硬铝合金半球形零件的渐进成形工艺研究

目的 研究冲压胀形工艺与渐进成形工艺成形半球形零件的区别。方法 使用两种热处理状态的硬铝合金,AA2024-O和AA2024-T4,分别用冲压胀形工艺和渐进成形工艺成形半球形零件。结果 相比较渐进成形零件而言,使用冲压胀形工艺得出的半球形零件的壁厚相对均匀,变形程度可以达到更大;在相同的试验条件下,AA2024-O的成形性能远高于AA2024-T4的成形性能;在本实验所研究的参数范围内,下压量越小,成形高度越大,对AA2024-O进给速率越快,成形高度越大;而对AA2024-T4进给速率越慢,成形高度越大;对于胀形零件,材料在胀形过程中处于双向拉伸应变状态,而渐进成形零件在成形过程中处于平面应变状态;胀形零件的最大应变和最大减薄处是半球的中心,而渐进成形零件的最大应变和最大减薄处是半球的边缘。结论 胀形零件的危险截面在半球的中心,渐进成形零件的危险截面在半球的边缘。     

5182铝合金椭圆孔电磁翻边数值模拟研究

目的 研究异形孔电磁翻边成形规律及不同预制孔尺寸对翻边质量的影响.方法 基于电磁成形平台实现椭圆孔电磁翻边试验,建立三维电磁成形仿真模型对3种预制孔的翻边过程进行模拟.通过显微硬度值、翻边轮廓、翻边高度及端部厚度等指标分析异形孔电磁翻边规律.结果 3种预制孔的翻边高度均表现为从长轴到短轴不断增大,随着预置高度从15 mm降到10 mm,长短轴两处的翻边高度差由2 mm下降至0.75 mm,且翻边零件与模具贴合效果逐渐变好.结论 电磁翻边件在长、短轴处的变形存在着明显差异;基于中性层不变原理的预制孔公式,在侧壁与模具贴合良好的案例中低估了电磁翻边高度;变形区域内较为均匀的电磁力密度分布有益于实现与模具良好贴合,同时翻边高度更加均匀.     

翻边系数及材料参数对空调面板成形的影响

用DYNAFORM软件对空调面板零件的成形过程进行了有限元模拟.研究分析了圆孔翻边系数和材料参数对翻边成形的最大应变值和厚度减薄率的影响规律,建立了翻边系数与材料参数的关系.研究结果对翻边成形的选材具有重要的意义.     

密封盖内外翻边模具改进

通过密封盖零件的翻边成形,介绍了密封盖翻边模具结构及工作过程,分析了黑色金属材料在翻边成形过程中产生划伤的原因,提出了采用硬质合金材料制造模具,解决了零件在翻边成形过程中,外表面产生划伤、划痕等问题。     

V型伸长翻边解析与数值研究

为了预示曲面翻边成形性能,采用有限元仿真、解析计算与人工神经网络的方法对V型零件翻边成形进行了分析.通过建立有限元模型研究了工艺参数对成形性能的影响;基于全量塑性理论及膜应变假定,推导了轴对称情况的解析计算模型;以数值模拟结果作为训练样本,建立了V型翻边成形性能预测的BP神经网络模型.研究结果表明:工艺条件对翻边成形有较大影响,其中以张角的影响最为显著;解析模型计算简便,但是只适用于零件张角较小以及相对翻边高度较小的情况;有限元仿真与人工智能相结合的BP人工神经网络模型可以快速有效地预测翻边成形性.     

工艺参数对AZ31B镁合金单点渐进翻边精度的影响

目的 以AZ31B镁合金板为研究对象,研究初始成形角、工具直径、成形温度及层间距对单点渐进圆孔翻边精度的影响规律。方法 使用有限元软件对2 mm厚的镁合金板材进行数值模拟,通过计算翻边直壁处的平均回弹量,得出不同工艺参数对单点渐进圆孔翻边直壁轮廓的影响规律。通过正交实验分析了交互作用下工艺参数对圆孔翻边直壁处平均回弹量的影响,通过极差分析确定了最优工艺参数组合,并通过实验对所得结果进行了验证。结果 随着初始成形角的增大、工具直径的增大、成形温度的升高及层间距的减小,圆孔翻边制件直壁处的成形精度提高,各因素按影响程度由大到小的顺序依次为:成形温度、初始成形角、工具直径和层间距。成形精度最高的工艺参数组合如下:初始成形角为30°、工具直径为10 mm、成形温度为275 ℃、层间距为0.5 mm。结论 采用仿真模型模拟单点渐进圆孔翻边过程具有较高的准确性,使用优化后的工艺参数得到翻边零件直壁区域的最小厚度以及平均回弹量与仿真结果误差均在3%以内,升高温度可以明显提高单点渐进圆孔翻边的制件精度。     

基于数值模拟的极限凸翻边研究

为了提高薄板冲压成形零件的疲劳寿命,将半手工操作的落锤压制(冲压)方法改为高压橡皮成形(静压)方法而进行的工艺研究试验;同时,为高压橡皮半模成形确定最合适的工艺过程设计(CAPP)进行计算机仿真.运用自行开发的静-动力有限元软件分析橡皮成形凸模圆角半径和板料厚度对凸翻边成形极限的影响,并建立预测橡皮成形凸翻边成败的t极限翻边高度Hmax、凸模圆角半径r凸、板料厚度t的关系曲面.根据所得数值模拟的极限凸翻边高度Hmax模与7.7万吨橡皮囊液压机的试验结果Hmax实的对比,吻合很好;数值模拟将凸翻边起皱-压贴的真实过程描述得很清楚,而理论计算结果与物理实验结果有一定的差值.     

