Applicability of 3 mm Reduced-Thickness Miniature C(T) Specimens for Fracture Toughness Characterization of Nuclear Reactor Materials

Enhancement of fracture mechanics small-scale specimen test techniques is important, especially in the nuclear industry for the safe lifetime extension of power plants. Miniature-sized test specimens enable more efficient use of the reducing amount of reactor pressure vessel surveillance reference materials. This paper studies the limits of specimen miniaturization by means of fracture mechanics testing and determination of reference temperature T0, supported by microstructural characterization, particle analysis, and Finite Element Modelling (FEM). Tests indicate the same reference temperature T0, −102°C, for both the 4 mm and 3 mm thick specimens investigated. Particle distribution analysis showed a statistically sufficient amount of initiating particles in the cross-section of the 3 mm thick specimen. FEM results including comparative analysis of four different specimen thicknesses showed similar stress and strain states in the 3 mm and 4 mm thick specimens. Maximum stress site versus crack initiation location is discussed, as well as the adaptability of ASTM standard E1921 and weakest-link theory regarding the applicability of miniature compact tension specimens with reduced thickness.