予加工を与えた炭素鋼横穴材の破れ挙動--ねじれ疲れの場合

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Carbon-steel specimens which had been pre-strained in tension and had a lateral hole made in them, were tested in cyclic torsion to examine the fatigue strength, fatigue crack propagation and opening as well, etc. Characteristic results obtained were as follows. 1) As the hole diameter δstayed constant and the pre-strain ε varied, τ-N, l-N/N_F, i-N/N_F and τ_ｗ-χ relations showed that the order of the parameterε as 0, 2, 14％ realized the order of the level of the fatigue strengthτ_T or τ_ｗ, crack length l, non-opening ratio i, and τ_ｗ-χ (endurance limit-stress gradient) curves. 2）The time strength τ_T increased before N≒10^<6.5> cycles as the lateral hole diminished as a δ＝3.6, 2.4, 1.2, 0 mm, though it was exclusively high byδ＝0 mm. For the later cycles, τ_T increased-not always as the hole size decreased, and their relations were expressed in the τ_ｗ-χ curves. The more the prestrain ε, the higher the level of the curve. The bottom of the endurance limit τ_ｗ lay for the diameter ratio δ/d≒0.2〜0.3. 3) The crack propagation was of Frost and Dugdale type as was also the case of the rotary bending and push-pull fatigue as well. 4) For the phenomena about the hardness, as the cycle ratio N/N_F increased, H_V increased by ε＝0，2％ from the early cycle or after a slight decrease, and decreased by ε＝14％ from the early cycle or after a slight increase. 5) The non-opening ratio i for N/N_F＝0.6〜0.7 levelled higher in the order of ε＝0, 2, 14％
北見工業大学の論文

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追分重義
北見工業大学

予加工を与えた炭素鋼横穴材の破れ挙動--ねじれ疲れの場合

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