<p class="MsoNormal" style="margin-top: 0cm; margin-right: -25.7pt; margin-left: -18.0pt; margin-bottom: .0001pt; text-align: justify; line-height: 150%">In recent years, Local Defect Resonance (LDR) has generated much interest in development and applications of new resonant acoustic modes for non-destructive testing (NDT) and imaging of planar defects in composite materials. The studies and applications are focused at LDR in composites where the most common defects are delaminations and impacts. This paper considers the mechanism of development and the attributes of LDR for through-thickness cracks in plates. The laser vibrometry experiments for cracks in steel and concrete validate that the LDR is caused by the resonance of the edge waves (EW) propagating along the crack faces. The EW manifest similar dispersion behaviour to that of the low-frequency A<sub>0</sub>–mode along with characteristic slow decay as a function of the distance from the crack face. At certain frequencies, the edge waves in the crack interfere constructively and the crack falls into the resonance (LDR). A reasonable accuracy in calculating fundamental the LDR frequencies is attained by using conventional wave resonance relation combined with additional account for the edge wave dispersion and can be applied for the crack metrology. The LDR-induced rise of the crack vibration amplitude provides clear opportunities for applications in other NDT techniques based on acoustic activation of damage.</p>

Local Defect Resonance of a Crack

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

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