Surface topography evolvement of galvanized steels in sheet metal forming

U-channel forming tests were performed to investigate the surface topography evolvement of hot-dip galvanized(GI) and galvannealed(GA) steels and the effects of die hardness on sheet metal forming(SMF). Experimental results indicate that the surface roughness values of the two galvanized steels increase with the number of forming, i.e., the surface topographies of galvanized steels are roughened in SMF. Moreover, GI steel has a better ability of damage-resistance than GA steel. The mechanisms of topography evolvement are different in the forming of GI and GA steels. Scratch is the main form of surface damage in the forming of GI steels. The severity of scratch can be decreased by increasing die hardness. GA steel results in exfoliating of the coating firstly and then severe scratching. The surface topography of galvannealed steels can be improved by increasing die hardness. However, the hardness should not be too high.     

工业AA1200铝合金薄板拉伸成形模拟和实验研究(英文)

对工业AA1200铝合金薄板拉伸成形的模拟和实验结果进行比较和评估。采用单向拉伸试验得到模拟所需输入参数。根据von Mises和Hill-1948屈服准则,采用Abaqus/Explicit有限元软件分析成形过程。将冲压力和应变分布的模拟结果与实验结果进行比较和验证。结果表明:在这两种情况下,使用各向异性屈服准则模拟的结果与实验结果更吻合。     

ZE10镁合金板拉胀复合成形与扩孔成形性能研究

为研究ZE10镁合金的成形性能,在20～300℃条件下对ZE10镁合金板进行拉伸力学性能、锥杯及扩孔试验.结果表明:随着变形温度的升高,ZE10镁合金板的抗拉强度逐渐下降而伸长率、“拉深 胀形“复合成形性能、扩孔成形性能显著提高.200℃、250℃锥杯实验时,ZE10镁合金试样可顺利拉深进入锥杯凹模底部直圆孔而不出现开裂,具有较小的锥杯值;而300℃时反而增加,说明在200℃、250℃时ZE10镁合金具有最佳的拉胀复合成形性能.150℃、200℃扩孔试验时,试样中心φ10 mm预制孔可胀大到凸模直径φ25 mm大小,成功实现翻边(翻边系数为0.37),显示ZE10镁合金具有很好的扩孔成形性能.     

On the effects of predeformation on work hardening of ultra-low-carbon sheet steel

Predeformation affects the work-hardening behavior of sheet metals in sequential forming operations by producing various strain histories in different parts of the sheet. Several investigators have reported the effects of two-stage deformation on the behavior of sheet metals, particularly justification has been presented on face-centered cubic (fcc) alloys. However, the works on low-carbon ferritic steels are not conclusive. This article reports some new findings of the effects of two modes of predeformation on the subsequent stress-strain relationship in ultra-low-carbon sheet steels. The details of a laboratory test system are presented along with methods used to reduce the data. The effect of the stability ratio, a measure of the degree to which the interstitial atoms are free, on the hardening rate at second-stage of deformation was studied. For stabilized sheet steels, it was found that changes in strain path from equibiaxial stretching to uniaxial tension cause an increase in the flow stress relative to the flow stress at similar effective strain in continued monotonic. For unstabilized sheet steels, a significant increase in the flow stress was not observed with either equibiaxial prestraining or cold rolling and equibiaxial stretching.     

可重构柔性模具蒙皮拉形有限元等效模型

等效模型是模拟计算精度和现实计算能力矛盾的产物。从实际生产工艺出发,在PAM-STAMP2G中构建贴近实际生产过程的可重构柔性模具蒙皮拉形有限元模型。鉴于该有限元模型模拟效率低的缺陷,从可重构柔性模面和弹性垫层描述两方面进行简化,引入5种等效模型。分析结果表明,光滑连续模面包覆垫层有限元模型,能够在保证模拟精度的前提下获得较好的模拟效果。在此基础上,提出连续模面单层实体单元包覆垫层等效模型,当弹性垫层厚度小于30mm时,它和连续模面多层实体单元包覆垫层等效模型有相同的模拟效果。     

