On the transfer of specimen J-R curve to piping components with throughwall circumferential flaw

摘要

Transferability of the specimen f-R/f-T curve to the component level is an important issue in the field of fracture mechanics. Towards this goal, fracture experiments have been carried out on single-edge bend (SE(B)) and compact tension (CT) specimens and throughwall circumferentially cracked straight pipes/elbows of 200 mm nominal bore (NB) diameter. The pipe material is SA 3 3 3 Gr 6 steel (low strength and high toughness material) and specimens are machined from the pipes. Subsequently, elastic-plastic finite-element analyses have been carried out on these cracked components/specimens in order to evaluate the stress triaxiality levels. It is found that the triaxial levels for these cracked components are similar. Hence, similar fracture behaviour is expected for these components. Consequently, one of the pipe f-R curves is used as a reference f-R curve to consider the crack growth in the analysis and the load deformation behaviour of other pipes/elbows is predicted. The load deformation behaviour of the piping components is also predicted using an extrapolated J-R curve from a specimen that exhibits the similar triaxiality level to that of the cracked components. The predicted results are in good agreement with the experiments.