Vision-based detection of loosened bolts using the Hough transform and support vector machines

In this paper, some recent piezoelectric wafer active sensors (PWAS) progress achieved in our laboratory for active materials and smart structures (LAMSS) at the University of South Carolina: http: //www.me.sc.edu/research/lamss/ group is presented. First, the characterization of the PWAS materials shows that no significant change in the microstructure after exposure to high temperature and nuclear radiation, and the PWAS transducer can be used in harsh environments for structural health monitoring (SHM) applications. Next, PWAS active sensing of various damage types in aluminum and composite structures are explored. PWAS transducers can successfully detect the simulated crack and corrosion damage in aluminum plates through the wavefield analysis, and the simulated delamination damage in composite plates through the damage imaging method. Finally, the novel use of PWAS transducers as acoustic emission (AE) sensors for in situ AE detection during fatigue crack growth is presented. The time of arrival of AE signals at multiple PWAS transducers confirms that the AE signals are originating from the crack, and that the amplitude decay due to geometric spreading is observed.

https://scholarcommons.sc.edu/cgi/viewcontent.cgi?article=1798&context=emec_facpub

Recent Advances in Piezoelectric Wafer Active Sensors for Structural Health Monitoring Applications

Quasi-autonomous bolt-loosening detection method using vision-based deep learning and image processing

This paper reviews the research of monitoring technologies for bolted structural connections. The acoustoelastic effect based method, the piezoelectric active sensing method, and the piezoelectric impedance method are the three commonly used to monitor bolted connections. The basic principle and the applications of these three methods are discussed in detail in this paper. In addition, this paper presents a comparison of these methods and discusses their suitability for in situ or real-time bolt connection monitoring.

Review of Bolted Connection Monitoring

Monitoring of bolt looseness is essential for ensuring the safety and reliability of equipment and structures with bolted connections. It is well known that tangential damping has an important influence on energy dissipation during wave propagation across the bolted joints, which require different levels of preload. In this paper, the energy dissipation generated by tangential damping of the bolted joints under different bolt preloads was modeled analytically based on fractal contact theory, which took the imperfect interface into account. A saturation value exists with the increase of the bolt preload, and the center frequency of emitted signal is demonstrated to affect the received energy significantly. Compared with previous similar studies based on experimental techniques and numerical method, the investigation presented in this paper explains the phenomenon from the inherent mechanism, and achieves the accurate quantitative monitoring of bolt looseness directly, rather than an indirect failure index. Finally, the validity of the proposed method in this paper was demonstrated with an experimental study of a bolted joint with different preload levels.

https://iopscience.iop.org/article/10.1088/1361-665X/aa9a65/pdf

A piezoelectric active sensing method for quantitative monitoring of bolt loosening using energy dissipation caused by tangential damping based on the fractal contact theory

Aimed at monitoring bolt connection status and detecting bolt loosening, a piezoceramic based active sensing method is developed in this article. Two piezoceramic patches are bonded to the two different parts of a bolted connection. In the active sensing approach, one piezoceramic patch is used as an actuator to generate an ultrasonic wave, and the other one is used to detect the wave that propagates through the bolted connection. The received energy depends on the interface fastening pressure which is determined by the bolt torque. By analyzing the received energy, the status of bolt connection and bolt loosening can be detected. To study the effectiveness of the proposed method, an experiment apparatus is set up, and the experimental results show that the wave energy propagated across the interface is proportional to the torque level that is used to pretension the bolt. This experimental study demonstrates the potential of the piezoceramic based active sensing method for the monitoring of bolt loosening status.

https://iopscience.iop.org/article/10.1088/0964-1726/22/8/087001/pdf

Proof-of-concept study of monitoring bolt connection status using a piezoelectric based active sensing method

An algorithm to detect damage size and shape using a lead zirconate titanate (PZT) transducer array for a plate structure is developed in this paper. During the process of detection, the pr...

Detecting Damage Size and Shape in a Plate Structure Using PZT Transducer Array

A new method of structural stress monitoring based on piezoelectric (PZT) impedance frequency shift is proposed in this paper. Since the sensitive frequency of the imaginary part of admitta...

Structural Stress Monitoring Based on Piezoelectric Impedance Frequency Shift

In this paper, an eddy current tuned mass damper (ECTMD) is utilized to control the vibration of a cantilever beam. The robustness of the ECTMD against frequency detuning is experimentally studied in cases of both free vibration and forced vibration. The natural frequency of the cantilever beam can be adjusted by changing the location of a lumped mass. For purposes of comparison with the ECTMD, the robustness of a tuned mass damper (TMD) is also studied. The experimental results in the free vibration case indicate that the ECTMD works well both in tuned and detuned situations, and the equivalent damping ratio of the cantilever beam equipped with the ECTMD is 2.08~5.91 times that of the TMD. However, the TMD only suppresses the free vibration effectively in the tuned situation. With forced vibration, the experimental results also demonstrate the robustness of the ECTMD in vibration suppression in detuned cases. On the other hand, the cantilever beam with TMD experiences 1.63~2.99 times the peak vibration of that of the ECTMD control.

Experimental Study on Robustness of an Eddy Current-Tuned Mass Damper

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