冲压变形对点焊拼接板中焊点的影响

点焊拼接板的冲压成形性能是构成点焊拼接板的母材以及相应焊点冲压成形性能的综合表现。点焊拼接板冲压变形后,焊点的组织和几何尺寸的变化更是影响点焊拼接板冲压质量的关键因素。本文对点焊拼接板进行了拉伸、胀形和扩孔等典型的冲压试验,并对变形后的焊点进行了宏观和微观的分析。结果表明:在点焊拼接板冲压变形时,焊点处材料的应变远远小于其母材部分的应变;而在焊点处,焊核变形困难,较大的应变产生于热影响区。     

点焊拼接板成形极限图的试验与模拟研究

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。本文采用试验与模拟结合的方法对点焊拼接板的成形极限进行研究。结果表明:在接近双向拉伸的应力应变状态下,点焊拼接板各种场量最大值的分布具有明显的方向性。下层板的破裂危险区位于宽度方向中轴线的焊点附近,上层板的破裂危险区则位于长度方向中轴线的焊点位置;当点焊拼接板越接近双向等拉时,两个方向上变量的最大值就越接近,其破坏的几率也就越接近。     

应变分析在C柱上内板成形中的应用

通过单向拉伸实验和成形极限实验,得到板料A和B的成形性能参数,A板料的最低应变值为23%,而B板料的最低应变值为34%。在此基础上,结合仿真模拟手段,以某车型的C柱上内板为例,在相同的模拟条件下,应用A板料冲压出的零件主要失效方式为起皱和破裂,而B板料冲压出的零件具有较好的成形性,成形安全裕度较大,不存在起皱和破裂的趋势。结果表明应变分析对汽车零件成形过程中的缺陷分析和零件选材的具有重要的指导作用。     

基于Dynaform汽车前纵梁延伸件的数值模拟及优化

针对汽车汽车前纵梁延伸件,以板料成形非线性有限元分析软件eta/DYNAFORM为平台,对其冲压成形过程进行数值模拟,得到了成形工艺未优化前的成形极限图.根据模拟结果对拉延型面以及拉延筋进行改进、优化,最终消除成形过程中的缺陷.将优化结果用于指导实际生产,得到了符合质量要求的拉延零件.     

某轿车C柱内板冲压分析与成形模设计

C柱内板是轿车中重要的结构件,冲压变形复杂。首先,对C柱内板零件进行冲压成形分析,确定其成形方案和成形毛坯。在三维计算模型基础上,采用Autoform软件对零件的成形进行数值模拟,得出零件的成形极限图。根据数值模拟结果,分析零件整体成形性能、材料变薄率,预测C柱内板成形过程中的起皱、拉裂等冲压缺陷,结果表明,零件整体成形到位,材料局部位置变薄超过20%,有拉裂危险。其次,基于UG和CAD软件设计了成形模具的上模、压边圈和下模。最后,通过生产实践压制出合格的C柱内板零件,验证了冲压分析的合理性和模具设计的正确性。     

TA1纯钛板成形极限图测定及应用

采用机械划线法制作网格,利用通用板料成形性能试验机和网格拓印测量的方法,获得了TA1纯钛板在不同应变路径下的极限应变值,以此数据为基础绘制了TA1纯钛板室温下的成形极限图,并基于最小二乘法对成形极限图进行拟合建立了成形极限图的预测模型。此外,将成形极限预测模型导入到有限元模拟软件中,作为成形破裂的判据,对TA1纯钛板胀形成形的破裂缺陷进行预测,并通过工艺试验对预测结果进行了验证。对比结果表明,采用成形极限预测模型作为破裂判据的有限元数值模拟能够较为精确的预测出TA1纯钛板的极限胀形高度和胀形发生破裂的部位。     

钢板各向异性对发动机罩外板成形的影响

采用有限元软件Autoform对轿车发动机罩外板的冲压成形过程进行数值模拟,分析了钢板长宽对调后各向异性对零件成形的影响;指出了在成形过程中的高应变区域.结果表明:长宽对调前后高应变区域的应变变化很大,长宽对调前没有发生开裂,而对调后产生开裂.结合FLD,分析得出高应变区域内的应变状态为平面应变状态.     

