中文摘要：

对六种不同厚度的试样进行了小冲孔试验，并进行了有限元模拟，此外还通过扫描电镜观察并分析了断裂面的微观结构。试验结果显示，试样的SP断裂变形能和断裂韧度随试样厚度的增大而增大。提出了裂纹起始遵循断裂应变准则及裂纹扩展遵循断裂能密度准则的观点。有限元模拟结果与试验结果基本吻合。断裂面呈典型的韧性断裂特征，试样变形后的半球状外表面布满微小的褶皱状突起和微裂纹。

英文摘要：

Small punch （SP） tests had been carried out at the room temperature on round specimens with six kinds of thicknesses. The fracture surfaces and crack details were observed by SEM. The results showed that the SP energy and the fracture toughness increased with the thickness of the samples. From the test results and theoretical analysis, fracture initiation criterion based on fracture strain and fracture propagation criterion based on fracture energy density were proposed. With the continuum damage model, the FEA simulations got the results of the crack propagation process which agreed Well with the experimental results. Fracture surface displayed typical ductile fracture, and the surface of the half-sphere part cut off by the punch was full of little bulgings around which there were micro cracks.