Temperature Dependence of JIC Fracture Toughness Values in the Structural Steels and Evaluation of the Testing Method
1981 Volume 67 Issue 2 Pages 382-390
Details
1981 Volume 67 Issue 2 Pages 382-390
The fracture toughness of four kinds of structural steels with relatively high elongation at room temperature has been evaluated by the electrical potential method and by other methods between at room and liquid nitrogen temperature. The results obtained are summarized as follows:
(1) At room temperature, (JIC) E value by the electrical potential method was very close to ( JIC) R value by the R curve method. ( JIC) S value by the SZW method was 15% higher than ( JIC) E value.
(2) At room temperature, the crack initiation detected by the inflection of the electrical potential corresponded to the stage where the formation of type II dimple and the internal necking occurred. Before the crack initiation, voids were already formed in front of the stretched zone.
(3) JIC value increased with decreasing the testing temperature because of an increase in the yield strength, while it decreased drastically when cleavage fracture occurred at the precrack tip.
(4) JIC value, CTOD (δ) and KIC were related with each other as follows:
JIC=1.79δy·δ (for ductile fracture)
KIC=0.81√JIC·E (for brittle fracture)
