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成形极限曲线可展现板料在塑性失稳前所能达到的最大变形程度,是板料成形分析中的重要判据。为获得准确的试验成形极限曲线,该文通过刚性半球凸模胀形试验、采用数字散斑图像相关方法对AA6061铝板的成形极限曲线进行测定,得出了成形极限试验测定和极限应变提取的方法;通过对AA6061铝板进行盒形件拉深试验,建立拉深过程的有限元模型,比较了数值模拟和试验测定的极限拉深深度。比较结果表明,数字图像相关方法能够有效获取变形过程中的全场应变信息、搜索临界破裂状态,且能采用曲线拟合方式计算极限应变,避免了人为误差,提高了测量精度。拉深试验表明,所测成形极限曲线对拉深极限具有较高的预测精度。
The forming limit curve can show the maximum deformation that the sheet can reach before plastic instability, which is an important criterion in sheet metal forming analysis. In order to obtain the accurate test forming limit curve, the forming limit curve of AA6061 aluminum plate was measured by digital speckle image correlation method through the rigid hemisphere convex die bulging test, and the method of forming limit test and ultimate strain extraction were obtained The finite element model of the drawing process was set up by the box-type drawing test of AA6061 aluminum plate, and the ultimate depth of drawing by numerical simulation and experiment was compared. The comparison results show that the digital image correlation method can effectively obtain the full field strain information in the deformation process, search for the critical rupture state, and can use the curve fitting method to calculate the ultimate strain, avoid human error and improve the measurement accuracy. The deep drawing test shows that the measured limit curve has higher prediction accuracy for the drawing limit.