Research On The Cross-scale Analysis Method Of Composite Wind Turbine Blade Under Extreme Load

The blade is the key component of wind turbine,with the highest manufacturing cost and extremely stringent reliability requirements.It is required to meet the characteristics of light weight,high strength and corrosion resistance,so composite materials have become the preferred material for wind turbine blade manufacturing.In order to deeply study failure modes of the blade,the cross-scale analysis of composite materials is employed to study the stress change and damage development mode of the blade from macro,meso and micro scales.To evaluate possible damaged parts of the blade before the damage occurs,through effective countermeasures to avoid or reduce economic losses and casualties.At the same time,a multiscale analysis system for integrated analysis of wind turbine blades is developed.The main contents of the thesis are as follows:(1)The airfoil data of wind turbine blade was obtained using Profili software,and the integrated modeling process of the composite wind turbine blade was completed using the finite element software.Using the wind turbine blade load calculation software to create the mathematical model of the wind turbine blade,and completing the extreme load of the blade in combination with the IEC61400-1 standard.The automatic finite element modeling and analysis system for composite wind turbine blades was developed based on the finite element simulation software.(2)A set of cross-scale analysis method for composite wind turbine blades based on bridging model is explored.Using the Tsai-Wu failure criterion and the maximum stress criterion as the failure criterion of the material,and the cross macro/meso/micro-scale structural analysis of the composite blade is completed.(3)With the developed system,combined with the cross-scale analysis method,the finite element analysis of the wind turbine blade is completed,and the stress distribution result of the dangerous part is automatically captured.The result indicates that,the wind turbine in normal operation conditions,once there are extreme gusts,stress concentration will occur at the wind turbine blade leading edge of the transition circle.The stress concentration of the composite materials middle layer at the corresponding position is very obvious and most likely to be damaged.(4)With the developed system,the comparison of the stress distribution of wind turbine blade under different working conditions are analyzed,including the extreme working conditions with continuous change of wind speed during normal operation,ultimate shear wind model and the conditions during emergency shutdown.The result indicates that,the blade does not fail under the extreme condition of continuous change of wind speed.Under the other two working conditions,the material at the transition circle of the blade is damaged in the micro scale,which is the matrix damage.Through the research work of this paper,the integrated modeling method and extreme load calculation method of composite wind turbine blades are proposed.A set of engineering methods for multi-scale analysis of composite wind turbine blades is explored to predict the possible damage areas of the blade under different working conditions.At the same time,a multi-scale analysis system for wind turbine blades is developed in this paper,and the feasibility of the system is verified with a 5MW wind turbine blade.