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Journal Articles

Allowable external flaws and acceptance standards for high toughness ductile pipes subjected to bending moment and internal pressure

Hasegawa, Kunio; Li, Y.; Lacroix, V.*; Mares, V.*

Proceedings of ASME 2020 Pressure Vessels and Piping Conference (PVP 2020) (Internet), 6 Pages, 2020/08

Authors have developed more precise equations using the Limit Load Criteria, which is called Modified Limit Load Criteria, hereafter. As the results of the Modified Limit Load Criteria, failure stresses for external flawed pipes are always smaller than the failure stresses obtained by the Limit Load Criteria provided by the ASME Code Section XI. It seems that the allowable flaw sizes of the Acceptance Standards provided by the ASME Code Section XI are less conservative for external flaws. The objective of this paper is to demonstrate difference of failure stresses by the Limit Load Criteria and Modified Limit Load Criteria for external flawed pipes. In addition, the allowable flaws of the Acceptance Standards are examined by large and small diameter pipes with external flaws using the Modified Limit Load Criteria.

Journal Articles

Assessment of flaw interaction under combined tensile and bending stresses; Suitability of ASME code case N877-1

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

Proceedings of ASME 2020 Pressure Vessels and Piping Conference (PVP 2020) (Internet), 7 Pages, 2020/08

When detected flaws are in close proximity, proximity rules given in the Fitness-foe Service codes require to combine the interacting flaws into a single flaw. ASME Code Case N877-1 provides alternative proximity rules for multiple radial oriented planar flaws. The calculations of flaw interaction have been performed under pure membrane stress. However, actual loading conditions induce non-uniform stresses in the component thickness direction. The objective of this paper is assess the suitability of ASME Code Case N877-1 with regards to the presence of a bending part in the applied stress distribution. For that purpose, various applied stress profiles and flaw configurations are covered. The effect on flaw interaction is assessed trough three-dimensional XFEM analyses.

Journal Articles

Treatment of the interaction with the free surface of the component for combined subsurface flaws; Technical basis for revision of IWA-3300 and Table IWB/IWC-3510-1

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

Proceedings of ASME 2020 Pressure Vessels and Piping Conference (PVP 2020) (Internet), 8 Pages, 2020/08

When flaws are detected in pressure retaining components, a flaw characterization has to be carried out in order to determine unequivocally the flaw geometry. This flaw characterization is done according to rules provided in the FFS codes. The first step of the flaw characterization addresses the interaction of the flaw and the free surface. The second step of the flaw characterization addresses the interaction of the flaw with the adjacent flaws. In the ASME Code Sec. XI, there is a lack on how to treat the interaction of a combined flaw and the free surface of the component. The ASME Code Sec. XI flaw characterization is not clear. Some typical examples of unrealistic flaw assessment rules are depicted in this paper. The paper is used as technical basis for improvement of the ASME Code in order to clarify the treatment of combined flaw in the flaw characterization (IWA-3300, IWB/IWC-3510-1)

Journal Articles

Application scope of limit load criterion for ductile material pipes with circumferentially external cracks

Hasegawa, Kunio; Li, Y.; Lacroix, V.*; Mares, V.*

Journal of Pressure Vessel Technology, 142(3), p.031506_1 - 031506_7, 2020/06

 Times Cited Count:1 Percentile:46.82(Engineering, Mechanical)

Bending stress at plastic collapse for a circumferentially cracked pipe is predicted by limit load criterion provided by the Appendix C of the ASME Code Section XI. The equation of the Appendix C is applicable for pipes with both external and internal surface cracks. On the other hand, the authors have developed a more precise equation. From the comparison of Appendix C equation and the new equation, the plastic collapse stress estimated by the Appendix C equation gives less conservative bending capacity prediction for external cracked pipes with thick wall thickness and large crack angle. This paper discusses the limitation scope to use the limit load criterion of the Appendix C equation.

Journal Articles

Plastic collapse stresses for thick wall pipes with external cracks

Hasegawa, Kunio; Li, Y.; Lacroix, V.*; Mares, V.*

Proceedings of 2019 ASME Pressure Vessels and Piping Conference (PVP 2019) (Internet), 8 Pages, 2019/07

Bending stress at plastic collapse for a circumstantially cracked pipe is predicted by limit load equation provided by the Appendix C of the ASME Code Section XI. The equation of the Appendix C is applicable for pipes with both external and internal surface cracks. On the other hand, authors had developed an equation taking into account the pipe mean radii at non-cracked area and at cracked ligament area. From the comparison of Appendix C equation and the new equation, the plastic collapse stress estimated by the Appendix C equation gives 20 to 30% less conservative for external cracked pipes with small $$R_{m}/t$$, where $$R_{m}$$ is the pipe mean radius and t is the pipe wall thickness. This paper discusses the limitation of the use of $$R_{m}/t$$ for the Appendix C equation.

