High-Precision Probabilistic Imaging for Interface Debonding Monitoring Based on Electromechanical Impedance

Solid rocket motors (SRMs) are widely used in the aerospace and missile industries. The interface debonding between propellant/insulator/case determines the life of an SRM. Therefore, monitoring and further locating interface debonding are crucial to prevent catastrophic structural failures of an SRM. The electromechanical impedance (EMI) technique based on piezoelectric wafer transducers is a simple and sensitive structural health monitoring (SHM) method. In this study, a high-precision probabilistic imaging method of EMI for the debonding monitoring of the SRM case–insulator interface is proposed. In this method, the Gaussian window function is used to describe the variation of debonding damage index with the position. In addition, an experimental procedure based on simulated damage is presented to determine the parameter in the Gaussian window function. Finite element models of the steel case–insulator structure based on Rayleigh damping are established to analyze the effects of debonding and simulated damage on EMI signals. An experiment is conducted to verify the proposed probabilistic imaging method and the finite element analysis results. It is proved that the proposed probability method can achieve high-precision imaging of debonding of SRM case–insulator, even after several months of storage.