Effects of contact gap on nondestructive evaluation using magnetic measurement for ferromagnetic steel

Issue title: Selected papers from the International Symposium on Applied Electromagnetics and Mechanics - ISEM 2019

Guest editors: Jinhao Qiu, Ke Xiong and Hongli Ji

Article type: Research Article

Authors: Kikuchi, Hiroaki^a; | Sato, Yuki^a

Affiliations: [a] Faculty of Science and Engineering, Iwate University, Morioka, Iwate, Japan

Correspondence: [*] Corresponding author: Hiroaki Kikuchi, Faculty of Science and Engineering, Iwate University, Morioka, Iwate, 020-8551, Japan. E-mail: [email protected]

Abstract: We investigated effects of contact gap on magnetic nondestructive evaluation technique using a magnetic single-yoke probe. Firstly, we evaluated hysteresis curves and impedance related to permeability of the material measured by a single-yoke probe, when an air gap length between the probe and specimens changes. The hysteresis curve gradually inclines to the axis of the magneto-motive force and magneto-motive force at which the magnetic flux is 0 decreases with increasing the gap length. The effective permeability also decreases with increasing the gap thickness. The incremental of gap thickness increases the reluctance inside the magnetic circuit composed of the yoke, specimen and gap, which results in the reduction of flux applying to specimen.

Keywords: Magnetic NDE, magnetic yoke probe, contact gap, coercive field, permeability, impedance, magneto-motive force

DOI: 10.3233/JAE-209411

Journal: International Journal of Applied Electromagnetics and Mechanics, vol. 64, no. 1-4, pp. 969-975, 2020