Life Prediction under Creep-Fatigue Loading Condition for SUS 316 Stainless Steel

Abstract

The understanding of long-term behavior and life prediction under creep-fatigue loading conditions are important subjects. It is considered that life prediction under creep-fatigue loading conditions should be related to the creep properties, because the long-term creep-fatigue behavior might be dominated by the creep properties. It was found from the combined creep-fatigue loading tests on SUS 316 stainless steel that the fracture criteria were correlatable to the creep fracture modes of the static creep tests performed under the creep loading condition of the combined creep-fatigue loading tests. A new life prediction method was proposed according to this result.
In order to verify this life prediction method, the fatigue tests with tensile strain holding wave form were carried out on SUS 316 stainless steel at 550, 650 and 750°C.
The predicted rupture life agreed well with the observed one. This life prediction method was more accurate than the method in which the life is predicted using only one fracture criterion (ex. φ_c+φ_f=1). The dominant fracture modes under creep-fatigue loading conditions could be predicted using this method.