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Journal Articles

Improvement of the return mapping algorithm based on the implicit function theorem with application to ductile fracture analysis using the GTN model

Mano, Akihiro; Imai, Ryuta*; Miyamoto, Yuhei*; Lu, K.; Katsuyama, Jinya; Li, Y.

International Journal of Pressure Vessels and Piping, 199, p.104700_1 - 104700_13, 2022/10

Elastic-plastic analyses based on finite element methods are widely applied to simulate the nonlinear behaviors of materials. When the analysis is conducted by an implicit method, the stress values are generally updated with a time increment by using the so-called return mapping algorithm. This algorithm requires solving simultaneous nonlinear equations related to a constitutive model. In the present paper, we proposed a general method to reduce the number of equations in the return mapping algorithm based on the implicit function theorem. In addition, the proposed method was applied to the Gurson-Tvergaard-Needleman (GTN) model that considers the influence of damage due to nucleation and growth of microscopic void in materials in the simulation of the nonlinear behaviors. By using the GTN model with the proposed method, an elastic-plastic analysis was performed by the implicit method for a 4-point bending test of pipe with a through-wall crack. The numerical solution of the variation of the load-load line displacement from the analysis agreed with experimental result. Thus, we concluded that the proposed method is useful for simulating nonlinear behaviors, including void nucleation and growth in materials.

Journal Articles

Recent improvements of probabilistic fracture mechanics analysis code PASCAL for reactor pressure vessels

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

International Journal of Pressure Vessels and Piping, 199, p.104706_1 - 104706_13, 2022/10

Journal Articles

Improvement of probabilistic fracture mechanics analysis code PASCAL-SP regarding stress corrosion cracking in nickel based alloy weld joint of piping system in boiling water reactor

Mano, Akihiro; Yamaguchi, Yoshihito; Katsuyama, Jinya; Li, Y.

Journal of Pressure Vessel Technology, 144(1), p.011506_1 - 011506_9, 2022/02

In the past few decades, the cracks because of stress corrosion cracking (SCC) have been detected in the dissimilar weld joints welded using nickel based alloy in piping system of boiling water reactors. Thus, the structural integrity assessment for such weld joints has become important. Nowadays, probabilistic fracture mechanics (PFM) analysis is recognized as a rational method for structural integrity assessment because it can consider inherent uncertainties of various influencing factors as probability distributions and quantitatively evaluate the failure probability of a cracked component. The Japan Atomic Energy Agency has developed a PFM analysis code PASCAL-SP for a probabilistic structural integrity assessment of weld joint in pipe in nuclear power plant. This study improves the analysis functions of PASCAL-SP for weld joint welded using nickel based alloy in boiling water reactor susceptible to SCC. As an analysis example of the improved version of PASCAL-SP, the failure probability of a weld joint is quantitatively evaluated. Furthermore, sensitivity analyses are conducted concerning the effect of leak detection and in-service inspection. From the analysis results, it is concluded that the improved version of PASCAL-SP is useful for structural integrity assessment.

Journal Articles

Benchmark analysis of ductile fracture simulation for circumferentially cracked pipes subjected to bending

Kumagai, Tomohisa*; Miura, Yasufumi*; Miura, Naoki*; Marie, S.*; Almahdi, R.*; Mano, Akihiro; Li, Y.; Katsuyama, Jinya; Wada, Yoshitaka*; Hwang, J.-H.*; et al.

Journal of Pressure Vessel Technology, 144(1), p.011509_1 - 011509_18, 2022/02

To predict fracture behavior for ductile materials, some ductile fracture simulation methods different from classical approaches have been investigated based on appropriate models of ductile fracture. For the future use of the methods to overcome restrictions of classical approaches, the applicability to the actual components is of concern. In this study, two benchmark problems on the fracture tests supposing actual components were provided to investigate prediction ability of simulation methods containing parameter decisions. One was the circumferentially through-wall and surface cracked pipes subjected to monotonic bending, and the other was the circumferentially through-wall cracked pipes subjected to cyclic bending. Participants predicted the ductile crack propagation behavior by their own approaches, including FEM employed GTN yielding function with void ratio criterion, are FEM employed GTN yielding function, FEM with fracture strain or energy criterion modified by stress triaxiality, XFEM with J or delta J criterion, FEM with stress triaxiality and plastic strain based ductile crack propagation using FEM, and elastic-plastic peridynamics. Both the deformation and the crack propagation behaviors for monotonic bending were well reproduced, while few participants reproduced those for cyclic bending. To reproduce pipe deformation and fracture behaviors, most of groups needed parameters which were determined toreproduce pipe deformation and fracture behaviors in benchmark problems themselves and it is still difficult to reproduce them by using parameters only from basic materials tests.

