Deforming analysis of sheet metal based on stereo vision and coordinate grid

A new approach based on stereo vision technology is introduced to analyzesheet metal deformation. By measuring the deformed circle grids that are printed on the sheetsurface before forming, the strain distribution of the workpiece is obtained. The measurement andanalysis results can be used to verify numerical simulation results and guide production. To getgood accuracy, some new techniques are employed: camera calibration based on genetic algorithm,feature abstraction based on self-adaptive technology, image matching based on structure feature andcamera modeling pre-constrains, and parameter calculation based on curve and surface optimization.The experimental values show that the approach proposed is rational and practical, which can providebetter measurement accuracy with less time than the conventional method.

Study on Process Parameters Optimization of Sheet Metal Forming Based on PFEA/ANN/GA

Sheet metal forming is widely applied to automobile, aviation, space flight, ship, instrument, and appliance industries.In this paper, based on analyzing the shortcoming of general finite element analysis (FEA), the conception of parametric finite element analysis (PFEA) is presented. The parametric finite element analysis, artificial neural networks(ANN) and genetic algorithm (GA) are combined to research thoroughly on the problems of process parametersoptimization of sheet metal forming. The author programs the optimization scheme and applies it in a research ofoptimization problem of inside square hole flanging technological parameters. The optimization result coincides wellwith the result of experiment. The research shows that the optimization scheme offers a good new way in die designand sheet metal forming field.

Numerical modeling and deformation analysis for electromagnetically assisted deep drawing of AA5052 sheet

Electromagnetic forming(EMF)is a high-velocity manufacturing technique which uses electromagnetic(Lorentz)body forces to shape sheet metal parts.One of the several advantages of EMF is the considerable ductility increase observed in several metals,with aluminum featuring prominently among them.Electromagnetically assisted sheet metal stamping(EMAS)is an innovative hybrid sheet metal processing technique that combines EMF into traditional stamping.To evaluate the efficiency of this technique,an experimental scheme of EMAS was established according to the conventional stamping of cylindrical parts from aluminum and the formability encountered was discussed.Furthermore,a "multi-step,loose coupling" numerical scheme was proposed to investigate the deformation behaviors based on the ANSYS Multiphysics/LS-DYNA platform through establishing user-defined subroutines.The results show that electromagnetically assisted deep drawing can remarkably improve the formability of aluminum cylindrical parts.The proposed numerical scheme can successfully simulate the related Stamping-EMF process,and the deformation characteristics of sheet metal reflect experimental results.The predicted results are also validated with the profiles of the deformed sheets in experiments.

Theoretical and Experimental Analysis of Deep Drawing Cylindrical Cup

There are mainly two methods of deep drawing analysis: experimental and analytical/numerical. Experimental analysis can be useful in analyzing the process to determine the process parameters that produce a defect free product, and the analytical/numerical modeling can be used to model and analyze the process through all stages of deformation. This approach is less time consuming and more economical. Sheet metal forming often includes biaxial in-plane deformation with non-proportional strain paths. In deep drawing of cylindrical cup, the deformation in the flange is dominated by pure shear deformation, while it changes to plane strain when the material is drawn into the die. This paper deals with the analysis of deep drawing of circular blanks into axi-symmetric cylindrical cup using numerical modeling. The blank drawability has been related both theoretically and experimentally with the initial diameter of the blank and deep drawing parameters. The strains in the radial and circumferential directions have been measured. A correlation on the flange thickness variation by taking into account the work hardening with the analytical and experimental values also has been searched.

基于传统工艺与新技术的《钣金成形原理与工艺》课程改革与实践

《钣金成形原理与工艺》作为飞行器制造工程专业学生的核心课程,涉及知识点多、涵盖领域广、知识体系更新速度快。以薄壁铝合金半球形件为实例,基于传统拉深成形方法及出现的质量问题,结合覆板成形、反向粘性介质压力成形等最新技术和研究成果,利用工艺参数调整、加载路径优化及工艺方法选取等提高钣金件成形性能,通过不同解决方案及结果对比,加深了学生对新技术、新工艺的认识,同时也为航空钣金零件的高质量成形提供新思路。

Determination of Flow Curve and Plastic Anisotropy of Medium-thick Metal Plate:Experiments and Inverse Analysis

