RE-EXAMINATION OF BATTELLE TWO CURVE METHOD

The possibility of fracture propagation is a significant concern for pipelines transporting gases. The need to arrest a running fracture in a pipeline is paramount to the integrity and safety of the pipeline's operation. The most commonly used method to predict pipe resistance to a ductile fracture is the Battelle Two Curve Method (BTCM). Recent full-scale fracture propagation tests have shown that the BTCM cannot give accurate predictions for modern high-toughness steels. A Computational Fluid Dynamics (CFD) model has been developed to identify the limitations of the BTCM. The predictions of the developed model are in good agreement with the available experimental data. It has been found from the simulation that the pressure drops very fast in the initial stages of fracture propagation, leading to an intersection between the fracture curve and the decompression curve. However, the fracture speed does not remain constant at the speed corresponding to the intersection point, as assumed in the BTCM. It generally decreases, following the decompression curve as the fracture propagates. This observation indicates that the J-type fracture propagation curve adopted in the BTCM does not accurately represent the fracture propagation behaviour.