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

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

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.