压力容器O形金属密封环的回弹行为研究

通过弹塑性有限元接触分析和循环压扁试验,对60Si2Mn、304不锈钢和TA16材料O形密封环管材在室温条件下的回弹行为进行了研究。结果表明:TA16合金O形管状试样回弹量H与60Si2Mn钢回弹量较为接近,且为304不锈钢回弹量的2～3倍;提出了用于O形环回弹量预测的回弹模型,该模型对这3种金属材料O形管状试样的预测结果和实验结果具有很好的一致性。     

板料成形过程回弹的三维检测与评价方法研究

针对板料成形回弹数值难以精确测量、实际误差无法全面估计等问题,采用近景摄影测量系统和面扫描系统相结合的测量方法对板料的成形过程回弹进行了研究,提出了一种精确获得板料成形空间回弹量的新方法,研究了该方法的原理、程序和步骤.结合本方法定义了板料回弹评价的新指标S,该指标用空间回弹值和x、y、z三个方向回弹值组成的向量来表示,以某型号冰箱门外壳为实例进行了成形回弹量的检测和评价.结果表明:对于冰箱门外壳大表面,三维空间回弹数值的影响主要来自z方向,x方向回弹数值为0,y方向影响较小,三维空间回弹数值大小和方向与z方向回弹值的大小和方向保持完全一致.     

The Recovery of Elastic Properties at 35 °C in TRIP 700 Steel Following Deformation

The influence of plastic deformation on the elastic properties that determine the magnitude of springback following forming was investigated using dynamic modulus analysis. For this study, the elastic modulus of TRIP 700 steel was measured continuously at 35 °C and a loading frequency of 1.0 Hz for 1000 min following deformation by cold rolling to varying levels up to 27%. The elastic modulus increased at an exponentially decaying rate during these experiments and with a magnitude that increased with pre-strain. These observations are consistent with the hypothesis that deformation creates microstructural defects that contribute compliance when the stress state changes and that these defects are removed by annealing at this low temperature. This article was presented at Materials Science & Technology 2006, Innovations in Metal Forming symposium held in Cincinnati, OH, October 15-19, 2006.     

基于不同强化模型的GTN损伤模型及其在板料回弹有限元分析中的应用

为了进一步提高板料成形中的回弹预测精度,分别建立了基于Ziegler 线性随动强化模型、Lemaitre-Chaboche 非线性随动强化以及非线性混合强化模型的Gurson-Tvergaard-Needleman(GTN)细观损伤本构模型,并给出有限元数值积分方法。通过用户自定义材料子程序VUMAT 将损伤模型嵌入到有限元软件ABAQUS 中,以NUMISHEET’93 板料U 型弯曲考题为例,应用显隐相结合的方法模拟分析了不同材料强化模型和损伤对板料回弹量的影响。结果表明:在相同GTN 损伤模型情况下,线性随动和非线性随动强化模型预测得到的板料回弹量较小,等向强化预测的板料回弹量偏大,非线性混合强化预测的板料回弹量介于它们之间。材料模型在考虑损伤因素后,预测的回弹严重程度比无损伤情况时略小,与实验值更相近。     

Numerical and Experimental Evaluation of Springback in Advanced High Strength Steel

The automotive industry is using more and more of Advanced High Strength Steel in order to reduce the weight of the car. Since this will generate more springback, it is of vital importance to be able to predict the amount of springback in the parts. Otherwise, many late changes have to be made in order to fit the parts in their position. In order to increase the ability to understand and test the behavior of the springback in sheet-metal parts, a new semi-industrial experimental tool, the flex-rail, has been developed. This is a very flexible tool, which can be used for various kinds of materials, from mild steel and aluminum to advanced high strength steel such as TRIP-steel and CP-steel by using different insert. The tool is designed for experimental analysis of 3D-springback, which is the case in the more complicated automotive parts, such as b-pillars and side members. The scope of this work is to analyze the springback behavior and prediction for Advanced High Strength Steel both numerically and experimentally. Sheet-metal-forming simulations were made in LS-DYNA. The results proved that the new geometry, flex-rail, gave a complex springback behavior for all tested materials. Furthermore, the prediction of springback showed good correlation in sections with small amounts of twist but that LS-DYNA under-predicts the springback for sections with large amounts of twist for all materials except DP600. This article was presented at Materials Science & Technology 2006, Innovations in Metal Forming symposium held October 15-19, 2006 in Cincinnati, OH.     

弯曲半径对凸曲面翻边成形及回弹影响的研究

影响曲面翻边成形回弹的因素主要有零件弯曲曲率半径R、凹模圆角半径r以及材料的厚度t,利用Dynaform软件重点模拟零件弯曲曲率半径R对压缩类翻边中的凸曲面直线翻边的成形回弹影响,得出了零件弯曲曲率半径R对曲面翻边的成形回弹影响规律。通过计算机数值模拟得到在R30mm、R45mm和R60mm 3种半径下的成形极限图以及回弹前、后的主应变分布图,并结合试验的结果,得到随着弯曲半径增大而成形的回弹有所改善的结论。     

卫星天线冲压成形仿真分析

针对用金属板材通过冲压成形制造卫星天线的方法中,冲压卸载后的回弹计算不精确,并且很难预示出能达到规定产品尺寸的最佳模面构形的情况,提出了一种回弹逆向补偿法,该方法成功地解决了这一问题.实际生产证明了该方法的可靠性,这对于其他冲压件模具设计具有普遍的指导意义.     

基于逆向工程技术实现修边线回弹后形状变化的预测

在有限元方法无法准确计算回弹的情况下,通过逆向工程技术对回弹后的型面进行测量和重构,利用弹性变形的特点,以冲压件典型特征为基准进行强制变形,从而找到变形前后单元和节点的拓扑映射关系。根据修边线在单元上的投影关系计算出变形后投影点和投影线交点的位置,并利用三次参数样条函数重构出修边线。