A high-frequency phase feature for the measurement of magnetic permeability using eddy current sensor. (October 2021)

• Record Type: Journal Article
• Authors: Lu, Mingyang; Meng, Xiaobai; Huang, Ruochen; Chen, Liming; Peyton, Anthony; Yin, Wuliang
• Is Part Of: NDT & E international. Volume 123(2021)
• Publication Date: 2021-10
• Subjects: Electromagnetic sensing -- Lift-off -- Eddy current -- Magnetic permeability -- Non-destructive testing; Nondestructive testing -- Periodicals; Contrôle non destructif -- Périodiques; Electronic journals; 620.1127
• DOI: 10.1016/j.ndteint.2021.102519
• Languages: English
• ISSNs: 0963-8695

Abstract

Abstract: Electromagnetic sensing has been used for diverse applications of non-destructive testing, including the surface inspection, measurement of properties, object characterization. However, the measurement accuracy could be significantly influenced by the lift-off between sensors and samples. To address the issue caused by lift-offs, various strategies have been proposed for the permeability measurement of ferromagnetic steels, which mainly involves different sensor designs and signal features (e.g., the zero-crossing feature). In this paper, a single high-frequency scenario for the permeability retrieval is introduced. By combining the signal of two sensing pairs, the retrieval of magnetic permeability is less affected by the lift-off of sensors. Unlike the previous strategy on reducing the lift-off effect (directly taking the phase term out of the integration) using the Dodd-Deeds analytical method, the proposed method is based on a high-frequency linear feature of the phase term. Therefore, this method has the merit of high accuracy and fast processing for the permeability retrieval (a simplified version of Dodd-Deeds analytical formulas after the integration). Experimental measurement has been carried out on the impedance measurement of designed sensors interrogating ferromagnetic dual-phase steels. For sensor lift-offs of up to 10 mm, the error of the permeability retrieval is controlled within 4% under the optimal frequency.