韧性损伤断裂是金属塑性成形分离工步中材料必经的过程，成形工步中的常见缺陷之一。为了预测成形工艺中的断裂，需要通过实验测量获得材料断裂特征和材料断裂因子。对韧性断裂特征的定量描述一直受到实验条件制约，因为断裂往往集中在非常小的区域，而且应变梯度较大，传统测量方法无法直接获得应变场。本项目拟应用非接触式变形测量方法-数字图像相关（DIC）法测量韧性断裂区的应变分布，分析断裂特征，在此基础上建立合理的断裂准则和准确的材料断裂参数。韧性断裂的主要特征是材料中裂纹出现前的损伤软化，通过实验建立软化特征描述变量，并将其耦合到材料弹塑性本构关系中，通过有限元方法模拟整个韧性损伤软化和断裂过程。在断裂准则中还将引入温度变量，考虑温度对韧性损伤断裂的影响，预测热成形中的韧性损伤。建立的断裂准则和材料模型与弹塑性有限元程序结合，模拟分析高强钢和铝合金成形中的韧性断裂，优化成形工艺。

Ductile damage and fracture of metal is inevitable in shearing or blanking, and also is one of defects in forging, stamping and drawing. The experiments is necessary to investigate fracture features and critical fracture factor of material, which is vital to prediction of ductile fracture during metal forming. Quantitative description of ductile fracture has always been limited by the experiment conditions. It is hard to get the strain filed of ductile fracture region with the traditional measurement method, because the large strains distribute at a very narrow region and stain gradient is high. In present proposal, the novel optical non-contact method will be applied in strain measurement of material ductile fracture, where full strain field and the strain history can be recorded. The fracture characteristic will be described on the base of measured strain, and the corresponding fracture criteria and material constitutive parameters will be obtained. These base date are used to prediction the material ductile fracture at the complex strain and stress state. Damage-induced softening prior to crack is main feature of ductile fracture, the calibrated soften factor will be coupled into material elastic-plastic constitutive material. To investigate the warm/hot forming, the temperature will be coupling into the fracture criterion as a variable. Ductile fracture criteria and material constitutive models are integrated into finite element program to simulate the metal forming. High strength steel and aluminum alloy will be focused as experiment material, and the ductile fracture will be predicted in their metal forming.