人工き裂のある軸材の疲れ強さ(続報) : 各種の材料におけるき裂および切欠き底のき裂

抄録

In this paper, following earlier test are described fatigue tests under rotary bending on the artificialy cracked specimens bv forging made from mild steel, 0.45 per cent C steel, 13 Cr steel and Ni-Cr steel. Axially cracked specimens gave considerable small strength-reduction factors, while the fatigue strength of specimens with partial circumferential crack is nearly equal to that of round cracked specimens for high tensile strength steel, e.g. Ni-Cr steel, although crack length is short. The strength reduction factors of circumferential round cracked specimens for materials tested except mild steel which has lowest value 2.4, are nearly equal to 3.4. The strength-rduction factor of specimen with semi-circular groove or vee notch having axial or circumferential partial cracks is equal to the product of the strength-reduction factor of notch itself and that of crack itself. However, from the test results it appears resonable to assume that the fatigue strength of notched specimen having circumferencial round crack, depends on the total sum of depth of notch and crack. The shot-peening trocess gave an increased fatigue strength of 18% for mild steel and 30% for Ni-Cr steel specimens with artificial cracks.