高張力低合金鋼における下限界近傍の疲労き裂進展挙動に及ぼす材料微視構造および応力比の影響

概要

論文の詳細を見る
The effects of stress ratio and microstructure on the fatigue crack propagation near the threshold in a high-strength low alloy steel were analysed based on the crack closure measurement and the microscopic observation of fracture surfaces. The following results were obtained. (1) The effects of microstructure and stress ratio on the relation between the crack propagation rate and the stress intensity range were large in region A near the threshold. The threshold stress intensity range increased linearly with the square root of the mean free path. When compared at the same crack propagation rate, the relation between the stress intensity range and the stress ratio was dividable into two regions, i.e., K_<max> controlled region with low R values, and ΔK controlled with high R values. (2) Region A was dividable into regions A1 and A2 in the relation between the rate and the effective stress intensity range. In regions A2 and B, the rate was expressed in a unique power function of the effective range without respect to the microstructure and the stress ratio. In region A1, very close to the threshold, the rate depended on the microstructure but not on the stress ratio. Thus, the effect of stress ratio on the crack growth rate can be ascribed to its effect on the crack closure. (3) The transition from region A to B can be caused by either the transition in crack closure behavior or the change in crack growth mechanism. The latter condition becomes predominant when the reverse plastic zone size is equal to the mean free path of dislocation motion. The transition in crack closure is dependent on the ratio of the reversed plastic zone size to the prior-austenite grain size as well as on the material itself.
1982-11-15

高張力低合金鋼における下限界近傍の疲労き裂進展挙動に及ぼす材料微視構造および応力比の影響

スポンサーリンク

概要

著者

関連論文

スポンサーリンク