B550CL高强钢轮辐反拉深-翻边复合成形损伤开裂研究

针对高强钢汽车轮辐在实际生产过程中经常出现反拉深-翻边复合工序中中心孔翻边开裂这一问题,采用有限元数值模拟的方法,建立了有限元模型,并通过试制轮辐验证其可靠性.模拟获得了新型高强钢材料B550CL在用于轮辐翻边成形时的应力应变的分布和变化规律,并进一步对轮辐的损伤和壁厚分布情况进行了分析.研究表明:反拉深-翻边复合工序中翻边区在成形过程中应力应变集中明显,变形量较大;同时,材料的损伤和壁厚减薄在翻边区域也比较严重,导致实际成形中翻边区可能出现开裂等缺陷.     

钛板圆孔翻边成形极限与形状非轴对称化研究

为确定钛板圆孔翻边成形性能,揭示各向异性对制件形状和尺寸精度的影响,在室温和600℃用TC1MS1.5 mm钛合金坯料分别进行了圆孔翻边成形试验.结果表明:与室温冷翻边相比,热翻边可有效提高成形极限、消除冷翻边制件形状翘曲以及唇口部位椭圆化现象,在唇口边沿完好与破裂状态之间存在集中颈缩形式,而冷翻边则在底孔尺寸小于极限值时会直接发生破裂;冷、热圆孔翻边变形程度越大,则形状非轴对称化程度越严重.     

车用千斤顶上支成形有限元分析及工艺优化

目的 解决千斤顶上支外缘不规则曲面混合翻边成形过程中容易出现的破裂等缺陷问题。方法 基于Dynaform软件对千斤顶上支进行冲压仿真模拟,分析凸凹模圆角半径、凸凹模间隙、压边力对千斤顶上支成形的影响规律,并结合成形极限图、厚度变化云图等,采用控制变量法、正交实验对其工艺和参数进行优化。结果 经有限元分析和正交优化的千斤顶外缘曲面翻边工艺如下:凸模圆角为过渡圆角结构,其齿顶大圆角和边缘小圆角半径分别为3.5 mm和0.7 mm,凹模圆角半径为3.5 mm,凸凹模间隙为2.8 mm,压边力为50 000 N。结论 采用最佳工艺方案可生产出合格制件,实际成形件的减薄情况与模拟结果基本一致,所得成形工艺参数对制件的影响规律可为研究不规则曲面混合翻边成形提供一定的参考。     

某汽车燃料箱隔热板翻边成形工艺设计及研究

目的 为了成形高质量、少缺陷的汽车燃油箱隔热板.方法 采用整体翻边-局部反拉深的工艺方法,以隔热板曲面凸台圆角处的最大减薄率为试验指标,采取正交试验及极差分析确定最优成形工艺参数,并利用有限元数值软件对其成形过程进行模拟.结果 各因素对曲面凸台圆角减薄的影响主次顺序为:凸模下压速度、摩擦因数、凸模与顶出块夹紧力,最优成形工艺参数组合为:下压速度为10 mm/s、摩擦因数为0.12、夹紧力为40 kN.由等效应变结果分析得出,随着变形量的增加,左侧翻边曲面等效应变分布大于右侧,两侧翻边曲面交接处也积累了较大应变.实际成形件的最大减薄率为凸台位置的17.1％,满足生产要求.结论 在最优工艺参数下生产出合格隔热件,实际成形件的减薄情况与模拟结果基本一致,验证了模具设计和模拟的准确性,这对于成形结构复杂的异形构件具有一定的指导意义.     

Lasererwärmung zur Verbesserung des Umformergebnisses beim Kragenziehen von Aluminium‐ und Magnesiumknetlegierungen

Laser heating for improvement of forming results in hole flanging of magnesium and aluminium wrought alloys Warm sheet metal forming has proven itself for the production of parts made of magnesium and aluminium wrought alloys. In many cases, e.g. in deep drawing, the heating of large surfaces makes sense. If only small areas of a larger part have to be formed, as with hole flanging, a local heating by means of laser irradiation is more advantageous. So the heat quantity can be brought in well metered temporally and locally. The expanding ratio could be increased, depending on material, with a local temperature of about 200 °C by more than double in comparison to cold conditions. It was shown that a narrow process window is to be kept, since material failure arises not only from too low, but also from to high forming temperatures.     

