Surface Defect 3-D Profile Reconstruction Using Eddy Current Pulsed Thermography

Accurately evaluating the 3-D profile of nonferromagnetic metal surface defects is essential for nondestructive evaluation. Eddy current pulsed thermography (ECPT) has been used for reconstructing surface defects, which utilizes multiphysics coupling of electromagnetic and thermal fields. Previous investigations mainly employ the thermal field for reconstruction. However, the thermal field varies slowly over time and has weak correlation, which causes serious blur and noise. In this article, a surface defect 3-D profile reconstruction method based on eddy current field distribution is proposed. The proposed method takes advantage of the strong global correlation of eddy current fields and proposes an inversion technique to reconstruct defects. Experimental results demonstrate that the proposed method can effectively reconstruct the 3-D profile of defects with depths within the skin depth, including complex-shaped defects and natural cracks.