Effect of plastic zone size on fracture characteristics according to shape of specimens

Abstract

To apply the leak before break concept to nuclear pipes, obtaining the fracture characteristics of nuclear pipes from real pipes would be ideal. But, conducting such experiments is difficult due to its efficiency and cost. Therefore, many specimens and test methods or theories have been proposed and studied to obtain fracture properties similar to real pipes. However, the theoretical formulation and quantification of the difference between the constraint effect and the fracture resistance characteristic are insufficient, and the results of previous studies are insufficient, which is explained only under a specific case and special conditions. In this study, the sizes of the plastic zones were calculated according to the crack length of each specimen shape used in the test and the differences in the fracture resistance curves depending on the change in shape were evaluated. Furthermore, we compare the different crack stability assessment values depending on specimen deformation, and crack stability assessment was performed using a crack driving force diagram. Using crack stability assessment results, the relationship between the size of the plastic zone and fracture toughness was evaluated.