PhD Studentship: Evaluation of Corrosion-Fatigue Behaviour in Offshore Wind Turbine Substructures

Supervisor: Prof. Ali Mehmanparast

Project Description:

Originally, the inside surface of offshore wind turbine structures was designed to be dry, and so ‘in air’ fatigue crack growth rate (FCGR) laws should have been relevant. In practice, corrosion is observed inside wind turbine structures. On the outside of the structures, the splash zone presents a different environment to that of being fully immersed in seawater. FCGR laws are provided in BS 7910 which includes in air, free corrosion in seawater and in seawater with cathodic protection. The FCGR laws in BS 7910 were obtained from analysis of results of tests performed on specimens and welds, fully immersed in seawater, so they may not be representative of the environment experienced by offshore wind substructures. If the environments experienced by offshore wind substructures are different enough to the immersed condition, they could result in different FCGR than predicted by current standard recommendations. If actual FCGRs are higher than expected, substructures may fail prematurely. On the other hand, if FCGRs are lower, unnecessary remediation and inspections may be carried out. Therefore, more representative FCGR laws are required to enable significant cost savings for the offshore wind industry.

In this project, through searching publicly available information and interviews with industrial contacts, information on the environment inside offshore wind substructures will be documented. The PhD student will review the basis of the existing FCGR laws in BS 7910. The environments used to generate the current FCGR laws and the environment experienced by offshore wind turbine substructures will be compared and contrasted. This analysis will be used to define the test environment needed. Moreover, novel test method(s) for obtaining FCGR from specimens in environments that represent those inside offshore wind substructures will be developed. Through analysis of conditions experienced by offshore wind substructures, test parameters such as seawater composition, temperature, wet-dry times etc will be proposed and methods to subject FCGR test specimens to those conditions will be suggested. It is expected that the methods that are developed will involve FCGR tests on specimens that are not immersed in seawater but are exposed to seawater, as it is understood that the environment inside a wind turbine structure will involve high humidity and condensation. The splash zone may be represented by a version of intermittent saltwater spray testing. In the course of this project, the student will work with TWI technicians to assemble the equipment needed to create those test conditions so that FCGR trials can be performed in the new environments.

This PhD project, which is funded by EPSRC and TWI, will be supervised by Prof. Ali Mehmanparast from the University of Strathclyde and co-supervised by Dr. Carol Johnston from TWI, and should commence by September 2024.

The successful candidate will receive full academic and professional training from the Wind & Marine Energy Systems & Structures Centre for Doctoral Training (WAMSS CDT). The Wind & Marine Energy Systems & Structures (www.wamss-cdt.co.uk) is an EPSRC-funded Centre for Doctoral Training, led by the University of Strathclyde, working collaboratively with Universities of Oxford and Edinburgh. The Centre aims to train the next generation of technical leaders, through EngD and PhD graduates, for the Offshore Renewable Energy (ORE) sector.

The awarded studentship covers tuition fees and tax-free stipend for 3 years. This studentship is open to UK and eligible EU citizens (with Settlement status) with a first class, or strong upper second-class honours degree in Mechanical/Civil/Materials/Marine/Structural Engineering. International students are welcome to apply provided that they can secure additional sources of funding to cover the living costs.

For informal enquiries, please contact Prof. Ali Mehmanparast (Email: ali.mehmanparast@strath.ac.uk).