Use of Instrumented Charpy Impact Tests for Master Curve Determination

The Master Curve concept (MC) allows to quantify the variation of fracture toughness with the temperature through-out the ductile-to-brittle transition region. Limit curves of fracture toughness for defined failure probabilities and a reference temperatures can be determined using this method. Thus, fracture mechanical values can be supplied for an integrity assessment of structural components.
The paper links MC concept and Charpy-V impact test to determine dynamic fracture mechanical parameters of ASTM A 533 B Cl. 1 nuclear pressure vessel steel. The MC based reference temperature, T0dy, is measured under impact loading using the instrumented impact test. The change in T0dy is 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 increase from the surface to the middle of the steel plate in the same course. However, in the middle section of the plate T0dy is in average approximately 38 K higher than TT and 88 K higher than T0st. The results show that the MC concept is applicable for the fracture mechanical characterisation of material with different microstructure using Charpy size specimens.