Study on Remeshing Technique for Three-Dimensional Rigid-plastic Finite Element Simulation

A new method of three-dimensional remeshing is proposed for rigid-plastic finiteelement analysis of a complicated forging process.The forging process of a cylindricalhousing has been simulated to show the effectiveness of the scheme.The result ofsimulation shows that the computation can be effectively carried out by using the des-cribed remeshing scheme.

Finite element simulation and microstructure of two-pass inner spinning process of curved-generatrix cone cylindrical parts with annealing/quenching

A two-pass annealing/quenching internal spinning process with small-end rotations is proposed to form a curved generatrix conical thin-walled shell.That is,annealing at 360°C for 2 h followed by the 1st pass spinning,and finally quenching in ice water after holding for 1 h at 498°C followed by the 2nd pass spinning.ABAQUS finite element software is used to simulate the internal spinning process of the products formed under different forming parameters.The distribution laws of spinning force,the stress and strain under different forming processes were compared and analyzed.The mechanical properties and microstructure of the products are subsequently analyzed.The results show that the strain and the residual stress in the skin area of the formed products under two-pass spinning process more uniform,and the hardness and the mechanical performance are improved.The microstructure of the products formed with the 0.15 mm thickness reduction at the 2nd pass is excellent.And the second phase grain size distributed uniformly in the range of 36μm.Whereas,the second phase particles are broken seriously and the size distribution inhomogeneity is increased when the thickness reduction in the skin area is greater than 0.20 mm at the 2nd pass spinning process.

基于SolidWorks Simulation带接头装配体有限元分析

在分析以大力钳为例的带接头的装配体的三维实体模型中,正确的设置边界条件、载荷、约束并且合理划分网格的情况下,把销钉和弹簧两种真实接头用simulation中的接头模型代替,加快分析的速度和减少网格和接触的数量,简单快速的完成装配体的有限元分析,且能反过来生成接头模型的相应参数,对大力钳及其接头的优化设计提供有利的参数和数据。

Dynamic Simulation and Tension Compensation Research on Subsea Umbilical Cable Laying System

For studying the dynamic performance of subsea umbilical cable laying system and achieving the goal of cable tension and laying speed control,the rigid finite element method is used to discrete and transform the system into a rigid-flexible coupling multi-body system which consists of rigid elements and spring-damping elements.The mathematical model of subsea umbilical cable laying system kinematic chain is presented with the second order Lagrange equation in the joint coordinate system,and dynamic modeling and simulation is performed with ADAMS.The dynamic analysis is conducted assuming the following three statuses:ideal laying,practical laying under wave disturbance,and practical laying with tension compensation.Results show that motion disturbances of the laying budge under sea waves,especially with heaving and pitching,will cause relatively serious fluctuations in cable tension and laying speed.Tension compensation,i.e.,active back tension torque control can restrict continuous tension increasing or decreasing effectively and rapidly,thus avoiding cable breach or buckling.

Effects of parameters on rotational fine blanking of helical gears

The application of fine blanking to the manufacturing of helical gears directly from a strip has been restricted due to the traditional linear cutting stroke of the punch and die.In this work,rotational fine blanking which combined the linear and rotational motion of punch and counterpunch was applied for the forming of helical gears.A three-dimensional(3D) rigid-plastic finite element model was developed on the DEFORM-3D platform.By finite element simulation and analysis,the influences of key parameters on the punch load and cut surface were investigated.It is shown that: 1) with increasing the counterforce or helical angle,the punch load and the depth of die roll increase; 2) with increasing blank holder force,the punch load increases while the depth of die roll decreases; 3) V-ring indenter facilitates an improvement in the quality.The results of this research reveal the deformation mechanism of rotational fine blanking of helical gears,and provide valuable guidelines for further experimental studies.

