Abstract
The combined creep-fatigue loading tests were carried out on SUS 304 stainless steel. The data obtained were evaluated using the linear life fraction damage rule. The results evaluated were discussed in connection with the creep fracture modes. The specimen under combined creep-fatigue loading was ruptured by an accumulation of either creep damage (φc) or fatigue damage (φf), when the creep loading condition of combined creep-fatigue loading test lay in the transgranular fracture region on the creep fracture mode map obtained from the static creep rupture test. When the creep loading condition lay in the region of intergranular fracture due to growth of cavities, the rupture life under combined creep-fatigue loading was affected by both φc and φf, and the relation of φc and φf was φc+φf≈1. The connection between the φc vs. φf relation and creep fracture modes obtained for SUS 304 stainless steel was the same as that obtained for SUS 316 stainless steel.
The φc vs. φf relation obtained for the present steel was compared with the φc vs. φf relation obtained from the interspersion test in MPC. It seems that the creep loading condition of the interspersion test lies in the region of intergranular fracture due to the growth of wedge-type intergranular cracks on the creep fracture mode map.
