Literature Review on Testing of Mini-CT Specimen to Characterize the Ductile-to-Brittle Transition Range and the Upper Shelf Regime

In recent years there have been significant research efforts toward the miniaturization of specimens when characterizing the fracture toughness of ferritic steels. In particular, the nuclear sector has been especially interested due to the strict structural integrity controls to which the different nuclear components are subjected, with the reactor pressure vessel being one of the most critical. In this sense, the use of the mini-CT specimen (a compact tension 4 mm thick specimen) constitutes a promising alternative that has been widely studied together with the Master Curve approach to characterize steels within the ductile to brittle transition range. Additionally, this type of specimen has also been used to characterize steel operating within the upper shelf regime. Within the transition regime, the majority of the results reveal an excellent correlation between the results obtained using mini-CT specimens and those obtained when using wellknown conventional size specimens (e.g., 1T-CT specimens or PCCv specimens), which seems not to be the case when dealing the ductile regime. However, testing such a small geometry brings a series of peculiarities that are necessary to consider. This work intends to briefly gather the knowledge found in the literature and to expose the best practices when testing this type of specimen. The effect of the specimen geometry, the possible use of side grooves, the measurement of the displacement (front face vs load line), or different conditions during testing (e.g., selection of testing temperatures) are analyzed and discussed.