低温における球状黒鉛鋳鉄およびNi-Zr鋳鋼の疲労強度について

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Regarding the mechanical properties of metals at low temperature the investigations have hitherto been mostly confined to the impact and tensile properties, and there have been but few works on the fatigue. In this paper, the fatigue strength of the nodular cast iron and Ni-Zr cast steel for the unnotched and notched specimens at +20℃, -16℃ and -78℃, were measured with the rotating cantilever Woher-type fatigue machine at the revolution speed of 4500 rpm. The experimental results are summarized as follows : - (1) The tensile strength of nodular cast iron decreases with lowering testing temperature from room temperature so that 61 kg/mm^2 at room temperature becomes 58.5 kg/mm^2 at room temperature increased to 25 kg/mm^2 at -78℃. Similarly, the value of Ni-Zr cast steel rose to 29.5 kg/mm^2 from 25 kg/mm^2. (3) The fatigue limit of 10 kg/mm^2 at room temperature for the notched Ni-Zr cast steel specimen increased to 13 kg/mm^2 at -78℃. For the notched nodular cast iron, 14 kg/mm^2 rose to 18 kg/mm^2. (4) The value of fatigue notch factor β_k of the Ni-Zr cast steel decreased from about 2.45 to 2.25 as the test temperature was lowered from +20 ℃ and -78℃. Similarly, the value of nodular cast iron decreased from 1.6 to 1.4. (5) The value of notch sensitivity η_k decreased as the test temperature was lowered. The value of η_k of Ni-Zr cast steel keeps twice as high as that of nodular cast iron, that is, for the Ni-Zr cast steel the range from 1.5 to 1.2 at the test temperature +20℃ and -78℃ respectively, corresponded to 0.7 to 0.4 of the nodular cast iron.
社団法人日本材料学会の論文
1965-11-15

低温における球状黒鉛鋳鉄およびNi-Zr鋳鋼の疲労強度について

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