国产轿车用冷轧薄钢板的成形性能评价

就评价国产轿车用冷轧薄钢板成形性力学性能参数做了详细的分析；并就轿车零件冲压成 的特点，将材料的ＦＬＤ图和冲压件应变图合成为零件应变极限图，从而对零件的冲压安全裕度进行评价，用于指导国产轿车用冷轧薄钢板的冲压生产。     

厚板小圆角端盖成形分析及模具设计

运用有限元分析软件eta-Dynaform对厚板小圆角端盖进行多工序成形过程模拟.通过对一组首次整形工艺参数进行有限元模拟,分析了首次整形的凸模和凹模圆角对零件多工序成形后壁厚、成形极限图的影响.从中找到一组最优化的冲压工艺参数,并成功完成了厚板小圆角端盖模具的设计.     

大型车车身覆盖件冲压成形特征分析及选材研究

为满足大型车身覆盖件冲压成形要求并实现钢板与零件的对路供应，必须在深入解析零件成形特征的基础上，确定高应变部位的成形敏感材料参数。在材料力学性能测试和成形极限分析的基础上，对侧围外板的冲压成形特征和成形敏感参数进行了分析。结果表明：侧围外板零件高应变部位的变形方式为胀形-深拉延变形，n值和r值为影响侧围外板零件成形的主要材料敏感参数。     

点焊拼接板扩孔的数值模拟

采用MSC.Dytrah对点焊拼接板的扩孔变形进行数值模拟.模拟结果表明:内缘翻边时,焊点的存在使得内缘周围的变形分布极不均匀,在有焊点分布的方向上,材料的应变分布梯度较大,而较高的应变区则沿焊点两侧分布.点焊拼接板扩孔内缘周围最大主应变的不均匀分布程度主要受变形程度和焊点位置两个因素的影响.     

Weldability criteria for mash seam tailored blank welds in ultralow carbon steel applied to automotive bodies

Abstract

Mash seam (MS) tailored blank (TB) welding is a production method for blanks involving welding together blanks of different material, thickness, and coating and is an attractive method for manufacturing car bodies because it leads to lighter parts, and can save cost and time in manufacture. However, quantified criteria to evaluate the quality of TB welds have not been developed. In the present work, the failure height ratio (FHR) was introduced to assess the weldability of MS welds, and the applicability of the FHR was confirmed via actual auto body forming and forming limit diagram tests. Furthermore, a new parameter, namely, a heat number based on the heat input calculated according to Q=I²Rt, was proposed and assessed. It was found that this heat number could be used to evaluate the soundness of MS welds.     

Static strength of hot-stamped spot welded joints: study on spot welding tailored blank technology

Hot stamping spot welding tailored blank technology is a process to produce spot welded automotive body parts by the following process: spot welding steel sheets in lap configuration → hot stamping (heating to about 900°C) → quenching and forming in water-cooled die → shot blasting to remove scale. This process has the advantage of producing high strength lap welded automotive body parts without increasing the number of forming dies. In this study, the mechanical properties of the hot stamped spot weld (spot welding → hot stamping) and conventional spot weld (hot stamping → spot welding) of the 1500 MPa class uncoated boron steel sheets were compared. The obtained results are as follows. The tensile shear strength (TSS) of the hot-stamped spot weld and conventional spot weld were comparable and the fracture modes were the same. On the other hand, the cross tension strength (CTS) of hot-stamped spot weld was significantly higher than that of the conventional spot weld. The fracture position of the hot-stamped spot weld was outside the nugget and conventional spot weld was inside the nugget. The high CTS of the hot-stamped spot welds might be caused by the improvement of the fracture toughness of the nugget, which was caused by reduction of the solidification segregation of the phosphorus. It is assumed that the heating process after spot welding leads to the reduction of the solidification segregation. For the tension test because there was no HAZ softening in the hot-stamped spot weld, no fracture was observed in HAZ and a higher elongation was obtained.     

