Study On The Dynamic Characteristic And Failure Mechanism Of The Large-scale Wind Turbine Tower

The Large-scale wind turbine tower is an important part, the capacity of the toweraffects the stability and reliability of the wind turbine, with the wind turbine capacityincreasing, the wind turbine structure strength, vibration and stability of the whole problemhave become increasingly prominent. Based on the national natural science fundation, theMW wind turbine tower is chosen as the research object. Based on the engineeringstandard, finite element analysis method, experimental method, the dynamic characteristicsand fatigue of large wind turbine tower are analyzed. The two main connection failuremode of tower, bolt connection and weld connection failure are analyzed and get mainparameters, the tower bolt connection failure and the weld fatigue are affected by the mainparameters. A checking method of tower is given.Firstly, the natural vibration frequency of tower are calculated by the engineeringstandard and finite element analysis method, Considering the mass of cabin and blades, thetower door, the working load of blade, and the random wind load. Got a suitablecalculation method for wind turbine tower vibration frequency, and compared results to theexperiment, using the standard to check it. During the analysis on the vibration frequencyof tower, the fluid-solid coupling method is used, the wind pressure on the surface of toweris calculated. Including its influence on the structure stiffness, get more reasonable towervibration frequency. In tower of dynamic analysis, the wind turbine wind vertical directionand horizontal direction response analysis are carried. In the horizontal direction responseanalysis, the maximum displacement at the top of wind turbine tower is calculated andcheck. In vertical wind response analysis, the tower to wake of vortex is analyzed, andunder the Extreme wind speed, tower at different height of cross section of the vortexshedding frequency is calculated. In tower vibration analysis, the natural vibrationfrequency of tower should be avoided blade rotation excitation frequency and tower vortexshedding frequency. Secondly, the wind turbine tower comply with the requirements of strength andvibration, the fatigue life is analysed. The fatigue load spectrum is from BLADE software,and stress distribution is calculated by the finite element analysis software, the tower underthe six load components of wind turbines blade, stress-life curve of materials is fromcertification of wind turbine standard, the local stress strain fatigue analysis of towerstructure is applied. The material surface machining quality, the average stress and theexternal load are taken into account in the fatigue analysis of tower. After fatigue analysis,the distribution of fatigue life found near the door is low, for fatigue life of toweroptimization provides a kind of analysis method.The large-scale wind turbine tower as the research object, after meet the requirementsof static strength, dynamic analysis and fatigue analysis. The main tower failure in theconnection parts, including bolts connection and weld connections. Tower bolt connectionanalysis model is set up, and get the bolt strength and fatigue are completely meet therequirements, will the bolt looseness as the main reason. The bolt looseness is analysedusing the experiment and simulation method. The natural vibration frequency of thestructure is the most sensitive. The experiments data and the analysis date of the doublebolt specimens is similar. The finite element method is feasibility, and then using thismethod to the natural vibration frequency of tower structure bolt connection analysis. Theparameters can serve as a judge for bolt looseness, for after the bolt looseness faultdiagnosis to provide technical foundation.Finally, tower welding connection failure is analysed. Welding line strength isgenerally higher than the base. The main failure of welding line is fatigue. Weld fatiguestructure stress method is adopted, which can analyse the stress concentration at weld toe.The finite element analysis software to establish model of butt welding seam, the fatigueanalysis software to calculate the thickness and the weld residual high impact on weldfatigue life. Get the relationship between the two main parameters and weld fatigue lifecurve. The tower weld model as the object, use structure stress method calculated thefatigue life of tower weld distribution, provide tower weld fatigue design and optimizationof a simulation method.