基于SolidWorks Simulation的取件机械手爪体结构仿真和优化设计

利用SolidWorks软件建立取件机械手爪体的三维实体模型,根据有限元理论对爪体建立有限元模型。根据实际的受力情况,通过SolidWorks Simulation软件对爪体进行应力等静态特性分析,依据有限元仿真分析结果提出结构的优化设计建议,并对优化后的结构进行力学性能仿真和分析,验证新结构的可靠性。给本产品设计探索了一种新的方法,缩短了产品的开发周期,节约了成本,一定程度上给设计人员提供了一种新的选择。

NUMERICAL SIMULATION AND EXPERIMENTS FOR PANEL FORMING BASED ON CAD/CAE SYSTEM

A comparison research about the implicit and explicit solutions of sheet forming simulation was presented. On the platform of Autoform and Ls dyna3D, a dynamic forming simulation of a sideframe, of Santana 2000 was done, and the engineering strain, the thickness distribution and the FLD between the two softwares were compared. It indicates that their results coincide with each other very much and the areas of the wrinkle and failure are the same roughly. Further, the characteristics of the two softwares in geometric model and preprocessing of the finite element were discussed and the questions which need attention provided.

LARGE EDDY SIMULATION AND SPECTRUM ANALYSIS OF FLOW AROUND TWO SQUARE CYLINDERS ARRANGED SIDE BY SIDE

Large eddy simulation cooperated with the second order full extension ETG(Euler-Taylor-Galerkin) finite element method was applied to simulate the flow around two square cylinders arranged side by side at a spacing ratio of (1.5.) The second order full extension ETG finite element method was developed by Wang and He. By means of Taylor expansion of terms containing time derivative, time derivative is replaced by space derivative. The function of it is equal to introducing an artificial viscosity term. The streamlines of the flow at different moments were obtained. The time history of drag coefficient, lift coefficient and the streamwise velocity on the symmetrical points were presented. Furthermore, the symmetrical problem of the frequency spectrum of flow around two square cylinders arranged side by side were studied by using the spectral analysis technology. The data obtained at the initial stage are excluded in order to avoid the influence of initial condition on the results. The power spectrums of drag coefficient, lift coefficient, the streamwise velocity on the symmetrical points were analyzed respectively. The results show that although the time domain process of dynamic parameters is non-symmetrical, the frequency domain process of them is symmetrical under the symmetrical boundary conditions.

Dynamic Reliability Assessment of Heavy Vehicle Crossing a Prototype Bridge Deck by Using Simulation Technology and Health Monitoring Data

Overloads of vehicle may cause damage to bridge structures,and how to assess the safety influence of heavy vehicles crossing the prototype bridge is one of the challenges.In this report,using a large amount of monitored data collected from the structural health monitoring system(SHMS)in service of the prototype bridge,of which the bridge type is large-span continuous rigid frame bridge,and adopting FEM simulation technique,we suggested a dynamic reliability assessment method in the report to assess the safety impact of heavy vehicles on the prototype bridge during operation.In the first place,by using the health monitored strain data,of which the selected monitored data time range is before the opening of traffic,the quasi dynamic reliability around the embedded sensor with no traffic load effects is obtained;then,with FEM technology,the FEM simulation model of one main span of the prototype bridge is built by using ANSYS software and then the dynamic reliability when the heavy vehicles crossing the prototype bridge corresponding to the middle-span web plate is comprehensively analyzed and discussed.At last,assuming that the main beam stress state change is in the stage of approximately linear elasticity under heavy vehicle loads impact,the authors got the impact level of heavy vehicles effects on the dynamic reliability of the prototype bridge.Based on a large number of field measured data,the dynamic reliability value calculated by our proposed methodology is more accurate.The method suggested in the paper can do good for not only the traffic management but also the damage analysis of bridges.

基于旋转圆柱三电极阵列的覆冰测量方法

覆冰严重会影响电网安全稳定运行,输配电装备的覆冰监测是电网冰灾防御的前提。为此,基于冰层的电容效应提出一种旋转圆柱三电极阵列覆冰测量方法。首先,推导电容值与覆冰厚度计算公式,从理论上说明该方法的可行性;其次,建立圆柱三电极阵列有限元模型并对其结构参数进行有限元数值计算;再次,以信号强度、灵敏度与穿透深度为评价指标对圆柱三电极阵列选取合适参数;最后,在野外自然环境下对旋转圆柱三电极阵列覆冰测量装置进行试验。仿真和试验结果表明,在穿透深度以内,旋转圆柱三电极阵列能够较为准确地测量覆冰厚度、分辨覆冰类型。在雨凇、混合凇覆冰条件下,覆冰电容值平均误差最大为4.83%,能够满足覆冰厚度的测量要求。该文为输配电装备覆冰监测提供了一种新型装置与测量方法,未来有望应用于架空线路覆冰在线监测。

