钛及钛合金板材冲压成形及有限元模拟

综述了钛及钛合金薄板的塑性及冲压成形性,在此基础上研究了钛板冲压成形的影响因素,着重分析了压边力、模具尺寸对钛板冲压成形的影响。然后介绍了有限元模拟的基本原理及壳单元、本构方程的选择,并利用DYNAFORM软件模拟了TA2纯钛半球形工件的成形过程,并对压边力进行优化,得出最适压边力范围为27~37 kN。     

铝合金半球形件拉深的变压边力优化研究

为获得铝合金半球形件的优化压边力,提出了成形结果的综合评价标准用于不同变压边力曲线模拟实验的评价,以正交实验法设计模拟试验获得样本,建立了预测不同压边力曲线下成形结果的神经网络模型。在精度可靠的神经网络基础上,运用遗传算法优化压边力,获得了先增后减的“最优”压边力曲线。     

基于Yoshida材料模型的帽形件回弹仿真分析

以1. 2 mm厚HC340/590DP帽形件为研究对象,采用Dynaform冲压仿真和冲压试验相结合的方法,探究了压边力、成形间隙、翻边角度等工艺参数对回弹的影响。结果显示,采用考虑随动硬化的Yoshida材料模型计算的回弹结果与试验测量结果的变化趋势一致,成形、翻边模拟结果精度在75%以上。对于帽形件的回弹,改变成形工艺对回弹量的影响最大,调整成形间隙或翻边角度也有一定影响,但在一定范围内调整压边力对回弹量的影响不大。     

压边力和液压力对椭球形件充液拉深成形的影响

起皱和破裂是板材零件的两大缺陷。充液拉深成形是一种新的塑性加工工艺,可以改善曲面形零件的成形质量。压边力和液压力是该工艺的关键参数。利用Dynaform有限元分析软件研究了旋转椭球形件在恒压边力变液压力、变压边力变液压力情况下的充液拉深成形情况。模拟结果表明,压边力和液压力的加载路径对于零件的成形有明显的影响,采用变压边力变液压力技术可以得到不破裂、不起皱、减薄率小、厚度均匀的零件,在很大程度上改善了零件的成形效果。     

热冲压工艺参数对零件成形性影响规律分析

主要研究了热冲压工艺参数对热冲压后零件成形性的影响规律。热冲压工艺参数主要包括冲压速度、压边力、摩擦因数和板料温度,每个工艺参数均分为低、中、高3个水平。结合测试方案设计和仿真模型,利用方差分析研究不同工艺参数对零件成形性的影响程度;同时,利用量化分析方法确定不同水平的工艺参数对零件成形性影响程度的量化值。结果表明,工艺参数对零件减薄率的影响程度由重到轻的顺序为摩擦因数、板料温度、冲压速度和压边力,其中摩擦因数影响程度的量化值约为97.3%。     

基于Autoform软件的汽车行李箱板冲压成形模拟

基于Autoform软件,讨论了汽车覆盖件参数化设计的方法,包括冲压方向、压料面、工艺补充面、等效拉延筋的生成方法。通过汽车行李箱板冲压成形过程仿真,得出可能出现的破裂、起皱等板料缺陷,调整压边力、等效拉延筋等工艺参数,使产品冲压成形工艺达到优化。结果表明,利用Autoform软件能快速地确定压边力大小,优化板料尺寸和形状,有利于减小产品研发周期、提高产品质量。     

圆锥形零件冲压成形皱曲和破裂三极限的预报与控制

根据变形区“多余三角形材料皱曲模型”和防皱曲压边力分别导出外皱曲极限预报与控制判据和内皱曲极限预报与控制判据,以及防外皱曲压边装置的选择判据和防内皱曲压边装置的选择判据。依据破裂模型和拉深变形力导出破裂极限的预报与控制判据,最后给出了圆锥形零件冲压成形皱曲和破裂三极限的预报与控制判据和图形。依据选定的压边力可计算出拉深变形力。实验验证和对比结果证明,将上述判据用于圆锥形零件冲压成形皱曲和破裂三极限的预报与控制是相当准确的     

钛及钛合金板材拉深成形的影响因素与技术进步

钛及钛合金相对铝、钢等金属材料塑性差、极限变形量小、成形时回弹大,拉深成形相对困难。介绍了钛及钛合金拉深成形的影响因素及其对成形的影响,综述了钛及钛合金拉深成形在各向异性控制、压边力控制、计算机模拟以及加热方法等方面的技术进步,指出了未来研究人员应充分利用计算机模拟技术,对影响钛及钛合金冲压成形的各种因素及其之间的相互关联建立详尽的数据库,以便该成形工艺在钛及钛合金零部件的成形得到更广泛的应用。     

基于ABAQUS的板材精冲工艺研究

构建厚度为1.5mm的板材精密冲裁有限元模型,分析板材精冲的变形过程.通过大量有限元模拟,重点分析压边力和反压力对精冲断面质量的影响规律,并将模拟结果和试验结果进行对比分析.结果表明:当压边力不变时,随着反压力的增大,精冲断裂带长度不断减小,而断面平整度逐渐变差;当反压力不变时,断裂带长度不随压边力的增大发生较大改变,但断面平整度提高;当压边力和反压力相互配合时,冲孔断裂带最小,断面平整度最好;模拟结果与试验结果非常接近,说明压边力对精冲断面质量影响规律的模拟结果准确.     

