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Bolt Looseness Detection Based on Piezoelectric Impedance Frequency Shift

Key Laboratory of Metallurgical Equipment and Control of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081, China
Author to whom correspondence should be addressed.
Academic Editor: Gangbing Song
Appl. Sci. 2016, 6(10), 298;
Received: 8 September 2016 / Revised: 8 October 2016 / Accepted: 11 October 2016 / Published: 15 October 2016
(This article belongs to the Special Issue Structural Health Monitoring (SHM) of Civil Structures)
PDF [2652 KB, uploaded 15 October 2016]


In this paper, a piezoelectric impedance frequency shift method is developed to estimate the bolt preload for the detection of bolt looseness in engineering structures. An experimental device that allows the precision control of the axial preload force on a bolt is designed and fabricated. A universal testing machine is used to preload accurately on the bolt in the experiments. Under different bolt preload conditions, the impedance analyzer measures the admittance (inverse of the impedance) signal of the PZT (Lead ZirconateTitanate) patches which are bonded on the bolt head. Firstly, a wide frequency band is swept to find a sensitive frequency band of the piezoelectric admittance with the imaginary part. Then in the sensitive frequency band, a specified peak frequency of the admittance signature is chosen to investigate the frequency shift with different bolt preloads. The relationship between the specified frequency shift and the bolt preload is established. The experimental results show that the specified peak frequency decreases as the bolt preload increases for both M16 and M12 bolts, and the frequency shift has a linear relationship with the preload on the bolt. The frequencies of the real and imaginary parts of the admittance signature have the same results. Therefore, the bolt preload can be determined by measuring the specified frequency shift and this method has a good application prospect. View Full-Text
Keywords: bolt looseness; piezoelectric impedance; frequency shift; Lead ZirconateTitanate (PZT) bolt looseness; piezoelectric impedance; frequency shift; Lead ZirconateTitanate (PZT)

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Shao, J.; Wang, T.; Yin, H.; Yang, D.; Li, Y. Bolt Looseness Detection Based on Piezoelectric Impedance Frequency Shift. Appl. Sci. 2016, 6, 298.

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