SUS 304鋼の高温低サイクル疲労強度に及ぼすひずみ波形変動の影響

概要

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The low-cycle fatigue life of SUS 304 stainless steel at elevated temperature was investigated for the cases that the slow-fast strain cycle was periodically (Type-I) or continuously (Type-II) introduced to the fast-fast strain cycling. It was found that the fatigue life in Type-I considerably deviated from that evaluated by the linear damage summation rule to the unconservative side. On the other hand, the linear damage summation rule could be approximately applied to the case of Type-II, whether the continuous slow-fast strain cycles were introduced before or after crack initiation. To discuss the above difference between Type-I and Type-II, the crack initiation and propagation behaviors were inverstigated. As the result, it be became clear that the shorter crack initiation life and/or propagation one in Type-I, compared with those in Type-II, attributed to the shorter fatigue life in Type-I. Furthermore, the crack growth rate and fatigue life under the combined strain wave cycling were predicted by modifying the linear cumulative damage rule. It was shown that the predicted crack growth curve and fatigue life were comparatively well consistent with the experimental ones.
1985-07-15