Electro-mechanical impedance method found applications in many disciplines ranging from medical diagnostics to civil engineering. However, the majority of applications of this method were reported in aerospace and mechanical engineering. This is primarily because of an ability of the electro-mechanical impedance method to assess local structural condition in the neighborhood of the sensor. Utilization of electro-mechanical impedance is most popular in metallic structures due to low attenuation of ultrasonic waves and straightforward installation of piezoelectric sensors. Recent studies have demonstrated utility of the method in composite structures despite of high attenuation of ultrasonic waves. This study explores theoretical and experimental aspects of electro-mechanical impedance assessment in composite and metallic structures. A theoretical model is considered to describe the attenuative response of composite structures and to lay out a foundation for the comparison of responses in structures made of different materials. For simplicity, the problem is confined to 1-D structures in which a piezoelectric active sensor is perfectly bonded to the structure and hence the contribution of the shear lag is neglected. In this case, interaction of the sensor and structure is described using the pin-force model reflecting the axial force and bending moment at the end of the sensor as sources of axial and bending vibrations. Classical and non-classical damping are considered in the model and respective manifestations in the electro-mechanical impedance are presented. In particular, viscous damping is modeled as a contribution of a term proportional of structural velocity and Kelvin–Voigt strain-rate damping is modeled as a contribution of a term proportional to the fifth derivative of displacement. It was found that each of these damping models influence differently the electro-mechanical impedance response. Experimental investigations were focused on exploring sensitivity of the electro-mechanical impedance method in structures made from different materials. A hypothesis of a correlation between the sensitivity of the electro-mechanical impedance method and attenuation characteristics of structures is validated. Sensitivity of the electro-mechanical impedance method was studies in a set of experiments. Structures made of metallic materials were considered first. Boundary conditions were altered locally and changes in the electro-mechanical impedance response were observed. It is suggested that sensitivity of the electro-mechanical impedance method to changes of boundary conditions or structural and material damage depends on the attenuation of the elastic wave transmitted and received by piezoelectric wafer active sensors. Recommendations of the utilization of the electro-mechanical impedance method in materials with different attenuation characteristics are presented.


Electro-Mechanical Impedance Assessment of Composite and Metallic Structures

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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