Verification of Master Curve testing on mini-0.16T-C(T) specimens

Fracture toughness evaluation by the Master Curve method using 4-mm-thick miniature compact tension (mini-C(T)) specimens has been proposed. There were round robin exercises to validate the reference temperature, T0, determined on mini-C(T) of RPV base and weld metal. The HZDR has contributed to these round robin exercises. In addition to the mandatory testing, the distribution of the cleavage initiation sites over the crack front was determined. The mini-C(T) testing was also verified on RPV base metal 22 NiMoCr 3-7 from the lower ring of the non-commissioned Biblis C RPV. The fracture toughness values and therewith evaluated reference temperatures, T0, measured on 1T-, 0.5T-, 0.25T and 0.16T-C(T) specimens are compared. The results show that the T0 values determined with C(T) specimens of different size scatter within one standard deviation according to ASTM E1921. The testing of mini-C(T) specimens machined from the broken halves of Charpy specimens is a promising option to determine fracture toughness values of already tested surveillance specimens. The advantage of using mini-C(T) specimens is that material from the weld region can be investigated directly.