Lift-off Trajectory Analysis for Eddy Current Detection of Millimetre-Scale Cracks in Curved Geometries

Le résumé fourni par la source

Curved geometry is supplied for industrial components due to its superior mechanical performance. Conventional inspection methods for curved geometries suffer from limited probe accessibility and stability. Eddy current testing (ECT) has high sensitivity to surface and near-surface defects, which are the primary defects in curved components, but its performance is strongly affected by lift-off variations. Hence, this paper proposes an ECT method that measures complex impedance over a lift-off range (0–5 mm) and maps it as a trajectory in the impedance plane. Specifically, a simulation model was built up for validating the methodology by investigating the lift-off trajectory with various crack lengths (15mm to 30mm), curvature radius (100, 200, 500mm), and excitation frequencies (300kHz to 1MHz). Subsequently, laboratory experiments were completed on a series of artificial cracks (typical radial cracks with 0.3 mm width) under conditions consistent with the simulation. The results show that crack length exhibits a linear relationship with the imaginary component of the impedance trajectory. By analysing the curvature and shape of this trajectory, it can effectively separate defect responses from geometric variations. Overall, this method can be deployed in a range of ECT applications to minimise geometric effects and realise millimetre-scale detection in curved geometries.

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