Defect reconstruction in non-ferromagnetic materials using magnetic field sensitivity matrix of planar array ECT

Eddy current tomography (ECT) is a visual metal defect detection technology. The coil sensors used in traditional ECT exhibit limited sensitivity at low frequencies. Magnetic sensors are popular because of their frequency-independent sensitivity property. This paper investigates defect imaging in non-ferromagnetic materials by planar array ECT based on magnetic sensors. On the basis of the voltage sensitivity matrix of traditional ECT, the magnetic field sensitivity matrix is obtained by introducing small virtual coils. The feasibility and the performance of the magnetic field sensitivity matrix were investigated. Different defects were reconstructed by the magnetic field sensitivity matrix and compared with the traditional voltage sensitivity matrix. The image reconstruction results show that the magnetic field sensitivity matrix performs better in reconstructing the longer length and small orientation of the crack defects at lower frequencies. This paper provides defect detection in non-ferromagnetic materials using the magnetic field sensitivity matrix by planar array ECT, which can be used to improve the detection accuracy of crack defects by ECT.