Research On Reliability Analysis And Testing Technology Of Wind Power Towers

Accidents involving wind turbine collapse have been more common in recent years,and the majority of these incidents are brought on by welding component fatigue cracks.Wind turbine tower production involves more than 80% welding,and the longevity of the welded structure directly affects the longevity of the towers.Neither the influence of weld flaws nor the actual weld size on fatigue was taken into account in current studies of tower fatigue.In this thesis,a model was created based on measured tower size data,and finite element analysis was used to locate the tower’s fatigue danger;examine the impact of various defect parameters on the fatigue strength reliability of the tower weld based on the discovered tower weld defect data and performs nondestructive testing on the weld toe site of the fatigue danger location of the in-process wind turbine tower.The major techniques utilized to investigate the tower weld fatigue strength reliability are the finite element master S-N curve method,the rain flow counting method,and the Miner linear damage accumulation.(1)Based on the technical parameters of a 5MW large wind turbine,the ultimate loads and wind-induced load time ranges of the tower under four different wind conditions were calculated.Based on the measured tower size data during the production process,three different models were established to analyze the influence of flange structure and tower weld structure on the fatigue hazard location of the tower.The results show that under the four working conditions,the stresses in model one are concentrated at the bottom of the tower,the stresses in model two and model three appear at the thin-thick plate intersection of the barrel,and the thin-thick plate intersection under model three was the ring weld,which was the fatigue hazard location.(2)In the process of making a wind power tower,the existence of fatigue weakness of its weld ultrasonic detection work,the S1-CW03 weld detection application of a new detection method-weld sawtooth sweep method,the application of the method of ultrasonic detection of defects at the toe of the weld.The test results show that the weld at the toe of the weld there are tiny slender defects of varying length and uniform location,if the tower was subjected to fatigue load,the defects will gradually expand,directly affecting the service life of the tower.(3)The weld life was evaluated using the principal S-N curve method considering the initial defect size.The IIW code was used to assess the reliability of the stress-concentrated welds,and the ratio of the structural stress of the weld to the allowable stress of the corresponding S-N curve of FAT112 was used as the safety factor,and the results showed that the safety factors of the fatigue hazard weld structures were all greater than 1.The node with the smallest safety factor was designated as the hazard node.The structural stress time spectrum at the hazardous nodes was calculated using the Rainflow-Miner linear accumulation method,and the results showed that the fatigue life of the welds met the requirements of the tower design life of 20 years.Based on the defect data,the maximum initial crack width of the weld and the weighted average initial crack width were calculated to obtain the I(r)formula for correcting the initial relative crack size and calculating the corresponding weld life.The results show that the weld life was substantially reduced for a/t > 0.1.Considering the effect of wind direction on weld life,the results show that when the wind direction remains constant for a long period of time,it was necessary to focus on the fatigue state of the weld in the radial plane of that wind direction.