金属板料多道次渐进成形过程的数值模拟

介绍了金属板料渐进成形工艺的基本原理.以ANSYS/LS-DYNA为分析平台,构建了板料多道次渐进成形的有限元模型,并以LS-PREPOST和ETA/Post-Processor为后处理平台,得到各道次厚度云图及网格变形图.对半球形制件的三道次成形过程进行了模拟,将模拟结果与实验结果进行比较,证明了模拟的可行性.     

金属板料多道次渐进成形过程的数值模拟

介绍了金属板料渐进成形工艺的基本原理。以ANSYS／LS—DYNA为分析平台，构建了板料多道次渐进成形的有限元模型，并以LS—PREPOST和ETA／Post—Processor为后处理平台，得到各道次厚度云图及网格变形图。对半球形制件的三道次成形过程进行了模拟，将模拟结果与实验结果进行比较，证明了模拟的可行性。     

金属板料渐进成形有限元仿真过程中复杂成形路径的构建方法

提出一种用于获得复杂空间运动轨迹的方法——虚拟靠模导向法。该方法借鉴了数控加工中COPY铣的思想,利用轨迹生成球在由零件派生出的虚拟靠模表面上的持续运动来模拟实际成形工具的运动过程,从而获得最终成形路径。基于该思想和简单的运动学原理,轨迹球与虚拟靠模有限元模型被构建起来。通过对计算过程进行分析,确定运用该法时适合的加载力、成形速度及计算精度的影响因素。因该法完全基于有限元模拟计算,故获得的成形路径可直接导入至后续的金属板料成形过程的模拟分析。该法已在有限元软件PAMSTAMP平台上得以实现,并主要用于金属板料渐进成形过程的有限元仿真。     

基于MARC的板料冲压成形过程有限元模拟研究

通过合理制定零件的成形工艺、模具参数来消除零件缺陷、提高成形品质是金属板料冲压成形的重要任务.通过探讨成形过程的数值模拟来分析金属板料各部分在冲压成形过程中的变形情况,预测成形缺陷,分析影响零件成形品质的因素的方法.以圆筒形拉深件的冲压成形为例,介绍应用商用有限元软件MARC对成形过程进行有限元模拟分析的实现技术,其分析结果与实验相符.     

金属板材拉深过程的数值模拟研究

针对金属板料拉深过程中材料变形十分复杂的问题,建立了适合钢板拉深过程的三维有限元模型,采用所建立的有限元模型对板料拉深过程进行了数值模拟研究,研究了板料拉深过程中的变形情况,并对拉深过程中冲压力和金属板料的应力分布进行了分析。数值模拟结果与实际拉深过程中材料的变形过程一致,验证了三维有限元模型的正确性。     

冲压件成形计算机模拟工艺参数优化方法研究

分析了常规有限元金属板料成形模拟的不足，提出了参数化有限元分析的概念，在对人工神经网络、遗传算法进行深入分析研究的基础上，采用参数化有限元分析方法进行分析，得到了训练样本。提出了采用人工神经网络技术建立冲压件成形多参数映射关系模型，采用遗传算法进行多参数组合优化，实现冲压件成形计算机模拟工艺参数优化的方法。实际应用结果表明，优化结果与试验结果基本吻合，该优化方案实用可行。     

金属板料数控渐进成形机床设计

首先介绍了金属板料渐进成形技术的原理和分类;然后介绍了一种小型金属板料数控渐进成形机床的总体布局、伺服进给系统以及升降台部件等主要机械结构设计.该机床能够满足科研以及教学上的使用要求,有利于提高学生对金属板料数控渐进成形机床的认识.     

三维板料成形过程的有限元分析

基于有限变形理论建立了三维金属板料成形过程的弹塑性有限元数学模型。数学模型采用物质坐标系中的Total Lagrange描述、J 2型本构方程和等向强化假设,考虑了板料的厚向异性,对于金属板料与模具的摩擦定律。为简化计算采用薄膜单元。为了改善节点接触状态变化时计算的收敛性,提出了“弹性边界层”方法。采用根据此模型编制的程序模拟了机油收集器基本件的成形过程,并与试验结果进行了比较。     

基于数控渐进成形技术的车身装饰件成形工艺

基于数控渐进成形技术进行板科成形工艺研究,提出完整的渐进成形工艺规划,并将其成功应用于车身装饰件成形.对影响成形的主要参数成形工具头直径d和每层进给量△h进行了分析.为今后完善和发展金属板料数控渐进成形技术起到重要作用.     

