Fracture resistance of A533B-I steel, a typical reactor pressure vessel material, has been investigated by the single specimen unloading compliance J-integral method in the Charpy upper shelf region up to the reactor operating temperature, 288℃. Experiments have been carried out using small size CT specimens with various test temperatures and orientations. Especially, various analysis methods have been compared and discussed to predict the stable crack growth.
It is found that the tearing modulus decreases as the test temperature increases while the Jic is changed insignificantly. Also the fracture resistance is found to show a large difference with the specimen orientation.
It is shown in this work that the J-integral based on the deformation theory does not exhibit the reliable material behavior with crack growth in the small specimen, but the modified J, J-integral based on the new definition, does. Accordingly, it is thought that the application of the modified J is more reasonable to characterize the material fracture behavior, even though this new definition of J is still studied theoretically and experimentally.
