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THE INFLUENCE OF TIGHTENING TORQUE ON MODAL PARAMETERS OF STRUCTURES WITH BOLTED JOINTS
Estênio Fuzaro de Almeida , São Paulo , Brazil
Co-Authors: Estênio Fuzaro de Almeida, Luccas Miguel, Rafael de Oliveira Teloli, Samuel da Silva
Presenter: Estênio Fuzaro de Almeida
Tightening torque monitoring is still expensive, with direct measures and principally not automatized. Verifying tightening torque from indirect vibration measures through structural health monitoring techniques instead of employing manual torque wrenches is of great technological interest. Nevertheless, finding sensitive vibration features that can predict tightening torque losses is still challenging due to the complexity of nonlinear effects and uncertainties related to bolted joints. Thus, this paper intends to investigate the capacity of detecting variations in tightening torque and classify if the structure is in a safe torque condition only by analyzing modal parameters for different torques. For this, experimental tests were performed to a white noise input on a two-part beam connected by a bolted joint attached to a shaker to extract resonance frequencies and damping ratios. The analysis was done using the Mahalanobis Squared Distance between the clusters of features in a healthy state of reference to the damaged ones. Despite the difficulty of dealing with the reassemblies' variability, the low false-negative rate when they are disregarded indicates that these modal parameters can be used as damage features related to variations of tightening torques smaller than those currently found in the literature.
Bolted joints, Torque Monitoring, Damage Detection, Mahalonobis Squared Distance