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Hasegawa, Kunio; Yamaguchi, Yoshihito; Udyawar, A.*
Journal of Pressure Vessel Technology, 147(3), p.034501_1 - 034501_7, 2025/06
Times Cited Count:0Negyesi, M.*; Yamaguchi, Yoshihito; Hasegawa, Kunio; Lacroix, V.*; Morley, A.*
Journal of Pressure Vessel Technology, 147(2), p.021201_1 - 021201_7, 2025/04
Times Cited Count:0 Percentile:0.00(Engineering, Mechanical)Negyesi, M.*; Yamaguchi, Yoshihito; Hasegawa, Kunio; Lacroix, V.*; Morley, A.*
Proceedings of ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 8 Pages, 2024/07
Lacroix, V.*; Dulieu, P.*; Hasegawa, Kunio
Proceedings of 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.
Morley, A.*; Negyesi, M.*; Hasegawa, Kunio
Proceedings of ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 7 Pages, 2024/07
Fatigue crack growth rates for stainless steels in air environment are provided by the ASME Code in Section XI. The crack growth rates increase with increasing temperature, and the temperature effect is expressed by a parameter ST. The current parameter ST is cumbersome, and original basis for the temperature function is questionable, consisting mostly of testing outside of the bounds of the temperatures of interest to its application in ASME Code Section XI. An alternative equation for ST for stainless steels in an air environment is proposed for ASME Code Section XI, based on the literature experimental data surveyed in this study.
Ha, Yoosung; Yamaguchi, Yoshihito; Hasegawa, Kunio; Negyesi, M.*
Proceedings of ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 6 Pages, 2024/07
Negyesi, M.*; Ha, Yoosung; Hasegawa, Kunio; Lacroix, V.*
Proceedings of ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 6 Pages, 2024/07
Hasegawa, Kunio; Li, Y.; Udyawar, A.*; Lacroix, V.*
International Journal of Pressure Vessels and Piping, 204, p.104952_1 - 104952_7, 2023/08
Times Cited Count:1 Percentile:21.45(Engineering, Multidisciplinary)When axial cracks were detected in pipes, failure stresses for high toughness pipes are estimated using the Limit Load Criteria. The allowable stresses for the cracked pipes are derived from the combination of the failure stresses and safety factors. The allowable sizes of crack depths and lengths are determined from the allowable stresses. From the comparison of the allowable and failure stresses for through-wall cracks, the allowable cracks are not uniform. They can be separated into three different characteristics, i) leak-before-break (LBB) and crack growth stability, ii) non-LBB and crack growth stability and iii) non-LBB and crack growth instability. Inspectors and users should pay special attention to allowable cracks with the third characteristic to prevent unexpected failure, particularly for thin-wall pipes. The allowable crack depths and lengths that require special attention can be expressed by appropriate equations.
Lacroix, V.*; Dulieu, P.*; Hasegawa, Kunio
Proceedings of ASME 2023 Pressure Vessels and Piping Conference (PVP 2023) (Internet), 5 Pages, 2023/07
In case of flaw detection during In-Service inspection of nuclear components, ASME Code Section XI provides Acceptance Standards. For ferritic steel materials, the size of allowable planar flaws is given in Table IWB-3510-1. The allowable flaw size only depends on three parameters: the component thickness, the flaw aspect ratio and the proximity of the flaw to the surface. However, a graphical analysis of the impact of those parameters highlights some inconsistencies. Consequently, the need to revise the allowable planar flaws of ASME Code Section XI Acceptance Standards using a robust technical basis is brought to light. This paper details the inconsistencies related to the present allowable planar flaws table and proposes improvement points to revise the allowable planar flaw Table IWB-3510-1.
Dulieu, P.*; Lacroix, V.*; Hasegawa, Kunio
Proceedings of 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.
Hasegawa, Kunio; Strnadel, B.*; Li, Y.; Lacroix, V.*
Journal of Pressure Vessel Technology, 144(6), p.061202_1 - 061202_6, 2022/12
Times Cited Count:2 Percentile:18.01(Engineering, Mechanical)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.
Hasegawa, Kunio; Strnadel, B.*; Lacroix, V.*; Udyawar, A.*
International Journal of Pressure Vessels and Piping, 199, p.104722_1 - 104722_5, 2022/10
Times Cited Count:1 Percentile:15.39(Engineering, Multidisciplinary)Fully plastic collapse stresses for high toughness pipes with circumferential cracks subjected to tensile loading can be predicted by Limit Load Criteria. The Limit Load Criteria are provided by the ASME Code Section XI. Allowable membrane stresses for part-through cracks were determined by plastic collapse stresses in combination with safety factors. The allowable stresses decrease with increasing angles of the part-through cracks. When crack angles are large, the allowable stresses of the part-through cracks are larger than the collapse stresses of through-wall cracks. For such large cracks, allowable stresses greater than the collapse stresses cause instability, and are thus detrimental to pipe integrity, especially in thin-wall pipes. In order to avoid the anxiety, it is necessary to establish maximum allowable crack angles. This paper proposes maximum allowable crack angles for allowable stresses.
Hasegawa, Kunio; Li, Y.; Strnadel, B.*; Udyawar, A.*
Journal of Pressure Vessel Technology, 144(5), p.051305_1 - 051305_6, 2022/10
Times Cited Count:1 Percentile:8.77(Engineering, Mechanical)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.
