L52037 Ductile Fracture Propagation Resistance for Advanced Pipeline Designs

The development of a method able to evaluate the ductile fracture behavior on pipelines has been documented. Therefore, methods for the determination of material fracture resistance and crack driving force have been accurately investigated. In particular, the techniques to determine the critical fracture characterizing parameter CTOA (crack tip opening angle) have been reviewed in-depth (back-slotted drop weight tear tests [DWTT], two specimen CTOA tests, etc.), and in view of a future pipe-mill application. For a more reliable CTOA estimate the needed following parameters have been investigated: 1) rotation factor in a DWTT and 2) the material flow stress to be used in dynamic tests. On the other hand, as far as the crack driving force is concerned, a finite element code developed by CSM (PICPRO) has been successfully used to evaluate the correlation between the CTOA inferred by DWT tests and that measured on pipe. In addition PICPRO has been used to determine the driving force acting on pipe in a wide range of operating conditions, finally supplying an appropriate formula for its calculation. Once the driving force and the fracture resistance have been determined their comparison allows crack arrest assessment.