Abstract
Piezoelectric ceramic Lead Zirconate Titanate (PZT) transducers, working on the principle of electromechanical impedance (EMI), are increasingly applied for structural health monitoring (SHM) in aerospace, civil and mechanical engineering. The PZT transducers are usually surface bonded to or embedded in a structure and subjected to actuation so as to interrogate the structure at the desired frequency range. The interrogation results in the electromechanical admittance (inverse of EMI) signatures which can be used to estimate the structural health or integrity according to the changes of the signatures. In the existing EMI method, the monitored structure is only excited by the PZT transducers for the interrogating of EMI signature, while the vibration of the structure caused by the external excitations other than the PZT actuation is not considered. However, many structures work under vibrations in practice. To monitor such structures, issues related to the effects of vibration on the EMI signature need to be addressed because these effects may lead to misinterpretation of the structural health. This paper develops an EMI model for beam structures, which takes into account the effect of beam vibration caused by the external excitations. An experimental study is carried out to verify the theoretical model. A lab size specimen with different external excitations is tested and the effect of vibration on EMI signature is discussed.
Highlights
The electromechanical impedance (EMI) method has emerged as a widely recognized technique for dynamic identification and health monitoring of structural systems
Piezoelectric material has been successfully used for structural damage detection in many areas, the influence of the external excitations on the signature of Piezoelectric ceramic Lead Zirconate Titanate (PZT) needs further study
This paper aims at ascertaining the effect of external excitation on the PZT signature
Summary
The EMI method has emerged as a widely recognized technique for dynamic identification and health monitoring of structural systems. The electromechanical admittance response of the smart system is derived from the dynamic interaction between the PZT transducer and the host structure. The. EMI method has been proven direct and easy to implement. The method is typically applied using an electrical impedance analyzer, which scans a predetermined frequency range band in the order of tens to hundreds of kHz. In doing so, the complex admittance or impedance spectrum may be recorded and meaningful information containing the physical properties of the structure may be extracted. For SHM applications, these spectra can be compared at various times during the service lifespan of the structure, with which any change between the spectra is an indication of the presence of damage or material deterioration
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