Abstract：The elasticplastic fracture J-A2 method was performed to study the semielliptical surface crack and the single edge through thickness crack tension specimens of X80 and X100 steels. By 3D and 2D finite element analysis, the fracture driving forces of Jintegral and the constraint parameters, A2 of semielliptical surface crack were calculated same length and different depths for X80 and X100. According to J-A2 failure curves of the two steels, the fracture analysis and comparison were conducted between the elliptical cracks and the corresponding single edge cracked tension specimens. The results show that the elliptical crack depth mainly affects the J-integral value with slight influence on cracktip constraint level. The constraint situation of the deepest point of semi-elliptical crack and the cracktip of the single edge cracked tension specimen is quite different when their crack depth and J-integral are same. Constraint level on the cracktip of the single edge cracked tensile specimen is higher than that of semi-elliptical crack in middle and large scale yielding. The failure assessment for X80 and X100 pipeline steel with deep semi-elliptical crack by the calculation of plane model is conservative, but the situation is the opposite for X100 steel with shallow crack.
2011, Vol. 32 
