クリープ・疲労条件下の微小き裂発生・成長に及ぼす圧縮ひずみ速度の影響

概要

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In order to clarify the effect of the compressive strain rate on initiation and growth of small cracks under creep-fatigue condition, the following tests were conducted using smooth specimens of Type 304 stainless steel at 650℃ in air, (i) slow-tension and fast-compression (c-p type fatigue), (ii) slow-tension and slow-compression (c-c type fatigue), and (iii) slow-tension and very-slow-compression (c-s type fatigue). The results obtained are summarized as follows. (1) Multiple small cracks initiated and grew at random along grain boundaries being nearly perpendicular to the stress axis at each specimen surface. (2) The compression-going strain rate affected the crack initiation life and the crack density. The c-p type fatigue brought about the shortest initiation life and the highest crack density, and the c-s type fatigue did the longest and the lowest. (3) The crack growth rate was not influenced by the compression-going strain rate but was primarily governed by the tension-going strain rate. (4) The difference of life between c-p type and c-s type fatigue was caused by the difference of crack initiation life and crack coalescence. The highest crack density in the c-p type fatigue made the crack coalesce easily to bring about a long crack.
社団法人日本機械学会の論文
1990-03-25