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摘要
Vibro-acoustic modulation( VAM) uses nonlinear sidelobe signals generated by interaction between low-frequency vibrations and high-frequency signals at damage position to identify structural damage. In practical engineering, boundary conditions often affect monitored structures, interfere identification of sidelobes, and lead to misjudgment of damage state. Here, aiming at the problem of bolt connection condition monitoring under boundary conditions, a bolt pre-tightening state identification method based on VAM signal cointegration analysis was proposed. Firstly, amplitudes of sidelobe signals under different boundary fixed forces were extracted as cointegration variable. Then, the bolt pre-tightening state was judged according to cointegration residual sequence to establish a robust quantitative index of bolt preloading force state. The experimental results show that cointegration analysis can eliminate effects of boundary conditions on VAM, and characterize bolt state nicely; the root mean square ( RMS) value of cointegration residuals can be used as a quantitative index to effectively identify bolt preloading state. ? 2022 Chinese Vibration Engineering Society.
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