焼入れ焼戻しした炭素鋼圧延丸棒材の回転曲げとねじり疲労における疲労限度と微小き裂伝ぱ則

概要

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Rotating bending and torsional fatigue tests were carried out on plain specimens and small-hole specimens of rolled round carbon steel bars which were quenched and tempered. The present specimens are regarded as isotropic materials although the original materials have a banded structure. The fatigue limit ratio between rotating bending and torsional fatigue (τ_w/σ_w) in the specimens is different from that in an annealed rolled round carbon steel bar, and is approximately the same as that in isotropic cast carbon steel. We should use isotropic materials in discussing effects of combined stresses on fatigue. In the torsional fatigue tests, crack propagation on plain specimens was of the shear type in the initial stage and of the tension type in the later stage. Cracks of the shear type were generated in both the circumferential and axial directions. The crack growth laws in bending and torsion are expressed by dl/dN∝ σ _a^nl or dl/dN∝τ_a^nl. The dependency of 1/N_f on the stress amplitude σ_a and τ_a in bending and torsional fatigue is approximately the same as the dependency of the crack growth rate on σ_a or τ_a, respectively.
一般社団法人日本機械学会の論文
1993-08-25