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Lacroix, V.*; Dulieu, P.*; Blasset, S.*; Tiete, R.*; Li, Y.; 長谷川 邦夫; Bamford, W.*; Udyawar, A.*
Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 10 Pages, 2018/07
When multiple flaws are detected in pressure retaining components during inspection, the first step of evaluation consists of determining whether the flaws shall be combined into a single flaw or evaluated separately. This combination process is carried out in compliance with proximity rules given in the Fitness-for-Service (FFS) Codes. However, the specific criteria for the rules on combining multiple flaws into a single flaw are different among the FFS Codes. In this context, revised and improved criteria have been developed, to more accurately characterize the interaction between multiple subsurface flaws in operating pressure vessels. This improved approach removes some of the conservatism in the existing ASME Code approach, which was developed in the 1970s based on two flaws interacting with each other. This paper explains in detail the methodology used to derive improved flaw proximity rules through three-dimensional FEM and XFEM analyses. After the presentation of the calculations results and the improved criteria, the paper also highlights the multiple conservatisms of the methodology using several sensitivity analyses.
Dulieu, P.*; Lacroix, V.*; 長谷川 邦夫; Li, Y.; Strnadel, B.*
Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 10 Pages, 2018/07
When multiple surface flaws are detected in pressure components, their potential interaction is to be assessed to determine whether they must be combined or evaluated independently of each other. This assessment is performed through the flaw characterization rules of Fitness-For-Service (FFS) Codes. However, the specific combination criteria of surface flaws are different among the FFS Codes. Most of the time, they consist of simple criteria based on distance between flaws and flaw depth. This paper aims at proposing alternative characterization rules reflecting the actual level of interaction between surface planar flaws. This interaction depends on several parameters such as the relative position of flaws, the flaw sizes and their aspect ratio. Thanks to numerous threedimensional XFEM simulations, best suited combination criteria for surface planar flaws are derived by considering the combined influence of these parameters.
Lu, K.; Li, Y.; 長谷川 邦夫; Lacroix, V.*
Proceedings of 2016 ASME Pressure Vessels and Piping Conference (PVP 2016) (Internet), 7 Pages, 2016/07
When multiple flaws are detected in structural components, remaining lives of the components are estimated by fatigue flaw growth calculations using combination rules in fitness-for-service codes. ASME, BS7910 and FITNET Codes provide different combination rules. Fatigue flaw growth for adjacent surface flaws in a pipe subjected to cyclic tensile stress were obtained by numerical calculations using these 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.
柴田 勝之; 横山 憲夫; 大場 敏弘; 川村 隆一; 宮園 昭八郎
Nucl.Eng.Des., 74(2), p.199 - 213, 1982/00
被引用回数：1 パーセンタイル：22.52(Nuclear Science & Technology)著者らはこれまでに、いくつかの配管試験体を使用し配管内面における複数欠陥からのき裂伝播、合体等の挙動を調べている。本論文は直管試験体および曲管試験体を用いて実施した疲労試験結果をまとめたものである。疲労試験は内表面に人工欠陥を加工した2体の直管試験体および2体の曲管試験体について行った。疲労試験中、超音波探傷法およびビーチマーク法によって複数き裂の伝播挙動を調べた。試験から得られた深さ方向へのき裂伝播曲線およびき裂形状変化について実験結果と2種類の方法によるき裂伝播解析結果との比較を行った。
