Study of preload relaxation and optimization of wind turbine bolted connections based on the improved elastic interaction coefficient method

The preload relaxation is always caused by elastic interaction in the process of the wind turbine bolt tightening. To address the problem, the effects of the initial preload level, the tightening sequence on the preload are investigated based on theory calculation and finite element (FE) analysis. Moreover, this study proposes a preload optimization method based on the improved elastic interaction coefficient method (EICM), and the effectiveness of the method is verified by using FE analysis. The result shows that the improved EICM can be employed to analyze the interaction between the bolts, predict the variation of preload and confirm the initial preload that satisfies the pre-tighting conditions, as well as improve the practicality of the EICM and the calculation efficiency.