Fatigue tests on SCM435 steel quenched at 860°C and tempered at 580°C were carried out under the frequencies of 0.2, 2 and 20 Hz with specimens containing a small artificial hole. An additional test in which the frequency was alternatively switched between 0.02 Hz and 2 Hz was also carried out. Hydrogen charging to specimens was carried out by immersion method. The fatigue life of hydrogen-charged specimens decreased in comparison with that of uncharged specimens. The acceleration of fatigue crack growth rate da/dN was observed at da/dA<1.0×10-7 m/cycle in test frequency f=20 Hz, da/dA<4.0 ×10-7 m/cycle in f=2 Hz and da/dN<1.5×10-6cycle in f=0.2 Hz. The acceleration of da/dN saturated at at ΔK <17 MPa √m in ≤2 Hz. It was found that there is the upper bound of the effects of hydrogen and test frequency on fatigue crack growth rate in hydrogen environment. The test with switching two frequencies between 0.02 Hz and 2 Hz showed that hydrogen concentration in the vicinity of the crack tip remarkably affects fatigue crack growth behavior and crack morphology. The most remarkable change of the slip bands around the crack tip was less and discrete in the hydrogen-charged specimens compared to uncharged specimens.
|ジャーナル||Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A|
|出版ステータス||出版済み - 12 2007|
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