Dynamic Master Curve Issues

The paper links the Master Curve (MC) concept and the Charpy-V impact test to determine dynamic fracture mechanical parameters of ASTM A 533 B Cl. 1 nuclear pressure vessel steel. Pre-cracked and side-grooved Charpy size specimens were tested under impact loading using the instrumented impact pendulum test. J-integral based fracture toughness values, KJc, were determined at cleavage failure of the specimen. MC based reference temperatures, T0dy, were determined on the basis of measured KJc values.
The change in T0dy was determined in dependence on the thickness position of a steel plate and compared with the quasi-static reference temperature, T0st, and the Charpy-V transition temperature (TT). All three parameters increased from the surface towards the middle of the steel plate in the same course. However, in the middle section of the plate T0dy is in average approximately 26 K higher than TT41J and 72 K higher than T0st. Different T0 were found when tested at different temperatures, but the trend is ambiguous.
The results show that the MC based T0 is sensitive to reflect rather small microstructural differences by testing small Charpy size specimens and, thus it is applicable for the fracture mechanical characterisation of materials.