浸炭材の疲労き裂の伝ぱ特性・停留特性に及ぼすγ粒径の効果

概要

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The effect of austenite grain size on the fatigue crack growth and arrest behavior of carburized steel was studied. On the fatigue test of same stress amplitude, the fatigue crack initiation of fine austenite grain steels is delayed in comparison with coarse austenite grain steels, but the difference of crack initiation life between fine grain steels and coarse grain steels is very slight against 107 cycles. The improvement of crack arrest property is dominant for increasing fatigue limit by refinement of austenite grain size. The critical stress intensity factor for crack arrest under fatigue tests at the stress amplitude of the each fatigue limit of carburized steels is calculated by considering the effect of compressive residual stress. As a result, it becomes clear that the finer the austenite grain size, the larger becomes the critical stress intensity factor for crack arrest, and crack arrest property is improved remarkably by the refinement of austenite grain size.