金属直壁筒形件数控渐进成形工艺研究

介绍了金属板料数控渐进成形工艺的成形原理、变形分析、直壁筒形件成形的工具路径设计、实验条件及结果分析。根据正弦定律 ,金属板料数控渐进成形工艺 ,不能一次成形出直壁筒形件 ,要成形直壁筒形件 ,必须进行多次成形。为了尽快逼近直壁筒形件 ,设计了平行直线型等三种工具路径方案 ,通过实验和结果分析 ,找到最佳方案。     

Study on multiple-step incremental air-bending forming of sheet metal with springback model and FEM simulation

A mathematical model of springback radius was developed with dimensional analysis and orthogonal test. With this model, the punch radius could be solved for forming high-precision semiellipse-shaped workpieces. With the punch radius and other geometrical parameters of a tool, a 2D ABAQUS finite-element model (FEM) was established. Then, the forming process of sheet metal multiple-step incremental air bending was simulated with the FEM. The result showed that average errors of the simulated workpiece were +0.68/?0.65 mm, and provided the process data consisting of sheet feed rate, punch displacement and springback angle in each step. A semiellipse-shaped workpiece, whose average errors are +0.68/?0.69 mm, was made with the simulation data. These results indicate that the punch design method is feasible with the mathematical model, and the means of FEM simulation is effective. It can be taken as a new approach for sheet metal multiple-step incremental air-bending forming and tool design.     

Mould correction for sheet-metal multi-step incremental air-bending forming based on close-loop control and FEM simulation

There exist errors between the manufactured workpieces and the CAD models due to the springback of sheet-metal incremental air-bending forming. To reduce these errors, an off-line closed-loop control iterative algorithm, combined by fast Fourier and wavelet transform, is developed from the displacement adjustment method (DAM), smooth displacement adjustment method (SDAM) and deformation transfer function method (DTFM) for die surface. With this algorithm, the mould surface of sheet-metal incremental air-bending forming could be properly corrected, and the springback errors of the formed workpieces could be effectively reduced. In order to reduce mould cost and labor cost, the springback tests of workpieces forming, needed in the iterative process of closed-loop control system, are substituted by finite element model (FEM) simulation. The above correction algorithm was used in a semiellipse-shape workpiece incremental air-bending forming. Its average errors are +0.74/−0.39 mm. The results show that the mould correction algorithm with Fourier and wavelet transform is reasonable and the means of FEM simulation are effective. It can be taken as a new approach for sheet-metal multi-step incremental air-bending forming and mould design.     

采用试错接触算法的板料成形有限元模拟技术－

以金属板料成形过程为对象,采用基于板壳理论的８节点壳单元,以Ｋｉｒｃｈｈｏｆｆ应力张量和Ｇｒｅｅｎ应变张量作为应力与应变的度量,采用有限变形的Ｕｐｄａｔｅｄ　Ｌａｇｒａｎｇｉａｎ列式,研究有限元方法模拟成形过程的技术。在此基础上,提出了一种直接试错的接触算法,将非线性的接触边界条件线性化处理,接触处理与有限元计算相对独立。通过试验结果与计算结果的比较,说明采用的模拟算法是合理可行的。     

