Comparison of reference temperature T0 from instability KJc and KIc fracture toughness

The application of the reference temperatures T0 and RTTo according to ASTM E 19 21 and ASME Code Cases N-629 or N-631, respectively, shall be established in the current revision of German KTA rules. The Master Curve reference temperature T0 characterizes the fracture toughness of ferritic steels that experience onset of cleavage cracking at elastic, or elastic-plastic KJC-instabilities, or both. The plane-strain fracture toughness, KIC, defined by ASTM E 399, is assumed to represent a size insensitive initiation based lower bound value. The majority of existing fracture toughness data are based on KIC-values. More recent data are KJ C, related to the issuing of ASTM E 1921 in 1997 and to the success of the Master Curve based T0. Therefore, the possible difference between T0 determined from KJC and from KIC was investigated with available data bases for RPV-steels. The comparison of T0(KJC) and T0(KIC) showed a 1:1 correlation proving equivalence o f KJC and KIC in the determination of T0.