SUS304鋼のクリープ・疲労条件下の高温低サイクル疲労における微小表面き裂の進展挙動(<小特集>粉体小特集)

概要

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The surface small crack growth behavior of SUS 304 stainless steel under fast-fast and slow-fast strain controlled low-cycle fatigue conditions was investigated at 873K with the specimens having different grain sizes. It was shown that the cumulative propability of crack length distribution in both fast-fast and slow-fast cyclings could be represented by a Weibull distribution as a function of crack length in the early stage of fatigue life. In the stage after the half fatigue life, the cumulative probability of crack length distribution showed a knee, and a small number of main cracks grew predominantly. The knee occurred when the crack length was comparable to one grain size. It was also shown that the surface small crack growth rate showed the minimum value when the cracks arrived at the grain boudaries. The above behavior resulted from that the grain boundaries temporarily impeded the small crack growth. Furthermore, the small crack growth ratet was compared with the macroscopic crack growth rate. The law for the macroscopic crack growth was applicable to the small crack growth in slow-fast cycling, up to the crack length being one grain size. On the other hand, the small crack growth rate in fast-fast cycling was about ten times as large as the macroscopic crack growth rate in the region where the crack length was smaller than or comparable to the grain size.
1987-11-15