抄録
The combined creep-fatigue tests, in which the creep loading and fatigue loading are repeated alternately, were carried out on SUS 304 stainless steel up to 3000hr at 700°C. The data obtained were analyzed using different linear damage rules, and the relationship between the results evaluated by them and the appearance of fracture was discussed.
When the creep damage was assumed to be defined as Σtc/tr (where Σtc is the time spent under creep stress, σc, in the combined creep-fatigue test, and tr is the time to rupture under σc in the creep test), the sum of creep and fatigue damage depended on σc and the degree of work hardening due to the cyclic deformation under fatigue loading. When the creep damage was assumed to be defined as Σεc/εf (where Σεc is the sum of creep strain accumulated in the combined creep-fatigue test, and εf is the true strain at fracture in the creep test), a better correlation between creep and fatigue damage was obtained with no dependence on the test variables of the combined creep-fatigue test. For higher creep damages the sum of creep and fatigue damage was less than 1 because the fracture resulted from the linkage of grain boundary cracks.
The important factors of creep-fatigue interaction under the combined creep-fatigue loadings were found to be the work hardening due to the cyclic deformation under fatigue loading and the linkage of grain boundary cracks.
