应用韧性断裂准则预测板料的成形极限图

将Oyan韧性断裂准则引入数值模拟预测板料的成形极限图(FLD).讨论了各向异性系数对不同应变状态下准则中各项的影响,通过测定单向拉伸和平面应变拉伸的断裂应变确定了准则中的材料常数.模拟凸模胀形实验得到每一时间步应力、应变值,代入韧性断裂准则预测板料的成形极限.应用Oyan韧性断裂准则预测了铝合金A5182-O和SPCC的成形极限图.模拟结果表明,用韧性断裂准则和数值模拟相结合能成功预测板料的成形极限图.     

板料成形极限的理论预测与数值模拟研究

本文针对目前板料成形极限的实验、理论计算和数值模拟方法以及成形极限应力图的研究进展 ,进行了综述与分析 ,提出了通过数值模拟方法预测板料成形极限所存在的一些问题。认为找到一种能够尽量减少对外部条件的依赖 ,从而更本质地反映材料性能的方法。     

基于韧性断裂准则的铝合金板材成形极限预测

为了准确地预测铝合金板材成形极限，将韧性断裂准则引入到数值模拟中。在数值模拟获得的应力应变值基础上，采用简单拉伸试验和数值模拟相结合的方法确定了韧性断裂准则中的材料常数，并应用该韧性断裂准则预测了铝合金LYl2(M)的圆筒件拉深和半球形凸模胀形的成形极限。预测结果与实验值吻合较好，该韧性断裂准则能够预测铝合金板材成形极限。     

AZ31镁合金成形极限图的实验研究与数值模拟

利用Nakazima半球凸模胀形实验构建了AZ31镁合金在170、200和230℃温度条件下的成形极限图,分析了温度对AZ31镁合金成形极限的影响。利用有限元方法对AZ31镁合金在200℃温度下的胀形过程进行了数值模拟,并将所得模拟结果与实验结果进行对比。结果表明,随着胀形温度的升高,AZ31镁合金的变形抗力不断降低,显著提高了其成形极限,并验证了AZ31镁合金的塑性从100℃快速上升,到200℃后上升变缓。数值模拟和实验研究的结果具有较好的一致性,证实了所构建模型的有效性。     

数值模拟在汽车覆盖件成形中的应用

有限元分析方法已被广泛应用于力学过程的计算机仿真,对冲压生产等工程问题的应用也逐渐得到人们的重视与认可。本文应用法国ＥＳＩ－ＧＲＯＵＰ的大型有限元软件ＰＡＭ－ＳＴＡＭＰＴＭ进行了汽车覆盖件成形仿真,并与实际生产结果进行了对比分析,以此介绍数值模拟在汽车覆盖件成形过程中的应用。     

汽车覆盖件冲压成形的数值模拟

总结了冲压数值模拟过程中考虑拉伸工艺性时应注意的几个问题。通过冲压成形数值模拟与实际冲压结果的比较,证实了采用PAM_STAMP数值模拟软件对汽车后盖内覆盖件进行数值模拟的准确性,并据此进行了工艺参数的调整和优化。     

5754-H111铝合金板材成形极限实验及数值模拟

为适应节能减排与轻量化需求,铝合金产品日益受到重视。通过实验与数值模拟方法研究了5754-H111铝合金板材在室温下的成形性能。通过刚模胀形实验,测试获得了成形极限图(FLD),其中平面应变条件下极限应变为0.174。并通过单拉、拉深及胀形实验,得到更实用的板材简易成形极限应力图(FLSD)。根据应变路径的变化,结合有限元模拟得到了FLD预测值,模拟结果与实验结果吻合较好,证明了该方法在预测板材成形极限上的准确性。     

减振复合钢板的成形性及其数值模拟研究进展

减振复合钢板是一种应用于汽车覆盖件方面的新型材料，有利于减振和减轻重量。介绍了其成形性和成形过程数值模拟的研究进展，并对未来发展进行了展望。     

点焊拼接板的概率化成形极限图及其应用

成形极限图是评定金属薄板成形性能最为简单和直观的方法,是解决板冲压问题的一个非常有效的工具.本文根据点焊拼接板的特点提出了概率化成形极限图P-FLD,并采用MSC.Dytran有限元分析软件对点焊拼接板的胀形及拉深过程进行模拟研究,得到了点焊拼接板成形时的应变分布.将点焊拼接板的P-FLD和有限元模拟的零件应变分布点结合起来,得到零件应变极限图,从而为初步选材和确定冲压零件的安全裕度提供了参考.     

基于Autoform的汽车覆盖件拉深成形数值模拟研究

以典型覆盖件(汽车外轮罩)为研究对象,板料三维成形分析软件Autoform为平台,研究了板料与凸模、凹模的摩擦、压边力、拉深筋等因素对成形性能的影响。通过Autoform的成形仿真预测板料成形过程中减薄、拉裂、起皱等缺陷,同时分析缺陷产生的原因,进而优化板料成形工艺参数和改进模具结构。     

高应变率成形极限图测试与仿真研究进展

高应变率成形是一种在极短时间内释放高能量而使金属变形的成形方法,研究表明高应变率能显著提高多种金属材料的成形极限能力.通过高速杯突实验绘制成形极限曲线,可反映金属在高应变率下的成形能力,从而指导冲压设计.文中介绍了目前常用的几种高速杯突实验设备,包含气压、液压和电磁等驱动方式,并对高应变率下的成形极限图进行了分析和总结...     

