Elastic plastic toughness of irradiated steels with the single specimen compliance technique

J-R curve trends of irradiated A533-B submerged arc weld metal containing a high copper impurity level have been characterized with the single specimen compliance technique. The R curve for these steels exhibits a power law behavior. This non-linearity precludes both an exact determination of Jsub(Ic) by the proposed ASTM multispecimen standard as well as the calculation of a single value of tearing modulus T in the region of J-controlled growth. A new experimental definition of Jsub(Ic) is proposed which accounts for the curvature in the R curve. The use of side grooves promotes a straight crack-front extension which results in T values which are less than those produced by smooth specimens. With side-grooved specimens irradiation has reduced T by a factor of 2.5 while a smaller reduction in Jsub(Ic) was observed under the same conditions. The phenomenon of an R curve interrupted by cleavage in the upper shelf region is also discussed. (Auth.)