<p>The detection of contact-type failures, such as fatigue crack tips, delamination crack of composites or adhesive failure, using linear ultrasonic waves or vibrations is difficult. The interaction of the contact interfaces of failure is occurred when ultrasonic vibrations, of which frequencies are slightly different, is inputted to the object with contact-type failure. As the result of this interaction, the low-frequency vibration, of which frequency is the different frequency of ultrasonic vibrations, is generated (Frequency down-conversion). The detection and evaluation method of contact-type failure based on frequency down-conversion has been proposed. As one of them, the localization and visualization method using structural intensity of low-frequency vibration caused by frequency down-conversion is studied. The low-frequency vibration caused by frequency down-conversion is generated only when the object has contact-type failures. For this reason, it is regarded the contact location as an exciting point of low-frequency vibration. Accordingly, the localization and visualization of contact-type failures are realized by measurement of the structural intensity as the localization and visualization method of exciting points. In this paper, the performance of the localization and visualization method using structural intensity of low-frequency vibration for multiple failures in the beam object is investigated. Firstly, the frequency down-conversion of elastic vibrations is introduced. The generation of low-frequency vibration only when the object has contact-type failure is determined by experiment using beam object. Secondly, the localization and visualization method using structural intensity is expressed. From the structural intensity, which visualize the energy flow, the localization of exciting point can be localized and visualized. The localization and visualization result by measurement of structural intensity of the low-frequency vibration is shown using the object with single failure. It is shown that the localization of contact-type failure from the cline of the structural intensity is possible. Finally, the localization experiment of multiple failures is done. Especially, the relationship between the localization accuracy and distance of failures is evaluated.</p>

Localization of Multiple Contact-Type Failures Using Structural Intensity of Low-Frequency Vibration Caused by Frequency Down-Conversion

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2021/volume/85499

ASME 2021 Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS2021)

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