中文摘要：

基于断裂力学理论，采用最大拉应力准则分析了压剪和拉剪应力状态下倾斜椭圆形裂纹的三维始裂状态．研究结果表明：（1）椭圆形裂纹的三维始裂位置受周边应力场的影响：在拉剪状态下，原生裂纹的始裂位置始终在裂纹短轴端部，而与原生裂纹的几何形状（b／a）和材料泊松比（v）无关，而在压剪状态下则受6／n和v的共同影响，并随6／a和v的改变，始裂位置在椭圆裂纹长、短轴端部之间变化；（2）拉剪应力作用下，简化分析中仅计算裂纹长短轴端部应力集中系数是合理的，但在压剪应力作用下，这种简化不合理且偏于危险，计算中需综合考虑裂纹几何形状和材料泊松比的影响；（3）无论是压剪还是拉剪应力作用下，弯扭破裂扩展面始终呈包裹状沿原生裂纹边界向外侧延展，但二者的弯扭方向相反，分析结果与实验结果一致；（4）Sih采用最小应变能密度因子准则给出的拉剪状态下裂纹的三维断裂结果仅为近似解，而压剪状态下的相关分析结果与实验结果明显不符．

英文摘要：

On the base of fracture theory, the initial fracture states of an inclined ellipse flaw are analyzed under tensile- and compressive- shear loading. The study results show： （1） the effects from different stress states are very important to determinate the initial fracture place on the flaw boundary, the initial fracture place is independent on the flaw＇s morphology （b/a） and material＇s Poisson Ratio （v）. It is always on the tip of the short-axis of the ellipse flaw under tensile-shear stress, but it is effected by the two parameters of b/a and v. And the place changes between long- and short-axis tips with the variation of b/a and under compression-shear stress; （2） the analytical results only calculated from the stress concentration factor of long- and short-axis is reasonable under tensile-shear stress, but unreasonable and dangerous under compressive-shear stress. In 3-D fracture analysis, the morphology property and Poisson Ration need to be considered; （3） In the compression-shear and tensile-shear stress states, the bending and torsion fracture faces always grow with a wrapping pattern towards the boundary outside of the inclined flaw, but the bending and torsion direction of the fractured growth faces is just contrary. The analytical results well agree with the experimental ones in this paper; （4） Because the torsion of the growth faces are not taken into account, the Sih＇s calculated results by the minimum strain energy density theory are only approximate solutions in tensile-shear states, not obviously consistent with the experimental ones in compressive-shear states.