Effect of Corrosive Environment on Fatigue Crack Propagation in Deep Water Riser

The corrosion fracture life of marine riser is investigated. Riser will be modeled as a long beam and the wave and current forces is estimated by short wave theory and modified Morison’s equation. Dynamic equilibrium equations of riser will be obtained on based of Euler theory. After bending stress calculation along the riser that includes effect of riser weight and platform motion، loading history can be obtained in riser cross section. Since risers exposed to seawater and sour crude oil، an initial crack can have destructive effects and corrosion fracture can be occurred. So effect of initial crack in riser cross sections in different depths and at present of corrosive fluid is studied. At the end the effect of seawater and crude oil on crack propagation and corrosion fracture life is investigated. In order to solve riser dynamic equilibrium equation Range-Kutta and finite difference methods will be used.