A new vibro-acoustic modulation technique for closed crack detection based on electromagnetic loading

摘要

The detection of closed cracks is crucial to the assessment of the integrity of metal structural components. In recent years, the ultrasonic nonlinear technology has been increasingly utilized in such detection. With this technology, the vibro-acoustic modulation (VAM) technique is found to be reliable and sensitive. In this study, the technique is implemented through electromagnetic loading to enhance the sensitivity of ultrasonic detection and evaluation of closed cracks. The proposed VAM technique based on electromagnetic loading involves opening and closing of the closed crack with Lorentz force emanating from the loading coil and magnet instead of mechanical equipment, which can concentrate the loading energy around the closed crack rather than on the whole specimen. The opening and closing of the closed crack can enhance the nonlinearity effect when ultrasonic signal propagates through it. The comparative experiments performed in this study demonstrate that the proposed VAM technique based on electromagnetic loading has a considerable potential in the ultrasonic evaluation of closed cracks. The influence of different electromagnetic loading parameters on the modulation effect are also investigated experimentally. (C) 2019 Elsevier Ltd. All rights reserved.