1981 年 30 巻 332 号 p. 434-440
Creep rupture tests were carried out on the specimens obtained from 12% Cr-Mo-W-V steel machine parts after long-term service. Then a method to estimate the residual rupture life of the machine parts from the rupture data was proposed.
The results obtained are summarized as follows:
(1) The test results at higher rupture stresses tended to show underestimated residual lives when the life fraction rule was used for the evaluation of creep damage.
(2) The residual life of 12% Cr-Mo-W-V steel should be evaluated by considering the effect of material deterioration in addition to the creep damage given by the life fraction rule.
(3) The material deterioration was quantitatively expressed in terms of the reduction of high-temperature tensile strength. On the assumption that the rupture strength was proportional to the tensile strength, the authors proposed a method how to evaluate the reduction in creep stress caused by the material deterioration.
(4) The experimental results obtained from the long-term used machine parts were well explained by the combination of the life fraction rule and the material deterioration. The estimated rupture life obtained after correction of the damage caused by long-term service coincided well with the rupture data of the material before service.