Distinctive Features of Zero Group Velocity Guided Waves for Damage Detection

Abstract

This paper presents the recent progress from Active Materials and Intelligent Structures (AMIS) lab at Shanghai Jiao Tong University on utilizing special features of ZGV guided waves for damage detection. As the first part of this investigation, the Electro-Mechanical Impedance (EMI) method is studied, focusing on a special “trembling” phenomenon in the spectrum at the ZGV resonance. Finite Element Modeling (FEM) is performed to showcase such an interesting feature. It is found that the trembling feature following the resonance peak can serve as a special signature for ZGV modes identification and damage evaluation. Experiments on delamination detection is performed to demonstrate the superb sensitivity of the ZGV impedance technique. As the second part of this investigation, the nonlinear ZGV waves for fatigue damage detection is studied. The nonlinear interactions between guided waves and the fatigue crack generate second higher harmonics. Residing the second harmonics at the ZGV mode allows the nonlinear wave features to accumulate in the vicinity of the cracks. FEM simulations are carried out to demonstrate and analyze the special phenomenon. It is found that the second harmonic ZGV renders a much stronger nonlinear signature, which considerably enhances the damage detection sensitivity. The paper finishes with summary, concluding remarks, and suggestions for future work.