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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

Effect of 3-D initial imperfections on the deformation behaviors of head plates subjected to convex side pressure

Yada, Hiroki; Ando, Masanori; Tsukimori, Kazuyuki; Ichimiya, Masakazu*; Anoda, Yoshinari*

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 9 Pages, 2018/07

Containment vessel (CV) of nuclear power plants is an important structure to prevent radioactive release, however, the safety margin of the CV against pressure are not numerically clarified. The head plate structure is included in CV boundary of fast reactor. In order to develop the evaluation method of the ultimate strength of the head plate structure at beyond the specified limit, pressure failure tests and finite element analysis (FEA) of the head plates subjected to convex side pressure were performed. In the test of the relative thin thickness head plate, non-axisymmetric deformations was observed in post buckling behavior and failure pressure was lower than other cases. To evaluate non-axisymmetric deformations in the test, FEA using 3-D solid model constructed by precise dimensions of the test specimen, moreover, FEA using simplified model with uniform or non-uniform thickness were performed. Through analyses, the feature of the post buckling behavior was discussed.

Journal Articles

Development of seismic countermeasures against cliff edges for enhancement of comprehensive safety of nuclear power plants; Cliff edges relevant to NPP building system

Nishida, Akemi; Choi, B.; Yamano, Hidemasa; Takada, Tsuyoshi*

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 11 Pages, 2018/07

This study identified and quantified possible cliff edge effects through a seismic safety evaluation of a nuclear power plant, based on the concepts of risk and defense in depth. Cliff edges of the both physical and knowledge-based type were considered in this study. We investigated a seismic isolation effect, etc., for physical cliff edges, and the modeling of the target structure, boundary conditions, etc., for knowledge-based cliff edges. Response analysis was performed using a sway-rocking (SR) model and a three-dimensional model of the target building. The seismic isolation effect of the base-isolated building was confirmed by comparison to the results of earthquake-resistant building. In the case of a collision with the retaining wall of the base-isolated building, the level of damage was found to depend on the modeling of the collision condition assumed. On the other hand, the study confirmed the differences between the results from the SR model and the three-dimensional model.

Journal Articles

Development of crack evaluation models for probabilistic fracture mechanics analyses of Japanese reactor pressure vessels

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

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 8 Pages, 2018/07

Journal Articles

Fracture toughness evaluation of heat-affected zone under weld overlay cladding in reactor pressure vessel steel

Ha, Yoosung; Tobita, Toru; Takamizawa, Hisashi; Hanawa, Satoshi; Nishiyama, Yutaka

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

Journal Articles

Development of probabilistic fracture mechanics analysis code PASCAL Version 4 for reactor pressure vessels

Lu, K.; Masaki, Koichi; Katsuyama, Jinya; Li, Y.; Uno, Shumpei*

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

Journal Articles

Verification of probabilistic fracture mechanics analysis code through benchmark analyses

Li, Y.; Uno, Shumpei*; Masaki, Koichi; Katsuyama, Jinya; Dickson, T.*; Kirk, M.*

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 11 Pages, 2018/07

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

Crack growth prediction for cracked dissimilar metal weld joint in pipe under large seismic cyclic loading

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

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 8 Pages, 2018/07

In order to assess the structure integrity of cracked pipes considering occurrence of large earthquakes, crack growth evaluation method for cracked pipes is important. In present study, evaluation method of crack growth by seismic loading was proposed for a dissimilar metal weld joint of nickel based alloy through experimental study using small specimens. Then, validation of the proposed method was performed through crack growth tests by using dissimilar metal weld pipe with circumferential through-wall crack. The predicted crack growth values were in good agreement with the experimental results and the applicability of the proposed method was confirmed.

Journal Articles

Fatigue crack growth for ferritic steel under negative stress ratio

Yamaguchi, Yoshihito; Hasegawa, Kunio; Li, Y.

