ガス切断が高張力鋼(50kg/(mm)^2 級)の疲れ強さにおよぼす影響について

概要

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It is unavoidable even at present the gas blemishes on cut sides remain in cutting process by the automatical flame-cutting machine. The object of this experiment was firstly in determining the fatigue strength of flame-cut specimens containing an intentional gas blemish (notch) (t : 1.8mm. ρ : 0.7mm), and moreover, in comparing the fatigue strength thus obtained with that of machined specimens; and secondly in examining several methods for the repair of notch. The plate used was SM 50 A. The experiment revealed the following; (1) The fatigue strength of the flame-cut specimens containing an intentional notch (stress concentration factor≒3) was 72 percent of that of the evenly flame-cut specimens. But the abovementioned value was greater than that of the machined specimens containing an identical, but machined notoch. (2) The location of crack-initiation was limited to the melted edges in the evenly flame-cut specimens. But the crack initiated from the whole surface of the notch root in the notched specimens (MN and GN testing series). (3) All the repair methods tried in this research succeeded in giving the same fatigue strength as that of non-notched specimens.
1963-08-25