中文摘要：

为了测试材料在应力三轴度接近1/3时的断裂应变,对9种不同厚度不同孔径的T2纯铜中心孔板试样,在MTS试验机上进行系列拉伸试验。结合数值模拟和显微观测,确定孔板试样的裂纹萌生位置及其应力三轴度数值及断裂应变。在此基础上,参照比较光滑试样拉伸试验,进一步探讨了对材料应力三轴状态与断裂应变的关系。研究发现：1材料断裂应变随应力三轴度减少而减少,似不服从以往基于孔洞模型研究总结出来的韧性材料断裂规律;2孔表面实际变形很不均匀,按连续介质力学方法估计的孔边断裂应变要明显低于其实际值。

英文摘要：

In order to study the fracture strain under a stress triaxiality close to 1 /3,tensile experiments were conducted on a series of pure copper plate specimens with a center hole and different thickness. Numerical study and microscopic observations were carried out to determine the location where the fracture initiated,the value of stress triaxiality and the fracturet strain. On this basis,further investigations on the relationship between stress triaxiality and fracture strain of a material was carried out by comparing the experimental results with those from the smooth specimens under tension. The analysis results show that： 1 Material fracture strain decreased with the decrease of stress triaxiality,which is seemly different from the ductile fracture law derived from void models; 2The actual deformation of the hole surface is very inhomogeneous,which is significantly higher than the value calculated by the continuum mechanics methods.