Detection of microcrack on thin plates using EMAT-based resonant ultrasonic spectroscopy

Currently, thin plate-type materials are widely used as structural materials in various industries. Defects in such a thin plate cause destruction of the structure, resulting in human and material damage. The ultrasonic inspection technique is the most widely used non-destructive inspection method to detect such defects. However, it is difficult to detect micro defects in a thin plate with thickness ≤ 5mm and analyze their signals. In this study, electromagnetic acoustic transducer-based resonant ultrasonic spectroscopy was applied to detect micro defects. Through finite element analysis, the change of the resonance frequency and output voltage depending on the presence or absence of defects was determined, and a test specimen was fabricated by incorporating fine defects to an actual aluminum plate. Our results indicate that it is possible to identify the presence of micro defects using this technique and to recognize the scanned image by changing the resonance frequency and output voltage