|Evaluation of methodologies to accelerate corrosion assisted fatigue experiments|
In: Experimental Mechanics. Springer: Norwell. ISSN 0014-4851; e-ISSN 1741-2765
Corrosion acceleration; Corrosion assisted fatigue; Testing; Potentialdrop; Temperature; Dissolved oxygen level
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The corrosive nature of a marine environment is an important factor to be considered during the fatigue design of offshore structures. Thereto S-N curves must be determined in close to real conditions which is highly time consuming. It is hypothesized that if the corrosion process is accelerated at approximately the same rate as the fatigue frequency, testing time could be highly reduced. Corrosion acceleration is possible by modifying physical and/or electrochemical properties involved in the redox reactions. In this work the first option was chosen. Based on a literature review temperature and dissolved oxygen level were concluded to be the most influencing parameters. Several test scenarios with different combinations of sea water temperature and dissolved oxygen level have been defined. Corresponding S-N curves have been constructed for HSLA steel (type DNV F460) specimens immersed in natural seawater. The direct current potential drop technique was used to quantify damage evolution for all tested scenarios. Additionally, a reference S-N curve for immersed behaviour was determined at a temperature and frequency close to North Sea conditions. Comparison of the experimental results indicates that an average acceleration of the corrosion assisted fatigue damage process of around 80 % could be obtained.