Abstract: The elastic－plastic fracture analysis for internal axial surface half elliptical cracks oil & gas in pipeline were provided and the corrected J－integral estimation method was established． First，based on detailed 3－D FE results using
deformation plasticity，some fully plastic solutions for fully plastic J components were tabulated for the mean radius－to－thickness ratio，the crack depth－to－ length ratio，the crack depth－to－thickness ratio，the strain hardening index for the R－O material ，and the location along the semi－elliptical crack front．Second，by means of the analysis of these fully plastic solutions for fully plastic J components，the improper of the EPRI method was described．Finally，based on the FE results，the GE／EPRI－type J estimation equation along the crack front was proposed．Then the J values calculated by FE，EPRI and the method were compared，which demonstrates the accuracy of the J－integral estimation method．

Key words: Surface crack , FE analysis , J estimation , Deformation plasticity

摘要： 对油气管道内部轴向表面半椭圆裂纹进行了断裂分析,提出了改进的J积分估算公式。首先，基于使用形变塑性的详细三维FE计算，列表给出了部分以径厚比、裂纹深度与长度比、裂纹深度与管壁厚比、R-O材料应变硬化系数和半椭圆裂尖位置等为变量的J积分全塑性解。然后，通过对这些全塑性解分析指出EPRI分析方法中的不足之处。最后，以本次FE计算为基础，给出了沿裂纹尖端基于GE/EPRI的J积分预测公式，并通过对计算公式、EPRI J积分估算公式与有限元计算结果的对比，说明提出公式的精确性，为油气管道的断裂评定奠定基础。

关键词: 表面裂纹 , 有限元分析 , J 积分估算 , 形变塑性