Prediction of large specimen fracture toughness from small specimen tests

Small specimen fracture toughness test has several advantages especially in the engineering use. However, scattering of measured fracture toughness in the transition temperature regime in such a test should be analysed to determine the valid fracture toughness value. In the present study, source of the scattering is investigated based on the microscopic observation of fracture surface of tested specimens and micromechanisms of scattering are discussed. On the other hand, dynamic fracture toughness of twelve heats of RPV steels are determined using small specimens based on the statistical analysis of the scattering. Further, the correlation between these fracture toughness transition behaviour and other small specimen test results are discussed. A method to predict the dynamic fracture toughness from the Charpy and tensile test results is presented. (orig.)