切欠き底微小疲労き裂の伝ぱおよび停留におよぼす微視組織の影響

概要

論文の詳細を見る
Single-edge-notched specimens of a low-carbon steel and an aluminum aloy were fatigued under cyclic in-plane bending. The growth behavior of a short fatigue crack formed at the notch root was discussed on the basis of the measurement of crack closure. For each material, the propagation rate of short fatigue cracks was uniquely related to te effective stress intensity range and the relation agreed well with that obtained for long cracks. The resistance curve was constructed in terms of the threshold value of the maximum stress intensity factor which was the sum of the threshold effective stress intensity range ΔK_<effth> and the opening stress intensity factor K_<opth>. The value of ΔK_<effth> was constant, while K_<opth> increased with increasing crack length c_<np> in accordance with K_<opth>=K_<opth∞>[(c_<np>-c_1)/(c_2-c_1)]^<1/2> where K_<opth∞> is the K_<opth> value for long cracks, and c_1 and c_2 are the characteristic crack lengths. The ratio of K_<opth∞> to (c_2-c_1)^<1/2> was independent of the material. The predicted values of the fatigue limit of crack initiation, the fatigue limit of fracture, and the non-propagating crack length agreed very well with the experimental results. A simplified method of determining the resistance curve was also proposed.
社団法人日本材料学会の論文
1989-11-15