Affiliations: [a] Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI, USA | [b] School of Information Science and Technology, ShanghaiTech University, Shanghai, China | [c] Department of Electrical and Information Engineering, Università di Cassino e del Lazio Meridionale, Cassino, Italy
Correspondence:
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Corresponding author: Zhiyi Su, Department of Electrical and Computer Engineering, Michigan State University, East Lansing MI, USA. E-mail: suzhiyi@msu.edu
Abstract: Eddy current methods are commonly used in the inspection of riveted multilayer structures. In a practical scenario, steel rivets may be magnetized to varying levels which can distort the magnetic field and pose a major challenge since the distortion can result in false positives and negatives. This paper presents an invariance transformation procedure that renders the signal insensitive to changes in magnetization while retaining the sensitivity to defect information. The approach is first implemented on simulated data, where the signals from magnetized steel rivets can be generated under controlled variation of relative permeability. The algorithm is then validated on experimental data acquired using steel rivets with different residual magnetization levels.
