Abstract
This letter proposes a novel motion-induced eddy current based thermography (MIECT) for high-speed inspection. In contrast to conventional eddy current thermography (ECT) based on a time-varying magnetic field created by an AC coil, the motion-induced eddy current is induced by the relative motion between magnetic field and inspected objects. A rotating magnetic field created by three-phase windings is used to investigate the heating principle and feasibility of the proposed method. Firstly, based on Faraday’s law the distribution of MIEC is investigated, which is then validated by numerical simulation. Further, experimental studies are conducted to validate the proposed method by creating rotating magnetic fields at different speeds from 600 rpm to 6000 rpm, and it is verified that rotating speed will increase MIEC intensity and thereafter improve the heating efficiency. The conclusion can be preliminarily drawn that the proposed MIECT is a platform suitable for high-speed inspection.
Highlights
As an emerging non-destructive testing method, eddy current thermography (ECT) combines eddy current testing and thermography with advantages such as non-contact, full-field coverage and high resolution.[1,2,3,4] In the traditional offline inspection such as for carbon fiber reinforced plastic,[5,6] propeller[7] and bond wires,[8] usually, a coil (e.g. Line-coil, Helmholtz-coil and Ferrite-yoke-coil)[9] is positioned above the inspected object
The above researches indicate that the motion-induced eddy current (MIEC) illustrates a unique character that the moving speed will increase MIEC intensity and thereafter improve the heating efficiency, which paths a better way for high-speed inspection
In the experiment at the defect position, for rotating speeds from 600rpm to 6000rpm, the rotational velocity is approximate from 8 km/h to 80 km/h, the experiment results preliminarily validate that the proposed motion-induced eddy current based thermography (MIECT) method is a platform suitable for high-speed inspection, such as on-line monitoring for rail track and wheel
Summary
As an emerging non-destructive testing method, eddy current thermography (ECT) combines eddy current testing and thermography with advantages such as non-contact, full-field coverage and high resolution.[1,2,3,4] In the traditional offline inspection such as for carbon fiber reinforced plastic,[5,6] propeller[7] and bond wires,[8] usually, a coil (e.g. Line-coil, Helmholtz-coil and Ferrite-yoke-coil)[9] is positioned above the inspected object. The above researches indicate that the MIEC illustrates a unique character that the moving speed will increase MIEC intensity and thereafter improve the heating efficiency, which paths a better way for high-speed inspection. To further understand this character, an experimental setup to build a highspeed relative motion between the magnetic field and inspected object is needed. To investigate the physical principle of MIEC heating and eliminate the above multiple factors, threephase windings are applied to create a rotating magnetic field This electronic-driven method can be and safely implemented without mechanical motion
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