多夹钳式柔性拉伸成形时过渡区长度的研究

多夹钳式柔性拉伸成形是一种新型的柔性成形工艺。以球形曲面件为研究对象,建立多夹钳式柔性拉伸成形时的有限元模型;对比分析不同过渡区长度对成形力、应变分布、厚度分布及回弹的影响,同时分析应变值及应变分布状态对成形件回弹的影响。结果表明,多夹钳式柔性拉伸成形时,过渡区长度越小,板料越容易贴模,所需的成形力越小,成形件的应变及厚度减薄越小,并且应变及厚度分布越均匀,越显著提高成形件质量;尤其是在过渡区长度为0时也能够圆满地完成板料成形,显著提高材料利用率,节省制造成本。另外与增加应变大小相比,提高应变均布程度可以更有效地减小回弹,在自主研发的多夹钳式柔性拉伸成形机上对数值模拟结果进行试验验证。     

多点数字化拉形成形性能的数值模拟分析

以鞍形曲面蒙皮件为例,对多点数字化拉形过程进行了数值模拟分析.通过模拟所得到的最佳水平预拉力与实际拉形工艺中通过经验公式确定的值相符,验证了算法的准确性.从材料、板厚、曲面形状和变形程度等方面入手分析多点数字化拉形的成形性能,结果表明:随着板料厚度减小、变形程度增大,板料起皱的趋势增大,并且不同的曲面形状及材料对板料的成形结果都有影响.同时给出了临界变形量极限图.研究结果为多点数字化拉形技术的实用化提供了重要依据.     

板料柔性拉边成形与压边成形方式的比较

柔性拉边成形是在已有冲压成形工艺的基础上结合柔性拉形原理诞生的一种新型板料柔性成形方法。用柔性拉边技术代替传统压边技术,可实现球形件、鞍形件、盒形件、非规则曲面件及带凸台曲面件等三维曲面件的柔性成形。探讨柔性拉边成形原理及工艺,建立柔性拉边成形过程的有限元模型;为验证柔性拉边成形工艺的可行性和通用性,建立鞍形件多点模具成形及带凸台曲面件整体模具成形过程的有限元模型,通过对比分析拉边成形和压边成形方式,研究不同成形方式对板料起皱拉裂缺陷、应力应变分布、流动及回弹情况的影响。结果表明:压边成形时,板料容易产生起皱、拉裂等缺陷,较难得到高质量的成形件;而在相同条件下,采用拉边成形方式所得成形件应力应变分布均匀、回弹小,拉边力抑制起皱、拉裂等缺陷的产生,同时板料流动更均匀。     

沟球断面环件冷辗扩三维有限元模拟与工艺设计

沟球断面环件冷辗扩是滚珠轴承套圈制造新工艺。以有限元软件Abaqus为平台,根据冷辗环机实际工作条件,建立从矩形断面毛坯冷辗扩成形沟球断面环件的三维弹塑性动力显式有限元模型。通过动力显式有限元数值模拟,研究沟球断面环件冷辗扩变形过程,揭示出该环件冷辗扩中直径增长和圆度变化规律。基于数值模拟结果,优化设计矩形断面环件毛坯尺寸和冷辗扩工艺参数。在D56G90冷辗环机上进行沟球断面环件冷辗扩试验,验证了数值模拟结果,并采用矩形断面环件毛坯成功冷辗扩出了沟球断面轴承套圈。     

带缺口筒形件毛坯展开的数值模拟分析

以一个带铂格矩形缺口的圆筒形拉深件为对象,分析了其成形规律和毛坯展开件形状和尺寸的特点,并用有限元分析软件DYNAFORM-PC对其成形过程进行了数值分析。模拟过程更直观地再现了该零件的冲压成形过程。模拟结果与试模样件基本一致,表明用数值模拟的方法确定大型、复杂冲件的毛坯较试模方法确定毛坯有着明显的优越性。     

基于BEW盒形件的成形工艺研究

以典型盒形件为例,基于毛坯展开和产品成形性分析软件———BEW软件,利用UG NX8.5建立了实体模型,分析了该矩形盒形件的毛坯展开和拉深成形性能,保证了毛坯形状尺寸和零件精度要求,达到了盒形零件的工艺要求。     

曲面形零件的拉深成形

曲面形状零件是指那些非平底、非直壁零件,包括有:球面形状零件、抛物面形状零件、锥形零件以及诸如汽车覆盖件一类的零件。这类零件在拉深成形时,整个坯料都是变形区,因为它不仅要求其外法兰部分产生拉深时相同的变形,而且还要求其中间部分由平面变成曲面或斜面,也成为了变形区,因此,可以说曲面零件成形是拉深和胀形两种变形方式的复合。 曲面形状零件拉深成形后实测变形数值如图1所示。图1a是电动喇叭罩变形分布示意(材料为08     

梯形轴承外圈冷辗扩的有限元模拟

基于阶梯形环件轧制理论,初步设计模具、毛坯和工艺参数,应用Abaqus软件建立轧制的三维模型,并利用Abaqus/Explicit显式算法对阶梯形环件轴承外圈的冷辗扩成形进行模拟分析,揭示出梯形环件轧制缺陷的成形机理和轧制过程中金属流动的特性.并在KKD160精密辗环机上进行轧制试验,验证了毛坯和模具的形状合理.     

