著者

佐野 謙一

出版者

社団法人日本鉄鋼協会

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.73, no.2, pp.380-386, 1987

被引用文献数

2 7

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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&deg;C. 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, <I>K</I><SUB>d</SUB>, was greater than the static one, <I>K</I><SUB>c</SUB>. 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&deg;C. 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&deg;C. 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.