Research On Damage Monitoring Technology For Wind Turbine Blade Girder Based On Acoustic Emission

With the large-scale development of wind turbine,it is urgent to strengthen the understanding of the failure behavior of blade structure and provide efficient performance evaluation and failure prediction methods.Under the influence of manufacturing process.some defects such as lamination,inclusion,lack of glue,fold and so on are inevitable.In the actual working condition,these tiny defects gradually accumulate and develop under the long-term load,resulting in the damage of blade structure,thus affecting the normal operation of wind turbine unit equipment.The main girder of wind turbine blade is the main bearing part of the blade.Therefore,this topic aims to study the defect evolution of the manufacturing process of the main girder of the blade.The main research contents are as follows:At first,the structure of the wind turbine blade was analyzed.The blade load through the main girder structure was passed on to the wheel hub.Through the stress analysis of main girder,the results showed that the girder stiffness of each single layer plate was discontinuous and the stress was different which explains why the girder material laminated plates injury began with a single layer.Based on the analysis of mechanical properties and tensile strength of the main beam composites,the damage forms and characteristics of the main beam composites were summarized.Secondly,the principle of acoustic emission technology and the advantages and limitations of acoustic emission processing technology applied to wind turbine blade monitoring were introduced,and the parameter analysis method and waveform analysis method of signal processing were discussed.Due to the existence of mechanical noise and electromagnetic noise,it is necessary to deal with the noise reduction of AE signal.In this paper,the fatigue loading was applied to the blades composite girder specimens containing the delamination damage,and the AE signal was collected by acoustic emission detector during loading.Thus,the blade girder composite delamination damage evolution of acoustic emission in the process of response characteristics,the influence of mechanical properties and its main failure damage model were studied.The acoustic emission characteristics of materials were distinguished by the qualitative analysis of peak frequency on the damage types and the changes of ringing count,RMS value and amplitude characteristic parameters.Finally,the acoustic emission signal characteristic information was extracted.Based on the wavelet analysis,two specimens signal were analyzed,and selecting suitable wavelet and threshold of wavelet de-noising function of the acoustic emission signal decomposition reconstruction spectral energy distribution was obtained.Through wavelet packet energy analysis and power spectrum analysis,different damage characteristics of the main girder composite materials of normal and containing delamination defect and damage evolution mechanism were concluded.This study will provide reference for the structural health monitoring of wind turbine blades...