Analysis of full-scale burst tests by FE modelling using constant CTOA fracture criterion

Several backfilled full-scale burst tests were recently performed by TC Energy on CSA Z245.1 Grade 550 Category II pipe steels. This paper presents a new interpretation of the recent full scale burst test data using the crack tip opening angle (CTOA) as fracture propagation criterion. ASTM E3039 was used to determine the CTOA of the pipe steels used in the tests. Correlations of fracture velocity with CTOA and with Charpy absorbed energy CVN were compared. A finite element (FE) model with shell elements and a constant CTOA fracture criterion was implemented for the simulation of dynamic fracture propagation. The commercial FE code ABAQUS was used to generate the models and perform the analyses. The CTOAs determined from ASTM E3039 were used as input to the model and the fracture velocities found from the simulations were in good agreement with experimental values. The polyurethane foam coating used in the tests was incorporated in the model and shown to have a significant effect on the predicted fracture velocity. The fracture resistance curves (pressure vs. velocity) from the present model were compared with those proposed in the HLP-Sumitomo model and shown to be in approximate agreement.