Study on Corrosion Imaging of Aircraft Riveted Structures Based on Pulsed Eddy Current

Abstract Precise quantification of minute defects in pulsed eddy current (PEC) testing is fundamentally limited by the broadening of defect boundary response signals caused by eddy current field diffusion — a key factor that undermines detection accuracy. To improve quantification precision for such small defects, this paper introduces an adaptive power-law sharpening signal processing approach. This method incorporates an algorithm that dynamically tunes the power-law exponent γ according to normalized peak height, thereby compressing the edges of the response envelope and reducing the impact of boundary effects. Subsequently, piecewise cubic Hermite interpolating polynomial (PCHIP) interpolation is applied to generate a high-density data field. This data field is then combined with K-means clustering for automatic segmentation of the defect region, enabling precise extraction of both the area and two-dimensional coordinates. Experiments were conducted using a pulsed eddy current array sensor to detect multi-layer riveted blocks containing corrosion defects. Experimental results verify that the proposed method effectively suppresses the adverse effects of eddy current diffusion on boundary resolution. For circular corrosion defects with diameters from 5 mm to 12 mm at identical burial depth, the method achieves a relative area error below 16.3% and a localization error within 1.5 mm, significantly outperforming conventional threshold-based approaches. This work provides a systematic signal processing framework that addresses the fundamental limitation of boundary broadening in pulsed eddy current testing, paving the way for high-precision quantification of minute defects.