Journal Articles

Constraint effect on fracture behavior of underclad crack in reactor pressure vessel

Shimodaira, Masaki; Tobita, Toru; Takamizawa, Hisashi; Katsuyama, Jinya; Hanawa, Satoshi

Journal of Pressure Vessel Technology, 144(1), p.011304_1 - 011304_7, 2022/02

In the structural integrity assessment of a reactor pressure vessel (RPV), the fracture toughness (K$$_{Jc}$$) should be higher than the stress intensity factor at the crack tip of an under-clad crack (UCC), which is prescribed in JEAC4206-2016. However, differences in crack depth and existence of cladding between the postulated crack and fracture toughness test specimens would be affected to the plastic constraint state and K$$_{Jc}$$ evaluation. In this study, we performed fracture toughness tests and finite element analyses (FEAs) to investigate the effect of cladding on K$$_{Jc}$$ evaluation. FEA showed that the cladding decreased the plastic constraint in the UCC rather than the surface crack. Moreover, it was also found that the apparent K$$_{Jc}$$ for the UCC was higher than that for the surface crack from tests and the local approach.

Journal Articles

A Novel method to uniquely determine the parameters in Gurson-Tvergaard-Needleman model

Zhang, T.; Lu, K.; Mano, Akihiro; Yamaguchi, Yoshihito; Katsuyama, Jinya; Li, Y.

Fatigue & Fracture of Engineering Materials & Structures, 44(12), p.3399 - 3415, 2021/12

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

The Gurson-Tvergaard-Needleman (GTN) model is considered a promising approach in failure prediction as it takes the micromechanical behavior of ductile metals into consideration and its function exhibits a relatively clear physical meaning. Although the GTN model has been widely investigated in the past decades, its engineering applications have scarcely progressed due to the difficulty in determining the eight strongly coupled parameters. Based on the physical background of GTN model, a set of methods was established to determine the parameters in the GTN model. The knowledge of continuum damage mechanics was used to experimentally determine the development of void volume fraction through the variation of effective Young's modulus in a uniaxial tensile test, and three parameters regarding void nucleation were analytically derived using a newly established method. Other parameters in the GTN model were also uniquely determined through a joint use of the chemical composition analysis (for the initial void volume fraction), the cell model analyses (for the two constitutive parameters), and the inverse finite element method (for the two failure parameters). The reliability of this novel parameter determination method was verified through the failure prediction of both cracked and uncracked specimens of carbon steel STPT410.

Journal Articles

Fracture toughness in postulated crack area of PTS evaluation in highly-neutron irradiated RPV steel

Ha, Yoosung; Shimodaira, Masaki; Takamizawa, Hisashi; Tobita, Toru; Katsuyama, Jinya; Nishiyama, Yutaka

Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 6 Pages, 2021/07

Journal Articles

Assessment of residual stress for thick butt-welded plate of a reactor pressure vessel steel

Ha, Yoosung; Okano, Shigetaka*; Takamizawa, Hisashi; Katsuyama, Jinya; Mochizuki, Masahito*

Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 6 Pages, 2021/07

Journal Articles

Benchmarking study on probabilistic fracture mechanics analysis codes xLPR and PASCAL-SP considering primary water stress corrosion cracking

Mano, Akihiro; Katsuyama, Jinya; Li, Y.

Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 7 Pages, 2021/07

Probabilistic fracture mechanics (PFM) is expected as a more rational methodology for the structural integrity assessments of nuclear power components because it can consider the inherent probabilistic distributions of various influencing factors and quantitatively evaluate the failure probabilities of the components. The Japan Atomic Energy Agency (JAEA) has developed a PFM analysis code, PASCAL-SP, to evaluate the failure probabilities of piping caused by aging degradation mechanisms, such as fatigue and stress corrosion cracking in the environments of both pressurized water and boiling water reactors. To improve confidence in the analysis results obtained from PASCAL-SP, a benchmarking study was conducted together with the PFM analysis code, xLPR, which was developed jointly by the U.S. Nuclear Regulatory Commission (NRC) and the Electric Power Research Institute. The benchmarking study was composed of deterministic and probabilistic analyses related to primary water stress corrosion cracking in a dissimilar metal weld joint in a pressurized water reactor surge line. The analyses were conducted independently by NRC staff and JAEA using their own codes and under common analysis conditions. In the present paper, the analysis conditions for the deterministic and probabilistic analyses are described in detail, and the analysis results obtained from the xLPR and PASCAL-SP codes are presented. It was confirmed that the analysis results obtained from the two codes were in good agreement.

