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Proceedings Paper

Practical issues in the implementation of electromechanical impedance technique for NDE
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Paper Abstract

The electro-mechanical impedance (EMI) technique, which utilizes "smart" piezoceramic (PZT) patches as collocated actuator-sensors, has recently emerged as a powerful technique for diagnosing incipient damages in structures and machines. This technique utilizes the electro-mechanical admittance of a PZT patch surface bonded to the structure as the diagnostic signature of the structure. The operating frequency is typically maintained in the kHz range for optimum sensitivity in damage detection. However, there are many impediments to the practical application of the technique for NDE of real-life structures, such as aerospace systems, machine parts, and civil-infrastructures like buildings and bridges. The main challenge lies in achieving consistent behavior of the bonded PZT patch over sufficiently long periods, typically of the order of years, under "harsh" environment. This necessitates protecting the PZT patch from environmental effects. This paper reports a dedicated investigation stretched over several months to ascertain the long-term consistency of the electro-mechanical admittance signatures of PZT patches. Possible protection of the patch by means of suitable covering layer as well as the effects of the layer on damage sensitivity of the patch are also investigated. It is found that a suitable cover is necessary to protect the PZT patch, especially against humidity and to ensure long life. It is also found that the patch exhibits a high sensitivity to damage even in the presence of the protection layer. The paper also includes a brief discussion on few recent applications of the EMI technique and possible use of multiplexing to optimize sensor interrogation time.

Paper Details

Date Published: 14 November 2002
PDF: 11 pages
Proc. SPIE 4935, Smart Structures, Devices, and Systems, (14 November 2002); doi: 10.1117/12.479821
Show Author Affiliations
Suresh Bhalla, Nanyang Technological Univ. (Singapore)
Akshay Surendra Kumar Naidu, Nanyang Technological Univ. (Singapore)
Chin Wee Ong, Nanyang Technological Univ. (Singapore)
Chee-Kiong Soh, Nanyang Technological Univ. (Singapore)

Published in SPIE Proceedings Vol. 4935:
Smart Structures, Devices, and Systems
Erol C. Harvey; Derek Abbott; Vijay K. Varadan, Editor(s)

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