煤矿液压定向钻机回转器结构设计校核及有限元仿真

以液压定向钻机回转器结构为研究对象,通过分析其传动原理,对其结构进行了设计,同时针对回转器组件开展了选型设计及强度校核,使其符合井下生产作业的需要。最后将回转器及其传动系统进行了有限元仿真分析,从极限载荷及动载效应两个角度出发,验证了所设计回转器的动态特性良好。

矿用重载轮胎接地印痕的研究

以14.00R25宽体自卸车轮胎为例,通过轮胎使用情况调研,结合实验室测试和轮胎有限元仿真,研究矿用重载轮胎接地印痕及接地压力分布。结果表明:宽体自卸车轮胎接地印痕形状应接近矩形且接地压力分布均匀;影响轮胎接地印痕及接地压力分布的主要因素为断面高宽比、胎冠弧半径和弧度高、带束层角度和宽度、花纹沟壁角度和花纹沟宽度等。通过有限元仿真优化设计可避免轮胎出现花纹掉块和非均匀磨损等问题,提高设计效率。

一种大口径平面镜支撑结构的仿真与实验

为提高600 mm大口径立式平面镜沿光轴旋转90°后的表面面型测量精度,对多孔支撑结构下5种不同材料的平面镜重力变形进行有限元仿真分析,并通过实验测量探究旋转后的静置时间对面型精度的影响等问题。结果表明,该多孔支撑结构下的平面镜表面由重力导致的轴向变形量不超过14 nm,满足精度要求。该多孔结构支撑的平面镜沿光轴旋转90°静置1 h后达到稳定状态,与静置2 h后的面型结果PV值仅相差0.337 nm,RMS值相差0.081 nm,实验探究了静置时间对面型结果的影响。研究发现,在至多去除6%外口径的条件下可以大幅降低平面镜表面面型PV值,PV值降低超过50 nm,由此提出一种制造大口径平面镜时通过设置支撑结构缓冲区以提高面型精度的方法,可以有效提高大口径平面镜的面型精度。

城市轨道交通列车脱轨碰撞事故仿真研究

[目的]针对2015年发生的一次城市轨道交通不锈钢车体列车脱轨事故的过程进行仿真,重现在复杂事故场景中的车体破坏的直接原因和过程。[方法]在调查事故场景和不锈钢车体结构与特点的基础上,使用有限元方法重建事故模型,分析了整个事故中车辆的速度、加速度、能量变化。[结果及结论]仿真研究的结果表明,事故发生时的巨大能量和地面的高低起伏,导致中间车辆发生爬车、蛇行及相互碰撞,是造成本次事故中不锈钢车体结构发生断裂失效的重要原因。车体断裂位置主要集中在驾驶室框架与底架、端墙与顶棚、底架与侧墙和端墙的连接处。

高墩大跨连续刚构桥施工全过程稳定性分析

本文以三门峡国道209上跨陇海铁路立交桥为研究对象,采用MIDAS/Civil建立裸墩、最大双悬臂和成桥合龙3种状态下的有限元模型,对主墩进行线性屈曲分析和几何非线性屈曲分析,计算出稳定性系数,探讨不同荷载工况下稳定性的影响因素。通过调整桥墩主要设计参数,对主墩进行稳定性影响参数的敏感性分析。结果表明:全桥施工及成桥状态下,墩顶施工荷载、挂篮荷载、温度效应和车道荷载对主墩的稳定性影响较大;在稳定性影响参数敏感性分析中,随壁厚和混凝土强度等级的提高,稳定性系数逐渐增大;墩高的增加会使稳定性系数逐渐降低,但降低速率会逐渐减缓;系梁数量和位置均会对稳定性产生显著影响;随主墩高差的减小,稳定性系数逐渐降低,桥梁结构荷载重分配,墩顶主梁弯矩逐渐降低。

