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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.
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.
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.