Journal Articles

Consideration on fatigue crack growth thresholds under negative stress ratio

Hasegawa, Kunio; Usami, Saburo*; Lacroix, V.*

Proceedings of 2019 ASME Pressure Vessels and Piping Conference (PVP 2019) (Internet), 6 Pages, 2019/07

Fatigue crack growth thresholds are provided by several fitness-for-service (FFS) codes. When evaluating cracked components subjected to cyclic loading, maximum stress intensity factor and/or minimum stress intensity factor are required. However, the definitions of the thresholds under negative stress ratio $$R$$ are not clearly written. In addition, the thresholds are given by constant values under negative $$R$$. This paper shows that the maximum stress intensity factor converted by the thresholds obtained by experimental data are not constant values under negative $$R$$. The thresholds for the FFS codes are less conservative. The definition of the thresholds under negative $$R$$ ratio are discussed.

Journal Articles

A Comparison of proximity rules for surface planar flaws

Bouydo, A.*; Dulieu, P.*; Lacroix, V.*; Hasegawa, Kunio; Mares, V.*

Proceedings of 2019 ASME Pressure Vessels and Piping Conference (PVP 2019) (Internet), 10 Pages, 2019/07

Journal Articles

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

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

Proceedings of 2019 ASME Pressure Vessels and Piping Conference (PVP 2019) (Internet), 9 Pages, 2019/07

Journal Articles

Plastic collapse stresses based on flaw combination rules for pipes containing two circumferential similar flaws

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

Journal of Pressure Vessel Technology, 141(3), p.031201_1 - 031201_5, 2019/06

 Times Cited Count:0 Percentile:100(Engineering, Mechanical)

When discrete multiple flaws are in the same plane, and they are close to each other, it can be determined whether they are combined or standalone in accordance with combination rules provided by Fitness-For-Service (FFS) codes. However, specific criteria of the rules are different amongst these FFS codes. On the other hand, plastic collapse bending stresses for stainless steel pipes with two circumferential similar flaws were obtained by experiments and the prediction procedure for collapse stresses for pipes with two similar flaws were developed analytically. Using the experimental data and the analytical procedure, plastic collapse stresses for pipes with two similar flaws are compared with the stresses in compliance with the flaw combination criteria. It is shown that the calculated plastic collapse stresses based on the flaw combination criteria are significantly different from the experimental and analytical stresses.

Journal Articles

Plastic collapse stresses for pipes with inner and outer circumferential cracks

Mares, V.*; Hasegawa, Kunio; Li, Y.; Lacroix, V.*

Journal of Pressure Vessel Technology, 141(2), p.021203_1 - 021203_6, 2019/04

 Times Cited Count:2 Percentile:61.04(Engineering, Mechanical)

Appendix C-5320 of ASME BPV Code Section XI provides an equation of bending stress at the plastic collapse, where the equation is applicable for both inner and outer surface cracks. That is, the collapse stresses for pipes with inner and outer surface cracks are the same. Authors considered the separated pipe mean radii at the cracked ligament and at the un-cracked ligament and equations of plastic collapse stresses for both inner and outer cracked pipes were developed. As the results of the calculations, when the crack angle and depth are the same, the collapse stress for outer cracked pipe is lower than that calculated by the Appendix C equation. It is found that the Appendix C equation gives un-conservative plastic collapse stress.

Journal Articles

Stress intensity factors for transformed surface flaws and remaining fatigue lives based on flaw-to-surface proximity rules

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

Journal of Pressure Vessel Technology, 140(5), p.051204_1 - 051204_7, 2018/10

 Times Cited Count:0 Percentile:100(Engineering, Mechanical)

Journal Articles

Prediction for plastic collapse stresses for pipes with inner and outer circumferential flaws

Hasegawa, Kunio; Li, Y.; Mares, V.*; Lacroix, V.*

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 5 Pages, 2018/07

Appendix C-5320 of ASME Code Section XI provides a formula of bending stress at the plastic collapse, where the formula is applicable for both inner and outer surface flaws. Authors considered the separated pipe mean radii at the flawed ligament and at the un-flawed ligament and formulas of plastic collapse stresses for each inner and outer flawed pipe were obtained. It is found that the collapse stress for inner flawed pipe is slightly higher than that calculated by Appendix C-5320 formula, and the collapse stress for outer flawed pipe is slightly lower than that by Appendix C-5320 formula. The collapse stresses derived from the three formulas are almost the same in most instances. For less common case where the flaw angle and depth are very large for thick wall pipes, the differences among the three collapse stresses become large.

