Sammenligning av moment og spiralmodeller for utmatningsanalyse av fleksible stigerør
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- Institutt for marin teknikk 
There are still quite a lot of unknown and unexplainable fields in riser section, whose fatigue damage may cause loss of lives, environmental pollution and threats to the economy. In this thesis, two methods to find the maximum damage of flexible riser by the local stress analysis tool Bflex are emphasized on. One is using LIFETIME module for ITCODE 0&1 and 31. Another is applying FATPROP (fatigue properties) and FAPLOT to 353FLEXCROSS. The locations of maximum fatigue damages are different from various cross-section types. Element type pipe52 is applied to ITCODE 31 for both core layers and tensile layers. As to ITCODE 0&1, pipe52 is used for core layers while hshear352 is used for tensile layers. Regarded with 353FELXCROSS, the new element hshear363 is exploited for carcass, seal, zeta, structape as well as outsheath, and hshear353 is exploited for tensile layers. In addition, contact element hcont463 is also applied to contact layers when using 353FLEXCROSS.With different cross-section types and different element types, the model of flexible riser bearing prescribed displacement and internal pressure has been established. After fatigue analysis with alternative shear parameters, the result which contains curvature-stress curves of three different size riser comes out.It is important to see the comparison of these curves among ITCODE 0&1, 31 and 353FLEXCROSS. ITCODE 0&1 show the conservative result for stress analysis. The clear differences of different shear modulus from 5 to 1000 can be illustrated vividly by ITCODE 31. Moreover, there is almost no difference modelled by 353FLEXCROSS. Therefore, ITCODE 31 would be the most reasonable option for stress analysis when we changing the shear modulus considering about slip behavior for flexible risers.