Evaluation of Arbitrary 3-D Crack Growth Behavior Under Residual Stress in Butt-Welded Pipe

Abstract

Arbitrary 3-D crack growth behavior due to stress corrosion cracking under residual stress was evaluated by finite element analyses. The analytical evaluation enables consideration of complicated stress distributions, such as weld residual stress, and expression of arbitrary 3-D crack shapes. The estimated weld residual stress for non-cracked components was distributed on the crack surface on the basis of the superposition principle to calculate stress intensity factors. Arbitrary 3-D crack shapes due to the crack propagation were expressed by FINAS/CRACK software. Moreover, stress corrosion cracking (SCC) crack growth evaluation under weld residual stress in a butt-welded large diameter pipe was conducted. The weld residual stress was estimated by finite element analyses considering a moving heat source during welding. An initial crack was postulated in a heat affected zone. The 3-D no planar crack growth behavior due to the complicated weld residual stress was observed by the analytical evaluation. To verify the applicability of flaw growth procedure in a fitness-for-service code on the SCC crack growth considering 3-D shape, SCC crack growth evaluation on the basis of the code procedure using a planar semi-elliptical crack shape was conducted and compared with the analytical results.