Zero group velocity mode enhanced electro-mechanical impedance spectroscopy and nonlinear ultrasonics

Abstract. The zero group velocity (ZGV) mode possesses the distinctive attribute of an elapsed group velocity with a finite wavenumber, indicating a spatially propagating wave under a motionless package. This stationary mode engenders a localized resonance, confining the wave energy in the vicinity of actuation. Researchers have utilized ZGV modes for structural health monitoring (SHM) scenarios mostly in transient analysis and linear ultrasonic regime. Nevertheless, it remains an uncharted frontier that how ZGV mode, especially via its peculiar characteristics, can empower SHM methodologies regarding harmonics analysis and nonlinear ultrasonics. Therefore, this paper, on one hand, explores the trembling feature of ZGV resonances in steady-state electro-mechanical impedance spectroscopy (EMIS) and utilizes it for structural sensing. On the other hand, this paper leverage nonlinear generation of ZGV modes to amplify the higher harmonics signal to enhance conventional nonlinear ultrasonic methodology. This paper culminates in summary, concluding remarks, and suggestions for future work.