Design and analysis of new test method for evaluation of sheet metal formability

A new test method including the tool shape and test procedure was developed to evaluate sheet metal formability using the finite element method (FEM). This method is intended to generate the various modes of deformation and to control the onset of failure independently under each mode so that the forming limit diagram (FLD) achieves a good representation of a wide range of strains.A blank holder force-punch stroke diagram with three failure loci is introduced to define the optimum process condition and the formability index by which each material is quantitatively evaluated. The test procedure of this method consists of three steps: drawing a blank holder force (BHF)-punch stroke diagram, measuring strains from the part stamped at the optimum process condition, and grading the test materials using the formability index. In numerical simulations under optimum process conditions, sheet metals can fail due to multi-mode rupture; this failure leads to a widely balanced strain distribution in the FLD such that strains are developed near the forming limit over a wide range of forming modes.Experiments were conducted on three grades of steel sheets to validate the proposed method. Stamping results yield well-defined strain signatures having a wide range of strain distribution in the FLD in all materials tested. The outcomes of the shape and strain behaviors agree well with the numerical results.     

数值仿真法在铝型材挤压成形模具设计与优化中的应用研究

针对某一截面较大、形状较为复杂的铝合金型材,研究了该铝型材的挤压工艺、并进行了模具设计.基于ALE的有限元软件HyperWorks,建立该铝型材挤压成形有限元数值仿真模型,对挤压过程进行数值仿真研究,从而获得型材挤压过程金属流动规律.根据仿真结果,分析了焊合室各层高度、尺寸形状和模具结构参数对型材挤压速度分布、材料粒子运动轨迹以及应力应变分布等金属流动行为的影晦规律,并对模具结构参数进行优化设计.计算结果表明:优化设计后的模具可以使模具出口处金属流动的速度相对比较均匀,减小产品扭曲变形程度,较好地满足该型材截面形状和尺寸精度方面的要求.     

Analysis of plastic flow localization under strain paths changes and its coupling with finite element simulation in sheet metal forming

Formability of sheet metal is usually assessed by the useful concept of forming limit diagrams (FLD) and forming limit curves (FLC) represent a first safety criterion for deep drawing operations. The level of FLC is strongly strain path dependent as observed by experimental and numerical results and therefore non-proportional strain paths need to be incorporated when analyzing formability of sheet metal components. Simulations using finite element method allow accurate predictions of stress and strain distributions in complex stamped parts. However, the prediction of localized necking is a difficult task and the combination of forming limit diagram analysis with finite element simulations often fail to give the right answer, if complex strain paths are not included in these predictions.     

7075铝合金蠕变时效成形过程数值模拟

蠕变时效成形技术是利用金属的蠕变特性,将成形与时效热处理同步进行的一种成形方法。文章运用有限元对成形过程进行数值模拟,就成形过程中的应力应变分布、主要成形参数对回弹的影响进行分析,为实际工艺参数的确定及优化提供参考。     

药物片剂压制成形过程的数值模拟研究

运用有限元软件ABAQUS,采用基于扩展的Drucker-Prager的本构模型对药物片剂成形过程进行了数值模拟.获得了药物片剂压制成形的密度分布及成形力等相关数据.结果表明:随着压制深度的增加,片剂材料密度及成形力整体呈现增大趋势.药物片剂压制过程数值模拟得到的片剂材料流动规律及力学行为,将为实际成形中工艺参数的改善...     

5754铝合金板材冲压成形材料模型研究与应用

建立准确的材料模型是冲压数值模拟的基础,通过3个方向的单向拉伸试验、以及单向压缩试验和成形极限试验,获得5754铝合金材料性能数据,基于Voce硬化模型、Barlat89屈服准则和成形极限,建立5754铝合金成形用材料模型。利用Pamstamp-2G软件,对5754铝合金汽车大梁的冲压成形进行数值模拟,并与冲压试验结果进行对比。结果表明:数值模拟获得的应变数据与试验测量获得的应变数据比较接近,且各区域最大减薄率误差在±10%以内,验证数值模拟的可靠性。     

车后灯座成形工艺分析及有限元数值模拟优化

采用基于动力显示算法的板料成形非线性有限元分析软件Dynaform对某轿车后灯座的拉深成形过程进行了数值模拟仿真。主要研究了不同工艺补充面及不同坯料形状对零件冲压成形的影响，通过FLD图和成形结果对比，对工艺补充部分和坯料形状进行了调整，并得到了优化的拉深件型面及坯料尺寸，为同类相关零件的生产起到了指导作用。     

有限元数值模拟在汽车覆盖件设计和制造中的应用

汽车覆盖件成形同时包含大变形、（粘）塑性、接触、摩擦等多种非线性因素耦合，利用有限元法在计算机上模拟出板材从坯件到成品的全过程并加以图形显示，进而研究影响成形的各种因素，可以为板材成形的设计和生产提供可靠的依据。本文主要介绍有限元数值模拟技术的现状，并讨论了其在汽车覆盖设计和制造上的应用。     

Thin-walled aluminum alloy tube NC precision bending based on finite element simulation

Elongation and springback are the bottleneck problems of thin-walled aluminum alloy tube NC precision bending. SO thin-walled alurninum alloy tube NC precision bending based on finite element simulation is put forward. The finite element model of thin-walled aluminum alloy tube NC bending is established based on the DYNAFORM platform. The process of thin-walled aluminum alloy tube NC precision bending is simulated with the model and the elongation and springback of tube bending can be gained. A new method of measuring the elongation of thin-walled tube NC precision bending named ＇pressure die measuring method＇ is put forward and the computing equations of bending angle, bending radius, blanking length and initial bending section based on elongation and springback angle are derived. The bending angle, bending radius, blanking length and initial bending section of tube bending can be gained with these equations based on the elongation and springback angle from the simulation. The study can be used to control the quality of thin-walled aluminum alloy tube NC bending so that precision bending without redundance can be realized.