Creep-fatigue crack propagation behavior in 2 1/4Cr-IMo steel for fast breeder reactor

摘要

A series of experiments were performed in order to clarify the creep-fatigue crack propagation behavior in 21/4Cr-1Mo steel, such as the effect of stress ratio including crack closure, previous creep damage, and tensile or compressive loadholding. The following results were obtained: (a) The low-cycle fatigue crack propagation rate at elevated temperature was characterized by the cyclic J-integral in consideration of the crack closure. (b) Acceleration occurred in the fatigue crackpropagation of the previously creep-damaged material, but the relationship between crack propagation rate and the cyclic J-integral corresponded with that of the virgin material. (c) In the tests with the tensile load hold during each cycle, the crackpropagation rate was accelerated and was characterized using the creep J-integral. (d) Whereas acceleration also occurred in the tests with the compressive load hold during each cycle, the creep J-integral could not characterize the crack propagationrate. Alternatively the crack propagation rate was characterized using the cyclic J-integral during the tension going period.