Digital Image Correlation-Based Bolt Preload Monitoring.

Bolt connections are widely used in engineering structures but are susceptible to loosening during operation, which can result in significant safety concerns. Consequently, reliable bolt-loosening detection is of paramount importance. Conventional detection methodologies frequently exhibit deficiencies, including reduced efficiency, constrained accuracy, and the requirement for contact sensors. To overcome these limitations, this study proposes a novel non-contact approach for bolt preload monitoring based on Digital Image Correlation (DIC). In this method, an industrial camera captures speckle images of the bolt head before and after deformation, thereby enabling measurement of the surface strain. The DIC technique is employed to calculate the strain field on the bolt head surface, which exhibits a linear relationship with the bolt preload. The proposed method utilizes strain field tracking to facilitate effective and precise monitoring of bolt preload. Experimental results demonstrate that the method provides a precise, efficient, and user-friendly solution for bolt preload monitoring, showing great potential for applications in structural health monitoring.