疲労き裂進展における下限界特性の板厚依存性とき裂開閉口
1986 年 52 巻 475 号 p. 655-662
詳細
1986 年 52 巻 475 号 p. 655-662
Characteristics of fatigue crack propagation have been investigated in a low carbon steel and a high tensile strength steel to evaluate the effect of sheet thickness. Crack propagation data are generated over a wide range of growth rates, from 10-8 to 10-3 mm/cycle, for load ratios of 0.05 and 0.70 at room temperature in laboratory air. Particular emphasis is placed on behaviour at near-threshold growth rates. Near-threshold fatigue crack propagation behaviour is found to show a marked sensitivity to sheet thickness, and near-threshold growth rates decrease and threshold values increase with increasing sheet thickness. Roughness- and oxide-induced crack closure are proposed as a mechanism for the effect of sheet thickness on near-threshold fatigue crack propagation. It is also shown that the requirement for specimen thickness recommended by ASTM, W/20≤B≤W/4, is not valid for near-threshold fatigue crack propagation.
