Monitoring of pin connection loosening using eletromechanical impedance: Numerical simulation with experimental verification

Pin connection, as an important structural connection mechanism, is widely used in various structures, especially spatial structures. In this article, numerical and experimental investigations are performed for monitoring the loosening of pin-connected structures using the electromechanical impedance technique. For this purpose, a finite element model for a pin-connected structure considering the contact interfaces between the pin and the support base is proposed to study the effect of pin connection loosening on the electromechanical impedance signatures. A multi-physics analysis is conducted to simulate the electromechanical behavior of lead zirconate titanate transducers bonded on the pin head and the steel base. The relationship between the force applied on the pin connection and the variation in electromechanical impedance signatures is established. Experiments are carried out to verify the accuracy of the proposed finite element model. The results show that the changes in the electromechanical impedance signatures consist of frequency shifts and peak splitting. The contact condition of the pin connection can be assessed by observing the changes in the electromechanical impedance signatures. The location of the piezoelectric patch has significant effect on the sensitivity of the electromechanical impedance signatures. The numerical study in this research helps to optimize the design of sensor placement and improve the detection accuracy of the electromechanical impedance method in practical applications of detecting the loosening of pin-connected structures.