A cone-shaped probe for eddy current focusing in electromagnetic testing

Eddy current probes are widely employed in a range of non-destructive testing (NDT) applications. The idea of eddy current focusing is to constrain the eddy current distribution within a certain area for spatial resolution improvement in imaging. In eddy current testing (ECT), cone coils have been evaluated based on their capability to focus magnetic fields. This article investigates their potential in focusing eddy currents. ‘−3 dB distance’ has been defined in this article to quantitatively describe eddy current focusing through the angle inclination of cone coils. Eddy currents from a cone coil of different inclination angles are calculated based on the Dodd-Deeds model and 2D numerical integration. The −3 dB distances are assessed for cone coils of different inclination angles under different lift-offs. Numerical and experimental results prove that the cone coil can achieve a more focused eddy current distribution and thus a defect image of higher spatial resolution.