Fatigue strength of hot-stamped spot welded joints*—study on spot welding tailored blank technology

Hot stamping spot welding tailored blank (TB) technology is a process to produce spot welded automotive body parts by the following process: Spot welding steel sheets in lap configuration → Hot stamping (Heating to about 900°C → Quenching and forming in water-cooled die → Shot blasting to remove scale). This process has the advantage of producing high strength lap welded automotive body parts without increasing the number of forming dies. In this study, the tensile shear fatigue strength of the spot welding TB joints (Spot welding → Hot stamping) and conventional spot welded joints (Hot stamping → Spot welding) of the 1500MPa class uncoated boron steel sheets are compared. The obtained results are as follows. The fatigue life of the spot welding TB joints was more than two times longer than that of the conventional spot welded joints. The long fatigue life of the spot welding TB joints was not caused by the heating and quenching process but by the shot blasting process after heat treatment. Shot blasting on the outer sheet surface caused the high compressive residual stress on the outer surface and did not affect the residual stress on the lapped surface. Shot blasting on the outer sheet surface increased the initiation life of fatigue crack which occurred on the lapped surface and also reduced the crack propagation speed which propagates from the lapped surface to the outer surface. FE-analysis suggested that compressive residual stress on the outer surface reduce the opening of sheet separation of joints in fatigue tests and reduce the maximum principal stress around the edge of corona bond.     

激光焊接的裁焊板及其在汽车中的应用

介绍了激光焊接用于汽车裁焊板的新技术。使用裁焊板可以实现汽车部件尺寸和材质的优花配合。与滚压缝焊相比，激光焊接具有焊接质量高、适应性广、生产费用和维护费用低的优点，特别适合进行裁焊板的焊接加工。激光焊接裁焊板的技术问题主要有：采用激光切割坯板方案的可行性、接头的成形性、焊接质量的控制和大板拼接变形的控制。     

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,文中还介绍了高速杯突成形目前常用模拟仿真方法,最后对高应变率成形极限图测试研究进行了展望。     

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.     

Superplastically Formed Friction Stir Welded Tailored Aluminum and Titanium Blanks for Aerospace Applications

The purpose of this study was to develop a specialized friction stir welding process for superplastic grade aluminum alloy 5083-SP and titanium alloy 6Al-4V, in thickness of 1.5-4 mm, such that the butt welded nugget would have equal superplastic forming (SPF) characteristics as the parent sheet material. The concept of using tailored blanks for the SPF process is proposed which will allow the joining of multiple pieces to fabricate much larger monolithic components than has been possible in the past. Another benefit of using tailored blanks for SPF applications was found to be a more closely matched blank shape relative to the plan size of the SPF forming die. However, shape of the tailored blanks is critical in SPF of a component. An example of this might be the case where a polygon-shaped blank might work in order to reduce the amount of material used, but a rectangular blank is currently used because a tailor made blank with superplastic joints was not found to be technologically feasible. Upon development of a suitable FSW process for each material, the technology was applied to fabricate full scale test components representing a generic jet engine nacelle Lipskin.     

一种建立板料成形极限应力图的新方法

基于塑性理论建立了比例加载条件下双向拉伸应力应变关系,结合Swift分散性失稳准则,提出了一种建立板料成形极限应力图的方法。分别应用Hill 48和Hosford屈服准则以及单向拉伸性能参数,建立了铝合金板(r<1)和薄钢板(r>1)两种材料的成形极限应力图(FLSD),分析表明,不同的屈服准则的选取对于成形极限应力曲线有不同的影响,对于不同类型的材料屈服准则的影响程度也不同。与由通常的成形极限图(FLD)转换所得到的成形极限应力图(FLSD)进行了对比分析,结果表明,所提出的方法计算过程更为简便,并能较为准确地建立成形极限应力图,可以作为复杂加载路径下的成形极限破裂判据。