【摘 要】
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Background, Motivation and Objective In structural inspection, it is important to detect closed cracks difficult to find by conventional ultrasonic techniques. Use of nonlinear ultrasonic waves can be
【机 构】
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Keio University, Japan
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Background, Motivation and Objective In structural inspection, it is important to detect closed cracks difficult to find by conventional ultrasonic techniques. Use of nonlinear ultrasonic waves can be a promising way, though their basic phenomena are complicated and not clear yet. In our previous research of nonlinear ultrasonics, instead of nonlinear signals, we found some lowfrequency components appearing only in propagated waves through contact surfaces, though the generation mechanism of such low-frequency components is not clarified. In this study, we attempt to reveal the cause of the low-frequency components, investigating effects of the contact surfaces, and suggest that the low-frequency components found in our experiments can be used as a new inspection method of closed cracks.
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