Fast 2D crack profile reconstruction by image processing for Eddy-Current Testing

Fast reconstruction of defects geometry is one of the main goal of Eddy Current Non-destructive testing. The information about the type of defects, their shapes, orientations and geometrical characteristics is of great importance in evaluating the impact of defects on structures' integrity and operation safety. From one point of view, the knowledge of the defect shape could give important information about the manufacturing, the use or the cause that have stressed the specimen and generated the defect, and from the other point of view the reconstruction of geometrical parameters of defect could be made easier if the shape of the defect is known. Although many inverse procedures have been developed for Eddy Current Testing, usually high-computational time and resources are requested, hampering the application of 3D reconstruction methods in on-line or in-situ inspections. In this paper a fast 2D defect profile reconstruction technique is presented based on image processing. The main idea of the proposed method is that images obtained from the maps of magnetic field on specimen with flaws, express a trend attributable to a class of known functions. In particular, the shape of the obtained image depends on both the type of defect that the type of measurement probe adopted. Then using a suitable reference image related to the response of the probe as a digital filter to process the acquired image through deconvolution or correlation operations, the shape of the flaw that has generated the image can be retrieved.