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Eddy Current Array Optimisation
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Egbeyemi, Abbas Akinola Akanni (2018) Eddy Current Array Optimisation. PhD thesis, University of Warwick.
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WRAP_Theses_Egbeyemi_2018.pdf - Submitted Version - Requires a PDF viewer. Download (16Mb) | Preview |
Official URL: http://webcat.warwick.ac.uk/record=b3419232~S15
Abstract
There is a drive in industry to reliably detect surface breaking sub-millimetre defects in low electrical conductivity materials, such as stainless steel, titanium, and titanium aluminide using eddy-current testing. The sensitivity of the eddy current method to these materials is hindered in part by their low conductivities, and complex grain structures, which makes the high sensitivity standards required by industry more difficult to achieve.
Eddy current measurements for sub-millimetre defects in low conductivity materials are routinely performed using a high excitation frequency, to decrease the skin depth of induced eddy currents into the material, which would otherwise be higher due to the reciprocal relationship between depth of penetration, and material conductivity.
The fundamental components of an eddy current array is a pair of coils, and thus finite element models are presented in this thesis, and are used to investigate the interaction between low conductivity materials, and a pair of eddy current coils operating in absolute, and transmit-receive modes. The model results give insight to the eddy current coil voltage response to defects, and the relationship between absolute mode, and transmit-receive mode data when taken concurrently.
Experiments are performed, which show how the combination of a voltage amplitude C-scan image with its corresponding voltage phase C-scan image, results in an image with a significantly improved signal to noise ratio. In the same experiments, absolute mode data is also combined with transmit-receive mode data to generate a single image with signal to noise ratio values significantly higher than anything achievable using individual images. Varying levels of noise are added to the data to investigate the limits at which this data processing method can be utilised.
Low conductivity materials such as titanium aluminide, containing defects as small as 0.25 mm were scanned, and promising results were achieved showing that defects this small can be reliably detected using the inspection method, and data processing techniques presented in this thesis.
Item Type: | Thesis (PhD) | ||||
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Subjects: | T Technology > TA Engineering (General). Civil engineering (General) T Technology > TK Electrical engineering. Electronics Nuclear engineering |
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Library of Congress Subject Headings (LCSH): | Eddy currents (Electric), Eddy current testing, Ultrasonic testing, Nondestructive testing | ||||
Official Date: | September 2018 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Physics | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Dixon, Steve M. | ||||
Sponsors: | Ether NDE Limited | ||||
Extent: | xxvii, 161 leaves : illustrations, charts | ||||
Language: | eng |
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