Research Diagnosis And Monitoring Technology Of Defects In Wind Turbine Tower Based On Acoustic Emission

Wind energy,as a kind of renewable clean and pollution-free energy,has been widely concerned by the world.Wind turbine tower is the main component of wind turbine and its bearing component,In the harsh natural environment and long service period,due to the impact of long time under periodic excitation and weld the existing defects,the tower is easy to produce fatigue crack,resulting in failure of the tower structure,the safe operation of the serious threat of wind turbine.Therefore,it is necessary to carry on the real-time on-line monitoring to the wind power tower,and to make the qualitative and location of the fatigue crack,so as to take effective remedial measures to avoid the collapse of the tower.Because the acoustic emission technology is a dynamic detection method,can be used for the overall detection of large structural parts,and can detect the defects,the detection efficiency is high.so,it is of great importance to apply the acoustic emission testing technology to the assessment and monitoring of the health status of the wind turbine tower.This paper from the engineering application of in-service wind power tower detection and real-time monitoring of the tower itself and the manufacturing material as the research subject,through the extraction of Q345 E steel with different welding defects and different tower location defect characteristics of acoustic emission signals with acoustic emission technique,carries on the processing and analysis of weld type of defect induced fatigue crack,the types of the defects existing in the tower were identified,and the defect location of positioning,discusses the feasibility of the application of acoustic emission technology in existing wind power tower monitoring.The main research work and achievements are as follows:According to the fatigue cracks of different weld defects and the tower has evoked the harm to the problems in the operation process of existing wind power tower in the tower of raw materials to the internal defects of the prefabricated seam(Q345E steel)as the research object,the three point bending test,the sound in the bending damage process of Q345 E not the same type of weld defect emission characteristics.Wavelet decomposition and reconstruction of the original AE signals of different weld defects,and the reconstructed AE signals of different weld defects are analyzed amplitude characteristic parameters analysis,3D HHT transform spectrum analysis,FFT transform,wavelet time-frequency analysis,and extract theenergy ratios of different types of defects of AE signal for the same frequency period.The results show that under the same experimental conditions,the AE signals of different weld defects are different in the characteristic parameters,frequency and the proportion of energy in the same frequency range;The noise reduction and reconstruction of the original signal can remove the noise signal in the signal,and make the AE signal reflect the real characteristics of the defect;Compare various processing methods of AE signal processing,find local analysis ability of amplitude of 3D HHT transform has better and more high resolution,can well reflect the characteristics of acoustic emission signal of different weld defects,can effectively identify the type of weld defect.According to the acoustic emission sensor distribution and signal attenuation,the influence on positioning the neural network output,under the tower section of2 WM wind turbine in Jiuquan hydropower four Bureau in the construction of the experimental platform,through the lead breaking methods of Crack Acoustic emission source for simulation,attenuation experiments and defect location.The rise in energy,needle count,amplitude and RMS to describe the acoustic emission signal attenuation performance,research results show that the acoustic emission signal in the transmission tower in the distance of 7 meters,the use of AE technology for wind turbine tower dynamic real-time monitoring is feasible;the AE signal through the 3welding seam,amplitude AE,the signal rise count,energy and RMS characteristic values with its attenuation,with the increase of the number after ring weld,AE signal conversion occurs in the process of communication,the characteristic parameters of mutation,and the mutation results showed no regularity,this change will lead to the source location of cracks accurate.