Monitoring of the Looseness in Cargo Bolts under Random Excitation Based on Vibration Transmissibility

Abstract

Bolted joints are widely used in industrial applications and joint failure can cause a disastrous accident if loosening happens. Bolt loosening detection can be made by regular manual inspection or by using sensors based on different physical principles, such as acoustoelastic effect, piezoelectric active sensing, and electromechanical impedance. Compared with the above methods, vibration based bolt looseness monitoring using accelerometers is appealing for its economy and convenience for measurement. In this paper, cargo bolts looseness monitoring under random excitation is studied based on vibration transmissibility, which overcomes the drawback of commonly used vibration methods in finding local bolt looseness. Vibration transmissibility analysis only uses two vibration transducers to monitor bolt group looseness, where the vibration signal below the cargo bolts is used as the “input” and the other one above the cargo bolts is used as the “output.” There are 12 bolts in the cargo bolts studied in this paper, providing an essential clamping force to fix cargo during transportation. Six kinds of bolt group looseness with an increasing degree are simulated in the experiment. The experimental analysis shows that variation of the spectral moment can be used to monitor the global variation of the torque wrench exerted on the cargo bolts. The early stage of the bolt group looseness is that some one or two bolts begin to loose; however, the spectrum moment factor is insensitive to the local bolt looseness in the bolt group. To address this issue, the eigensystem realization algorithm (ERA) based on random input and output is utilized to find the subtle eigenvalue variation of the system matrix, which is neglected by the frequency transmissibility function. The experimental results show the effectiveness of the proposed method for detecting local bolt looseness.

Diagnostics of a Clamping Joint System

“…4 Generally, important point in the analysis of the clamping system is that the modal parameters of the desired tightened system, which is considered as a reference, must be known. Against the reference system, another system is compared, which can be called the system under assessment [24].…”

Early bolt looseness monitoring using the leading waves energy in piezoelectric active sensing

“…This approach exhibits a high level of measurement accuracy, however, it is subject to limitations in terms of installation of strain gauge or optical fiber and prolonged monitoring. The vibration-based method [12][13][14] utilizes acceleration sensors to measure structural vibration information and determines the bolt connection status through signal analysis. However, this method exhibits sensitivity only to the global dynamic characteristics of the structure and lacks sensitivity towards the local dynamic characteristic changes induced by the bolt looseness.…”

Proof-of-concept study of bolt connection status monitoring using fiber Bragg grating curvature sensor

“…Therefore, it is efficient and feasible to predict bolt connection status by monitoring clamping force or bolt loosening angle. Concerning clamping force as a crucial factor in the reliability of the bolted joint, many bolt loosening monitoring methods have been proposed and investigated, mainly including percussion-based methods [5,10,11], vibration-based methods [12][13][14], electromechanical impedance (EMI)-based methods [15][16][17][18], and ultrasonicbased methods [19][20][21][22]. These methods study the influence of the clamping force reduction on the physical parameters of the bolted structure and evaluate the bolt connection status through the related physical parameters changes.…”