Research on the monitoring friction hysteresis for the bolted interface by electromechanical impedance

Friction hysteresis manifests at the bolted interface when subjected to external excitation, leading to nonlinear structural responses. But the interface evolution is rarely considered in the health monitoring. In this paper, we introduce the pioneering concept of effective mechanical impedance of the contact interface (EMICI) and formulate a coupled structural impedance model that comprehensively incorporates both tangential loading and contact impedance considerations. EMICI was deemed to encapsulate intricate information pertaining to contact nonlinearity, and the theoretical equation was derived using principles of contact mechanics. Tangential loading experiments, time domain impedance analysis and impact hammer tests were conducted to confirm the close relationship between EMICI and the structural properties. The coupled structural impedance model is proved to be effective, in which EMICI can be identified by changing the tangential force and torque. Subsequent analysis revealed that the proposed model could additionally serve in the identification of system-related parameters. The loading coefficient in the model is linearly related to the tangential force, and the calculated EMICI corresponds to the slip characteristics of the bolted interface. The introduced concept of EMICI could be considered as a metric for assessing interface properties, offering dependable insights into contact evolution, and facilitating a deeper understanding of interface dynamics.