The elastic-plastic fracture toughness (J
IC) and fracture resistance (J-R curve) of a carbon steel, STS42, used for piping in a nuclear reactor were evaluated according to the several evaluating methods recommended or proposed so far to discuss their applicability and utility. The results obtained are as follows: (1) In evaluating J
IC, the multiple specimen method recommended by the Japan Society for Mechanical Engineers (JSME standard S001) gives the most reliable results by using smaller sized specimens. (2) The single specimen methods by using the compliance technique, adopted in the ASTM standard (E813, E813 modified, Tentative test procedure for determining the plain strain J-R curve), do not give an accurate J-R curve of J
IC, due to an error in the calculated crack length. (3) In evaluating the J-R curve, it is necessary to account for crack extension in calculating the J-integral. (4) According to the above results, a new standard method for determining the J-R curve including the J
IC test method should be poprosed.
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