汽车高强度钢板冲压件热成形技术研究

介绍了热成形技术的原理,分析了加热温度、加热时间、成形速度、冷却速度等工艺参数对热成形过程的影响,并选取汽车典型件成功进行了热成形工艺实验试制,获得了合格的成形件。检测结果表明,成形件的微观组织为理想的条状马氏体,抗拉强度达到1500MPa,完全满足生产要求。     

实用钣金展开CAD系统的开发技术与应用研究

在分析钣金展开计算和绘图方法的基础上，详细地讨论了实用钣金展开CAD的系统结构和开发方法。最后结合钣金展开应用实例。系统地说明利用几何数学计算法结合计算机辅助设计和AutoCAD系统的绘图环境，如何进行钣金件展开计算，自动生成钣金展开图和相应的展开计算数据文件。目前，该方法已经成功地用于开发钣金展开CAD系统。     

拉形与渐进成形在钣金零件快速制造中的复合应用研究

分析了拉形与数控渐进成形的工艺特点,开发了利用有限元分析来确定拉形不贴模区域边界的系统;设定了复合成形工艺参数,在数控渐进成形机床上实现一次装夹的复合成形。通过试验对渐进成形和复合成形的成形件质量进行了分析,结果证明,复合成形比渐进成形加工的零件成形精度高,厚度分布更均匀。对于复合成形,拉形行程越大,精度越高,但厚度减薄更严重,拉形行程过大会导致零件拉裂。凹陷区域的成形采用了固定轴跟随零件层加工,与传统的等高线层加工相比,具有较好的表面质量和较高的精度。     

汽车用双相钢钢板的发展

介绍了双相钢钢板的发展史,其强化机制、典型的显微组织以及性能方面的特点。国外的双相钢研究进展以及生产能力,国内的研究情况及生产现状。预测了其发展前景。     

In-situ springback compensation in incremental sheet forming

Limited geometric accuracy in incremental sheet forming is a major obstacle for its wide adoption in industry. This paper develops a generic methodology, suitable for arbitrary part geometries and various ISF processes, for addressing one of the main causes of geometric inaccuracy, i.e., in-process springback. The methodology consists of three main elements: determination of key control points to treat geometric complexity, simplified simulation models to predict springback offline, and in-situ toolpath modification during forming. It is shown experimentally that the method provides an efficient and robust solution for various geometries with negligible setup cost.     

TA2纯钛板的成形极限

为了探究TA2纯钛板的成形极限,通过电化学腐蚀方法印制网格,在室温下使用BCS-50AR板材试验机分别对厚度为0.5和0.8 mm的TA2纯钛板进行了Nakizima胀形试验.通过网格分析系统采集网格的畸变,获得材料的主、次应变,并绘制了TA2纯钛板在室温下的成形极限图.根据单位体积塑性功相等的原理改进了Hill48屈...     

DC04钢板胀形-渐进复合成形锥形件成形能力的实验研究

为了提高渐进成形过程中板料的成形极限和加工效率,提出了胀形-渐进成形的复合成形方法,通过胀形-渐进成形复合成形锥形件实验,研究了DC04钢板胀形-渐进成形复合成形锥形件和纯渐进成形锥形件的成形极限角和应变变化以及壁厚分布规律。结果表明:预成形高度为h=15 mm和h=25 mm时,复合成形零件的成形极限角分别为α极=66°和α极=69°;采用胀形-渐进成形复合成形锥形件,当胀形的最大减薄量发生在局部渐进成形区内,并且胀形和渐进成形的最大减薄量位置方向相反时,锥形件壁厚趋于均匀,提高了胀形-渐进成形的复合成形能力。     

A new incremental in-plane bending of thin sheet metals for micro machine components by using a tiltable punch

This paper proposes an innovative incremental in-plane bending of thin metal sheets for manufacturing microscopic machine components. The unique feature of the process is that a tiltable punch having a beating face with trapezoidal profile is used. The beating face enables the punch to bend thin metal sheets in in-plane manner. Working conditions, including indentation and feeding pitch, can easily and flexibly control the bending radius and even the bending direction. The in-plane bent thin sheet products are expected to be used as springs, conical cylinders, bushes and other components of micro machines such as medical instruments.     

