Crack detection of high-strength wind turbine bolts based on fiber bragg grating sensors

With the rapid development of the wind energy industry, there is an increasing concern about operation safety and reliability of high-strength wind turbine bolts. The aim of this paper is to monitor the strain change around the cracks in wind turbine bolts by means of fiber Bragg grating (FBG) sensors for crack detection. Firstly, the strain distributions of wind turbine bolts’ cracks with different locations and angles in the service condition are simulated using finite element analysis (FEA). Then, three-point grating string FBG sensors were pasted on the surface of wind turbine bolts with fatigue cracks to monitor the strain changes around the cracks in real time. By analysing the monitored strain data elaborately, the location of the crack on the bolt surface was successfully detected by identifying the location of the maximum strain detected by FBG sensors. In addition, the strain distributions in the vicinity area of the crack at different angles (0°, 45° and 90°) were also monitored and analysed in depth. The different types of crack angles could be distinguished based on of different strain distribution of the vicinity of the crack tip at different angles. The experimental results show that the FBG sensing technology has a high degree of sensitivity and accuracy in crack detection of high-strength wind turbine bolts.