Vortex-induced fatigue reliability evaluation of deepwater riser vdth corrosion defects

Key words:  corrosion  deepwater riser  fatigue life  fatigue reliability

Abstract:

The vortex-induced fatigue life of riser system with corrosion defects were evaluated by finite element method. In this method, corrosion areas on riser joints were simulated by local finite element analysis and the stress concentration factor (尺c) of corrosion defects was calculated. The Kc can be used in fatigue life prediction of deepwater riser system. Defect models were divided into two categories such as pitting and local corrosion. Deficiencies in shape，size and direction of corrosion were taken into account. To ensure the reliability of the whole system, the joints with corrosion defects should be arranged where the fatigue damage predictions are as small as possible. For the ideal system and the system with joints containing corrosion defects, the fatigue life and reliability of each system were calculated respectively. Stress and damage flunctu-ate only in the defect locations，and reliability results also reveal the reasonability of layout scheme for injured joints.