Evaluation of stress intensity factor interactions between adjacent flaws with large aspect ratios

Azuma, Kisaburo*; Li, Y. ; Hasegawa, Kunio

Multiple flaws detected during in-service inspections are evaluated in accordance with the flaw combination rule provided in the ASME B&PV Code Section XI. The rule treats adjacent two flaws as a single combined flaw if the distance between the two flaws is equal to or less than half of the flaw depth. That is, the combination rule is consisted of flaw depth basis. However, its applicability has not been clarified systematically to the flaws with large aspect ratio, the depth of which are greater than half its length. Interactions of stress intensity factors for multiple flaws under membrane stress were investigated using finite element analyses. The numerical results suggest that the flaw combination rule might be better to use flaw length basis, instead of flaw depth.