インコネル718の時間依存性疲労き裂伝ぱに及ぼす小規模クリープから大規模クリープへの遷移の影響

概要

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"In order to investigate the effect of the transition from small scale creep (SCC) to large scale creep (LSC) on the behavior of time-dependent fatigue crack propagation, stress-controlled fatigue crack propagation tests were carried out at 923 K under trapezoidal stress wave forms on Inconel 718 in which such a transition was expected to occur. The results obtained were summarized as follows: (1) Grain-boundary facets were observed on the fracture surface in all cases. This indicates that the crack propagation proceeds by creep fracture. (2) The crack propagation rate, dl/dt, could not be correlated with the stress intensity factor. Also, the steady state creep J integral, J_s^*, was not a good parameter to represent dl/dt. These findings were associated with the effect of the transition from SCC to LSC on the crack propagation behavior. (3) As a new parameter giving a good correlation with dl/dt, the time-averaged creep J integral, J_t^*, was proposed. It was defined as follows: J^*_t=(∫^<tH>_0J^*dt)/tH where t_H: tensile stress hold-time, and J^*: creep J integral under the transition from SCC to LSC. (4) The dl/dt vs. J_t^* relation obtained in the time-dependent fatigue coincided with the dl/dt vs. J_s^* relation in static creep under the LSC condition."
社団法人日本材料学会の論文
1984-05-15