Fundamental consideration of maximum allowable flaw lengths for limit load evaluation based on flat plates for the ASME Code Section XI

Negyesi, M.*; Hasegawa, Kunio

Journal of Pressure Vessel Technology, 148(4), p.044501_1 - 044501_4, 2026/08

https://doi.org/10.1115/1.4071195

Allowable axial flaw sizes based on code given and actual measured flow stresses for high toughness ductile pipes subjected to internal pressure

Negyesi, M.*; Ha, Yoosung; Hasegawa, Kunio; Lacroix, V.*

Proceedings of the ASME 2025 Pressure Vessels & Piping Conference (PVP2025) (Internet), 6 Pages, 2025/07

https://doi.org/10.1115/PVP2025-152377

Characteristics of fatigue crack growth rates for ferritic steels in water environment provided by the ASME Code Section XI

Yamaguchi, Yoshihito; Hasegawa, Kunio; Negyesi, M.*

Proceedings of the ASME 2025 Pressure Vessels & Piping Conference (PVP2025) (Internet), 8 Pages, 2025/07

https://doi.org/10.1115/PVP2025-154765

Technical basis for revising the fatigue crack growth rates for ferritic steels in the ASME Code Section XI

Hasegawa, Kunio; Yamaguchi, Yoshihito; Udyawar, A.*

Journal of Pressure Vessel Technology, 147(3), p.034501_1 - 034501_7, 2025/06

https://doi.org/10.1115/1.4067679

Proposal of a new flaw-to-surface proximity rule for the re-characterization of a subsurface flaw into a surface flaw

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

Proceedings of the ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 5 Pages, 2024/07

When a subsurface flaw is detected close to the surface of a pressure retaining component, the subsurface flaw shall be transformed into a surface flaw in accordance with flaw to surface proximity rules. This re-characterization process from subsurface to surface flaw is adopted in ASME Code Section XI. The limit value for this proximity rule depends on ratio between the subsurface flaw to the free surface distance and the flaw depth. This limit value does not depend on the flaw aspect ratio. This paper proposes an interaction limit criterion and presents a new limit value for the flaw-to-surface proximity factor, depending on the flaw depth, the remaining ligament and the flaw aspect ratio.

Allowable Stress and Allowable Flaw Sizes Estimated by Converted Tensile Properties from Hardness for Austenitic Stainless Steel Pipe

Ha, Yoosung; Yamaguchi, Yoshihito; Hasegawa, Kunio; Negyesi, M.*

Proceedings of the ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 6 Pages, 2024/07

Proposal of negative stress ratio R for fatigue crack growth rates of austenitic stainless steels in air for ASME Code Section XI based on trend in experimental data

Negyesi, M.*; Yamaguchi, Yoshihito; Hasegawa, Kunio; Lacroix, V.*; Morley, A.*

Proceedings of the ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 8 Pages, 2024/07

https://doi.org/10.1115/PVP2024-122614

Revision of allowable planar flaw tables of ASME B&PV Code Section XI for ferritic steel materials

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

Proceedings of the ASME 2023 Pressure Vessels and Piping Conference (PVP 2023) (Internet), 7 Pages, 2023/07

When defects were found during in-service inspection in nuclear components, the ASME Code Section XI provides allowable flaw sizes to assess the flaw severity. For ferritic steel materials, the sizes of allowable planar flaws given in Table IWB-3510-1 were determined by the stress intensity factors. The objective of this methodology is including some basic criteria to prevent plastic collapse and brittle failure. As far as the prevention from plastic collapse, a uniform limit load reduction is considered whatever the flaw aspect ratios. For the prevention of brittle failure, a reference surface flaw configuration is defined to derive a reference stress intensity factor. This methodology is applied to surface flaws with various aspect ratios. It is also coherently applied to subsurface flaws considering the proximity of the flaw to the surface as an additional parameter. Finally, a revision of the allowable planar flaw Table IWB-3510-1 of ASME Code Section XI is proposed.

Stability of allowable flaw angles for high toughness ductile pipes subjected to bending stress in the ASME Code Section XI

Hasegawa, Kunio; Strnadel, B.*; Li, Y.; Lacroix, V.*

Journal of Pressure Vessel Technology, 144(6), p.061202_1 - 061202_6, 2022/12

https://doi.org/10.1115/1.4054620

When pipe walls are thin, part-through flaws are easily develop into through-wall flaws, and the likelihood of coolant leakage is high. The ASEM Code Section XI provides final allowable flaw angles of through-wall flaw for thin-wall pipes. The final allowable angles are applied to pipes in order to maintain structural integrity if the part-through flaws become through-wall flaws. To ensure that this stability is compromised, plastic collapse stresses for through-wall flaws are combined with allowable stresses. However, the final allowable angles of through-wall flaws are not identified for thin-walled pipes. This paper compares plastic collapse stresses of through-wall flaws and allowable stresses of part-through flaws for pipes. The comparison of these stresses is used to derive the final allowable angles of through-wall flaws. The angles can be expressed either in the form of exact solutions or as conventional options that are appropriate for various service level conditions.

Allowable cracks related to penetration for part-through cracks in pipes subjected to bending stresses

Hasegawa, Kunio; Li, Y.; Strnadel, B.*; Udyawar, A.*

Journal of Pressure Vessel Technology, 144(5), p.051305_1 - 051305_6, 2022/10

https://doi.org/10.1115/1.4053482

Fully plastic collapse stresses for circumferentially part-through cracked pipes subjected to bending stresses are estimated by Limit Load Criteria provided by the ASME Code Section XI. Allowable crack depths were determined by using the Limit Load Criteria and that are tabulated in the ASME Code Section XI for different plant service level conditions. On the other hand, crack penetration bending stresses for part-through cracked pipes were estimated by using the Local Approach of Limit Load Criteria. By using these Criteria, the study presented in this paper obtained allowable crack depths at penetration for circumferentially part-through cracked pipes. Comparing the allowable crack depths obtained by both methods for each service level, it is evident that the allowable crack depths at penetration calculated by the Local Approach of Limit Load Criteria are almost always smaller than those at fully plastic collapse stresses calculated by the Limit Load Criteria. It was found that the allowable crack depths provided by the ASME Code Section XI are less conservative for crack penetrations.