改良9Cr-1Mo鋼の高温多軸クリープ疲労寿命評価; ヒステリシスエネルギーを考慮した数式化による寿命整理の検討

Multiaxial creep-fatigue life evaluation of Mod.9Cr-1Mo steel at elevated temperature; Study of life arrangement by mathematical formula considering hysteresis energy

小川 文男*; 今川 裕也 ; 橋立 竜太 ; 若井 隆純 ; 旭吉 雅健*; 伊藤 隆基*

Ogawa, Fumio*; Imagawa, Yuya; Hashidate, Ryuta; Wakai, Takashi; Hiyoshi, Noritake*; Ito, Takamoto*

550Cにて改良9Cr-1Mo鋼の引張・ねじりの多軸クリープ疲労試験を行った。ひずみ速度,保持時間依存性に関して特異性が見られ、最大応力と応力緩和の度合いに寿命が支配されることを明らかにした。ヒステリシスエネルギーを算出するとともに、非比例負荷の影響を考慮した寿命整理を行った。具体的にはヒステリシスの発現機構を検討し、硬化指数と緩和応力を考慮したエネルギー定式化を行った。寿命評価についてはこれまでに係数2.9と2.2で整理できているが、本研究ではまず係数2で整理できることを目標に検討を進めた。

Multiaxial creep-fatigue tests in tension and torsion were performed on Mod.9Cr-1Mo steel at 550C. Specificity was observed with respect to strain rate and retention time dependence, indicating that creep-fatigue life is governed by the maximum stress and the degree of stress relaxation. The hysteresis energy was calculated and the lifetime was organized considering the effect of non-proportional loading. Specifically, the mechanism of hysteresis onset was examined, and the energy formulation was made considering the hardening index and relaxation stress. Although the life evaluation has been organized with coefficients of 2.9 and 2.2, this study was conducted with the goal of first organizing the life evaluation with a coefficient of 2.