A Non-Linear Model for Corrosion Fatigue Lifetime Based on Continuum Damage Mechanics

Abstract

Abstract. Many structures, such as oil platforms and wind turbines, are built in the marine environment. These structures do not merely suffer from variable cyclic loading due to wind, waves and current, but also from corrosion. Their interaction can give rise to corrosion fatigue, thus reducing the service life and integrity of the structure. The research community witnesses a challenge to identify damage mechanisms of combined fatigue loading and corrosion, and to link this to the lifetime prediction of offshore structures. In this paper, a non-linear corrosion fatigue model is proposed to describe damage accumulation based on continuum damage mechanics. Fatigue endurance limit, load frequency and corrosion rate are included in the model as basic parameters which influence the interaction between fatigue and corrosion. A sequential load effect is revealed via integration of the non-linear accumulation of damage. Parametric studies are conducted to show the abilities of the model. Preliminary simulation results agree to a strong extent with experimental data in the form of corrosion fatigue S-N curves. Nonetheless, deviations are observed at lower life times and these are prone to further investigation. In the future, parameters will be calibrated and further validation experiments will be performed.

Profiling Corrosion Rates for Offshore Wind Turbines with Depth in the North Sea

“…Corrosion in an OWT has been observed at different locations and it has to be specified that there are various corrosion mechanisms existing. Different regions affected by corrosion can be broken down as listed below and further illustrated in thriving shown in Figure 1a,b [16][17][18] In a sealed structure, the dissolved oxygen is rapidly absorbed and the medium becomes anaerobic causing hydrogen sulphide to be released as a product of the new corrosion mechanism. Within a closed environment it is expected that this form of corrosion would be limited as the internal conditions would not continue to support the chemical reaction [15].…”