Journal Articles

Development of guideline on seismic fragility evaluation for aged piping

Yamaguchi, Yoshihito; Katsuyama, Jinya; Masaki, Koichi*; Li, Y.

Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 9 Pages, 2021/07

The seismic probabilistic risk assessment is an important methodology to evaluate the seismic safety of nuclear power plants. In this assessment, the core damage frequency is evaluated from the seismic hazard, seismic fragilities, and accident sequence. Regarding the seismic fragility evaluation, the probabilistic fracture mechanics can be applied as a useful evaluation technique for aged piping systems with crack or wall thinning due to the age-related degradation mechanisms. In this study, to advance seismic probabilistic risk assessment methodology of nuclear power plants that have been in operation for a long time, a guideline on the seismic fragility evaluation of the typical aged piping systems of nuclear power plants has been developed considering the age-related degradation mechanisms. This paper provides an outline of the guideline and several examples of seismic fragility evaluation based on the guideline and utilizing the probabilistic fracture mechanics analysis code.

Journal Articles

Effect of plastic constraint and cladding on semi-elliptical shaped crack in fracture toughness evaluation for a reactor pressure vessel steel

Shimodaira, Masaki; Tobita, Toru; Nagoshi, Yasuto*; Lu, K.; Katsuyama, Jinya

Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 8 Pages, 2021/07

In the structural integrity assessment of a reactor pressure vessel (RPV), the fracture toughness (K$$_{Jc}$$) should be higher than the stress intensity factor at the crack tip of a semi-elliptical shaped under-clad crack (UCC), which is prescribed in JEAC4206-2016. However, differences in crack depth and existence of cladding between the postulated crack and fracture toughness test specimens would be affected to the plastic constraint state and K$$_{Jc}$$ evaluation. In this study, we performed fracture toughness tests and finite element analyses to investigate the effect of plastic constraint and cladding on the semi-elliptical shaped crack in K$$_{Jc}$$ evaluation. The apparent K$$_{Jc}$$ value evaluated at the deepest point of the crack exceeded 5% fracture probability based on the Master Curve method estimated from C(T) specimens, and the conservativeness of the current integrity assessment method was confirmed. Few initiation sites were observed along the tip of semi-elliptical shaped crack other than the deepest point. The plastic constraint state was also analyzed along the crack tip, and it was found that the plastic constraint at the crack tip near the surface was lower than that for the deepest point. Moreover, it was quantitatively showed that the UCC decreased the plastic constraint. The local approach suggested higher K$$_{Jc}$$ value for the UCC than that for the surface crack, reflecting the low constraint effect for the UCC.

Journal Articles

Benchmark analysis by Beremin model and GTN model in CAF subcommittee

Hirota, Takatoshi*; Nagoshi, Yasuto*; Hojo, Kiminobu*; Okada, Hiroshi*; Takahashi, Akiyuki*; Katsuyama, Jinya; Ueda, Takashi*; Ogawa, Takuya*; Yashirodai, Kenji*; Ohata, Mitsuru*; et al.

Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 9 Pages, 2021/07

Journal Articles

Effect of coolant water temperature of emergency core cooling system on failure probability of reactor pressure vessel

Lu, K.; Katsuyama, Jinya; Masaki, Koichi; Watanabe, Tadashi*; Li, Y.

Journal of Pressure Vessel Technology, 143(3), p.031704_1 - 031704_8, 2021/06

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

Journal Articles

Application of probabilistic fracture mechanics to reactor pressure vessel using PASCAL4 code

Lu, K.; Katsuyama, Jinya; Li, Y.; Yoshimura, Shinobu*

Journal of Pressure Vessel Technology, 143(2), p.021505_1 - 021505_8, 2021/04

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

JAEA Reports

Guideline on seismic fragility evaluation for aged piping (Contract research)

Yamaguchi, Yoshihito; Katsuyama, Jinya; Masaki, Koichi*; Li, Y.

JAEA-Research 2020-017, 80 Pages, 2021/02

JAEA-Research-2020-017.pdf:3.5MB

The seismic probabilistic risk assessment (seismic PRA) is an important methodology to evaluate the seismic safety of nuclear power plants. Regarding seismic fragility evaluations performed in the seismic PRA, the Probabilistic Fracture Mechanics (PFM) can be applied as a useful evaluation technique for aged piping with crack or wall thinning due to the age-related degradation. Here, to advance seismic PRA methodology for the long-term operated nuclear power plants, a guideline for the fragility evaluation on the typical aged piping of nuclear power plants has been developed taking the aged-related degradation into account.

