Generic proximity rules for multiple radially oriented planar flaws; Technical basis of code case N-877 revision 1

放射線状分布の複数亀裂の一般的合体評価ルール; 事例規格-877の技術根拠

Dulieu, P.*; Lacroix, V.*; 長谷川 邦夫

Dulieu, P.*; Lacroix, V.*; Hasegawa, Kunio

In the case of planar flaws detected in pressure components, flaw characterization plays a major role in the flaw acceptability assessment. When the detected flaws are in close proximity, proximity rules given in the Fitness-for-Service (FFS) Codes require to combine the interacting flaws into a single flaw. However, the specific combination criteria of planar flaws vary across the FFS Codes. These criteria are often based on flaw depth and distance between flaws only. However, the level of interaction depends on more parameters such as the relative position of flaws, the flaw sizes and their aspect ratio. In this context, revised and improved proximity criteria have been developed to more precisely reflect the actual interaction between planar flaws. Thanks to numerous three-dimensional XFEM analyses, a wide range of configurations has been covered, including interaction between two surface flaws, interaction between two subsurface flaws and interaction between a surface flaw and a subsurface flaw. This paper explains in detail the steps followed to derive such a generic proximity rules for radially oriented planar flaws.