In this paper, effect of geometric imperfections on peak stress in softened heat affected zone (HAZ) of longitudinally-welded hot reheat steam piping of mod. 9Cr-1Mo steel was investigated by parametric two-dimensional finite element analyses. Four parameters representing amount of ovalization, amount of flattening, range of flattening and amount of linear misalignment were used in order to express the geometric imperfections of the pipe. The peak stress of a longitudinally-welded pipe with a flattening ratio of about 1% reached about 1.5 times of mean diameter stress. Then, estimation formulas of the stress-increase factor were developed based on the results of finite element analyses. In addition, creep damage distributions were also calculated using three kinds of creep damage models and changes of the creep damage due to the geometric imperfections were compared. The ratios of creep damage increase due to the geometric imperfections were found to be equivalent in the three creep damage models applied.
Evaluation of Stress-Increase Caused by Geometric Imperfections in Longitudinally-Welded Hot Reheat Steam Piping of Mod. 9Cr-1Mo Steel
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Shigeyama, H, Takahashi, Y, & Yaguchi, M. "Evaluation of Stress-Increase Caused by Geometric Imperfections in Longitudinally-Welded Hot Reheat Steam Piping of Mod. 9Cr-1Mo Steel." Proceedings of the ASME 2017 Pressure Vessels and Piping Conference. Volume 6A: Materials and Fabrication. Waikoloa, Hawaii, USA. July 16–20, 2017. V06AT06A070. ASME. https://doi.org/10.1115/PVP2017-65900
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