Imaging and quantitative detection of complex defects with a flexible electromagnetic array sensor

Abstract

The eddy current non-destructive testing (NDT) method has the advantages of high sensitivity and fast speed and is widely used in the inspection of key metal parts in the military and in industry. The existing scanning imaging method based on eddy current detection will cause the defect and the image to be inconsistent when the angle between the sensor and the defect is different, which will result in the inability to accurately quantify the defect based on the image. Therefore, this paper proposes a method based on a three-axis platform and a flexible eddy current array sensor to realise defect imaging and quantitative detection. First, the sensor is installed on the three-axis motion platform through a flexible substrate. It is intended that the three-axis motion platform will achieve full coverage detection of the surface of the test-piece and the overall image of the surface of the test-piece can be obtained by splicing. Then, the characteristic signal is subjected to bicubic interpolation to obtain clearer two-dimensional and three-dimensional defect images. Finally, morphological image processing is used to binarise the defect greyscale image and then the shape and size of the defect are obtained through contour pixel analysis. Experimental results show that this method can effectively overcome the impact on imaging when the sensor and the defect are at different angles and ensure the consistency of the imaging of the defect at any angle, so as to realise the imaging and quantification of any defect.