Design and Experimental Investigation of a Bolt Monitoring Sensor for Wind Turbine Using Magnetic Field Signals

The development of wind power generation is a critical measure for achieving the “dual carbon” goals. The safe and reliable operation of wind turbines is the foundation for ensuring their sustainable operation. As key fastening components of wind turbines, connection bolts are subjected to alternating loads and environmental corrosion over long periods, making them prone to loosening, fatigue fractures, and other safety risks that threaten the operational safety of the turbines. To address this issue, this study proposes a stress state detection sensor device for tower and blade root bolts based on magnetic field signals. On this basis, a dedicated experimental testing system is established to quantitatively investigate the correlation between magnetic memory signals and bolt stress. Experimental results demonstrate that stress-induced magnetic signals can be effectively detected on the bolt surface. Under tensile loading, the magnetic memory signals exhibit a clear linear response to stress variations, enabling reliable stress state monitoring through magnetic measurements. Furthermore, the influence of bolt material on the relationship between stress and magnetic signal variation is relatively minor. In contrast, significant differences are observed in the slopes of the magnetic signal–stress curves for bolts of different strength grades, indicating the necessity of prior calibration. The test analysis in this paper can provide the necessary experimental foundation and reference data for engineering applications such as remote monitoring and early diagnosis of wind turbine bolt conditions.