毛坯外形对盒形件拉深成形的影响

盒形件是典型非轴对称件，其拉深成形是一种包含几何非线性、材料非线性，接触非线性的强非线性问题的复杂力学过程，影响因素很多，规律难以定量表达，用ANSYS有限元软件，模拟了在同一套模具和成形条件下，不同毛坯外形的盒形件成形过程，找出了毛坯外形对盒形拉深件应力应变影响规律，并用实验验证了模拟结果的可靠性。     

斜壁矩形盒件多点拉深成形的数值模拟

通过对斜壁矩形盒件多点拉深成形的有限元数值模拟,分析了成形过程中起皱与拉裂缺陷的产生,研究了四种不同压边力加载曲线即恒压边力、↘形压边力曲线、V形压边力曲线、■形压边力曲线对成形结果的影响。结果表明:斜壁矩形盒件在整个多点拉深成形过程中,在宽度方向的侧壁底部极易发生破裂缺陷,在法兰直边对称轴处起皱最严重;不同的压边力曲线对斜壁矩形盒件多点拉深最终成形结果的影响很大,其中■形状的压边力加载曲线最有利于斜壁矩形盒件的多点拉深成形。     

防皱多点成形及其误差分析

防皱多点成形是一种在调形单元之间布置防皱单元,使防皱单元与调形单元交错排列,从而在成形区内对板料表面进行约束,无需压边圈就可以产生防皱效果的多点成形方法。以球形件为例,运用有限元法针对起皱问题比较防皱多点成形和多点模具成形的成形效果。分析防皱多点成形在采用不同工艺参数时的成形误差,并探讨防皱多点成形对成形较小尺寸件的成形质量。研究发现,防皱多点成形方法能够很好地抑制板料在成形过程中的起皱现象;防皱多点成形时的球形件边缘的成形误差大于其内部区域的成形误差,减小防皱单元压力能够减小成形误差,但同时也会相应降低防皱单元的防皱能力;防皱多点成形采用头部具有转动自由度的单元能够增大单元与板料的接触面积,降低其成形误差;当防皱多点成形采用具有转动自由度的单元,并保证板料边缘外侧多设置一排单元时,成形件具有较高的成形质量。     

Modeling and numerical simulation of multi-gripper flexible stretch forming process

Multi-gripper flexible stretch forming (MGFSF) is a recent technological innovation of sheet metal forming process. Straight jaws in traditional stretch forming machines are substituted for a pair of opposed clamping mechanisms movable relative to each other during the forming process. In this paper, spherical part is selected as the study object, and numerical simulations of the MGFSF process under two representative loading paths of horizontal-vertical (HV) loading path and horizontal-tilting-vertical (HTV) loading path have been carried out using a commercially available FEM software (ABAQUS). Four levels of horizontal forces in HV loading path are selected to investigate their influences on strain and forming error distributions of the simulated parts. In addition, four levels of tilting forces in HTV loading path are also taken into consideration. The simulation results reveal that HV loading path would result in a larger strain but a smaller forming error in the forming zone. In contrast, HTV loading path would result in a smaller strain but a larger forming error in the forming zone. Finally, experimental validations are conducted on self-developed apparatus, and the experimental results show a good correlation with the simulation results.     

基于铸辗复合成形的42CrMo钢环坯铸造工艺与试验研究

针对目前环形零件生产工艺流程长,加热次数多,浪费材料和能源等问题,提出和研究环形零件短流程铸辗复合成形新工艺。该工艺采用铸造环坯直接辗扩成形,具有节能、节材和缩短工艺流程等优点。在这种新工艺中,环坯的铸造质量、组织和力学性能对后续的辗扩工艺和环形零件组织、性能具有重要的影响。以轴承环件常用的42CrMo钢为研究对象,通过理论分析和模拟研究,提出高质量环形铸坯铸造工艺;并进行实际工业试验。通过试验研究和性能测试,表明该铸造工艺生产的环形铸坯具有良好的质量、组织和力学性能,可以为轴承环件铸辗复合成形提供高质量的铸坯。     

