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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

Investigation on the plasticity correction of stress intensity factor calculations for underclad cracks in reactor vessels

Lu, K.; Katsuyama, Jinya; Li, Y.

Nippon Kikai Gakkai M&M 2016 Zairyo Rikigaku Kanfarensu Koen Rombunshu (Internet), p.499 - 501, 2016/10

When conducting structural integrity assessments for reactor pressure vessels (RPVs) subjected to pressurized thermal shock (PTS) events, the stress intensity factor (SIF) is evaluated for a postulated surface crack in the inner surface of RPVs. It is known that the cladding made of a stainless steel is a ductile material which is overlay-welded on the inner surface, therefore, the plasticity of cladding should be considered in SIF calculations for a postulated underclad crack to ensure a conservation evaluation. Recently, the authors performed three-dimensional (3D) elastic and elastic-plastic FEAs for Japanese three-loop RPVs and proposed a rational evaluation method on SIFs of underclad cracks. In this paper, further studies were conducted to discuss the applicability of the proposed plasticity correction method. The effect of neutron irradiation was considered. In addition, different Japanese RPV geometries such as two-loop and four-loop RPVs were also investigated.

Journal Articles

Comparison of stress intensity factor solutions for surface cracks with high aspect ratio

Nagai, Masaki*; Lu, K.; Kamaya, Masayuki*

Nippon Kikai Gakkai M&M 2016 Zairyo Rikigaku Kanfarensu Koen Rombunshu (Internet), p.481 - 483, 2016/10

In nuclear power plants, a number of cracks attributed to stress corrosion cracking (SCC) have been detected in welds made with nickel alloy weld metals. One of the characteristics of these cracks is that crack aspect ratio $$a/l$$ is greater than 0.5, where a is the crack depth and $$l$$ is the crack length. When a crack is detected in components of nuclear power plants during in-service inspection, flaw evaluation is conducted according to the requirement of codes such as JSME Rules on Fitness-for-Service for Nuclear Power Plants. Here, the stress intensity factor plays an important role for predicting crack growth behavior due to fatigue and/or SCC. Although several solutions of the stress intensity factor are already given in the JSME code, no solutions are available for the cracks with $$a/l >$$ 0.5. According to the current code, surface cracks with $$a/l >$$ 0.5 are characterized as semi-circular shape $$l = 2a$$. To evaluate these cracks in a rational manner, several solutions have been proposed for cracks with $$a/l >$$ 0.5. In this paper, comprehensive comparison was made between solutions for cracks $$a/l >$$ 0.5, and benchmark analysis on SCC crack growth was performed.

Journal Articles

Stress intensity factor solutions for subsurface flaws in plates subjected to polynomial stress distributions

Lu, K.; Katsuyama, Jinya; Li, Y.; Iwamatsu, Fuminori*

Proceedings of 2016 ASME Pressure Vessels and Piping Conference (PVP 2016) (Internet), 7 Pages, 2016/07

Stress intensity factor (SIF) solutions for subsurface flaws near the free surface in plates were numerically investigated based on the finite element analyses. The flaws with aspect ratios $$a/l$$ = 0, 0.1, 0.2, 0.3, 0.4 and 0.5, the normalized ratios $$a/d$$ = 0, 0.1, 0.2, 0.4, 0.6 and 0.8 and $$d/t$$ = 0.01 and 0.1 were taken into account, where a is the half flaw depth, l is the flaw length, $$d$$ is the distance from the center of the subsurface flaw to the nearest free surface and t is the wall thickness. Fourth-order polynomial stress distributions in the thickness direction were considered. In addition, probabilistic fracture mechanics analyses were also performed and some example solutions obtained in this work were used to evaluate the conditional probability of failure of a reactor pressure vessel under a pressurized thermal shock event. The results indicated that the numerical SIF solutions calculated in this study are effective in engineering applications.

