PhD Studentship: Data rich imaging approaches assessing early fatigue crack growth mechanisms in Ni
Engineering & the Environment
Location: Highfield Campus
Closing Date: Friday 09 March 2018
Nickel base superalloys are used widely in aeroengine and power generation turbomachinery, where they experience extremes of temperature and cyclic loading conditions. The very early stages of crack growth involve the evolution of strain localisation processes that have not been fully characterised or understood in these alloys. Characterisation of this strain localisation is important in understanding the mechanisms of fatigue crack initiation and propagation, and provides critical validation data to develop appropriate crystal plasticity models for prediction of these processes. In this study, strain localisation during fatigue crack initiation and early crack propagation in an advanced Ni-based superalloy (RR1000, supplied by Rolls-Royce) for turbine disc application will be characterised at the grain level with a sub-micron resolution by digital image correlation on SEM images using the secondary g' themselves as the speckle pattern. Effects of oxygen-related damage (i.e. oxidation and dynamic embrittlement) on fatigue crack propagation behavior in an advanced disc alloy will also be assessed in air and vacuum under dwell-fatigue conditions at 725 oC. Enhanced fatigue crack propagation is closely related to oxygen-related damage at the crack tip, which is determined by the testing environment, the dwell period and the crack propagation rate itself based on two dimensional (2D) observation of the crack tip in an optical microscope and scanning electron microscope. X-ray computed tomography will also be employed to examine the differences between three dimension (3D) crack morphology in air and vacuum conditions at different temperatures, and the crack features will be quantified in terms of crack opening displacements, secondary cracks and bridging ligaments. By the combination of 3D X-ray computed tomography and traditional 2D observations, together with surface strain localization analysis, a deeper understanding will be provided of the mechanisms of fatigue crack initiation and propagation behaviour in this model turbine disc alloy under a range of service relevant applications.
This project is part of a strategic partnership between the Universities of Southampton, Manchester and Loughborough working with ALSTOM, dstl and Rolls Royce, and you will be joining a research network working on various aspects of this as part of your PhD
The ideal candidate for this project will have a bachelors or master degree in mechanical, aerospace or materials engineering and have studied some fracture mechanics at undergraduate level.
If you wish to discuss any details of the project informally, please contact Prof. Philippa Reed, Engineering Materials research group, Email: email@example.com, Tel: +44 (0) 2380 59 3763.
To apply, please use the following website: http://www.southampton.ac.uk/engineering/postgraduate/research_degrees/apply.page
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