Structural Integrity Analysis of Cracked Pressure Vessel Welds Using Conventional and Constraint-modified Failure Assessment Diagrams

In this study, four assessment procedures were used for the integrity analysis of the cracked Al alloy pressure vessel welds (PVWs), and the four methods are (1) to use BS 7910 Option 1 that is a conventional procedure, (2) to involve a modification to the FAD but retain the definition of Kr, (3) to retain the FAD but modifie the definition of Kr (4) to use constraint-based FAD and true Kmat values for SENB specimens with different a/W values. The fracture toughness tests were performed for single-edge notched bending (SENB) specimens with different a/W values to obtain the corresponding Kmat values and to determine the relationship between crack tip constraint (via a/W) and fracture toughness. To determine the constraint-based FAD curves, finite element analyses were performed to derive the functional relationships between normalized load and Q-constraint for SENB specimens. The results showed that the predictions using the second and third procedures was in good agreement with the experimental results of residual strength, and that BS 7910 Option 1 procedure was proved to be conservative for the shallow-cracked vessel specimens, and that the fourth method overestimated the residual strength.