9%Ni 鋼の破壊靱性に及ぼすき裂先端における温度上昇の影響

概要

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The effect of loading rate on fracture toughness of 9% Ni steels with four levels of Charpy absorption energy was studied at various loading rates between impact and static at -196℃. In contrast to the ordinary ferritic steel, the fracture toughness of 9% Ni steel was foud to increase with the loading rate above 20mm/min. The transition of the fracture mode from brittle to ductile took place at the loading rate of 100mm/min, the fracture was completely ductile above this level. The dynamic fracture toughness, K_d, was greater than the static one, K_c. These observations are attributed to the temperature rise at a crack tip during the adiabatic heating at high strain rate, which is emphasized by decreased specific heat and the thermal conductivity at -196℃. The temperature rise during the fracture was measured by a Cu-Constantan thermocouple, and was in good accordance with the previous theoretical prediction. The observed maximum temperature rise was 188℃. The results suggest that not only in 9% Ni steel but in other metals and alloys as well the effect of temperature rise at a crack tip can be an important factor in the dynamic fracture.
社団法人日本鉄鋼協会の論文
1987-02-01