This report summarizes the major findings from a PRCI Project on developing fracture initiation criteria for axial flaws (both through-wall and surface flaws) in high-strength line-pipe materials. This work was originally done on the basis to see if improvements were needed for higher-grade steels, but interestingly there were several outcomes that affect predictions for all piping steels. One of the outcomes of this work is a new correlation between Charpy USE and J-R curve for high-strength materials. Although it is based on limited data, it was demonstrated that there is significant difference...
This report summarizes the major findings from a PRCI Project on developing fracture initiation criteria for axial flaws (both through-wall and surface flaws) in high-strength line-pipe materials. This work was originally done on the basis to see if improvements were needed for higher-grade steels, but interestingly there were several outcomes that affect predictions for all piping steels. One of the outcomes of this work is a new correlation between Charpy USE and J-R curve for high-strength materials. Although it is based on limited data, it was demonstrated that there is significant difference compared to the existing correlation. Another interesting finding is the effect of the internal patch on burst pressure of axial through-wall-cracked pipe test. Careful experimental and detailed finite element analyses showed patching affects burst pressure by at least 10-percent which affects the leak-rupture boundary. For axial surface-cracked pipes, the effect of crack shape on the crack-driving force was investigated. Finally, it was demonstrated that the actual axial surface-cracked pipe bulging factor is considerably lower than bulging factor empirically derived at Battelle in the 1970s. If past bulging factor is used for subcritical crack growth (e.g., for SCC or fatigue analyses), the crack growth and start of ductile tearing can be significantly overpredicted. Overall, J-T analysis provided the most accurate results when proper crack-driving forces and J-R curves were used (both for axial through-wall-cracked pipe and axial surface-cracked pipe). This report also includes recommendations for future work.