Integrity of offshore structures

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dc.contributor.advisor Brennan, Feargal
dc.contributor.author Adedipe, Oyewole
dc.date.accessioned 2016-02-11T15:58:12Z
dc.date.available 2016-02-11T15:58:12Z
dc.date.issued 2015-08
dc.identifier.uri http://dspace.lib.cranfield.ac.uk/handle/1826/9692
dc.description.abstract Corrosion and fatigue have been dominant degradation mechanisms in offshore structures, with the combination of the two, known as corrosion fatigue, having amplified effects in structures in the harsh marine environments. Newer types of structure are now being developed for use in highly dynamic, harsh marine environments, particularly for renewable energy applications. However, they have significantly different structural details and design requirements compared to oil and gas structures, due to the magnitude and frequency of operational and environmental loadings acting on the support structures. Therefore, the extent of corrosion assisted fatigue crack growth in these structures needs to be better understood. In this research, fatigue crack growth in S355J2+N steel used for offshore wind monopile fabrications was investigated in air and free corrosion conditions. Tests were conducted on parent, HAZ and weld materials at cyclic load frequencies similar to what is experienced by offshore wind monopile support structures. The seawater used for testing was prepared according to ASTM D1141 specifications and was circulated past the specimens through a purpose designed and built corrosion rig at a rate of 3 l/min, at a temperature of 8-100C and at a pH of 7.78-8.1. A new crack propagation method accompanied by constant amplitude loading was used. Crack growth rates in parent, HAZ and weld materials were significantly accelerated under free corrosion conditions, at all the stress ratios used compared to in air environment. However, in free corrosion conditions, crack growth rates in the parent, HAZ and weld materials were similar, particularly at a lower stress ratio. The results are explained with respect to the interaction of the loading condition, environment and the rate of material removal by corrosion in the weldments. A new model was developed to account for mean stress effects on crack growth rates in air and in seawater, and was found to correlate well with experimental data as well as with the other mean stress models tested. en_UK
dc.language.iso en en_UK
dc.publisher Cranfield University en_UK
dc.rights © Cranfield University, 2015. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder. en_UK
dc.subject Corrosion fatigue en_UK
dc.subject Monopiles en_UK
dc.subject Crack growth en_UK
dc.subject Mean stress en_UK
dc.subject Free corrosion en_UK
dc.title Integrity of offshore structures en_UK
dc.type Thesis or dissertation en_UK
dc.type.qualificationlevel Doctoral en_UK
dc.type.qualificationname PhD en_UK


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