Electro-Mechanical Impedance Method for Crack Detection in Thin Plates

TLDR

The study applies the electro‑mechanical impedance method to monitor structural health in thin plates. The authors develop and experimentally validate a two‑dimensional analytical model that uses electro‑mechanical impedance signatures to detect cracks and compute damage metrics in thin plates. Experimental results confirm that crack presence markedly alters the impedance spectrum, with the αth‑power correlation coefficient deviation in the 300–450 kHz band providing the most reliable damage metric, and that detection sensitivity diminishes with increasing sensor‑crack distance.

Abstract

This paper describes the utilization of Electro-Mechanical (E/M) impedance method for structural health monitoring of thin plates. The method allows the direct identification of structural dynamics by obtaining its E/M impedance or admittance signatures. The analytical model for two-dimensional structure was developed and verified with experiments. Good matching of experimental results and calculated spectra was obtained for axial and flexural components. The ability of the method to identify the presence of damage was investigated by performing an experiment where the damage in the form of crack was simulated with an EDM slit placed at various distances from the sensor. It was found that the crack presence dramatically modifies the E/M impedance spectrum and this modification decreases as the distance between the sensor and the crack increases. Several overall-statistics damage metrics, which may be used for on-line structural heath monitoring, were investigated. Among these candidate damage metrics, the αth power of the correlation coefficient deviation, CCD α ,3< α <7, used in the high frequency band 300-450 kHz, was found to be most successful. Careful selection of the high frequency band and proper choice of the appropriate damage metric were found to be essential for successful damage detection and structural health monitoring.