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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
Tsuji, Akihiro*; Zhang, S.*; Hashimoto, Tadafumi*; Okano, Shigetaka*; Shobu, Takahisa; Mochizuki, Masahito*
Zairyo, 65(9), p.665 - 671, 2016/09
It is necessary to control weld residual stress which has negative influence on fracture strengths. In structural steel welds, complex residual stress fields are formed due to phase transformation that occur according to the thermal cycles. In this study, in-situ evaluation of phase transformation and transitional stress simultaneously during welding is discussed. In the test using SM490A, after cooling process, stress evaluated by this system showed good agreement with that evaluated by lab X-ray. During austenite to ferrite transformation in weld metal, tensile stress occurred in austenite and compressive stress occurred in ferrite. Moreover, stress concentration was occurred in ferrite phase immediately after the start of phase transformation. Also, stress concentration was occurred in austenite phase just before the end of phase transformation.
Ihara, Ryohei*; Hashimoto, Tadafumi*; Mikami, Yoshiki*; Katsuyama, Jinya; Onizawa, Kunio; Mochizuki, Masahito*
Nihon Hozen Gakkai Dai-7-Kai Gakujutsu Koenkai Yoshishu, p.611 - 616, 2010/07
In light-water reactor nuclear power stations, stress corrosion cracking (SCC) has been observed near the welded joint in recirculation piping made of low-carbon austenitic stainless steel. Residual stress is one of the most important factors in the occurrence and propagation of SCC. The joining process of pipes which usually consists of surface machining and welding results in high tensile residual stress. In this study, finite element analysis method was developed to evaluate residual stress generated by surface machining considering the shape of machining tool and machining condition. Residual stress due to surface machining was measured by X-ray diffraction method and analysed the method developed. It was shown that high tensile residual stress due to machining occurred very limited surface region. It was also shown that surface machining affected SCC growth behavior significantly from the SCC analysis results based on residual stress distributions due to surface machining and welding.
Mochizuki, Masahito*; Mori, Hiroaki*; Katsuyama, Jinya
Proceedings of 2010 ASME Pressure Vessels and Piping Conference (PVP 2010) (CD-ROM), 8 Pages, 2010/07
To make clear the effects of residual stress and work hardening on IGSCC behavior in the welds of the austenitic stainless steel with surface hardening, residual stress and hardness in butt-joints of pipes are evaluated by 3D thermo-elastic-plastic analysis. The grain boundary (GB) sliding behavior is examined using constant strain rate tensile test with the numerically simulated tensile residual stress due to welding and surface machining. It was made clear that GB sliding occurred at 561 K. It was also indicated that the GB sliding in cold-rolled one occurred in smaller strain conditions than that in solution treated one, and that the amount of GB sliding increased with added strain. In addition, it was clarified that the GB energy was raised by the GB sliding. It is concluded from these results that the cause of IGSCC in the welds of stainless steel with surface hardening is the increase in GB energy due to GB sliding accelerated by residual stress of welding and surface hardening.
Ihara, Ryohei*; Katsuyama, Jinya; Onizawa, Kunio; Hashimoto, Tadafumi*; Mikami, Yoshiki*; Mochizuki, Masahito*
Yosetsu Kozo Shimpojiumu 2009 Koen Rombunshu, p.393 - 396, 2009/11
Stress Corrosion Cracking (SCC) has been observed near the weld zone of the primary loop recirculation pipes made of SUS316L. For the evaluation of initiation and propagation of SCC for non-sensitization material, residual stress distribution generated by surface-machining is the most important factors. In this study, residual stress distributions generated are evaluated by varying cutting speed, and crack growth analysis are performed using evaluated residual stress distributions. As a result, crack growth highly depends on residual stress distributions by surface-machining.
Mochizuki, Masahito*; Katsuyama, Jinya; Ihara, Ryohei*; Mori, Hiroaki*; Mikami, Yoshiki*; Onizawa, Kunio
Proceedings of 2009 ASME Pressure Vessels and Piping Division Conference (PVP 2009) (CD-ROM), 8 Pages, 2009/07
Stress corrosion cracking near the welded zone of core internals and recirculation piping has been observed at the surface where tensile residual stress exists due to welding and/or surface machining. The tensile residual stress in the inner surface of the pipe is caused by welding and surface machining. In this study, Vickers hardness and residual stress distributions at the inner surface of butt-weld joint with surface-machining before and after welding were experimentally evaluated. Welding simulation has been performed to study the distribution and the occurrence mechanism of tensile residual stress. It was shown that residual stress and hardness distributions by welding after surface machining depended on the welding condition and that the effect of surface machining disappeared. Residual stress distributions due to surface-finishing after welding were also found to depend on surface-machining condition but the region was limited to a thin area of surface hardened layer.
