Surface Profile Reconstruction of Complex Cracks Using the Signals of Rotating Eddy Current Testing Through the Eddy Current Imaging Method

In industry, natural cracks usually exist in complex forms such as adjacent, colony, irregular, and crossing. Mere magnetic field is inadequate to accurately evaluate the complex cracks using eddy current testing. In this study, an improved eddy current imaging method using the signal of rotating eddy current testing (RECT) was proposed to reconstruct the surface profile of complex cracks. A transformation method was adopted to transform the signals of RECT into those under uniform eddy current testing at the desired orientation. The deconvolution of the transformed signals and square current dipole was carried out to obtain eddy current images at eight orientations around complex cracks. By accumulating the eddy current images, the surface profile of the complex cracks was reconstructed. Simulations and experiments were carried out to illustrate, validate, and test the proposed method. The results indicated that the obtained surface profiles were clearer than those obtained by the previous method using uniform eddy current testing. The improved method was effective for artificial complex slits and irregular stress corrosion crack colonies. Moreover, its performance was stable for the cracks with different angles and depths.