Sheet bulk metal forming is widely used for medium thick metal plate due to its convenience in the manu- facture of accurately finished 3D functional components. To obtain precise anisotropy and flow curve of metal plate is a prerequisite for correct simulation of sheet bulk metal forming processes. Inverse analysis of compression test was introduced here to evaluate the sensitivity of different flow curve models and geometric influence of compression test specimen. Besides, a methodology was proposed to compute plastic anisotropic coefficients of Hill quadratic yield cri- terion, which is based on the ratios of flow curves obtained by inverse analysis of compression tests using specimens cut in six directions on the medium-thick metal plate. The obtained flow curves and anisotropic coefficients were compared with those calculated from tensile tests. Flow curves based on inverse analysis of compression tests cover the curves of the tensile tests well, while the anisotropic coefficients are different, especially for the coefficient relat- ed to the RT45 direction. To estimate the effectiveness of the proposed method, the calculated material properties and those based on the traditional tensile tests were applied in a rim-hole process simulation. The simulation results based on the material properties from inverse analysis of compression tests accorded with the tested properties better.

板料成形优化技术进展与质量工程研究

板料成形过程的优化研究对于改进模具设计、提高产品质量具有重要意义。综述了板料成形工艺优化的研究现状。考虑到在有约束的设计优化中,最优结果常位于约束边界附近,随机因素的波动易导致产品质量不稳定甚至失效,难以保持产品的可靠性和稳健性。为此,本文应用质量工程学中的6σ理念,提出了基于数值模拟的板料成形6σ稳健设计优化方法。

材料成形计算机模拟中的参数化有限元法

在分析常规有限元法在材料成形模拟中的不足的基础上 ,提出了参数化有限元分析的概念 ,阐述了其基本任务、基本过程、实现方法和进行参数化有限元分析的技术要点。针对方孔翻边问题进行了编程式参数化有限元法研究 ,其结果与现有文献试验结果基本吻合 ;针对方盒拉深中的坯料形状优化问题进行了交互式参数化有限元法研究 ,其结果与现有文献试验结果基本吻合。研究表明 ,提出的参数化有限元法实用、可行 ,为材料成形计算机模拟探索出了一种高效快捷。

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。

多工步板料成形问题的多步反向模拟法

提出一种新的多步反向模拟法,该方法建立在虚功原理的基础上,为提高计算精度,采用弹塑性材料模型。提出一种适用于多步反向模拟法的本构关系,可以充分考虑弹/塑性变形状态、加载/卸载状况。提出一种“双截面线法”来快速获取中间构型,可以充分考虑塑性变形对构型的影响。提出一种快速接触搜索算法来实现中间构型各个节点在约束滑移面上的移动,采用全局搜索和局部搜索策略相结合的方法,加快搜索速度。理论成果已经在自主开发的板料成形反向模拟软件InverStamp/Multi-step模块中实现。在盒形件多步拉深实例中,坯料轮廓、等效应变分布等计算结果与基于Is-dyna的增量法模拟软件Dynaform计算的结果十分吻合,验证了多步反向模拟法相比于一步反向模拟法的优势。

基于量纲分析法的金属板材折弯回弹数学模型

回弹是影响金属板材工件成形精度的一个非常重要因素。准确控制回弹是工件精密成形和模具设计的关键所在。针对用于修正回弹的传统试错法的不足,提出一种基于量纲分析和正交试验相结合的方法来建立金属板材折弯回弹半径数学模型。并讨论回弹数学模型的适用范围。该模型定量求解了板料回弹半径与凸模半径、板材厚度、屈服强度、弹性模量之间的非线性关系。将此应用于折弯凸模的设计制造,且用该凸模多道次渐进成形了一半椭圆形工件,它的平均误差是+0.63/-0.65mm。该制造结果表明,基于量纲分析法和正交试验法建立的板料回弹半径数学模型是合理有效的,该建模方法有助于加快模具设计进程,降低生产成本,为金属板料折弯成形及模具设计提供了一条新的途径。

基于有限元的板料拉延成形质量评价准则及工艺参数优化研究

近年来,以有限元分析工具并结合优化算法来提高板料的成形性能已成为新的研究热点。然而,如何建立合理的板料成形质量评价准则以形成目标函数,从而量化冲压件的成形质量是其关键技术之一.该文在研究国内外现有的各种评价拉裂和起皱缺陷准则的基础上,提出了指数加权评价准则,该准则量化了单元落在成形极限图上不同区域和离安全区域距离远近不同分别对拉裂和起皱权值贡献的差异.结合方形盒标准考题验证了提出的评价准则的合理性.将该质量评价准则应用到了一个实际零件的成形优化研究中,优化的结果显著的提高了板料的成形性能.

