ねじり疲れき裂の表皮および深さ方向進展の相関について

概要

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Fatigue crack propagation is investigated for carbon steel test pieces of plain circular section in torsional　fatigue test，with a special intention to find relation between the propagation for the superficial direction and the radial one. The results obtained by this study are as follows.　1.　The deeper the cracks progress for the radial direction， the higher the propagating rate for the superficial one， and vice versa， it was derived by analysis. 2.In both the total length of the superficial cracks and the mean depth of the radial cracks versus cycles curve， there is a sudden bent on the way. As for the former curve，the bent lies in the early cycle， before which cracks having originated from the persistent slip bands seem to be dominant， and after which cracks from the crack tips do. With the progress of the cycle， the rise of the superficial propagating rate diminishes due to the thinner plastic zones around the crack tips through the principle stated in the previous item. 　　　3.Experiment shows that the fatigue internal energy is proportional nearly to the cubic root of the fatigue crack surface area， e.g. the total length of superficial cracks multiplied by the mean radial depth of cracks.
北見工業大学の論文