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Loose bolt detection in a complex assembly using a vibro-acoustic sensor array
Journal Contribution - Journal Article
© 2019 Elsevier Ltd A non-destructive testing strategy is proposed that combines microphone measurements and structural measurements in one array. The aim is to lower the total inspection time by reducing the number of structural sensors. This is possible by making use of the easier and faster installation of microphones as compared to structural sensors. Structural sensors are needed to limit the influence of background noise. The proposed algorithm is based on the theory of the Time-Reversal MUltiple SIgnal Classification (TR-MUSIC) algorithm. In addition to the novelty of using a vibro-acoustic array, this publication presents a strategy on how to select only the most ‘valuable’ regions of the frequency spectrum for the TR-MUSIC algorithm and an option to use the algorithm with a number of excitations below the theoretically necessary minimum. The proposed procedure is applied in an experiment that targets the localisation of loose or removed bolts in an assembly of aluminium beams and a honeycomb panel, mounted with rivets, bolts and double-sided tape. Although none of the bolts is in the line of sight of the sensor array, all introduced defects can be found in this experiment. This includes the localisation of multiple defects as well. By adding artificial measurement noise to the microphone measurements, it is demonstrated that a combined vibro-acoustic array can cope with a high ambient noise level, while the process fails if a comparable measurement error is also applied to the structural sensors.
Journal: Mechanical Systems and Signal Processing
Pages: 433 - 451