過大過小応力の疲労き裂伝ぱと設計基準の考え方について

概要

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The effect of periodic overstressing on fatigue crack propagation was studied with circumferentially cracked specimens in rotating bending of low carbon steels (a rimmed steel and an Al-killed steel), a medium carbon steel, a high strength steel and an aluminum alloy. Some tests were con-ducted also with surface cracked specimens. A very small number of cycles of overstress applied intermittently during a very large number of cycling of under stress below threshold stress intensity K_<th> caused remarkable acceleration of crack propagation (about or more than one hundred times) in all materials tested except the high strength steel, indicating that K_<th> loses its physical meaning as the threshold for fatigue crack propagation under such variable stress conditions. The acceleration was more remarkable in materials of lower strength. A Iower limit seems to exist in the value of understress that causes significant acceleration and the limiting value does not seem to vary appreciably with the strength of the material. Some discussions were made on the design criterion which takes account of the acceleration b understress.
社団法人日本材料学会の論文
1978-09-15