Review and analysis of three representative electromagnetic NDT methods

• Published in: Insight (Northampton) Vol. 59; no. 4; pp. 176 - 183
• Main Authors: Liu, Shiwei, Sun, Yanhua, Gu, Min, Liu, Changde, He, Lingsong, Kang, Yihua
• Format: Journal Article
• Language: English
• Published: The British Institute of Non-Destructive Testing 01.04.2017
• Subjects: Eddy Current Testing (ect); Electromagnetic Non-Destructive Testing (ndt); Magnetic Flux Leakage (mfl); Permanent Magnetic Perturbation (pmp); Physical Mechanism; Signal Feature
• ISSN: 1354-2575
• DOI: 10.1784/insi.2017.59.4.176

For three representative electromagnetic non-destructive testing (NDT) methods, namely magnetic flux leakage (MFL), eddy current testing (ECT) and permanent magnet perturbation (PMP), the development, physical mechanism, detected features, signal features, test procedure and test apparatus are systematically analysed and explained from a new perspective. MFL involves the leakage of a magnetic field by magnetic refraction and is characterised by a peak in the test signal. ECT is based on the interruption of the secondary magnetic field of the eddy current by a flaw in the test object, causing a decrease in the test signal. PMP is based on spatial magnetic perturbations in the magnetic field established by a permanent magnet and the test objects caused by a flaw in the object, creating a distortion in the test signal. The simultaneous and systematic explanation and summary of the three classical methods are helpful in the exploration of the theory of electromagnetic NDT systems.