70MPa水素ステーション蓄圧器用SNCM439鋼の疲労特性に及ぼす水素と繰返し速度の影響

概要

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Tension-compression fatigue tests on SNCM439 steel for storage cylinder of 70MPa hydrogen station were conducted under frequencies of 0.2, 2, 20 and 500Hz with smooth specimens and specimens containing a small artificial hole. Hydrogen charging of the specimens was carried out by the hydrogen gas exposure method or the aqueous solution immersion method. The fatigue life of the hydroged charged specimens decreased in comparison with the uncharged specimens. The cluster of Al_2O_3 inclusions with the length of about 270μm was at the fracture origins of smooth specimens. For the specimens containing a small artificial hole, it was observed an acceleration of fatigue crack growth rate for the hydrogen charged specimens when compared to the uncharged ones. However, it was verified that this acceleration rate has reached an upper limit, which was approximately 10 times the acceleration rate found for uncharged specimens. Considering this upper limit value of the acceleration of fatigue crack growth rate, the √<area> parameter model was applied to predict the fatigue strength of uncharged and hydrogen charged specimens.
2010-07-25