Study on unified criteria for preventing plastic strain accumulation due to thermal stress with long range travel

長距離移動する熱応力による塑性ひずみ累積防止のための統一的クライテリアに関する研究

岡島 智史 ; 若井 隆純 ; 川崎 信史 

Okajima, Satoshi; Wakai, Takashi; Kawasaki, Nobuchika

The prevention of excessive deformation by thermal ratcheting is important in the design of high-temperature components of fast breeder reactors (FBR). As the result of experimental study that models the fast breeder reactor vessel nearby the coolant surface, it has been reported that long range traveling of temperature distribution causes new type of thermal ratcheting, even if there is no primary stress. In this paper, we propose screening criteria to prevent continuous accumulation of plastic strain derived from thermal stress that is caused in wide range. We proposed the criteria referring to the definition of primary local membrane stress, which limit the axial length of the yielding region. And then, based on finite element analyses using elastic-perfectly plastic material, we have validated the proposed criteria for various type of traveling temperature distributions.