A brittle failure evaluation of a semi-elliptical surface crack in a pipe mock-up using three variations of the advanced master curve assessment accounting for ductile crack growth, constraint loss and crack front length

Recently, an experiment on a ferritic pipe mock-up, with a semi-elliptical surface crack, loaded in four-point bending, failed by brittle fracture following ductile crack growth. The experiment serves as a case-study to validate advanced methods for assessing brittle failure affected by constraint-loss, ductile crack growth and the crack front length. Previous work has focused on the determination of the component J-R curve. In this work, three variations of the advanced Master Curve assessment are conceptualized and applied to evaluate the probability of brittle failure of the pipe. The sensitivity of the brittle failure prediction to the three variations of the advanced method is investigated by gradually increasing the complexity of the assessment and by varying the input parameters related to constraint, ductility and the crack front length. The J-integral and constraint along the crack front are evaluated using finite element modelling. The results demonstrate the significance of the component J-R curve in the assessment and provide insight into how the input parameters and the assessment method affect the brittle failure prediction. The work contributes to the efficient operation of pressurized components and affects standards development. • Conceptualization of three variations of the advanced Master Curve assessment • Combined effect of ductile crack growth and constraint-loss on failure probability • The advanced Master Curve assessment provides a failure probability of 7 % • The crack driving force estimate should be based on component J-R curve • The simplified assessment based on maximum constraint is conservative