Lacroix, V.*; Dulieu, P.*; Hasegawa, Kunio; Mares, V.*
Proceedings of ASME 2022 Pressure Vessels and Piping Conference (PVP 2022) (Internet), 7 Pages, 2022/07
In the ASME Code Section XI, a simplified approach is proposed: a nonplanar flaw is resolved into two planar flaws by projection of the flaw area into planes normal to the maximum principal stress. However, simplified resolution of nonplanar flaws is not conservative for all types of loading and flaw inclinations. Consequently, an improvement of the resolutions of nonplanar flaws must be provided in the ASME Code Section XI. This paper carries out an exhaustive assessment of the conservatism of the ASME approach and then proposes an alternative approach to deal with nonplanar flaws allowing to overcome the non-suitability of current ASME Code.
Yamaguchi, Yoshihito; Hasegawa, Kunio; Li, Y.; Lacroix, V.*
Proceedings of ASME 2022 Pressure Vessels and Piping Conference (PVP 2022) (Internet), 4 Pages, 2022/07
Lacroix, V.*; Hasegawa, Kunio; Li, Y.; Yamaguchi, Yoshihito
Proceedings of ASME 2022 Pressure Vessels and Piping Conference (PVP 2022) (Internet), 7 Pages, 2022/07
Hasegawa, Kunio*; Dvok, D.*; Mare
, V.*; Strnadel, B.*; Li, Y.
Journal of Pressure Vessel Technology, 144(1), p.011303_1 - 011303_6, 2022/02
Times Cited Count:5 Percentile:42.21(Engineering, Mechanical)Fully plastic failure stress for circumferentially surface-cracked pipe subjected to tensile loading can be estimated by means of limit load criterion (LLC) based on the net-section stress approach. LLC of the first type (labelled LLC-1) was derived from the balance of uniaxial forces. LLC of the second type, derived from the balance of bending moments and axial forces (labelled LLC-2), is adopted in Section XI of the ASME (American Society of Mechanical Engineering) Code. From the literature survey of experimental data, failure stresses obtained by both types of LLCs were compared with the experimental data. It can be stated that failure stresses calculated by LLC-1 are better than those calculated by LLC-2 for shallow cracks. On the contrary, for deep cracks, LLC-2 predictions of failure stresses are fairly close to the experimental data. It can be stated that the allowable cracks given in Section XI of the ASME Code are conservative.
Lacroix, V.*; Dulieu, P.*; Hasegawa, Kunio
Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 5 Pages, 2021/07
When flaws are detected, assessments are done to demonstrate the fitness-for-service. The first step is the flaw characterization determining the flaw geometry for analyses. This key step is done by flaw characterization rules provided in FFS Codes. According to the flaw characterization rules of ASME Code Section XI, a nonplanar flaw shall be resolved into two planar flaws by projection of the flaw area into planes normal to the maximum principal stresses. This approach allows to simplify the flaw assessment but remains conservative. Therefore, the conservatisms by the simplified projection for nonplanar flaws are investigated in this paper. Current computations have been improved so that the modelling of nonplanar flaws are not significant difficulty. This paper compares the stress intensity factors (SIF) of projected nonplanar flaws and the mixed mode SIF of actual nonplanar flaws. The scope is to quantify how the flaw projection into planes normal to the maximum principal stresses is conservative.
Desclaux, C.*; Lacroix, V.*; Hasegawa, Kunio
Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 10 Pages, 2021/07
The plastic collapse bending stress for a pipe is defined in ASME Code Section XI, using simplified equilibrium equations. One of the authors demonstrated that the simplified equilibrium equations are not conservative for externally cracked pipes and he proposed taking into account the cracked ligament mean radius. This paper demonstrates that the accuracy of the collapse bending stress equation can be refined considering the neutral axis position of the cracked pipe section. This leads to exact collapse bending moment equations. As the results, it is shown that the ASME equations for externally cracked pipes might be less conservative collapse bending stress than with the exact equations.
Yamaguchi, Yoshihito; Hasegawa, Kunio; Li, Y.
Journal of Pressure Vessel Technology, 142(4), p.041507_1 - 041507_6, 2020/08
Times Cited Count:1 Percentile:0.00(Engineering, Mechanical)The phenomenon of crack closure is important in the prediction of fatigue crack growth. Several experimental data indicate the closing of fatigue cracks both under negative and positive loads at constant amplitude loading cycles, depending on the magnitude of stress amplitude and stress ratio. Appendix A-4300 of the ASME Code Section XI provides two equations of fatigue crack growth rates expressed by the stress intensity factor range for ferritic steels under negative stress ratio. The boundary of two fatigue crack growth rates is classified with the magnitude of applied stress intensity factor range, in consideration of the crack closure. The boundary value provided by the ASME Code Section XI is validated in this study through an investigation of the influence of the magnitude of the applied stress intensity factor range on crack closure, with the application of fatigue crack growth tests using ferritic steel specimens in air environment at room and high temperatures. Crack closures are obtained as a parameter of stress ratio, and herein, were found to occur at a smaller applied stress intensity factor range, as opposed to the definition given by Appendix A-4300.