双凸板材件的数控渐进成形研究

针对数控渐进反向成形中无法直接成形加工双凸板材件的问题,提出了基于双面挤压的双凸板材件数控渐进反向成形方法。该方法通过设计从正反两面可接近各形体的支撑模,并把板材用两个支撑模装夹,从正反两面挤压板材来实现双凸板材件成形。给出了双凸板材件的成形工艺方案和支撑模设计方法,研究了双凸板材件数控渐进反向成形过程数字模拟分析的方法并运用数值模拟分析了该方案的可行性,并且通过成形试验,完成了双凸板材件的制作。研究结果表明,基于双面挤压的数控渐进反向方法可应用于双凸板材件的制作。     

A geometrical model of the kinematics of incremental sheet forming for the prediction of membrane strains and sheet thickness

The sine law is a simple geometrical model for incremental sheet metal forming (ISF). It is based on the assumption that the deformation is a projection of the undeformed sheet onto the surface of the final part. The sine law provides approximations of sheet thinning for shear spinning and ISF at negligible computational cost, but as a plane strain model it can be applied only when plane strain deformation prevails.     

热基镀锌高扩孔钢的组织性能研究及其工业试制

热基镀锌是提高高扩孔钢耐腐蚀性能的重要手段之一。利用光学显微镜、扫描电镜、拉伸试验机和成形试验机等设备,研究了退火温度对铁素体贝氏体型高扩孔钢组织性能的影响,并进行了450 MPa级热基镀锌高扩孔钢的工业试制。结果表明:随退火温度由710 ℃升高至790 ℃,钢中渗碳体颗粒逐渐溶解,贝氏体体积分数先升高后降低,铁素体晶粒尺寸先增大后趋于稳定,屈服强度和抗拉强度先升高后降低,断后伸长率先降低后升高。不同退火温度下,试验钢的扩孔率均达到85%以上。工业试制产品具有良好的组织和性能均匀性,其横向屈服强度为396 MPa、抗拉强度为477 MPa、断后伸长率为27.5%、烘烤硬化值为42 MPa、扩孔率大于80%,各项性能均达到标准要求。     

板材冲压成形回弹模拟的评述

回弹是板材成形过程中不可避免的一个普遍现象,直接影响到冲压件的尺寸精度和零件最终形状.因此,回弹模拟是板材成形过程模拟中的一个关键问题,也是最为棘手的问题.本文在系统地归纳了国内外众多学者在应用有限元技术进行回弹模拟研究的基础上,对回弹模拟的历史发展、回弹模拟的计算方法、影响回弹模拟的主要因素以及回弹的预测和补偿等方面作了详尽的论述,对回弹模拟研究有着很好的参考价值与指导意义.     

板料直壁零件数控渐进成形

板料直壁零件成形是渐进成形的难点之一。为了成形直壁零件,一般采用多次成形的方法。文章对直壁零件多次成形法从理论上进行了分析,并且通过实验,验证了这种方法的正确性。     

Investigation into a new hybrid forming process: Incremental sheet forming combined with stretch forming

Asymmetric incremental sheet forming (AISF) is a process for the flexible production of sheet metal parts. In AISF, a part is obtained as the sum of localised plastic deformations induced by a simple forming tool that moves under CNC control. Three main problems exist in AISF: material thinning, geometric accuracy and the process duration. These limits restrict the range of applications of AISF. This paper focuses on a new hybrid process, the combination of AISF and stretch forming. First results are presented that show the positive impact of this hybrid process on the process limits.     

金属板材单点渐进成形过程的数值模拟

利用有限元软件LS_DYNA模拟金属板材单点渐进成形过程。并利用LS_DYNA的显式求解器分析当压头压下时,不同压头半径条件下,压头与板材接触区域的应力分布。根据对模拟数据的分析比较,讨论不同压头半径对板材成形时的影响。