板材质量对冲罐工艺及罐性能的影响(下)

2.对冲杯过程的影响冲杯过程是带压边圈的拉探过程,变形区是产生塑性变形的法兰区。冲杯过程的主要能量消耗在法兰变形区,其他部分是传力区不参与主要变形,但是极限变形参数却主要受毛坯传力区的承载能力限制。法兰部分是在切向压应力和径向拉应力的作用下产生切向压缩和径向伸长的—向受拉—向受压变形。因毛坯边缘变厚,故压边力是不均匀分布在全部法兰面积上,而是集中在离毛坯边缘一定距离的环形面积上,其余部分则无压边力作用。此环形区除了受平面切向压缩应变和径向拉伸作用外,还承受轴向压边力。压边力的作用主要是防止产生皱折,但过大将增大毛坯的径向拉应力。     

退火和平整工艺对08Al钢冷轧包芯线用冷轧薄带力学性能的影响

试验研究了退火工艺(820℃连续退火,670℃罩式退火和730℃罩式退火)和平整延伸率(0.8%,1.2%和1.5%)对包芯线用08Al钢(0.07%C,0.05%Al,0.0040%N)0.4 mm冷轧薄带组织和性能的影响。结果表明,连续退火薄带组织为铁素体+珠光体,屈服强度(300 MPa)和屈强比(0.78)高,延伸率(35%)较低,塑性差,不适合压制成形;730℃罩式退火薄带晶粒粗大,不均匀,成形性能差;670℃罩式退火薄带组织为再结晶铁素体和呈点链状的游离渗碳体,屈服强度(252 MPa)和屈强比(0.69)低、延伸率(48%)较高,成形性能好;随平整延伸率的增加,屈服强度和屈强比先降低后升高,延伸率下降。合适的平整率应控制在1.2%左右,成形性能最佳,应用效果良好。     

Development of a Robot‐Based Sheet Metal Forming Process

This paper describes a new sheet metal forming process for the production of sheet components for prototypes and small lot sizes. The generation of the shape is based on kinematics and is implemented by means of a new forming machine consisting of two industrial robots. Compared to conventional sheet metal forming machines, this newly developed forming process offers a high geometrical form flexibility, and comparatively small deformation forces enable high deformation degrees. The principle of the procedure is based on flexible shaping by means of a freely programmable path‐synchronous movement of the two robots. The final shape is produced by the incremental infeed of the forming tool in depth direction and its movement along the contour in lateral direction at each level of the depth direction. The supporting tool with its simple geometry is used to support the sheet metal and follows the forming tool at the rear side of the sheet metal. The sheet metal components manufactured in first attempts are of simple geometry like frustum and frustum of pyramids as well as spherical cups. Among other things the forming results are improved by an adjustment of the movement strategy, a variation of individual process parameters and geometric modifications of the tools. In addition to a measurement of the form deviations of the sheet with a Coordinate Measurement Machine, screened and deformed sheets are used for deformation analyses. Furthermore, the incremental forming process is analysed with assistance of the finite element method. In total the results show that a robot‐based sheet metal forming with kinematic shape generation is possible and leads to acceptable forming results. In order to be able to use the potential of this process, a goal‐oriented process design is as necessary as specific process knowledge. In order to achieve process stability and safety, the essential process parameters and the process boundaries have to be determined.     

Modeling of continuous strip production by rheocasting

A process was experimentally and mathematically modeled for continuous and direct production of metal strip from its molten state by the use of Rheocasting. The process comprises 1) continuous production of a Rheocast semisolid alloy, and 2) direct shaping of the semisolid into strip. Sn-15 pct Pb was used as the modeling alloy. Crack formation and surface quality of the strip produced depend on fraction solid and deformation force. Continuous, sound strip could be obtained with good surface quality when fraction solid was between 0.50 and 0.70 and deformation force did not exceed a given maximum. Sheet thickness depends on deformation force, fraction solid, rotor rate of Rheocaster and production line speed. At constant deformation force, sheet thickness increases as fraction solid increases, rotor rate decreases and line speed is reduced. Sheet thickness is larger in the center than in the edge, but the difference is reduced by applying edgers. Some segregation of lead toward the edges is observed, and the segregation increases as amount of deformation is increased. A mathematical model for heat flow, solidification and deformation was constructed. The model predicts the point of completion of solidification in the strip and sheet thickness as a function of deformation force and line speed. Calculations are in good agreement with experimental results. T. MATSUMIYA, formerly with Massachusetts Institute of Technology, Cambridge, MA.     

