Journal of Applied Mathematics / 2012 / Article / Tab 2

Research Article

A Theoretical Approach to Predict the Fatigue Life of Flexible Pipes

Table 2

Load characteristics for each possible deformed shape of a typical unbonded flexible pipe considering different annulus conditions and axisymmetric loading.

ShapeLoad characteristicsAnnulus

1High tension (no axial compression), low internal pressure, high external pressure, moderate torsion
2Low tension or axial compression, high internal pressure, low external pressure, low torsion
3High tension, high internal pressure, moderate external pressures (internal pressure higher than external pressure), low torsion
4High axial compression (no tension), high internal pressure, low external pressure, low torsionDry
5High tension and internal pressure, no external pressure, moderate torsion
6High axial compression, low internal and external pressures, low torsion
7High tension and low internal and external pressures, low torsion

8Analogous to shape 1
9Analogous to shape 2
10Analogous to shape 3
11Analogous to shape 4
12Analogous to shape 5Flooded
13Analogous to shape 7
14High axial compression, no internal pressure, high external pressure, low torsion
15High tension, no internal pressure, high external pressure, low torsion
16Pure external pressure

The fundamental aspect is to maintain the proportionality between the loads. Therefore, a high load value could be its limit for the studied flexible pipe; a low value may be, for instance, 1% of the limit value, and a moderate value could be 50% of the limit value.