Journal Articles

Proximity factor on transformation from subsurface to surface flaw

Hasegawa, Kunio*; Li, Y.; Serizawa, Ryosuke*; Kikuchi, Masanori*; Lacroix, V.*

Procedia Materials Science, 12, p.36 - 41, 2016/00

 Times Cited Count:0 Percentile:100

If subsurface flaws are detected that are close to component free surfaces, flaw-to-surface proximity rule is used to determine whether the flaws should be treated as subsurface flaws as is, or transformed to surface flaws. However, specific factors for the proximity rules on transforming subsurface to surface flaws differ among fitness-for-service codes. The objective of the paper is to reveal the proximity factor from the stress intensity factor interaction between the subsurface flaw and the free surface.

JAEA Reports

Study on structural integrity evaluation of core shroud based on crack growth analysis (Contract research)

Onizawa, Kunio; Tsutsumi, Hideaki*; Suzuki, Masahide; Shibata, Katsuyuki; Ueno, Fumiyoshi; Kaji, Yoshiyuki; Tsukada, Takashi; Nakajima, Hajime*

JAERI-Tech 2003-073, 125 Pages, 2003/08

JAERI-Tech-2003-073.pdf:11.62MB

Concerning the cracks due to stress corrosion cracking (SCC) observed on the core shrouds of BWRs, a study was conducted on structural integrity evaluation based on crack growth analysis. The cracks investigated were those observed on the regions of lower ring and support ring of the core shroud at Kashiwazaki-Kariwa Nuclear Power Station (NPS) Unit-3, and that on the middle shell region of the core shroud at Fukushima Daiichi NPS Unit-4 of Tokyo Electric Power Company. It was confirmed through data analysis of past SCC growth rate experiments applicable to the condition of the ring regions that the SCC growth rate prescribed in the JSME rule was conservative. The analysis on the core shroud rigidity with a crack indicated that the rigidity reduction was small enough not to affect the dynamic seismic response for the regions studied. Through the comparison of the required area in a cracked section or the allowable crack length, and crack growth analysis results, it was confirmed that the integrity of the core shrouds would be maintained even 4 effective full power years later.

Journal Articles

Fatigue strength reduction factor of partial penetration weldments for ITER vacuum vessel

Nishi, Hiroshi; Eto, Motokuni; Tachibana, Katsumi; Nakahira, Masataka

Transactions of 16th International Conference on Structural Mechanics in Reactor Technology (SMiRT-16) (CD-ROM), 8 Pages, 2001/08

Fatigue test of the weldments was performed to investigate their fatigue behavior and the effect of the incomplete penetrations on the fatigue strength. Fatigue crack propagation test of their weld metals was also carried out using CT specimen. By calculating stress intensity factors of the weldments contained the incomplete penetrations and cracks using FEM analysis, the fatigue crack propagation rates of weldments were evaluated and compared those of their weld metals. Fatigue life of the weldments was evaluated based on fracture mechanics to discuss the effect of incomplete penetrations on the fatigue strength. As the results, the incomplete penetration behaved as a crack and most of total fatigue life for the weldment was crack propagation life. The crack propagation rates of weldment were in accordance with those of the weld metals. The fatigue strength of the weldment was considerably lower than that of smoothed specimen. The incomplete penetrations affected greatly the fatigue strength of the weldments even if the depth of incomplete penetrations was small.

Journal Articles

Crack propagation tests of HIPed DSCu/SS joints for plasma facing components

Hatano, Toshihisa; Goto, Masahiro*; Yamada, Tetsuji*; Nomura, Yuichiro*; Saito, Masakatsu*

Fusion Engineering and Design, 49-50, p.207 - 212, 2000/11

 Times Cited Count:3 Percentile:72.19(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Corrosion fatigue behavior of zirconium weldments in boiling nitric acid

Motooka, Takafumi; Kiuchi, Kiyoshi

JAERI-Research 96-021, 14 Pages, 1996/03

JAERI-Research-96-021.pdf:0.91MB

no abstracts in English

JAEA Reports

Corrosion fatigue behavior of zirconium in boiling nitric acid

Motooka, Takafumi; Kiuchi, Kiyoshi

JAERI-Research 95-032, 21 Pages, 1995/03

JAERI-Research-95-032.pdf:1.52MB

no abstracts in English

JAEA Reports

Revisions of fracture mechanics parameters analysis code CANIS-J(2D)

