An Eddy Current Probe for the Detection of Subsuperficial Defects of Any Orientation

The article introduces a novel four-coil probe designed for eddy current (EC) nondestructive testing (NDT) on conductive materials. The key innovation lies in its capability to identify small surface and subsurface cracks regardless of their orientation. This is achieved through a suitable probe developed using two pairs of exciting coils that allow to generate two orthogonal magnetic fields. Using two excitation currents with an amplitude modulation approach, a rotation of the ECs induced in the conductive sample is obtained. This novel approach ensures the effective detection of deep and arbitrarily oriented cracks. Both numerical tests and experimental evaluations were employed to assess the performance of the proposed probe. The probe's effectiveness was particularly observed in detecting a buried crack measuring 5 mm in length, 1 mm in height, and 0.1 mm in thickness at depths up to 3 mm in an aluminum plate. The results demonstrated the robustness of the probe's detection capability, affirming its potential as a reliable tool for NDT in industrial applications.