Preparation and Performance Research of Smart Bolts Based on ALN Piezoelectric Thin Films

The preparation of smart bolts is mainly achieved by pasting or embedding piezoelectric ceramic transducer (PZT) patchs on the bolt head. However, these two methods are easily affected by temperature and noise due to the presence of the adhesive layer. In this study, a novel smart bolt based on ALN piezoelectric thin film (PTF) is developed. Firstly, a probe based thin film piezoelectric coefficient testing model was established to provide a theoretical basis for measuring the internal electric field distribution of PTF sensors and the equivalent voltage applied to ALN thin films; secondly, Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM), X-ray Diffraction (XRD), and Energy Dispersive Spectrometer (EDS) were used to characterize and analyze the piezoelectric layer of the PTF sensor, and the longitudinal piezoelectric coefficient was measured, providing a basis for the feasibility of the proposed new smart bolt; finally, a comparative analysis was conducted between the four performance indicators of high-temperature resistance, sensitivity, signal to noise ratio, and repeatability with the PZT adhesive smart bolt. The verification results indicate that the new smart bolt can more accurately identify the health status of the bolt.