Asano, Wataru*; Katsuyama, Jinya; Onizawa, Kunio; Mochizuki, Masahito*; Toyoda, Masao*
Proceedings of 2008 ASME Pressure Vessels and Piping Division Conference (PVP 2008) (CD-ROM), 8 Pages, 2008/07
Stress corrosion cracking near welding zone of core internals and/or recirculation pipes of Type 316L stainless steel are initiated and grown at inner surface due to tensile residual stress and hardening. Surface-machining is conducted before and after piping butt-welding to match the ID of pipes and to provide a smooth surface finish, respectively. In present work, simulation evaluated residual stress by surface-machining before welding by using full scale FEM analysis was compared with experimental measurements. Piping-butt welding simulation was conducted after the surface-machining to evaluate redistribution behavior of residual stress by welding. Estimation of Vickers hardness distribution by surface-machining was carried out based on strained region map observed by FE-SEM equipped with EBSD and compared with experimental measurements. The effect of surface-machining before/after welding on distribution of residual stress and hardening are presented.
Mori, Hiroaki*; Katsuyama, Jinya; Mochizuki, Masahito*; Nishimoto, Kazutoshi*
Hozengaku, 7(1), p.36 - 41, 2008/04
To clarify the effects of residual stress and hardening on intergranular stress corrosion cracking (IGSCC) behavior in welds of low-carbon austenitic stainless steels with surface machining, residual stress and hardness were evaluated by 3-dimentional thermo elastic-plastic analysis and grain boundary sliding behavior was examined using a constant strain rate tensile test. It was revealed that grain boundary sliding occurred in the material at 561 K by the tensile test with the numerically simulated tensile residual stress due to welding and surface machining. In addition, it was clarified that the grain boundary energy is raised by the grain boundary sliding. On the basis of these results, it was concluded that the cause of IGSCC in the welds of low-carbon austenitic stainless steel with surface hardening is the increase in grain boundary energy due to grain boundary sliding accelerated by residual stress of multi pass welding and surface hardening.
Katsuyama, Jinya; Mochizuki, Masahito*; Mori, Hiroaki*; Asano, Wataru*; An, G. B.*; Toyoda, Masao*
Materials Science Forum, 580-582, p.573 - 576, 2008/00
Recently, stress corrosion cracking (SCC) of primary piping of stainless steel has been observed. SCC is considered to initiate and progress at near the welding zone in butt-welded pipes, because of the tensile residual stress introduced by welding. In present work, three-dimensional and axisymmetric thermo-elastic-plastic finite element analyses have been carried out, in order to clarify the effect of geometrical and welding conditions on through-thickness residual stress. In particular, butt-welding joints of SUS316L pipes have been examined. The residual stress was simulated by three-dimensional and axisymmetric models and the results were compared and discussed in detail.
Mori, Hiroaki*; Katsuyama, Jinya; Mochizuki, Masahito*; Nishimoto, Kazutoshi*; Toyoda, Masao*
Zairyo To Kankyo, 56(12), p.568 - 575, 2007/12
no abstracts in English
Mori, Hiroaki*; Katsuyama, Jinya; Mochizuki, Masahito*; Nishimoto, Kazutoshi*; Toyoda, Masao*
Corrosion Engineering, 56(12), p.757 - 770, 2007/09
In order to clarify the effects of residual stress and hardening on intergranular stress corrosion cracking (IGSCC) behavior in the welds of Type 316L stainless steel with surface hardening, the residual stress and hardness in the butt joint of pipes were estimated and grain boundary sliding was analyzed from the viewpoint of microdeformation. The residual stress and hardness in hard-machined surfaces near welds was clarified from experiment and analysis method. Grain boundary sliding in the cold-rolled specimen occurs in smaller strain conditions than that in as-received specimen; the amount of grain boundary sliding increases remarkably with an increase in rolling reduction. We also clarified that grain boundary energy is raised by grain boundary sliding. On the basis of the results, we concluded that the cause of IGSCC in the welds of Type 316L stainless steel with surface hardening is the increase in grain boundary energy induced by residual stress of welding and surface hardening.
