深い切欠きをもつ高強度鋼材の疲労き裂の発生
見掛けの応力拡大係数による検討
1976 年 25 巻 270 号 p. 296-301
詳細
1976 年 25 巻 270 号 p. 296-301
The behavior of fatigue crack initiation in a deep notched specimen of Ni-Cr-Mo high strength steel is studied using the apparent stress intensity factor Ka which is obtained by substituting the notch length for the crack length in the equation of stress intensity factor K. The results obtained are as follows:
(1) When the notch root radius ρ is constant, the number of cycles at fatigue crack initiation N is decided by the range of apparent stress intensity factor ΔKa regardless of the notch length a0.
(2) At constant ΔKa, N decreases with decreasing ρ. The thickness of specimen, B, has no effect on the relation between ΔKa and N.
(3) The notch opening displacement Φ depends only on the apparent stress intensity factor Ka, but not on a0 and ρ.
(4) The fatigue crack initiation life of a notched specimen with arbitrary a0, ρ and B under arbitrary ΔKa can be predicted from the relation between the strain range and N of smooth specimens, by relating Φ with the strain at the notch root.
