University: University of Warwick
Main academic supervisor: Prof. Rachel Edwards
Project description
Summary
The PhD project will design, build, and test arrays of electromagnetic acoustic transducers (EMATs), made conformable to attach to different geometries. The array will be designed and controlled such that it can generate a range of ultrasonic waves to inspect for surface, near-surface, and volumetric flaws, with enhanced defect detection capabilities. Routes to production of high-temperature EMATs arrays will be investigated, to offer high-temperature ultrasonic inspection without the requirement for couplant or contact with the sample.
Background
Electromagnetic acoustic transducers (EMATs) provide non-contact ultrasonic inspection solutions for electrically conducting materials and welded joints. The use of EMATs is couplant-free, non-contact, and does not require material surface preparation – but can suffer from low efficiency. EMATs make up for this by being extremely adaptable; Warwick have designed and built EMATs generating shear horizontal (SH) waves for welding defect inspections [1], high-temperature EMATs for material thickness gauging [2], as well as mini-EMATs (dimensions of around 3 to 5mm per side) [3,4] and miniaturised EMAT arrays for corrosion inspection in metallic samples [5,6] alongside the electronics for operation of the arrays. A recent preliminary study has also shown promising results when using EMATs on fusion pipe materials: miniature EMAT arrays were used to generate Rayleigh and SH-like waves on SS316 samples and measure reflections from slot defects in the weld. In addition, the EUROFER 97 ferromagnetic material used for fusion reactor cooling pipes gives extremely efficient generation, which would allow inspection using much smaller EMAT elements in an array. In contrast, EMATs have typically been considered not suitable for inspection of titanium, but recent advances have enabled inspection of welds in Ti-alloys despite low SNR [7]. EMAT arrays offer, in the longer-term, the potential for array operation at high temperature, or in other inaccessible environments.
Research path
This PhD aims to develop a miniaturized EMAT array with a configurable design that is suitable for inspecting welds, including pipe welds from in-bore. The project will involve;
- Guided by industry requirements, identification of suitable ultrasonic wavemodes for inspection of defects in chosen locations, including guided waves for remote inspection. This will be done using FEM of sample geometries and defect types for different generation modalities.
- Design EMAT arrays for generating chosen wavemodes, making them conformable (using flexible coils and magnet arrays rather than large fixed magnets); this step will use Huygens modelling to test different EMAT force geometries, followed by building and testing of the optimal solutions.
- Test arrays on simple geometries – e.g. plates, pipes with no features other than the weld / defects, and test efficiency and detection capabilities using calibration defects.
- Further FEM and design stage for complex geometries, producing mini conformable arrays.
- Test on samples with complex geometry.
Target applications:
1. Inspection of power plants at high temperatures, removing the requirement for shut-downs.
2. Maintenance of service pipes in a fusion device, by enabling inspection of a large number of welded joints non-destructively during the reactor downtime, conducted using remotely operated tools from in-bore.
3. In-service inspections where flexibility is required but use of just a single transducer / array would be beneficial – whether this requires a transducer which can generate surface or guided waves with a tuneable frequency [5], operation for different wavemodes (e.g. A0 vs. S0 for Lamb waves, or SH0 vs. SH1), or with unidirectional behaviour [6].
1. PA Petcher and S Dixon, NDT & E International 74, 58-65 (2015)
2. N Lunn, S Dixon and MDG Potter, NDT & E International 89, 74-80 (2017)
3. O Trushkevych and RS Edwards, NDT & E International 107, 102140 (2019)
4. O Trushkevych et al., IEEE Sensors 21(2), 1386-1394 (2021)
5. L Xiang et al., IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 67(7), 1403-1411 (2020)
6. RS Edwards et al., Tuneable SH wave EMATs for unidirectional imaging, in preparation
7. C Peyton et al., Nondestructive Testing & Evaluation, 39(8), 2330-2353 (2024)
8. O Trushkevych et al., Journal of Physics D: Applied Physics, 46, 105005 (2013).
Please enquire to r.s.edwards@warwick.ac.uk
Applications will be made to the University of Warwick