高強度鋼の高サイクル疲労域における内部き裂進展挙動

概要

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In order to examine the precise fatigue mechanism of so-called "fish eye" type fatigue failure emerging in very high cycle fatigue, rotating bending fatigue tests were carried out on a high strength low alloy steel. Differently fatigue damaged specimens were prepared and their cross section was carefully observed so as to gather statistical information of initiation and growth of subcracks in subsurface region. The results showed that penny-shaped subcracks were nucleated at very small inclusions before stress cycles of 10^4. All of the subcracks initiated at inclusions grew up at maximum to a length of the non-propagating crack, being formed in the matrix of subsurface and controlled the "true fatigue limit" of the material. To observe the internal crack growth on specimen surface, a surface-wrapped specimen was fatigued. The result revealed that the shielding of oxygen results in decreasing the fatigue strength.
社団法人日本機械学会の論文
1998-10-25