Fatigue crack growth behaviour for adjacent two surface flaws in accordance with combination rules

Lu, K. ; Li, Y. ; Hasegawa, Kunio*; Lacroix, V.*

When multiple flaws are found in a structural components, fitness-for-service (FFS) codes such as ASME Code Section XI, BS 7910 and FKM Guideline provide flaw combination rules. However, the specific criteria are different among FFS codes. In this paper, fatigue flaw growth for adjacent surface flaws in a pipe subjected to cyclic tensile stress were obtained by numerical calculations using different combination rules. In addition, fatigue lives taking into account interaction effect between the two flaws were conducted by extended finite element method (X-FEM). As the calculation results, it is found that the fatigue lives calculated by the X-FEM are close to those by the ASME Code. Finally, it is worth noticing that the combination rule provided by the ASME Code is appropriate for fatigue flaw growth calculations.