Exploring high-frequency eddy-current testing for sub-aperture defect characterisation using parametric-manifold mapping

Accurate characterisation of small defects remains a challenge in non-destructive testing (NDT). In this paper, principle-component parametric-manifold mapping approach is applied to single-frequency eddy-current defect problems for surface breaking planar half-space. A broad 1–8 MHz frequency-range FE-circuit model & calibration developed validated simulate scans surface-breaking notch defects. This used generate parametric databases an aluminium half-space and experimental measurements performed. Parametric-manifold was conducted N-dimensional principle component space, reducing the dimensionality problem. study characterising slot depth, shown accurately invert depth with comparable accuracy equivalent peak amplitude-phase inversion method. The characterise sloped demonstrating good up ≈ 2.0 mm over range frequencies, indicating applications geometric feature inversion. Finally technique finite rectangular extents smaller than diameter inspection coil (sub-aperture) sub-resonant frequencies. results highlight limitations these indicate how inherent modelling uncertainty around resonance can severely limit at