某型列车板梁混合建模仿真分析研究

车体底架作为车体的主要承载部件,其底架横梁截面形式对车体的力学特性起决定作用,实际设计中,往往需要对车体底架横梁的设计参数进行反复修改论证,延长了设计的周期。从加快仿真分析流程,提高研发设计效率的角度出发,文中提出了一种基于板梁混合单元的有限元建模方法,并依据车体常用的EN 12663设计评价标准,分别对板壳有限元模型和板梁混合有限元模型进行仿真分析计算,得到了两种不同建模方式的仿真分析结果。并在此基础上,对两种不同建模方式从刚度、强度等方面进行对比评价,结果表明,在车体强度和刚度方面,采用板梁混合建模的方式能够在保证结果精度的前提下对板壳有限元模型起到很好的替代作用。

数值模拟技术在高坠案法医学分析中的应用

高坠案的焦点、难点是推演重建坠落轨迹,分析损伤机制,为综合判断坠落性质提供依据,并将结论向死者家属等非专业人士进行直观、有效的解释。近年来,得益于数值运算方法发展和计算能力提高等有利条件,数值模拟技术在损伤生物力学研究领域取得了一定进展。该技术具有模拟结果客观化、直观化、参数化以及可重复等优势,为分析研究人体坠落轨迹及坠落伤等开辟了新的途径。高坠数值模拟技术主要有两种方法,一种是基于多刚体动力学方法进行坠落轨迹的推演重建;另一种是基于有限元方法进行坠落伤的推演重建。本文综述了近年来国内外数值模拟技术在高坠案中的应用研究,展示了该技术应用于高坠案法医分析的潜力。

用于阻挡Z箍缩飞溅物的旋转开口圆盘系统

针对Z箍缩等离子体内爆后期,由于等离子体柱反弹产生的飞溅物会对诊断设备的光学器件造成污染的问题,设计了一种使用旋转开口圆盘进行飞溅物阻挡的系统,可实现在X射线入射到探测器后迅速遮挡光学通道,达到保护诊断系统的目的。分析了旋转开口圆盘的阻挡原理,并根据该原理设计了开口圆盘的形状、尺寸、转速等参数,计算了开口圆盘能够遮挡的飞溅物速度范围为112.4~104 m·s^(-1),允许的时间抖动为12.5μs。通过有限元分析对旋转开口圆盘的应力、形变及模态进行了分析,并基于分析结果对开口圆盘的设计进行了优化,使其最大应力值降低了45%。最后给出了同步触发方案,以确保在光学通道开放时同步触发X射线发射。

条间力简化对边坡稳定性计算结果的影响

由于条间力的简化处理,导致采用不同的条间力简化方式得到的边坡稳定性系数计算结果,以及相应的滑面位置均存在差异。有限元强度折减法采用边坡岩土体的本构关系,对岩土体强度进行折减,计算边坡体的应力、应变大小及分布,依据计算收敛情况,确定边坡稳定性系数;依据最大剪应变区,确定边坡潜在滑动范围。得到的计算结果不受条间力简化处理的影响。以澳大利亚计算机应用协会(ACADS)通用考题1均匀土质边坡为例,分别采用有限元强度折减法(SRM),不同条间力简化的刚体极限平衡方法,求得边坡潜在滑动区域、条间力的大小与分布、稳定性系数,并进行对比分析。在此基础上,分析探讨了条间力简化对边坡的稳定性系数,以及滑面位置的影响。

四川省某露天矿石灰岩质高陡边坡稳定性分析

为研究高陡露天边坡的稳定性,本文以四川省某露天矿石灰岩质边坡为工程背景,选取1个典型剖面分析,运用赤平投影分析法对岩质边坡的稳定性进行分析评价,并采用强度理论的刚体极限平衡法与二维有限元数值模拟、三维数值模拟等进行了相互验证比较分析。研究结果表明:1个典型剖面在3种工况下的整体边坡安全系数均符合规范要求值,边坡整体稳定性较好。所得结论对后期施工设计提供了理论依据及数据支持,同时为类似工程的边坡稳定性分析提供了参考。