S20C焼なまし材および予ひずみ材の二段二重重複回転曲げにおける疲労き裂の挙動

概要

論文の詳細を見る
Previous studies of fatigue tinder two-step loading have shown that the value of cumulative cycle ratio is usually smaller than unity when the first stress level is higher than the second, but in some cases it becomes larger than unity. This phenomenon may be related to the existence of work hardened layer in the specimen. In the present study, rotating bending fatigue tests were performed by using the annealed or the pre-strained 0.21%C steel specimens under two-step loading. The behavior of fatigue cracks was observed successively by the replication method and the effect of the work hardened layer on the cumulative fatigue damage was examined. The main results obtaind are as follows. (1) The Miner's rule holds good in the crack initiation process under double repeated stress in two stress levels. (2) On the annealed specimens: (a) When σ_1<σ_2, the value of the cumulative cycle ratio based on fracture, n_1/N_<f1>+n_2/N_<f2>, is nearly equal to unity in general. (b) Whenσ_1>σ_2, the value of n_1/N_<f1>+n_2/N_<f2> is nearly equal to unity excepting the case where the cycle ratio of the first stress level, n_1/N_<f1>, is small. In that case, the value of n_1/N_<f1>+n_2/N_<f2> is often larger than unity. This may be due to the work hardening under the first stress level. (3) On the pre-strained specimens: (a) Whenσ_1<σ_2, the value of n_1/N_<f1>+n_2/N_<f2> is larger than unity. (b) Whenσ_1>σ_2, the value of n_1/N_<f1>+n_2/N_<f2> is smaller than unity including the case where n_1/N_<f1> is small. This may be due to the work softening under the first stress level. (4) The results of the pre-strained specimens agreed with the previous results showing that n_1/N_<f1>+n_2/N_<f2>>1 when σ_1<σ_2 and n_1/N_<f1>+n_2/N_<f2> <1 whenσ_1>σ_2. Therefore, the validity of the Miner's rule depends upon the existence of work hardened layer.
社団法人日本材料学会の論文
1984-06-15

S20C焼なまし材および予ひずみ材の二段二重重複回転曲げにおける疲労き裂の挙動

スポンサーリンク

概要

著者

関連論文

スポンサーリンク