Katsuyama, Jinya; Asano, Wataru*; Onizawa, Kunio; Mochizuki, Masahito*; Toyoda, Masao*
Proceedings of 2007 ASME Pressure Vessels and Piping Division Conference/8th International Conference on Creep and Fatigue at Elevated Temperatures (PVP 2007/CREEP-8) (CD-ROM), 8 Pages, 2007/07
Stress corrosion cracking (SCC) of recirculation pipes of austenite stainless steel has been observed. The SCC initiates and grows near the welding zone because of high tensile residual stress by welding. Therefore, the residual stress analysis due to welds of piping is becoming important. In present work, the through-thickness residual stress distributions near multi-pass butt-welds of Type 316L pipes have been calculated by thermo-elastic-plastic analyses. Then crack growth simulations were performed using calculated residual stress distributions. The effects of geometric and welding conditions on crack growth behavior were also discussed.
Mochizuki, Masahito*; Higuchi, Ryota*; Katsuyama, Jinya; Toyoda, Masao*
Proceedings of 2007 ASME Pressure Vessels and Piping Division Conference/8th International Conference on Creep and Fatigue at Elevated Temperatures (PVP 2007/CREEP-8) (CD-ROM), 8 Pages, 2007/07
The strength properties of structural steels or their weld zone are influenced by the microscopic heterogeneity. It is important to investigate the stress distribution for clarification of the mechanism of fracture and the material design by considering a grain boundary or its neighborhood because either can be a zone where the stress concentration is likely to occur due to a mismatch of the displacement. For this purpose, FEM-MD coupling method is one of the useful methods because it can treat the mismatch of the displacement caused by the microscopic heterogeneity. In this study, FEM-MD coupling method is proposed and the influence of the microscopic heterogeneity of steels is investigated by using FEM-MD coupling method.
Katsuyama, Jinya; Mochizuki, Masahito*; An, G. B.*; Toyoda, Masao*
Proceedings of International Welding/Joining Conference-Korea 2007 (IWJC-Korea 2007), p.316 - 317, 2007/05
Recently, stress corrosion cracking (SCC) of primary piping of stainless steel has been observed. SCC is considered to initiate and progress at near the welding zone in butt-welded pipes, because of the tensile residual stress introduced by welding. In present work, three-dimensional and axisymmetric thermo-elastic-plastic finite element analyses have been carried out, in order to clarify the effect of geometrical and welding conditions on through-thickness residual stress. In particular, butt-welding joints of SUS316L pipes have been examined. The residual stress was simulated by three-dimensional and axisymmetric models and the results were compared and discussed in detail.
Takano, Masahito*; Mochizuki, Hiroyasu
no journal, ,
An empirical heat transfer correlation of air on finned heater tubes was derived on the basis of experimental results obtained in air coolers (outside: air, inside: sodium) of fast reactor. Real capacity of the air cooler at Monju was evaluated by taking into account of the fin efficiency into the correlation. A transient analysis was aloso conducted using a plant dynamics analysis code.
Takano, Masahito*; Mochizuki, Hiroyasu
no journal, ,
An intermediate heat exchanger (IHX) of a sodium cooled fast reactor is a component to transfer heat generated in the core to the secondary heat transport system. In the present study, an empirical correlation about heat transfer coefficient has been discussed using test data of IHXs at the Joyo with the MK-III core, at the 50MW-SG facility, and also at the prototype reactor Monju in order to apply it to plant analysis of Monju, and the system and component design of the future reactor. After the obtained correlation is incorporated into the plant dynamics analysis codes, it has been confirmed that a test of the natural circulation in the secondary heat transport system of Monju can be tranced by the codes.
Mori, Hiroaki*; Katsuyama, Jinya; Mochizuki, Masahito*; Nishimoto, Kazutoshi*; Toyoda, Masao*
no journal, ,
no abstracts in English
Ihara, Ryohei*; Katsuyama, Jinya; Onizawa, Kunio; Hashimoto, Tadafumi*; Mikami, Yoshiki*; Mochizuki, Masahito*
no journal, ,
Stress corrosion cracking (SCC) has been observed near the weld zone of core shroud and recirculation pipes made of Type316L stainless steel. Residual stress distribution generated by welding and/or surface machining is very important for the evaluation of occurrence and propagation of SCC in such a non-sensitized material. In this work, residual stress distribution due to surface machining at the piping-weld has been evaluated by numerical simulations with the cutting speed varied. Analysis results showed that the thickness of hardened layer due to surface machining was limited only to a thin area of 0.2 mm, although higher cutting speed caused higher residual stress at the surface.
Zhang, S.; Shobu, Takahisa; Shiro, Ayumi; Hashimoto, Tadafumi*; Tsuji, Akihiro*; Okano, Shigetaka*; Mochizuki, Masahito*
no journal, ,
no abstracts in English
Zhang, S.; Shobu, Takahisa; Shiro, Ayumi; Hashimoto, Tadafumi*; Tsuji, Akihiro*; Okano, Shigetaka*; Mochizuki, Masahito*
no journal, ,
