回転曲げと平面曲げにおけるき裂伝ぱ速度の差異とそれらの簡便な評価法

概要

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Fatigue strength under plane bending is higher than that under rotating bending at the same stress. This is due to the difference in the crack growth rates. In the present study, rotating bending and plane bending fatigue tests of an annealed 0.42% carbon steel were carried out on smooth specimens and specimens with a small blind hole in order to investigate the difference in the crack growth rates, and a unified evaluation method for crack growth rates in the two types of loading was proposed. The crack growth rate is expressed by the small-crack growth law based on the nominal stress amplitude σ, dl/dN=Cσ^nl, in each type of loading, while the constants C and n differ in these types of loading. However, the crack growth rates in both cases can be expressed by the same small-crack growth law based on the plastic strain amplitude ε_p, dl/dN=C'ε^n'_pl (C'and n'are constants in both types of loading). Consequently, fatigue lives in both types of loading can be predicted using the former expression, the small-crack growth law based on the plastic strain amplitude, and the cyclic stress-strain curve in each type of loading.
社団法人日本機械学会の論文
1996-06-25