Derivation of ductile fracture resistance by use of small punch specimens

Conventional fracture mechanics cannot address the influences of stress triaxiality since the assumption of geometry independence is valid only in limited conditions. Various local approaches have been proposed to investigate the material’s fracture behaviours covering a broad range of loading and flaw shapes. However, unfortunately, standard test specimens have been difficult to obtain from operating facilities. This paper investigates the characterization of ductile fracture resistance (J–R) curves by the small punch (SP) testing technique in conjunction with finite element analyses incorporating well-known damage models. In this context, basically, standard tensile tests and SP tests using tiny specimens are carried out. Furthermore, micro-mechanical parameters constituting the Gurson–Tvergaard–Needleman and Rousselier models are calibrated for typical nuclear materials based on experimental and estimated load–displacement data of their miniaturized specimens. Then, the J–R curves of larger (compact tension) as well as standard 1T-CT specimens are predicted by detailed finite element analyses employing the calibrated parameters. Finally, the estimated J–R curves are validated by fracture toughness tests using the standard CT specimens. The estimated results suggested confidence in the use of the proposed method for ductile crack growth evaluation.