Existing engineering critical assessment (ECA) procedures in BS 7910 and DNV OS F101 are based on uniaxial loading conditions only and do not have any means of accounting for biaxial loading scenarios. This paper considers a yield strength adjustment method for addressing the ECA under biaxial loading. Different reference stress solutions with or without the yield strength adjustment method were compared with 3D FEA in terms of crack driving force. The following conclusions can be drawn from work presented in this document: (1) The plate reference stress solution gives an over-conservative prediction of crack driving force. It is particularly over-conservative when using the uniaxial stress-strain curve without any biaxial adjustment in constructing the failure assessment diagram (FAD). (2) It is recommended to consider the Kastner reference stress solution with the biaxial adjustment which would give a less conservative estimate of the crack driving force. However, it should be noted that without biaxial adjustment, the Kastner solution is still over-conservative. (3) It should be mentioned that the combined effects of the nature of lateral buckling, the shakedown experienced at the buckle apex following first buckle, the defect sizes involved, all other conservatisms included in the ECA (weld residual stress, misalignment, etc.) should make the yield strength adjustment method conservative. (4) However, for the purpose of assurance before the recommended solution is confirmed with further studies, FEA as presented in this paper can be used when performing the ECA for end-of-life (EOL). Note that the FEA is intended to provide a verification of the conservatism associated with the reference stress solution with the biaxial adjustment. Therefore, it is not necessary for the FEA model to include the detailed weld information.
Engineering critical assessment of pipeline under axial straining with internal pressure
Kritische technische Bewertung von Pipelines unter axialer Verformung mit Innendruck
2013
5 Seiten, 10 Bilder, 1 Tabelle, 9 Quellen
Conference paper
Storage medium
English
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