Journal Articles

Plastic collapse stresses for pipes with circumferential twin flaws using combination rules

Hasegawa, Kunio; Li, Y.; Kim, Y.-J.*; Lacroix, V.*; Bohumir, S.*

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 6 Pages, 2018/07

When discrete multiple flaws are close to each other, it is determined whether they are combined or standalone in accordance with combination rules provided by fitness-for-service codes. However, specific criteria of the rules are different. On the other hand, plastic collapse bending stresses for stainless steel pipes with circumferential twin flaws were obtained by experiments. Using the experimental data and the analytical procedure, plastic collapse stresses for pipes with twin flaws are compared with the stresses in compliance with the combination criteria. It is shown that the calculated plastic collapse stresses based on the combination criteria are significantly different from the experimental and analytical stresses.

Journal Articles

Rules for flaw interaction for subsurface flaws in operating pressurized vessels; Technical basis of code case N-877

Lacroix, V.*; Dulieu, P.*; Blasset, S.*; Tiete, R.*; Li, Y.; Hasegawa, Kunio; Bamford, W.*; Udyawar, A.*

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 10 Pages, 2018/07

Journal Articles

Alternative characterization rules for multiple surface planar flaws

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

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 10 Pages, 2018/07

Journal Articles

Proposal of a new subsurface-to-surface flaw transformation rule for fatigue crack growth analyses

Lacroix, V.*; Bouydo, A.*; Katsumata, Genshichiro*; Li, Y.; Hasegawa, Kunio

Proceedings of 2017 ASME Pressure Vessels and Piping Conference (PVP 2017) (CD-ROM), 7 Pages, 2017/07

Journal Articles

Introduction of subsurface proximity criteria in the world and stress intensity factors for transformed surface flaws

Hasegawa, Kunio; Li, Y.; Katsumata, Genshichiro*; Dulieu, P.*; Lacroix, V.*

Proceedings of 2017 ASME Pressure Vessels and Piping Conference (PVP 2017) (CD-ROM), 6 Pages, 2017/07

Net-section stress at the ligament between component free surface and subsurface flaw increases when the ligament distance is short. It can be easily expected that stress intensity factors increase when the subsurface flaw locates near the free surface. To avoid catastrophic failures caused by ligament failure, fitness-for-service (FFS) codes provide flaw-to-surface proximity rules. The proximity rules are used to determine whether the flaws should be treated as subsurface flaws as-is, or transformed to surface flaws. The stress intensity factor for the transformed surface flaw increases furthermore. The increment of the stress intensity factor before and after transformation depends on the location of the subsurface flaw. Although the concept of the proximity rules are the same, the specific criteria for the rules on transforming subsurface flaws to surface flaws differ amongst FFS codes. Particularly, the criteria are different amongst the same organizations of ASME (American Society of Mechanical Engineers). The proximity criteria of the FFS codes in the world were introduced in this paper. In addition, the stress intensity factors based on the different criteria used in the ASME Codes are compared.

Journal Articles

Stress intensity factor interaction of subsurface flaws under notches

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

Proceedings of 2017 ASME Pressure Vessels and Piping Conference (PVP 2017) (CD-ROM), 5 Pages, 2017/07

The stress intensity factors of the subsurface flaws are affected by the stress concentrations caused by the notches. The interaction of stress intensity factor increases with increasing stress concentration factor and decreasing the ligament distance between the tips of the subsurface flaws and the notches for a given notch width. Such subsurface flaws shall be transformed to surface flaws at far distance of the notch tips for conservative evaluations. This paper shows the interactions of stress intensity factors of subsurface flaws under stress concentration fields. Based on the interaction, a flaw-to-surface proximity criterion for a circular flaw is proposed under the stress concentration field induced by a notch.

Journal Articles

Remaining fatigue lives of similar surface flaws in accordance with combination rules

Lu, K.; Li, Y.; Hasegawa, Kunio*; Lacroix, V.*

Journal of Pressure Vessel Technology, 139(2), p.021407_1 - 021407_6, 2017/04

 Times Cited Count:1 Percentile:87.61(Engineering, Mechanical)

Journal Articles

Effect of interaction of embedded crack and free surface on remaining fatigue life

Katsumata, Genshichiro*; Lacroix, V.*; Li, Y.

AIMS Materials Science, 3(4), p.1748 - 1758, 2016/12

28 (Records 1-20 displayed on this page)