薄规格箱板在1422热连轧产线上生产研究

在1422热连轧产线上生产宽薄规格集装箱板(如1.6 mm×1 185 mm)的试轧初期,存在较多问题：如因精轧机组负荷偏大,要求中间坯厚度较薄,同时要提高出炉温度,但会带来表面氧化铁皮问题,后段轧机没有钢也会出现压靠(即负辊缝)导致有钢信号提前产生以及活套偏高等问题;通过优化出炉温度、除鳞制度、有钢信号的逻辑条件、活套的张力系数以及精轧机架的负荷分配等手段,有效地解决了上述问题并提升了实物质量。     

热轧U型钢板桩精轧过程金属流动行为的有限元分析

针对热轧U型钢板桩(SY390BZ/%:0.23C、1.60Mn、0.44Si、0.18V,0.18Ti、0.05Nb)轧制过程中产生翘曲缺陷,采用有限元分析软件ABAQUS显式动力学算法,结合实验室试验测量参数,对钢板桩的精轧过程进行了仿真计算。在仿真计算的基础上,根据轧制平面内节点位移矢量分布情况,分析了轧件横向和纵向断面内金属流动规律。模拟结果显示轧件断面在孔型轧制的压下方向上存在零位移线,表明U型钢板桩轧制中坯料翼缘和锁口处在轧制压力方向上轧件内金属流动存在位移中性面,并伴有轧件锁口凸缘处金属流动过快,腹板处金属流动较慢而产生翘曲的现象。     

Ensuring Specified Surface Roughness in the Production of Thin Cold-Rolled Steel Sheet

The formation of surface microrelief on rolled strip is considered. The influence of the surface state of the rolls, the strip reduction, the rate of reduction, the mechanical properties of the metal, the lubricant employed, and other rolling and tempering parameters on the roughness of cold-rolled steel strip is analyzed. Practical means of ensuring compliance with the surface-roughness standards for thin sheet are proposed.     

Simulation of the shaping of blanks for large-diameter pipe

An analytical method is outlined for calculating the bending parameters of thick sheet (thickness up to 40 mm) used in pipe production: the size and shape of the punch-blank contact zone; the elasticity coefficient of the blank and its residual surface curvature; the maximum force of the punch at different stages of stepwise shaping on a press. At all stages of the process, the model of an elastoplastic medium is employed. The results may be used in developing production technologies for large-diameter steel pipe used in pipelines.     

Preventing surface defects in the uncoiling of thin steel sheet

The formation of surface defects when annealed thin cold-rolled steel sheet is uncoiled for temper rolling is analyzed. The appearance of such defects is mainly due to adhesion and welding of the contacting surfaces of the turns in the coil. The influence of the strip thickness, surface roughness, temperature, properties of the metal, and other factors on the stress–state of the coil and the likelihood of surface defects is analyzed. Preventive measures are recommended.     

Elastoplastic shaping of metal in an edge-bending press in the manufacture of large-diameter pipe

An analytical method is outlined for calculating the edge-bending parameters of thick sheet: the size and shape of the thick sheet in shaping and after shaping on an edge-bending press; the spring-action coefficient; and the residual curvature of the edge. At all stages of the process, the model of an elastoplastic medium is considered. The results may be used in developing a production technology for large-diameter steel pipe used in oil pipelines.     

不锈钢电磁约束成形的稳定性分析

金属熔体电磁约束成形的稳定性始终是困扰该技术进一步发展和阻碍其大规模推广应用的难题，尤其是大比重合金的稳定成形更加困难。为此，作者对电磁约束成形过程中熔体的温度和熔体受力随电流的变化过程以及上、下液一固界面处于不同位置时熔体表面的受力状况进行了理论分析，并对制备圆形1Cr18Ni9Ti不锈钢试件和大宽厚比矩形截面不锈钢试件的电磁约束成形方法的稳定性进行了实验研究。结果表明：电磁约束稳定成形时，熔体的上液一固界面应位于合适位置，下液一固界面必须高于临界位置；熔体的静压力对电流变化非常敏感，且随熔体密度的增加而增大；另外，电磁约束成形实验还表明，熔体静压力对电流也非常敏感，这与理论分析结果一致；而且在变截面电磁成形中，当成形试件与棒料的截面比大于1时，随截面比及抽拉速率的增加，熔体的成形稳定性变差，所以变截面电磁约束成形时截面比和速率都不宜太大。