基于预偏移的激光拼焊板焊缝优化补偿方法

激光拼焊板成形时,由于两侧母材性能不同会产生焊缝移动现象,造成实际焊缝与设计焊缝位置不符。利用增量有限元解算工具,针对激光拼焊板的拉深成形过程,提出一种基于预偏移的激光拼焊板焊缝补偿方法。建立激光拼焊板成形有限元分析网格模型,通过对比成形前后设计焊缝和实际焊缝之间的差异,推导拼焊板焊缝偏差评价模型。以毛坯焊缝节点的位移预偏移量作为设计变量,以成形后的焊缝位置与设计焊缝位置的偏差最小作为优化目标,建立优化设计的数学模型。利用坯料网格的变形实现焊缝的预偏移,自定义外部优化程序实现预偏移策略。通过有限元迭代求解,补偿拼焊板成形过程中的焊缝移动,使成形后的焊缝位置与设计焊缝位置保持一致,对所提方法的有效性进行实例验证。     

金属板材单点渐进成形技术的研究进展

金属板材单点渐进成形技术是一种新的板材无模成形技术,它可直接从CAD数据快速、经济地制造出复杂形状的板材件而无需昂贵的模具,并可广泛应用于样件试制和小批量生产。本文分析了金属板材单点渐进成形技术的基本原理、研究现状,探讨了存在的问题和发展趋势。     

复杂钣金零件渐进成形方法

以复杂钣金零件－人面部模型零件为例,论述基于UG软件的建模及建模过程中应注意的问题、支撑模型的制作及其加工代码的生成、适用于渐进成形正成形过程的加工代码生成处理过程,给出加工代码的详细信息,成功加工出质量较高的人面部模型。人面部模型渐进成形试验结果表明,利用渐进成形正成形方法可以成形出形状复杂的钣金零件,生产小批量复杂零件可以节省时间与费用;UG生成的三轴数控加工代码需要通过处理才能应用于渐进成形正成形过程;复杂钣金件渐进成形过程中定位精度非常重要,定位精度高的零件厚度分布符合 的规律,并可以成功成形出设计的零件,定位精度误差较大时零件厚度分布不均匀,成形工具头与板 料的过度挤压侧板料厚度变薄急剧从而引起零件的过早破裂。     

DEFORMATION ANALYSIS OF SHEET METAL SINGLE-POINT INCREMENTAL FORMING BY FINITE ELEMENT METHOD SIMULATION

Single-point incremental forming （SPIF） is an innovational sheet metal forming method without dedicated dies, which belongs to rapid prototyping technology. In generalizing the SPIF of sheet metal, the deformation analysis on forming process becomes an important and useful method for the planning of shell products, the choice of material, the design of the forming process and the planning of the forming tool. Using solid brick elements, the finite element method（FEM） model of truncated pyramid was established. Based on the theory of anisotropy and assumed strain formulation, the SPIF processes with different parameters were simulated. The resulted comparison between the simulations and the experiments shows that the FEM model is feasible and effective. Then, according to the simulated forming process, the deformation pattern of SPIF can be summarized as the combination of plane-stretching deformation and bending deformation. And the study about the process parameters＇ impact on deformation shows that the process parameter of interlayer spacing is a dominant factor on the deformation. Decreasing interlayer spacing, the strain of one step decreases and the formability of blank will be improved. With bigger interlayer spacing, the plastic deformation zone increases and the forming force will be bigger.     

金属板料冲压成形的数值模拟

本文采用有限元动力显式算法模拟金属板料冲压成形的加工过程。四结点蜕化壳单元和刚体壳单元分别用来建立权和模具的有限元模型;更新Ｌａｇｒａｎｇｅ法和速率型本构关系被用来处理板料变形中的大应变和大转动;材料模型采用塑性各向异性屈服与等向强化模型;通过主从面模型定义板料和模具的接触,接触算法采用运动约束法,摩擦力用库仓定律计算;并利用动力松弛法对回弹过程进行了计算。模拟结果和实际零件比较,证明模型合理,算法稳定,结果可靠,具有良好的应用价值。     

The performance of flat end and hemispherical end tools in single-point incremental forming

Single-point incremental forming is a novel sheet metal-forming process. It can provide an economical alternative of stamping process to produce small batches. In the current study, the effect of tool shape on the profile accuracy of U-shaped channel and sheet formability was studied. Two kinds of tools with flat end and hemispherical end were employed. It was found that the flat end tools can provide better profile accuracy and formability than the hemispherical end tools. In addition, flat end tools required relatively lower forming force compared to hemispherical end tools.