A new method with digital image correlation (DIC-method) is proposed for the calibration of ductile fracture parameters and a partition optimizing method based on multi-group fracture parameters is utilized for the establishment of forming limit diagram (FLD). Both of the two methods are verified with the application of Lou-Huh ductile fracture criterion on AA7075-T6 sheet in this paper. A comparison study with conventional method combining simulation with experiment (SE-method) shows that DIC-method can provide objective experimental data for fracture parameter calibration without virtual simulation. It is also indicated that the plastic flow of AA7075-T6 sheet has stress state dependence and it is necessary to build related material subroutine into FEA software. A research on the establishment of FLD is conducted with the calibrated fracture parameters. It is demonstrated that the FLD of AA7075-T6 sheet could not be accurately built by a single group of fracture parameters. Fracture morphology shows the reason is that the fracture of AA7075-T6 is not pure ductile fracture. The partition optimizing method based on multi-group fracture parameters could better improve the FLD of AA7075-T6. The optimized FLD is well verified by the result of punch-stretch experiment.

提出了一种具有数字图像相关性的新方法（DIC方法）用于延性断裂参数的标定，并基于多组断裂参数的分区优化方法建立了成形极限图（FLD）。本文采用Lou-Huh韧性断裂准则在AA7075-T6板材上验证了这两种方法。与传统方法结合模拟与实验（SE方法）的比较研究表明，DIC方法无需虚拟模拟即可为断裂参数校准提供客观的实验数据。还表明，AA7075-T6板材的塑性流动具有应力状态依赖性，有必要在FEA软件中建立相关的材料子程序。利用标定的断裂参数对FLD的建立进行了研究。结果表明，单组断裂参数不能准确地建立AA7075-T6板材的FLD。断裂形态表明原因是AA7075-T6的断裂不是纯延性断裂。基于多组断裂参数的分区优化方法可以更好地改善AA7075-T6的FLD。穿孔拉伸实验的结果很好地验证了优化后的FLD。