福岡 克弘

2020年度日本AEM学会技術賞 受賞

© 2019 IOS Press and the authors. All rights reserved. In this study, we developed and characterised a method for detecting microcracks in steel materials by eddy current testing (ECT). Magnetic saturation ECT is applied because magnetic noise is generated by steel materials during ECT. Although direct-current (DC) magnetisation is generally used for magnetic saturation ECT, the use of alternate-current (AC) magnetisation offers several advantages. When using AC magnetisation for surface flaw detection, the magnetisation is not influenced by the thickness of the test object owing to the skin effect; therefore, demagnetisation is unnecessary. In this study, we evaluated microcrack detection results obtained using AC magnetisation ECT with different synchronous positions (conditions) of the magnetisation and ECT; and identified the optimum synchronous position. In addition, the magnetisation distribution in a test object was evaluated by the finite element method analysis and the flaw detection results were verified.

© 2019 IOS Press and the authors. All rights reserved. Non-uniform permeability distributions in steel materials reduce signal-to-noise (S/N) ratios in eddy current testing (ECT). Therefore, steel materials must be magnetised to reduce magnetic noise. In this study, microcrack detection in spring steel materials using ECT was considered. An ECT system that was able to detect 40-μm-deep crack with S/N ratio of 3 or more was developed. In addition, the depth profile of microcracks using the detection signal was accurately estimated.

© 2018 Wiley Periodicals, Inc. Mechanical parts, plants, and cross-linkages inspected with magnetic-particle testing (MT) are typically complex 3D shapes. In complex 3D shape portions, because a magnetizer often cannot be configured to inspection portions and the test object cannot be appropriately magnetized, there is a possibility of overlooking a crack in such an instance. Thus, MT system development that was successfully able to detect omnidirectional cracks in 3D shape portions was considered in this study's trials. Two multi-coil type magnetizers were hence arranged face-to-face, and the magnetization of omnidirectional scenarios for all surfaces of 3D shape test object was evaluated.