Furuhashi, Ichiro*; Wakai, Takashi

PNC-TN9410 95-080, 84 Pages, 1995/02

PNC-TN9410-95-080.pdf:2.82MB

Revisions have been done on CANIS-J(2D) that calculates fracture mechanics parameters of 2-dimensional structures containing cracks or notches. (a)Evaluation of △K between arbitrary two steps on the basis of △$$sigma$$. (b)Evaluation of △J and △J$$_{hat}$$ between arbitrary two steps on the basis of △$$sigma$$, △ε and △u. (c)Evaluation of each terms of J (△J)-integral and J$$_{hat}$$ (△J$$_{hat}$$)-integral. (d)Execution of following three mode calculations in one job run. Mode- 0 $$sim$$ calculation of K, J and J$$_{hat}$$ at any step. Mode- 1 $$sim$$ calculation of △K, △J and △J$$_{hat}$$ between arbitrary two steps. Mode- 2 $$sim$$ calculation of J and J$$_{hat}$$ between any continuous steps. To verify the validity of the revised code, we performed fracture mechanics analyses and crack growth simulations of thermal fatigue crack growth tests of circumferentially slitted cylinders subjected to cyclic thermal transients. And we got following results. (1)At thermal-elastic and at thermal-elasto-plastic conditions, J (△J) - integral is not path-independent and can not be properly evaluated. The reason is that J - integral is defined at elastic condition. (2)At thermal-elastic and at thermal-elasto-plastic conditions, J$$_{hat}$$ (△J$$_{hat}$$) -integral is good enough path-independent and can be properly evaluated. The reason is that J$$_{hat}$$ -integral is defined at more generalized stress conditions. (3)△J$$_{hat}$$hat, thermal-elastic △K △$$sigma$$ (or △ε) at near the crack tip, and net-section bending stress range S$$_{n}$$ at crack ligament, these take approximate maximum values between the common two steps. (4)Crack growth simulations based on △J$$_{hat}$$ agree well with the behaviors observed at tests. (5)These results assist that, on the fracture mechanics evaluations of flawed structures subjected to complicated thermal-elasto-plastic load cycles, J$$_{hat}$$ (△J$$_{hat}$$) -integral will be a possible fracture mechanics parameter which corresponds to ...

Journal Articles

Brittle fracture in view of micromechanics; Fatigue under reverse stress cycles

Nihon Kikai Gakkai Dai-8-Kai Keisan Rikigaku Koenkai Koen Rombunshu, 0, p.65 - 66, 1995/00

no abstracts in English

Journal Articles

Material qualification in terms of EIFS statistics calculated from fatigue fracture data

Proc. of 12th Japan-Korea Seminar on Ceramics, 0, p.301 - 305, 1995/00

no abstracts in English

JAEA Reports

Journal Articles

Effect of hold time and frequency on the fatigue crack growth rate of irradiated cold-worked type 316 stainless steel

Jitsukawa, Shiro; ; ; Iida, Shozo; ; *; Hishinuma, Akimichi

Effects of Radiation on Materials, p.1083 - 1094, 1992/00

no abstracts in English

Journal Articles

Effect of $$Delta$$K control modes on variability/reproducibility of fatigue crack growth rate data

Tsuji, Hirokazu; Nakajima, Hajime; Kondo, Tatsuo

Journal of Nuclear Materials, 189, p.65 - 71, 1992/00

 Times Cited Count:4 Percentile:57.01(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Low cyclic fatgue on fine-grained isotropic graphite

;

Nippon Genshiryoku Gakkai-Shi, 30(2), p.181 - 192, 1988/02

 Times Cited Count:2 Percentile:67.87(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Effect of stress ratio on crack extension rate of fine-grained isotropic nuclear graphite

; ;

Journal of Nuclear Science and Technology, 24(9), p.719 - 723, 1987/09

 Times Cited Count:5 Percentile:48.44(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Calculation of stress intensity factors of surface cracks in complex structures; Application of efficient computer program EPAS,J1

; *; Yagawa, Motoki*

Nucl.Eng.Des., 68, p.71 - 85, 1987/00

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

no abstracts in English

34 (Records 1-20 displayed on this page)