軸受鋼の動的ねじり-静的圧縮軸荷重下でのモードII疲労挙動と組織変化に及ぼす水素の影響

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In order to clarify the effect of hydrogen on Mode II fatigue behavior, fatigue tests were conducted using hydrogen-precharged and uncharged specimens of bearing steel (SUJ 2) tempered at 438K loaded under cyclic torsion with and without a compressive axial mean stress (σ_m=0, -750MPa). The fatigue lives in the hydrogen-precharged specimens were shorter than those in the uncharged specimens under cyclic torsion with and without a compressive axial mean stress. In both hydrogen-precharged and uncharged specimens, Mode II fatigue cracks initiated and propagated along the axial direction of specimen due to the longitudinal microstructure texture formed in the rolling direction, and finally branched into two Mode I cracks. In the case of hydrogen-precharged specimens under cyclic torsion without a compressive axial mean stress, however, Mode I crack initiated and propagated directly from subsurface inclusion in two specimens and Mode II crack initiated and propagated from the matrix in one specimen. Mode II fatigue crack growth rate and Mode I fatigue crack growth rate of the hydrogen-precharged specimen were higher than those of uncharged specimen under cyclic torsion with a compressive axial mean stress. More mode II fatigue cracks were observed at the final stage (N/N_f=0.97) in the hydrogen-precharged specimen than in the uncharged specimen. Microstructural changes caused by the shear slip deformation were formed in the hydrogen-precharged specimens. From these observations, it is presumed that hydrogen enhances slip deformation and localized slip bands, and eventually produces more mode II fatigue cracks along slip bands in the hydrogen-precharged specimens.
社団法人日本機械学会の論文
2009-02-25

軸受鋼の動的ねじり-静的圧縮軸荷重下でのモードII疲労挙動と組織変化に及ぼす水素の影響

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