板料成形坯料形状与应变分布的快速精确预测

采用有限元逆算法和四边形单元开发了板料冲压成形与模具设计快速分析软件FastAMP。模拟了比较典型的L形盒冲压件的坯料形状和厚向应变,并分别与实验结果和商业软件AutoForm的计算结果进行了比较,说明FastAMP软件可以精确地预测冲压件的坯料形状和应变分布规律,而且计算速度很快。     

Research on three-dimensional surface parts in multi-gripper flexible stretch forming

Multi-gripper flexible stretch forming (MGFSF) is a novel flexible forming process of sheet metal based on the multi-point forming principle. The straight jaws in traditional transverse stretch forming (TSF) are replaced by several discrete clamping mechanisms on both sides. To help understand the forming characters of MGFSF, spherical and concave–convex parts were selected as the research objects and finite element analyses on TSF and MGFSF were implemented using an explicit nonlinear finite element code. The influence of the transition length on the forming results in MGFSF was also taken into account in the present work. The simulation results reveal that a shorter transition length in MGFSF would result in an easier conformability of the sheet metal to the desired shape as well as a smaller strain variation in the forming zone. It is also found that, compared to TSF, the sheet metal can be formed without transition zone by utilizing MGFSF, which could significantly improve the material utilization and save the manufacturing costs. Finally, experimental validations were conducted on the self-developed MGFSF apparatus and the experimental results show a good agreement with the numerical results.     

Numerical and experimental study of stretching effect on flexible forming technology

The flexible stretch forming technology (FSFT) is suitable for flexible manufacturing because it affords several advantages including applicability to various forming processes such as sheet metal forming, single curved surface forming, and quadratic curved surface forming. In this study, the formation of a quadratic curved surface with a saddle-type shape by the flexible stretch forming process is systematically investigated through a numerical simulation. A 4-mm-thick Al 3003-H14 aluminum alloy is used as the initial blank material. Urethane pads are defined based on a hyperelastic material model as a cushion for the smooth forming surface. The elastic recovery deformation behavior is also investigated to consider the exact result after the last forming process. The simulation indicates that the stretch forming process can be used to apply more stress to the blank and to reduce the elastic recovery effect. An experiment was then performed to confirm the process formability and reduction of the elastic recovery effect. A comparison of the objective surface between the simulation and the experimental results verified that the stretch forming process reduced the elastic recovery effect. This confirms that FSFT can be feasibly used to manufacture quadratic curved surfaces.     

不规则件优化排样的小生境遗传模拟退火算法

提出一种基于小生境遗传模拟退火算法求解不规则件排样问题的方法。该方法首先充分考虑不规则形状零件自身的形状特征,采用组合矩形包络算法将二维不规则零件的排样问题转化为矩形件的排样问题,克服了以往简单采用最小包络矩形代替零件排样存在空白区域,从而导致材料可能发生的利用率过低问题;然后利用遗传模拟退火算法及小生境技术相结合,寻找排样件在排样时的最优次序及各自的旋转角度;最后用"最低水平线与填充算法相结合"策略的启发式排样算法实现自动排样。实例表明了该算法的有效性和实用性。     

有限元逆算法与板料成形工艺的评价

依据理想形变理论，研究开发了冲压成形过程模拟的有限元逆算法，根据变形体的整体塑性功取相对极值的条件，导出了塑算法有限元方程。提出了求逆算法初始解以及求解与给定形状的毛坯相对应的冲压件形状的迭代计算方法。采用有限元塑算法预测了与冲压件形状相对应的冲压件毛坯的展开形状，根据给定的板坯形状计算了冲压件最终构形及应变分布。分析计算实例表明，逆算法可用于对板料成形工艺方案进行快速评价，对冲压工艺参数进行优化。     

汽车覆盖件冲压成形仿真研究进展

汽车覆盖件冲压成形仿真技术的发展,突破了原有汽车冲压件模具及工艺设计的设计方法,对保证工件质量、减少材料消耗、缩短产品开发周期、降低制造成本具有重要意义.概述了目前汽车覆盖件冲压成形仿真所涉及到的热点领域,如摩擦与接触、回弹分析、模具系统和工艺参数、材料屈服模型和板料形状设计,讨论了这些领域的研究进展和进一步研究的发展方向.     

拉深工艺变压边力控制数值模拟研究

根据实际生产中压边力的控制状况和理论分析确定了几种压边力变化曲线，以非轴对称抛物面车灯反光罩的成形为例，采用Dynaform软件对多种变压边力控制的成形工艺分别进行了数值模拟计算，分析了各种变压边力控制对成形的影响，并确定了对成形最为有利的压边力的变化趋势。