Early detection of bolt loosening is a major concern in the oil and gas industry. In this study, a vibration-based health monitoring strategy has been developed for detecting loosened bolts in pipeline. Both numerical and experimental studies are conducted to verify the integrity of the proposed method. Several damage scenarios for a bolted joint connecting two steel pipes (ASTM A53/A53M–07) are considered by simulating the loosening of the bolts through varying the applied torque on each bolt. An electric impact hammer is used to excite the pipe’s vibration in a consistent manner. The induced vibration signal is collected remotely via piezoceramic sensors bonded onto the pipe as well as the flange. The gathered vibration signals are transferred remotely to an in-house developed MATLAB code by a wireless data acquisition (DAQ) module. The data is processed with the embedded signal processing code, which incorporates normalization, filtering of data and the empirical mode decomposition (EMD) to establish an effective energy-based damage index. The assessment of the damage indices obtained for the damage scenarios verifies the integrity of the proposed methodology in identifying the damage and its progression in bolted joints.

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