Flange bolt looseness is one of the common problems of wind turbine tower, and is the main factor leading to the collapse of wind turbine tower. In this paper, based on ANSYS Based on the finite element analysis method of workbench, the local finite element vibration analysis model of tower drum is established and verified by experiments. Based on this model, the influence of bolt looseness number, wind strength and wind direction on the phase difference between the upper and lower flange plates is studied. The results show that the flange plate with certain bolt looseness ratio is at the top and bottom. The absolute value of the phase difference between the plates is obviously larger than that when the bolts are tightened. Therefore, the phase difference between the upper and lower flanges can be used as the basis for judging the looseness of the bolts in the tower flange.

According to the current main wind turbine design specifications, the necessary parameters for wind load assessment of wind turbine tower are discussed. According to IEC61400-1 (IEC2019) and Japan’s Guidelines for Design of Wind Turbine Support Structures and Foundations (JG2010), the wind load assessment of the tower structure of a 2MW horizontal axis generator is carried out, and the calculation results are compared. It can be seen from the comparison that the design value from the evaluation formula of JG2010 and the design value from the load condition of IEC2019 by using GH bladed simulation matches well. The main reason is that the evaluation formula of JG2010 itself is derived according to the response spectrum method. So, JG2010 is a good reference for the design of domestic wind turbines and the formulation of relevant specifications.

Taking the wind turbine tower as the research object, based on the finite element software, a simplified beam-shell hybrid element model was first established; through the simulation, the phase difference between the loose position and the unloose position was compared to verify the feasibility of the phase difference detection method; Secondly, the influence of the number of loose bolts, the position of loosening, and the magnitude of the wind force on the phase of the flange bolt connection structure and the response characteristics of the system are analyzed. The research results show that the number of loose bolts, the position of loosening, and the magnitude of the wind have certain effects on the phase difference and response characteristics of the flange. With the increase in the number of loose bolts, the connection stiffness of the bolt connection continues to decrease. The linear characteristic is enhanced; the closer the loosening is to the excitation force loading position, the greater the detected phase difference; as the wind increases, the phase of the upper flange of the tower changes, and the phase of the lower flange remains unchanged, and the wind is on the flange The disc connection strength has little effect.