Development of tooling concepts to increase geometrical accuracy in high speed incremental hole flanging

Incremental Sheet Forming (ISF) has been developed as a flexible manufacturing technology for small batch production and prototyping. ISF can also be used to form additional features or stiffening elements such as hole flanges. Incremental Hole Flanging (IHF) operations seem to be a promising alternative to conventional hole flanging. If it was possible to exploit the extended formability of ISF while achieving accuracy and process times of conventional hole flanging, IHF could substitute conventional flanging operations in many cases. However, the long process times and limited geometrical accuracy hinder industrial take-up. In this work, two different tooling concepts which allow incremental hole flanging operations at high speeds are investigated. The first tool is designed as a single forming tool that offers high flexibility and a comparison to conventional Incremental Hole Flanging. The second tool consists of four forming tools to improve the geometrical accuracy of hole flanges. In order to achieve high speeds, the experimental setup is installed on a turning machine. Compared to hole flanging with a conventional CNC machine, the forming time to expand a hole from 50 mm to 100 mm could be reduced from 1680 s to 15.7 s. The geometrical accuracy of the parts formed with the second tool concept could be improved significantly (up to 3 times regarding to the mean surface deviation to at maximum speed). Furthermore, it is shown that forming at high speeds has no significant influence on the characteristics of sheet thickness, strain, forces or geometrical accuracy.     

运输支板成形仿真及模具设计

目的运输支板的曲线边较长,在钣金翻边过程中易开裂,为提高模具设计的合理性,避免重复试模、返修以及设计失败的风险,开展有限元仿真研究。方法使用仿真软件Pam-Stamp,并与模具实物、产品试验件相结合,确定单动压边、双动压边翻边两次成形工艺,并优化参数、设计新模具。结果新设计的模具经过产品试验件生产,无开裂问题,目前已用于正式产品生产。结论仿真结果的成形趋势与实际生产基本符合。在选择工艺、工装设计方案时,仿真结果具有较高的参考价值。     

Innovative approach to mass production of fiber metal laminate sheets

Although, lightweight composite structures like sandwich panels and fiber metal laminates (FMLs) are greatly used as a superior material to produce modern structures to provide a substitutive item for monolithic metallic parts, but still there are some challenges in their forming process. There are some inherent limitations for forming FML parts. Also, because the strain of the fibers is limited, conventional approaches are not appropriate for forming complex-shaped laminate parts. Understanding the material behavior during the forming process is critical to find a new technique for relatively intricate and smaller FML parts. To understand the material behavior to present a new forming method, the finite element software and experiments are utilized and the thinning of layer thickness, stress distributions in different layers, and the fiber orientation are studied. Blanks made of intermittent glass fabric/fibers and Al 2024-O alloy sheets. The behavior of the material was appraised utilizing ABAQUS according to Hill yield criteria and then evaluated with the empirical outcomes. Results exhibited that FML parts manufactured by utilizing multilayer hydroforming can enhance the FML applications.     

Improving geometrical accuracy for flanging by incremental sheet metal forming

Incremental Sheet Forming (ISF) is a manufacturing technology for individualized and small batch production. Among the opportunities this technology provides there is the possibility of a short ramp-up time and to cover the whole production chain of sheet metal parts by using a single reconfigurable machine set-up. Since recent developments proved that manufacturing of industrial parts is feasible, finishing operations such as flanging and trimming gain importance, which are an integral part of manufacturing process chains of many sheet metal parts. This paper analyses the technological capabilities of performing flanging operations by ISF. Due to the localized forming zone and the absence of surrounding clamping devices, ISF exhibits a different material flow than conventional flanging processes. In this paper, the influence of the tool path characteristics, the flange length as well as the flange radius is analysed in order to establish a process window and to compare it to the process limits of conventional flanging operations. Since geometrical deviations occur when flanging operations are performed by ISF, a new adaptive blank holder is developed, which acts in the vicinity of the forming tool and reduces unwanted deformation outside the primary forming zone. The experimental results show the benefits of the adaptive blank holder with respect to geometric accuracy. The established process window and the adaptive blank holder hence contribute to the applicability of incremental flanging operations, such that ISF can be used for all forming and flanging operations along the process chain.     

汽车加油管翻边开裂原因分析

采用化学成分分析、金相检验以及扫描电镜分析等方法分析了St12铜高频焊管在制作加油管翻边过程中开裂的原因。结果表明:在St12钢冷轧板化学成分和焊缝质量均符合标准要求的条件下,裂纹主要位于距离焊缝2～3 mm的刮除毛刺区域,裂口为在翻边应变作用下因厚度方向明显减薄而开裂;开裂的主要原因是变形量过大,超过了St12钢冷轧板的变形极限。选择两种力学性能的St12钢冷轧板,通过Dynaform软件系统对加油管翻边过程进行数值仿真分析,结果显示对于变形量较大的加油管,应选择塑性应变比r值更高的深冲冷轧钢板。