Abstract
Magnetic induction tomography (MIT) is largely focused on applications in biomedical and industrial process engineering. MIT has a great potential for imaging metallic samples; however, there are fewer developments directed toward the testing and monitoring of metal components. Eddy-current non-destructive testing is well established, showing that corrosion, fatigue and mechanical loading are detectable in metals. Applying the same principles to MIT would provide a useful imaging tool for determining the condition of metal components. A compact MIT instrument is described, including the design aspects and system performance characterisation, assessing dynamic range and signal quality. The image rendering ability is assessed using both external and internal object inclusions. A multi-frequency MIT system has similar capabilities as transient based pulsed eddy current instruments. The forward model for frequency swap multi-frequency is solved, using a computationally efficient numerical modelling with the edge-based finite elements method. The image reconstruction for spectral imaging is done by adaptation of a spectrally correlative base algorithm, providing whole spectrum data for the conductivity or permeability.
Highlights
Engineering Tomography Laboratory, Department of Electronic and Electrical Engineering, University of Bath, Claverton Down, Bath BA2 7AY, UK
Absolute detector dwell times are directly related to the field excitation frequency; in the present system, this is fixed to 10 ms to cater for the lowest expected frequency of 1 kHz
The application of Magnetic induction tomography (MIT) for metal component testing is growing, the methods described for eddy-current testing suggest the potential for generating cross-sectional images indicating corrosion and fatigue
Summary
Magnetic induction tomography (MIT) is largely focused on applications in biomedical and industrial process engineering. Non-destructive testing and eddy-current testing (NDT and ECT, respectively) of metal components has been extensively investigated and successfully adopted as a tool in industry. A recently developed system is described for primarily investigating the application of MIT in metal component imaging. Li et al have used a similar system for studying defect measurements in hot steel [29] In this first development, the system operates from 1 to 100 kHz and collects the magnitude of the perturbed excitation field only. Studies have shown that it is possible, using alternating magnetic fields, to determine the condition of metal components non-destructively without physical contact. Depending on the electromagnetic properties of the metal under test, the nature of the field perturbation differs
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