JAEA Reports

User's manual and analysis methodology of probabilistic fracture mechanics analysis code PASCAL-SP Ver. 2 for piping (Contract research)

Yamaguchi, Yoshihito; Mano, Akihiro; Katsuyama, Jinya; Masaki, Koichi*; Miyamoto, Yuhei*; Li, Y.

JAEA-Data/Code 2020-021, 176 Pages, 2021/02

JAEA-Data-Code-2020-021.pdf:5.26MB

In Japan Atomic Energy Agency, as a part of researches on the structural integrity assessment and seismic safety assessment of aged components in nuclear power plants, a probabilistic fracture mechanics (PFM) analysis code PASCAL-SP (PFM Analysis of Structural Components in Aging LWR - Stress Corrosion Cracking at Welded Joints of Piping) has been developed to evaluate failure probability of piping. The initial version was released in 2010, and after that, the evaluation targets have been expanded and analysis functions have been improved based on the state-of-the art technology. Now, it is released as Ver. 2.0. In the latest version, primary water stress corrosion cracking in the environment of Pressurized Water Reactor, nickel based alloy stress corrosion cracking in the environment of Boiling Water Reactor, and thermal embrittlement can be taken into account as target age-related degradation. Also, many analysis functions have been improved such as incorporations of the latest stress intensity factor solutions and uncertainty evaluation model of weld residual stress. Moreover, seismic fragility evaluation function has been developed by introducing evaluation methods including crack growth analysis model considering excessive cyclic loading due to large earthquake. Furthermore, confidence level evaluation function has been incorporated by considering the epistemic and aleatory uncertainties related to influence parameters in the probabilistic evaluation. This report provides the user's manual and analysis methodology of PASCAL-SP Ver. 2.0.

Journal Articles

Stress intensity factor solutions for surface cracks with large aspect ratios in cylinders and plates

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

International Journal of Pressure Vessels and Piping, 189, p.104262_1 - 104262_12, 2021/02

 Times Cited Count:1 Percentile:76.99(Engineering, Multidisciplinary)

Journal Articles

Plasticity correction on stress intensity factor evaluation for underclad cracks in reactor pressure vessels

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

Journal of Pressure Vessel Technology, 142(5), p.051501_1 - 051501_10, 2020/10

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

Journal Articles

Constraint effect on fracture mechanics evaluation for an under-clad crack in a reactor pressure vessel steel

Shimodaira, Masaki; Tobita, Toru; Takamizawa, Hisashi; Katsuyama, Jinya; Hanawa, Satoshi

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

In JEAC 4206 which prescribes the methodology for assessing the structural integrity of reactor pressure vessels (RPVs), an under-clad crack (UCC) at the inner surface of RPV is postulated, and it is required that the fracture toughness of RPV steels is higher than stress intensity factor for at the crack tip during the pressurized thermal shock event. In the present study, to investigate the effect of cladding on the fracture toughness, we performed three-point bending fracture toughness tests and finite element analyses (FEAs) for an RPV steel containing an UCC or a surface crack, and the constraint effect for UCC was also discussed. As the result, we found that the fracture toughness for UCC was considerably higher than that for surface crack. On the other hand, the FEAs showed that the cladding decreased the constraint effect for UCC.

Journal Articles

Probabilistic fracture mechanics benchmarking study involving the xLPR and PASCAL-SP codes; Analysis by PASCAL-SP

Mano, Akihiro; Katsuyama, Jinya; Li, Y.

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

A probabilistic fracture mechanics (PFM) analysis code PASCAL-SP has been developed by Japan Atomic Energy Agency (JAEA) for evaluating the failure probability of piping in nuclear power plant considering aged-related degradations such as primary water stress corrosion cracking (PWSCC) in pressurized water reactor environments and fatigue. To strengthen the confidence of analysis results, benchmarking study is being performed with PFM analysis code xLPR which has been developed by U.S.NRC in collaboration with EPRI. The benchmarking study consists of deterministic and probabilistic analyses on PWSCC under the common analysis conditions. In addition, deterministic sensitivity analysis on weld residual stress distributions is also included in the benchmarking study. These analyses are carried out by U.S.NRC and JAEA independently using their own codes. At current stage, the deterministic analyses by both xLPR and PASCAL-SP codes have been finished and probabilistic analyses are underway. This paper presents the details of conditions and comparisons of the results between the two codes in the deterministic analyses. In the deterministic analyses, both codes provided almost the same results including the values of stress intensity factor. In addition, probabilistic analysis conditions and results obtained from PASCAL-SP are presented.

258 (Records 1-20 displayed on this page)