Liner Wrinkling in a Lined Pipe – A Finite Element Approach
of the region of interest are the same. Furthermore, the extra length of outer pipe confines the liner when buckles in the liner propagate during postbuckling behaviour. The longitudinal edges and cylinder ends are symmetrically constrained, while an axial displacement is applied at the end opposite the region of interest. In Figure 6, the region of interest of the deformed lined pipe, with an initial imperfection of 10-3mm, is shown following axial compression.
When comparing the results of the frictionless confined liner to the unconfined liner, both having an initial imperfection of 10-3mm, it can be seen from the stress–strain curves in Figure 7 that the axially compressed confined liner buckles at a much higher strain than the liner on its own. Just as for the unconfined liner, it was found that the maximum load capacity of the confined liner increases with smaller initial imperfections. Furthermore, the results based on flow theory exceed those based on deformation theory, although there is a better agreement for increasing imperfection amplitude.
Further Research
Further investigation of liner behaviour under axial compression includes extensive parameter studies for the confined and unconfined
1. Yoshida T, Matsui S, Atsuta T, et al., Offshore Technology Conference, 5–8 May 1980, Houston, Texas, OTC3891, 1980;361–70.
2. Focke ES, Delft University of Technology, 2007. 3. De Koning AC, Nakasugi H, Ping L, Stainless Steel World, January/February 2004;53–61.
4. Reddy BD, Int J Solids Structures, 1979;15:669–83.
liner, taking geometry parameters, material parameters, friction and contact pressure between liner and outer pipe into account.
After finishing the research into axial compression, investigations will continue with simulation of the pipes during pure bending. 2D models subjected to pure bending will be used to determine the load limit due to ovalisation for both the confined and unconfined liner. 3D models in which the pipes will be subjected to pure bending will be used where the two possible failure modes can interact, i.e. liner wrinkling and ovalisation. Pure bending tests will be executed on TFPs to obtain results with which the numerical results for pure bending can be compared. Additionally, the results from pure bending will be compared with those previously obtained from reeling tests2
to
determine the effect of the additional contact force of reel on lined pipe during reeling. More detailed results of this research will be published at conferences later this year. n
Acknowledgements
Thanks to the partners and sponsor – Heerema Marine Contractors, Delft University of Technology, Kuroki Tube and Pipe Co Ltd, Dosto Engineering and Senter Novem – who have made this research possible.
5. Kyriakides S, Shaw PK, Journal of Pressure Vessel Technology,
1987;109:169–78.
6. Corona E, Kyriakides S, Int J Solids Structures, 1988;24(5):505–35.
7. Ju GT, Kyriakides S, Int J Solids Structures, 1992;29(9):1143–71.
8. Corona E, Lee LH, Kyriakides S, Int J Solids Structures, 2006;43;7099–7118.
9. Bardi FC, Kyriakides S, Yun HD, Int J Mech Sci, 2006;48:842–54. 10. Bardi FC, Kyriakides S, Int J Mech Sci, 2006; 48:830–41. 11. Bushnell D, Computers & Structures, 1976;6:221–39. 12. Deerenberg E, Delft University of Technology, 1994. 13. Blachut J, Galletly GD, James S, J Mech Eng Sci, 1996;210:477–88.
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