Cr-Mo-V 鋼および SUS 304 鋼の熱疲労き裂伝ぱと破損寿命評価

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In order to investigate the fracture mechanics law of macroscopic crack propagation in thermal fatigue, strain-controlled thermal fatigue tests on Cr-Mo-V rotor steel and SUS304 stainless steel were carried out by using a notched specimen. A smooth specimen was also employed for thermal fatigue tests under the same conditions as the crack propagation tests to discuss the applicability of the fatigue life law (i. e., the strain-energy-parameter approach) derived from the macroscopic crack propagation law to thermal fatigue life evaluation. The results obtained were summarized as follows: (1) The characteristics of thermal fatigue crack propagation could be classified into two types (i. e., cycle-dependent and time-dependent) by applying the transition criterion between the types. (2) The fracture modes in the cycle-and time-dependent thermal fatigue were of transgranular and intergranular types, respectively. (3) The fatigue J-integral range, ΔJ_f, was a fracture mechanics parameter controlling the crack propagation rate, dl/dN, in the cycle-dependent thermal fatigue, while the creep J-integral range, ΔJ_c, in the time-dependent thermal fatigue. In this case, rapid straining could be successfully applied to the partition of the inelastic strain into plastic and creep components for evaluating the ΔJ_c-value. The crack propagation law (i. e., the dl/dN-ΔJ_f and dl/dN-ΔJ_c relations) in thermal fatigue was identical with that obtained in isothermal fatigue. (4) The thermal fatigue failure life of the smooth specimen was correlated with the strain-energy parameter, and the correlation agreed with that in isothermal fatigue. Also, it could be predicted from the crack propagation characteristics obtained by using the notched specimen.
社団法人日本材料学会の論文
1989-04-15

Cr-Mo-V 鋼および SUS 304 鋼の熱疲労き裂伝ぱと破損寿命評価

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