Study on Flaw-to-Surface Proximity Rule for Transforming Subsurface Flaws to Surface Flaws Based on Fatigue Crack Growth Experiments

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Koichi Saito
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Surface Flaw ◽  
Crack Growth Behavior ◽  
Surface Flaws ◽  
Asme Code ◽  
Tensile Experiment ◽  
Growth Experiments ◽  
Surface Proximity

If a subsurface flaw is located very near a component surface, the subsurface flaw is categorized as a surface flaw. The boundary of the subsurface and surface flaws is required for flaw evaluation. The subsurface flaw is transformed to a surface flaw in accordance with a flaw-to-surface proximity rule. The recharacterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes. However, the specific criteria of the recharacterizations are different among the FFS codes. Cyclic tensile experiment was conducted on a carbon steel flat plate with a subsurface flaw at ambient temperature. The objective of the paper is to compare the experiment and calculation of fatigue crack growth behavior for a subsurface flaw and the transformed surface flaw, and to check the validity of the flaw-to-surface proximity rule defined by ASME Code Section XI, JSME S NA1 Code and other codes.

Fatigue Crack Growth for Subsurface Flaws Near Component Surface and Proximity Rules

2013 ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Katsumasa Miyazaki ◽  
Koichi Saito
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Behavior ◽  
Surface Flaw ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior ◽  
Asme Code ◽  
Tensile Experiment ◽  
Surface Proximity

If a subsurface flaw is located near a component surface, the subsurface flaw is transformed to a surface flaw in accordance with a flaw-to-surface proximity rule. The re-characterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes. However, the criteria of the re-characterizations are different among the FFS codes. Cyclic tensile experiment was conducted on a carbon steel flat plate with a subsurface flaw at ambient temperature. The objective of this paper is to compare the experiment and calculation of fatigue crack growth behavior for a subsurface flaw and the transformed surface flaw, and to describe the validity of the flaw-to-surface proximity rule defined by ASME Code Section XI, JSME S NA1 Code and other codes.

Comparison of Experiment and Calculation on Fatigue Crack Growth for Transformed Surface Flaw

2012 ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Katsumasa Miyazaki ◽  
Koichi Saito
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Behavior ◽  
Surface Flaw ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior ◽  
Asme Code ◽  
Tensile Experiment ◽  
Surface Proximity

If a subsurface flaw is located near a component surface, the subsurface flaw is transformed to a surface flaw in accordance with a flaw-to-surface proximity rule. The re-characterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes. However, the criteria of the re-characterizations are different among the FFS codes. Cyclic tensile experiment was conducted on a carbon steel flat plate with a subsurface flaw at ambient temperature. The objective of this paper is to compare the experiment and calculation of fatigue crack growth behavior for a subsurface flaw and the transformed surface flaw, and to confirm the flaw-to-surface proximity rule defined by ASME Code Section XI and JSME S NA1 Code.

Proposal of a New Subsurface-to-Surface Flaw Transformation Rule for Fatigue Crack Growth Analyses

2017 ◽  
Author(s):  
Valéry Lacroix ◽  
Afaf Bouydo ◽  
Genshichiro Katsumata ◽  
Yinsheng Li ◽  
Kunio Hasegawa
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Surface Flaw ◽  
Transformation Rule ◽  
Limit Value ◽  
Aspect Ratios ◽  
Asme Code ◽  
Growth Experiments ◽  
Surface Proximity

When a subsurface flaw is located near the component free surface, the first step consists of characterizing the flaw as surface or subsurface in compliance with subsurface-to-surface flaw proximity rules. The re-characterization process from subsurface to surface flaw is addressed in all Fitness-for-Service (FFS) Codes. However, the specific criteria for the rules on transforming subsurface flaws to surface flaws are different among the FFS Codes. This re-characterization concept is essential and important for subsurface flaws in the flaw assessment procedures. It is applied for three stages of the flaw assessment: at service inspection for flaw characterization, at subcritical crack growth calculation, such as fatigue crack growth, and at ductile/brittle fracture assessment. In this frame, fatigue crack growth experiments were recently conducted by the authors and it was highlighted that the subsurface-to-surface transformation is highly sensitive to the aspect ratio a/l of the flaw whereas the proximity factors in the rules are defined by constant values i.e., regardless of the flaw aspect ratios a/l. The authors have therefore proposed a new subsurface-to-surface flaw proximity rule based on experimental data and equivalent fatigue crack growth rates. Then, the authors demonstrated through numerous Fatigue Crack Growth (FCG) calculations that the current ASME B&PV Code Section XI surface proximity factor should be updated according to the type of component i.e., piping or vessel. The paper summarizes all the steps leading to the improvement of the ASME Code Section XI subsurface-to-surface proximity rule, from the fatigue crack growth experiments to the studies of the suitability of the current flaw-to-surface proximity factor. Furthermore, based on additional fatigue crack growth calculations and more refined investigations, the paper proposes finally a new limit value for the surface proximity factor. As a result, a proposal for modification of the ASME Code Section XI, Appendix C is provided. The paper is used for the technical basis of this proposal.

