Effect of loading frequency on fatigue strength of age-hardenable steel.

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  • 時効性鋼の疲労強度に及ぼす繰返し速度の影響
  • ジコウセイ コウ ノ ヒロウ キョウド ニ オヨボス クリカエシ ソクド ノ

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Abstract

To investigate the effect of loading frequency on fatigue strength of age-hardenable steel, rotating bending fatigue tests were carried out under two different frequency conditions (3000 and 300rpm) by using the low-temperature quenched rimmed steel. Hardness change and crack propagation were observed during the fatigue process under both loading frequency conditions.<br>The main results obtained were as follows;<br>(1) At a high cyclic stress region, the effect of loading frequency on fatigue life was not observed. However, at lower stresses, the fatigue life in 300rpm became longer and eventually the fatigue limit in 300rpm became higher than that of 3000rpm.<br>(2) The rate of increase in hardness with number of cycles was larger in 300rpm than in 3000rpm. This was mainly caused by the time dependence of age-hardening.<br>(3) As the cyclic stress was lowered, the fatigue crack growth in 300rpm became slower than that in 3000rpm. Near the fatigue limit in 300rpm, a long non-propagating crack was found at a relatively low number of cycles.<br>(4) The fatigue behavior mentioned above might be explained as follows; the effect of strengthening of material due to age-hardning on fatigue appears remarkably in 300rpm when cyclic stress is low, owing to the enough time available for ageing than in 3000rpm.

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