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PhD Studentship (Sponsored by TWI) – Development of Advanced Crack Modelling Techniques for Fracture Mechanics Assessments

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  • Full or part time
    Dr T London
  • Application Deadline
    Applications accepted all year round
  • Funded PhD Project (Students Worldwide)
    Funded PhD Project (Students Worldwide)

Project Description

Applications are invited to undertake a PhD programme in partnership with TWI.

The demanding conditions experienced by welded structures create significant challenges for design and assessment. This is especially true for new markets in the oil and gas industry where pipelines are required to operate in extreme conditions such as those found in deep water installations and encountered in arctic exploration and production projects.

To achieve structural integrity targets whilst meeting operational requirements, various design and manufacturing concepts have been proposed and implemented. The design concepts in particular have increased the level of structural complexity. As a consequence, existing fracture mechanics assessment codes and standards may lead to either over-conservative assessments or the crack tip conditions may be underestimated depending on the nature of the case analysed.

Hence, in this project, the emphasis will be on obtaining more accurate and detailed fracture mechanics analyses of these complex welded structures through the direct modelling of crack propagation. Whilst there has been extensive research into this field, the objective will be to improve and validate existing models to provide techniques that are suitable for assessing the integrity of structures in the framework of an Engineering Critical Assessment (ECA).

Within this proposed research programme, the aim is to gain a fundamental understanding of the mechanisms involved in the failure and damage tolerance of welded structures which operate under severe cyclic and static loading conditions.

Project Outline
In the project, the focus will be on the coalescence, implementation and experimental validation of advanced models of crack propagation for fracture mechanics assessments.

The first phase of the project will involve a review of existing models for fatigue crack propagation and ductile tearing. Methods that will be considered will allow for non-constant crack extension along the crack front due to varying crack tip constraint, geometric discontinuities or the presence of residual stresses. The approaches to consider may include cohesive zone models, micro-mechanical or ductile damage models, XFEM-type approaches or automatic/adaptive re-meshing techniques.

As it will be necessary to develop robust test data to support the development of the proposed numerical models, the second phase of work will involve a detailed experimental testing programme. A series of constant amplitude and static loading tests will be performed. The tests will include standard specimens as well as bespoke test plates containing geometric discontinuities such as a hole, attachments or changes in thickness. The experimental programme will be used to validate and fine-tune the proposed numerical models for crack propagation.

Throughout the project, a focus will be on the development of automation software for modelling crack propagation. This will allow for efficient computations and simulation run-times, enabling a high-level of functionality for the advanced crack propagation models.

The results of this project are expected to have a significant impact on existing knowledge as well as integrity assessment methods, where crack propagation and ductile tearing play important roles in the life cycle of complex welded structures.

About the Sponsor
TWI is one of the world’s foremost independent research and technology organisations, with expertise in materials joining and engineering processes as applied in industry. TWI specialises in innovation, knowledge transfer and in solving problems across all aspects of manufacturing, fabrication and whole-life integrity management.

Working with academic and industrial partners, NSIRC will advance fundamental research to support the safe operation of products and structures, develop innovative, fit-for-purpose technologies and design rules and will demonstrate solutions for long-term asset management. This will include risk-based management, engineering critical assessment, NDT, structural health and condition monitoring and health management for use in industrial applications. The collaborating partners will provide academic excellence to address the need for fundamental research, as well as high-quality, industry-relevant training for the next generation of structural integrity engineers.

Candidate Requirements
Candidates should have a relevant degree at 2.1 minimum, or an equivalent overseas degree in Mechanical, or Civil/Structural Engineering, Material Science, Metallurgy, Applied Mathematics or Physics. Candidates with suitable work experience and strong capacity in numerical modelling and experimental skills are particularly welcome to apply. Overseas applicants should also submit IELTS results (minimum 6.5) if applicable.

Funding Notes

This project is funded by TWI and academic partners. The studentship will provide successful Home/EU students with a stipend of £16k/year and will cover the cost of tuition fees. Overseas applicants are welcome to apply, with total funding capped at £20k/year.

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