are verified by extensive simulations.     

一种面向3D场景的实时自动路径搜索方法

提出一种应用于实时渲染3D场景中的路径搜索实现方法,该方法以3D虚拟场景模型中的多边形为基本对象,根据多边形的拓扑关系,将虚拟场景抽象成连通图形式的中间结果。在这个中间结果中,根据场景地形的通用性属性,利用启发式搜索进行路径搜索,并在路径搜索中有效的任务调度机制优化渲染循环中的路径搜索性能。与传统方法比较,该方法不需要在场景中额外增加人工标记,具有良好计算通用性与性能。     

A novel CAD tool for the wideband modeling of 3D waveguide components

This paper describes a fast and flexible CAD tool for the wideband modeling of arbitrarily shaped three‐dimensional waveguide components. The algorithm is based on the evaluation of the poles and the residues of the Y‐parameters by the “boundary integral‐resonant mode expansion” (BI‐RME) method. Some examples demonstrate the efficiency and flexibility of the method. © 2000 John Wiley & Sons, Inc. Int J RF and Microwave CAE 10: 183–189, 2000.