Small fracture toughness specimen for post-irradiation experiments

A subsized specimen for fracture-mechanics tests as well as the associated test devices have been developed and applied to examinations of ferritic–martensitic steels in irradiated and unirradiated conditions. Non-conservative results are prevented by geometrical modification of the fracture zone and appropriate test and evaluation techniques. Experimental and computational comparison to standard samples is presented. The shift in ductile-to-brittle transition of the fracture toughness – compared to full-scale specimens – is examined in experiments at different temperatures. Evaluation of samples irradiated to 0.8 dpa at temperatures between 250 and 450 °C provides reproducible values for J and K and allows complete J–R-curves to be derived. Fracture toughness in the upper shelf is strongly reduced by up to 60% by irradiation, and the ductile-to-brittle transition temperature is raised to 140 °C.