Development of Fatigue Crack Growth Thresholds for Austenitic Stainless Steels Exposed to Air Environment for ASME Code Section XI

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Kunio Hasegawa ◽  
Saburo Usami
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Stainless Steels ◽  
Stress Ratio ◽  
Austenitic Stainless Steels ◽  
Stress Intensity Factor Range ◽  
Asme Code ◽  
American Society ◽  
Growth Experiments

Fatigue crack growth thresholds ΔKth define stress intensity factor range below which cracks will not grow. The thresholds ΔKth are useful in industries to determine durability lifetime. Although massive fatigue crack growth experiments for stainless steels in air environment had been reported, the thresholds ΔKth are not codified at the American Society of Mechanical Engineers (ASME) Code Section XI, as well as other fitness-for-service (FFS) codes and standards. Based on the investigation of a few FFS codes and review of literature survey of experimental data, the thresholds ΔKth exposed to air environment have been developed for the ASME Code Section XI. A guidance of the thresholds ΔKth for austenitic stainless steels in air at room and high temperatures can be developed as a function of stress ratio R.

Analysis of Environmental Fatigue Crack Growth Behavior of Type 347 Stainless Steels Under Simulated PWR Water Conditions

2017 ◽  
Author(s):  
Seokmin Hong ◽  
Ki-Deuk Min ◽  
Soon-Hyeok Jeon ◽  
Bong-Sang Lee
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Stainless Steels ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior ◽  
Water Conditions ◽  
Asme Code

In this study, the fatigue crack growth behavior of Type 347 stainless steel (SS) used in pressurizer surge line in Korea Standard Nuclear Power Plant was analyzed. Environmental fatigue crack growth rates (FCGRs) were evaluated using pre-cracked compact tension (CT) specimens under the various simulated PWR water conditions; different levels of dissolved oxygen (DO) and loading frequencies. FCGRs of 347SSs were accelerated under PWR water conditions. When DO levels increased and frequency decreased, FCGR of 347SS increased. Under the more corrosive environment at crack tip, FCGRs were accelerated more. FCGRs of 347SSs under PWR water condition were compared with reference FCGR curves of stainless steel in ASME code section XI, ASME Code Case N-809, and JSME based on FCGR data of 304SS and 316SS. In this study, FCGRs of 347SS were slightly faster than reference curves in JSME under PWR environment but slower than that in JSME under BWR environment. Compared to reference FCGR curve in ASME Code Case N-809, FCGRs of 347 stainless steels are similar or slightly higher.

Effect of the Thickness on Re-Characterisation of Subsurface to Surface Flaw: Application on Piping and Vessels

2016 ◽  
Author(s):  
Valéry Lacroix ◽  
Genshichiro Katsumata ◽  
Yinsheng Li ◽  
Kunio Hasegawa
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Surface Flaw ◽  
Thick Wall ◽  
Thin Wall ◽  
Rule Based ◽  
Asme Code ◽  
Crack Growth Rates ◽  
Wall Components

If a subsurface flaw is located near a component surface, the subsurface flaw is transformed to a surface flaw in accordance with a subsurface-to-surface flaw proximity rule. The re-characterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes in different countries. However, the specific criteria of the recharacterizations are different among the FFS codes. The authors have proposed a new subsurface-to-surface flaw proximity rule based on experimental data and equivalent fatigue crack growth rates. Recently, the authors have highlighted through numerous fatigue crack growth calculations that, on one hand, the proximity rule provided in the current ASME Boiler and Pressure Vessel Code Section XI (ASME Code Section XI) can provide non conservative fatigue lives for thin wall components like pipes and, on the other hand, for thick wall components like vessels, the current proximity rule and the proposed one provide relatively similar fatigue lives. It appears therefore that the flaw-to-surface factor should be updated according to the thickness of the component or according to the type of component i.e. pipe or vessel. In this study, fatigue crack growth calculations were carried out on additional flaw configurations in thick wall pipes and thin wall vessels in order define the best limit for the thickness-dependence of the fatigue lives. Finally, a new subsurface to surface proximity rule depending on the thickness of the component is proposed.

Fatigue Crack Growth Calculations for Vessels Considering Subsurface to Surface Flaw Proximity Rules

2015 ◽  
Author(s):  
Valéry Lacroix ◽  
Kunio Hasegawa ◽  
Yinsheng Li
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Surface Flaw ◽  
Thick Wall ◽  
Intensity Factors ◽  
Extended Finite Element ◽  
Rule Based ◽  
Aspect Ratios ◽  
Asme Code

If a subsurface flaw is located near a component surface, the subsurface flaw is transformed to a surface flaw in accordance with a subsurface-to-surface flaw proximity rule. The re-characterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes. However, the specific criteria of the re-characterizations are different among the FFS codes. Recently, the authors have proposed a new subsurface-to-surface flaw proximity rule based on the experiments data and the interaction of stress intensity factors. In this study, extended Finite Element fatigue crack growth calculations were carried out for thick wall component like vessels with subsurface flaws, using the proposed subsurface-to-surface flaw proximity rule and the proximity rule provided in the current ASME Code Section XI. Different, flaw aspect ratios and ligament distances from subsurface flaws to inner surface of vessel were taken into account. As the results, the current proximity rule and proposed one provide relatively similar fatigue lives, whatever the aspect ratios of the initial subsurface flaws. However, when the thickness of the component decreases this similarity between both proximity rules appears not to be valid anymore.

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