Health monitoring of high-damping viscoelastic materials using sub-resonator enriched electro-mechanical impedance signatures

Abstract

This article presents a recent progress of the electromechanical impedance spectroscopy methodology for monitoring high-damping viscoelastic materials (solid rocket motor propellant for instance). It employs piezoelectric wafer active sensors (PWAS) with sub-resonators which can create additional resonance peaks for enriching the diagnostic information. In order to develop an in-depth understanding of the mechanism behind the sub-resonator sensor system, an analytical investigation is conducted first. The theoretical formulation treats the sub-resonator PWAS as a mass-in-mass model, which can be seamlessly merged into the traditional 1D constrained PWAS case. The analytical solution for the impedance signature of the new sub-resonator PWAS transducer is derived. Meanwhile, parametric case studies are carried out to analyze the influence of material damping and additional mass of the sub-resonators on the impedance signature. Moreover, numerical simulations are performed to demonstrate the effectiveness of the new sensor creating additional resonance peaks. Comparative investigations are carried out with both the conventional PWAS and the sub-resonator PWAS. EMIS damage indices based on the spectral amplitude and frequency variation features are used to quantify the material degradation. Additionally, the performance of the proposed sub-resonator PWAS is demonstrated via a material creep experiment. The article finishes with summary, concluding remarks, and suggestions for future work.