Fracture Toughness Estimation of Miniature Specimens by Considering Geometry Effects

Since small-sized specimens are widely used for fracture toughness tests to assure safety of a reactor pressure vessel in service, as a part of surveillance program, various geometry parameters affecting on the stress level near the crack-tip should be investigated for realistic assessment of cleavage fracture behavior. The aim of the present paper is to improve the current master curve method for typical miniature specimens, especially pre-cracked Charpy V-notched (PCVN) specimens. In this context, effects of thickness and side-grooves were quantified from comparing finite element (FE) analyses results in use of various PCVN specimens with and without side-grooves. Then, a scale factor to deal with geometry effects was suggested by employing the fracture toughness diagram, which was derived from FE analyses data of compact tension specimens and PCVN specimens. The scale factor was applied to calculate equivalent stress intensity factors influencing on the reference temperature embodied in the master curve method. The approach proposed in this paper will be useful to estimate fracture toughness of PCVN specimen made of SA508 carbon steel.