タフライド処理鋼の疲労強度に及ぼす圧縮残留応力の効果

概要

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It is generally said that the compressive residual stress near the surface of tufftrided steel contributes to the improvement of fatigue strength. However, the mechanism of its contribution is hardly clear. In this paper, the author prepared several kinds of specimens for which the conditions of the compressive residual stress were different, and investigated the mechanism from a viewpoint of the fatigue crack initiation and propagation. The main results obtained are as follows; (1) The compressive residual stress had hardly an effect on the prevention of fatigue crack initiation and on the obstruction of fatigue crack propagation in the larger region of the stress intensity factor range, ΔK, too. However, the fatigue crack propagation in the smaller region of ΔK was delayed by the compressive residual stress. (2) Therefore, the compressive residual stress near the surface contributed to the improvement of fatigue strength in the case that the fatigue crack initiated at the surface of specimen, but it had little or no influence on the fatigue strength in the case that the fatigue crack initiated at the subsurface.
1982-07-15