Fracture mechanics assessment of flaws in pipeline girth welds

摘要

The application of conventional fracture mechanics assessment methods to high strength steel pipeline girth welds may be challenging. To ensure integrity, there may be a need to assess plastic axial straining combined with internal pressure in steels with limited work hardening capacity and strength mismatch between the weld metal and parent pipe with a flaw present in the girth weld. This paper explores some of the limitations of conventional fracture mechanics assessments when applied to X100 pipeline girth welds. These are revealed by comparison of J driving force based on modifications to the basic BS 7910 assessment procedures with elastic-plastic finite element analyses. Tensile properties from a representative X100 pipeline steel are used to demonstrate the effects of girth weld strength mismatch and weld width on driving force under the combined effects of internal pressure and axial plastic straining with a weld flaw present. The effects of girth weld strength under- and over-matching on J driving force are explored.