Engineering Critical Assessments of Marine Pipelines with 3D Surface Cracks Considering Weld Mismatch

Document Type: Research Paper

Authors

1 Department of Offshore Structures Engineering, Faculty of Marine Science, Petroleum University of Technology, Abadan, Iran

2 Automotive Fluids and Structures Analysis Research Laboratory, School of Automotive Engineering, University of Science and Technology, Tehran, Iran

Abstract

Offshore pipelines are usually constructed by the use of girth welds, while welds may naturally contain flaws. Currently, fracture assessment procedures such as BS 7910 are based on the stress-based methods and their responses for situations with large plastic strain is suspicious. DNV-OS-F101 with limited modifications proposes a strain-based procedure for such plastic loads. In this paper 3D nonlinear elastic-plastic finite element analyses using the ABAQUS software are performed in order to compare existing stress- and strain-based procedures beside newly strain-based method which is called CRES approach in order to improve the criteria used in current guidelines particularly at large plastic strains. It is concluded that although BS 7910 values are closer to finite element results than other methods in elastic region, but it is still conservative. In the area of large plastic strain, CRES method is very less conservative in both case of with and without internal pressure in comparison to others. The comparison of numerical simulation results with those available experimental data reveals a good agreement.                  

Keywords

[1] BS 7910 , 2005, Guide on Methods for Assessing the Acceptability of Flaws in Metallic Structures, BSI.
[2] Schwalbe K.H., 1994, The crack tip opening displacement and J integral under strain control and fully plastic conditions estimated by the engineering treatment model for plane stress tension, Journal of Fracture Mechanics 24: 636-651.
[3] Linkens D., Formby C.L., Ainsworth R.A.A., 2000, Strain-based approach to fracture assessment-example applications, Proceedings of 15th International Conference on Engineering Structural Integrity Assessment, Cambridge, EMAS.
[4] Wang Y., Liu M., Stephens M., Petersen R., Horsley D., 2009, Recent developments in strain-based design in North America, Proceedings 19th International Offshore and Polar Engineering Conference, ISOPE, Osaka, Japan.
[5] Stephens M., Petersen R., Wang Y., Gordon R., Horsley D., 2010, Large-scale experimental data for improved strain-based design models, 8th International Pipeline Conference, Calgary, Alberta, Canada, ASME 2010.
[6] Wang Y.Y., Liu M., Song Y., Horsley D., 2012, Tensile strain models for strain-based design of pipelines, Proceedings of the ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering, OMAE2012, Rio de Janeiro, Brazil.
[7] DNV-OS-F101, 2012, Offshore Standard – Submarine Pipeline Systems, Det Norske Veritas, Hovik, Norway.
[8] Raju I.S., Newman Jr J.C., 1982, Stress-intensity factors for internal and external surface cracks in cylindrical vessels, Journal of Pressure Vessel and Technology 9: 104-293.
[9] Jayadevan K.R., Østby E., Thaulow C., 2004, Fracture response of pipelines subjected to large plastic deformation under tension, International Journal of Pressure and Vessel Piping 81: 771-783.
[10] Østby E., Jayadevan K.R., Thaulow C., 2005, Fracture response of pipelines subject to large plastic deformation under bending, International Journal of Pressure Vessel and Piping 82: 201-215.
[11] CSA Z662, 2007, Oil and Gas Pipeline Systems, Canadian Standards Association.
[12] Hibbitt, Karlsson and Serensen, 2014, ABAQUS/STANDARD, User’s Guide and Theoretical Manual, Version 6.14.
[13] Anderson T. L., 2005, Fracture Mechanics Fundamentals and Applications, CRC Press.
[14] McMeeking R., Parks D. M., 1979, On Criteria for J-Dominance of Crack Tip Fields in Large-Scale Yielding, Philadelphia, ASTM International.
[15] Yi D., Idapalapati S., Xiao Z. M., Kumar S. B., 2012, Fracture analysis of girth welded pipeline with 3D embedded subjected to biaxial loading conditions, Journal of Engineering Fracture Mechanics 96: 570-587.
[16] Chattopadhyay J., Kushwaha H.S., Roos E., 2009, Improved integrity assessment equations of pipe bends, International Journal of Pressure Vessels and Piping 86: 454-473.