Imaging method of interfacial anomalies in layered structures

Layered structures are progressively critical to several fields like aerospace, pipeline transportation, and petrochemical engineering. However, the anomalies located on the interfaces between the layers are troublesome yet problematic to image through traditional non-destructive evaluation methods. This study presented an imaging method utilizing interface waves and visualized the interfacial anomalies in layered structures. The paper first derived and solved the dispersion equations of a layered plate. The wave structure of the interface waves and their interaction mechanisms with interfacial anomalies make them inherently sensitive to interfacial anomalies. Moreover, the interface wave modes are non-dispersive at high frequencies, causing macroscopic differences between the signals with or without abnormal features. On that basis, correlation analysis and probabilistic reconstruction formed the imaging algorithm in this work. Lastly, the experimental system was tested on two different layered metal plates. The results show that the system can precisely depict interfacial anomalies of different shapes. Especially for the circular anomalies, the produced images coincide with the pre-manufactured defects with relatively minor errors of location and area.