Fatigue Analysis Of High-strength Bolts At The Flange Joint Of Wind Turbine Tower

Wind turbine consists of many structural parts,and the tower is the heaviest part of the entire structure.the wind turbine is subject to complex alternating loads all the year round,so the tower is the most prone to structural damage in the wind turbine due to fatigue damage.This paper takes an 80-meter-high wind generator as the analysis object,and combines engineering algorithms,finite element analysis and experimental methods to calculate the fatigue damage of the high strength bolts of the tower tube for 20 years and predict how long bolts can be used.The main contents are as follows:(1)In the context of increasing demand for human renewable energy,the research on fatigue damage of high-strength bolts by domestic and foreign scholars is summarized,and the follow-up research of this article is carried out based on relevant theories.(2)Related fatigue analysis methods and cumulative fatigue damage theory are summarized.Based on the principle of torque method,hydraulic torque wrench is used to apply pre-tightening force to the flange bolt connection solid model used in the experiment.The classic Schmidt-Neuper algorithm and experimental method are used to establish the relationship between the external load of the tower and the internal stress of the bolt.ABAQUS is used to establish the single-sector flange bolt connection model,and the bolt adopts solid model and beam element respectively.The relationship between the load and the internal stress of the bolt is compared with the engineering algorithm and experimental method.(3)In GH bladed,the time series external load of the tower under various working conditions is obtained,and the time series internal stress of the bolt is calculated by Matlab interpolation.Set the S-N curve of the bolt in Design Life according to the GL 2010 specification.Then calculating fatigue damage of high-strength bolts under a single working condition by using rain flow counting method.According to the classic Miner’s rule,the fatigue damage of each working condition is accumulated to meet the fatigue design requirements.(4)In order to study the factors influencing the fatigue of high-strength bolts of wind turbine towers,the bolts’ pre-tightening force,bolt number and flange thickness were changed to calculate the fatigue damage of bolts.The results show that properly increasing flange thickness,the bolt preload,bolt diameter,and the bolt number can reduce the fatigue damage of high-strength bolts at the flange.