基于试验和有限元方法的橡皮囊液压成形回弹规律

橡皮囊液压成形中常见的缺陷包括破裂、起皱和回弹等成形缺陷,其中回弹缺陷直接影响钣金件的尺寸精度。文章针对带下陷直弯边和凸弯边钣金件进行橡皮囊液压成形试验。结果表明,随着压力的增加,回弹值减小;弯曲线取向为90°的回弹值,大于弯曲线取向为0°的回弹值;弯曲成形性能与轧制方向的选取有关。有限元模拟结果与试验结果进行对比分析表明,模拟所得回弹值与试验结果相比偏小。

板材成形有限元仿真技术的应用

就板材成形仿真技术的发展和关键技术进行了介绍,并用DYNAFORM软件对拉深杯零件模型进行了仿真计算,对仿真计算结果与实际测试结果进行了比较,两者吻合性较好,为有限元仿真计算奠定了基础。

金属板料拉深回弹成因及回弹补偿研究

分析现有金属板料拉深回弹产生的机理中,对影响板料成形回弹的多个因素如材料的机械性能、凹模圆角半径R、压边力F等进行了解析,并对回弹补偿进行了研究。以某风机叶片为应用实例,研究了该风机叶片成形后回弹分布的规律,并采用了多步隐式算法对其进行了回弹补偿,最终达到工件精确成形的目的。

金属板料单点无模渐进成形数值模拟及分析

有限元数值模拟对单点无模渐进成形技术的研究起着重要的理论指导作用。本文介绍了数值模拟的基本步骤,重点介绍了圆/方锥台形件模拟轨迹的改进,轨迹环采用正逆相间方式可避免成形件发生扭曲变形。此外,基于Matlab软件编程,可快速生成不同工艺参数的模拟轨迹。最后通过多次数值模拟得出,工具头半径越小,工件成形角度越大,板料发生的等效应变就越大。结论与实验结果完全吻合。

板材多点成形工艺的数值模拟研究

本文简要介绍了多点成形的基本原理，并应用有限元方法针对多点模具成形与多点压机成形两种工艺对压痕、起皱等缺陷及回弹的不同影响进行了数值模拟研究，同时对多点模具成形过程中起皱现象的发生进行了实验验证。另外，为了更好地抑制回弹，提出了利用多点压机成形方式围绕目标形状反复成形的方法，并进行了数值模拟。结果表明，多点压机成形比多点模具成形可以更好地抑制压痕、起皱及回弹的发生。

中空激光冲击金属板料变形的数值模拟

为了研究中空激光参量对金属板料变形的影响,采用数值仿真的方法,选用不同的中空激光参量对3003铝合金板料进行了冲击成形数值模拟,分析了板料变形的动态响应过程以及成形规律。结果表明,中空激光加载后,板料获得初速度,光斑区域的速度逐渐减少,区域外的速度逐渐增加,带动整个板材的运动;与实心激光冲击板料变形比较,板料底部变形区较为平坦,变形比较均匀,提高了板料的成形性和成形极限。该研究通过选择不同的中空激光参量获得板料的成形规律,为中空激光冲击成形技术提供了依据。

基于板料成形数值模拟的冲压模具结构分析方法

针对结构复杂的大型汽车冲压件成形模具,提出一种基于板料成形数值模拟的冲压模具结构分析方法。先通过板料成形数值模拟获得变形板料对模具的作用力,然后在模具结构分析时,将此作用力施加到模具上以代替板料对模具的作用,从而简化模具结构分析模型。论述基于板料成形数值模拟的冲压模具结构分析方法的实现过程以及联系两个过程的关键技术——边界力的映射算法。运用该方法分析双曲底面盒形件拉深成形时模具的受力,并利用自主设计的模具应力采集系统进行试验验证。结果表明,模具上选取的若干特征点的等效应力数值计算结果和实际测量结果吻合良好。

TC4板料电辅助加热数控渐进成形工艺分析及优化

采用有限元分析软件MSC．Marc对TC4板料的电辅助加热渐近成形进行了数值分析，研究了进给速度、层距和电流等因素对工具头受力、板料温度和应变的影响规律。通过成形实验对数值分析进行了验证，并提出了工艺优化方法。实验表明：电流是影响TC4板料成形性能和温度的最主要因素，最佳成形温度为500～600℃。加工后板料的强度极限降低约10％，硬度增高14％左右，为该技术的应用提供了工艺指导。