Evaluation of impacts of stress triaxiality on plastic deformability of RAFM steel using various types of tensile specimen

Kato, Taichiro; Ohata, Mitsuru*; Nogami, Shuhei*; Tanigawa, Hiroyasu

Plastic deformability of material shows general tendency to decrease due to become hard and brittle. Also, the plastic deformability tends to decrease as the stress triaxiality of a parameter to evaluate the magnitude of plastic constraint increases. Therefore, it is necessary to accurately understand the ductility loss limit of RAFM in order to conduct the structural design assessment of a fusion reactor demo blanket. In this study, plastic deformability of RAFM was evaluated the impacts of stress triaxiality on variation of tensile specimen shape and testing conditions. In the results, the fracture was defined as not the point of macro-crack but that of micro-crack. It was confirmed that the true strain rate significantly increases in the vicinity of the point of micro-crack. The relationships between the fracture ductile and stress triaxiality of the full size tensile specimen and the miniature size one were shown on the single curve regardless of the specimen size.