• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.4
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• pp.287-293
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• 2005

Ultrasonic guided waves are gaining increasing attention for the inspection of platelike and rodlike structures. At the same time, inspection methods that do not require contact with the test piece are being developed for advanced applications. This paper capitalizes on recent advances in the areas of guided wave ultrasonics and noncontact ultrasonics to demonstrate a superior method for the nondestructive detection of defects thinning simulating hidden corrosion in thin aluminum plates. The proposed approach uses EMAT(electro-magnetic acoustic transducer) for the noncontact generation and detection of guided waves. Interesting features in the dispersive behavior of selected guided modes are used for the detection of plate thinning. It is shown that mode cutoff measurements provide a qualitative detection of defects thinning. Measurement of the mode group velocity can be also used to quantify depth thinning.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.2
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• pp.144-149
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• 2004

The objective of this investigation is to develop an efficient method to generate and measure torsional waves in non-ferromagnetic waveguides by using magnetostrictive transducers. In existing methods using a nickel strip that is attached circumferentially to the test specimen, large current input to the magnetostrictive transducer often generates undesired wave modes in addition to the desired torsional wave. However, we propose a new method to generate the torsional waves without being accompanied with other undesirable wane modes regardless of the input current magnitude. The specific transducer configuration is suggested and its performance is also checked through a series of experiments.