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Katsuyama, Jinya; Nishikawa, Hiroyuki*; Udagawa, Makoto; Nakamura, Mitsuyuki*; Onizawa, Kunio
Journal of Pressure Vessel Technology, 135(5), p.051402_1 - 051402_9, 2013/10
Times Cited Count：27 Percentile：72.14(Engineering, Mechanical)The residual stresses generated within the weld-overlay cladding and base material of reactor pressure vessel (RPV) steel was evaluated for as-welded and post-welded heat-treated conditions using thermo-elastic plastic creep analyses considering phase transformation. By comparing the analytical results with the experimentally determined values, we found a good agreement for the residual stress distribution within the cladding and the base material. It was shown that considering phase transformation during welding was important for improving the accuracy of residual stress analysis. Using the calculated residual stress distribution, we performed fracture mechanics analyses for an RPV during pressurized thermal shock events. We evaluated the effect of the weld residual stress on the structural integrity of an RPV. The results indicated that consideration of residual stress produced by weld-overlay cladding and PWHT is important for assessing the structural integrity of RPV.
Nishikawa, Hiroyuki; Katsuyama, Jinya; Udagawa, Makoto; Nakamura, Mitsuyuki; Onizawa, Kunio
Nihon Kikai Gakkai Rombunshu, A, 76(770), p.56 - 64, 2010/10
In order to evaluate residual stress distributions in the vessel wall of a reactor pressure vessel (RPV) due to weld-overlay cladding and post-weld heat-treatment (PWHT), thermal-elastic-plastic-creep analysis considering the changes of material properties in heat-affected zone (HAZ) has been performed. Analytical results of stress distributions considered the material property changes in HAZ agreed well with the ones measured experimentally from weld-overlay cladded plates. Applying the analysis method to a RPV model, through-wall residual stress distributions caused by weld-overlay cladding, PWHT, hydrostatic test, operational load and transient loads during pressurized thermal shock (PTS) events have been computed. Effects of the weld-overlay cladding on the stress distributions in the vessel wall of a RPV have been evaluated. Using the stress distributions, stress intensity factors for a postulated crack during PTS events have been studied.
Katsuyama, Jinya; Udagawa, Makoto; Nishikawa, Hiroyuki*; Nakamura, Mitsuyuki*; Onizawa, Kunio
E-Journal of Advanced Maintenance (Internet), 2(2), p.50 - 64, 2010/08
Weld residual stress is the most important factors to assess the structural integrity of RPV since it affects crack initiation and growth behaviors. Inner surface of the RPV is protected against corrosion by cladding. At the J-weld of the vessel head penetrations, Ni-based alloys are used for weld material. After the fabrication process, the residual stress remains in such dissimilar welds after PWHT. The residual stresses were measured using the DHD method. Thermal-elastic-plastic-creep analyses considering phase transformation were also performed. By comparing analytical results with measured ones, it was shown that there was a good agreement of residual stress distribution. It was suggested that taking phase transformation into account was important to improve the accuracy of analysis. Using the residual stress distributions, PWSCC behavior was calculated using PFM analysis code. Effects of the residual stress and scatter of PWSCC growth rate on the crack penetration were evaluated.
Katsuyama, Jinya; Nakamura, Mitsuyuki; Tobita, Toru; Onizawa, Kunio
no journal, ,
Weld residual stress distributions have been measured for several specimens with various diameters and thicknesses of typical butt-weld joints in recirculation piping in light water reactors. Residual stress by means of welding simulation based on thermo-elastic-plastic analysis has been validated by comparing with the experimental results. Using the welding simulation method, effects of the shape of welds and the welding conditions of each welding pass on residual stress distribution have been evaluated. From the analysis results, it was confirmed that the axial residual stress was dependent on the pipe diameter, and that the magnitude of residual stress was proportional to the weld heat input. It was also clearly shown that welding condition of final welding pass has the largest influence on weld residual stress distribution.
Nishikawa, Hiroyuki; Nakamura, Mitsuyuki; Udagawa, Makoto; Katsuyama, Jinya; Onizawa, Kunio
no journal, ,
In order to evaluate residual stress distributions in a reactor pressure vessel (RPV) due to weld-overlay cladding and post-weld heat-treatment (PWHT), thermal-elastic-plastic-creep analysis considering the changes of material properties in heat-affected zone (HAZ) has been performed. By considering the material property changes in HAZ, stress distributions obtained from the analysis agree well with the experimental results measured from weld-overlay cladded plate. Applying the analysis method, residual stress distributions for RPV model caused by weld-overlay cladding, PWHT, hydrostatic test, operational load and transient loads during pressurized thermal shock (PTS) event have been computed. Effect of residual stress on the structural integrity of RPV has been evaluated by comparing the difference in stress distributions and the values of stress intensity factor calculated by assuming a postulated crack.