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

Crack closure during fatigue crack growth is an important phenomenon for predicting fatigue crack growth amount. Much experimental data shows that fatigue cracks close at not only negative loads but also positive loads during a constant amplitude loading cycle. The Appendix A-4300 in the ASME Code Section XI provides two equations of fatigue crack growth rates expressed by stress intensity factor range for ferritic steels under negative stress ratio. One is the equation taking into account crack closure and the other does not consider the crack closure. The boundary of crack closure is classified by the magnitude of applied stress intensity factor range. The objective of this paper is to investigate the influence of the magnitude of stress intensity factor range on crack closure. Fatigue tests have been performed on ferritic steel in air environment at room and high temperatures. Crack closures were obtained as a parameter of stress ratio. It was found that crack closure occurs more small applied stress intensity factor range than the definition given by the Appendix A-4300.

Journal Articles

Sensitivity study on the effects of nondestructive examinations on failure probabilities of reactor pressure vessels

Arai, Kensaku*; Katsuyama, Jinya; Li, Y.

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 7 Pages, 2018/07

We have developed an analysis code called PASCAL for assessing failure frequencies of RPVs based on probabilistic fracture mechanics. In failure frequency analyses, flaw size distribution in RPVs is one of the most important parameters, and it is determined by considering possible flaws generated during fabrication and the flaw-detection capabilities of nondestructive examinations (NDEs). In this study, the effects of NDEs on failure frequencies of RPVs are evaluated using PASCAL considering probability of detection (POD) in terms of minimum detectable flaw size, the smallest probability of non-detection (PND), and flaw size where POD value reaches the smallest PND.

Journal Articles

Appropriate damping on seismic design analysis for inelastic response assessment of piping

Watakabe, Tomoyoshi; Morishita, Masaki

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

A new Code Case for seismic design of piping is now under development in the framework of JSME Nuclear Codes and Standards as an alternative rule to the current design rule. Simplified analysis with an additional damping taking the response reduction due to plasticity into account is now under consideration to incorporate the convenience in design. In this study, a series of analysis was made to see the adequacy of the simplified inelastic analysis. Design margins contained in the current design analysis method composed of response spectrum analysis and stress factors was quantitatively assessed in the view point of additional damping.

Journal Articles

Application of JSME Seismic Code Case by elastic-plastic response analysis to practical piping system

Otani, Akihito*; Kai, Satoru*; Kaneko, Naoaki*; Watakabe, Tomoyoshi; Ando, Masanori; Tsukimori, Kazuyuki*

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

This paper demonstrates an application result of the JSME Seismic Code Case to an actual complex piping system. The secondary coolant piping system of Japanese Fast Breeder Reactor, Monju, was selected as a representative of the complex piping systems. The elastic-plastic time history analysis for the piping system was performed and the piping system has been evaluated according to the JSME Seismic Code Case. The evaluation by the Code Case provides a reasonable result in terms of the piping fatigue evaluation that governs seismic integrity of piping systems.

Journal Articles

Fast reactor core seismic experiment and analysis under strong excitation

Yamamoto, Tomohiko; Iwasaki, Akihisa*; Kawamura, Kazuki*; Matsubara, Shinichiro*; Harada, Hidenori*

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 8 Pages, 2018/07

To design fast reactor (FR) core components, seismic response must be evaluated in order to ensure structural integrity. Thus, a core seismic analysis method has been developed to evaluate 3D core vibration behavior considering fluid structure interaction and vertical displacements (rising). 1/1.5 scale 37 core element mock-ups hexagonal-matrix experiment was performed to validate the core elements vibration analysis code in three dimensions (REVIAN-3D). Based on the test data, the analysis model newly incorporated to respond to strong excitation was verified.

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

Numerical study on longitudinal distance effect on failure stress of non-aligned twin cracked pipe

Nguyen, T.-L.*; Lee, M.-W.*; Hasegawa, Kunio; Kim, Y.-J.*

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 7 Pages, 2018/07

The effect of longitudinal distance H between non-aligned twin cracks is investigated using finite element damage analysis. It is shown that the failure bending stresses are raised by increasing longitudinal distance H for deep short cracks. On the contrary, shallow long cracks are unaffected by the distance H.

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