Quantitative Inversion and Complementary Visual Evaluation of Cracks Based on Equivalent Planar Array ACFM

ABSTRACT

This paper proposes an equivalent planar array method based on a linear sensor array. This approach aims to evaluate the geometric features of surface-breaking cracks beneath coatings, thereby improving the reliability of traditional alternating current field measurement (ACFM). By integrating multi-line parallel scanning with 2D surface imaging, a comprehensive evaluation strategy combines one-dimensional curve characteristics with intuitive two-dimensional visual representations. This strategy reconstructs the basic crack profile from spatial magnetic perturbations and calculates the crack length and deflection angle. Simulations demonstrate that the system possesses spatially independent detection capability. For extreme crack morphologies where the numerical inversion fails, 2D visual imaging provides a complementary qualitative assessment, reducing the likelihood of missed detections. Experimental validation using specimens with artificial cracks confirms the effectiveness of the proposed method in practical hardware environments. The results demonstrate that the complementary use of 1D and 2D evaluations provides a reliable physical framework for precise defect assessment in nondestructive testing applications.

KEYWORDS: alternating current field measurement, equivalent planar array, 2D visual imaging, magnetic field perturbation, quantitative inversion, coating-covered surface-breaking cracks

https://doi.org/10.32548/2026.me-04594

1. Introduction