It is one of the important subjects to evaluate appropriately the growth of surface cracks to ensure the integrity of a structural component with surface flaws, since the flaws are most frequently detected at the surface of a structural component by non-destructive examinations. Authors have been investigating the growth of surface cracks and the crack growth evaluation method, in which interaction and surface effect in multiple crack growth are considered, was proposed previously using empirical expressions.
In the meanwhile, verification tests using structural component models were performed to confirm the validity of the evaluation method. In this paper is described the growth behavior of multiple surface cracks obtained from fatigue tests of straight pipes with multiple surface cracks in the inner surface, and is discussed the applicability of the growth evaluation method proposed in this study and that specified by the ASME Code Sec. E. Reasonable fatigue behavior evaluations were obtained by the proposed method for the straight pipes, whereas the method of the ASME Code Sec. XI gave overly conservative fatigue lives.
