Research On Weld Detection Method Of Wind Power Tower Based On Ultrasonic

Aiming at the problem that the weight of wind turbine,environmental p H,temperature difference and other factors threaten the safety of steel tower welds,the traditional methods generally use ultrasonic and radiographic testing to detect the welds during preparation.After the wind turbine is installed and formed,it needs to climb the tower manually for detection,which has low detection efficiency and requires high labor intensity.In order to reduce the labor consumption in the detection process and improve the detection accuracy of wind power tower weld,this thesis designs a detection scheme for total focusing method imaging and defect quantitative analysis of the weld depth plane by using the linear array of electromagnetic ultrasonic transducers placed on both sides of the weld.Firstly,the ultrasonic testing theory and the weld characteristics and testing methods of wind power tower are studied.When preparing the steel wind power tower,first roll the plate and weld the longitudinal joint,then weld the circumferential joint to make the tower section,and finally assemble the tower section and welding flange on the installation site.Circumferential weld is more prone to stress concentration during the operation of wind turbine,which is the focus of tower weld inspection.In terms of detection technology,compared with piezoelectric ultrasonic transducer,electromagnetic ultrasonic transducer does not need to clean the detection surface and add coupling agent during detection.It is suitable for wind power tower with multiple coatings and other detection environments that need indirect contact with the measured object.Experiments show that the acoustic wave will produce energy accumulation in the weld.Using ultrasonic phased array to delay the signal excitation can deflect and focus the ultrasonic beam.Secondly,the application scenarios of different coils and permanent magnets in the electromagnetic ultrasonic transducer are studied,and the coil,permanent magnet and excitation signal are selected for the electromagnetic ultrasonic transducer required in the scheme.The simulation results show that the designed electromagnetic ultrasonic transducer can stimulate the ultrasonic signal.In terms of imaging,total focusing method is an ultrasonic post focus imaging technology with high signal-to-noise ratio.Experiments show that the imaging effect of total focusing method is affected by imaging resolution,array element number,array element spacing and defect angle.Taking Q345 low alloy steel weld with 30 mm plate thickness as an example,aiming at the problems of scattered linear array elements on both sides,uneven total focusing method imaging field strength and false defects,this thesis uses Hilbert transform to obtain the envelope for original signal processing,uses the reciprocal modulation field calibration coefficient matrix of standard block imaging matrix,layered de averaging optimization and other acoustic path lines to realize the uniform extraction of defects in the detection area and improve the signal-to-noise ratio of imaging.After realizing the frame selection of defects in the imaging,the causes of false identification of defects are analyzed,and the topology thinning algorithm is studied.Using the characteristics of equal path line crossing at the real defects,the identification of true and false defects is realized by extracting the equal path line skeleton.The results show that the detection scheme realizes the total focusing method imaging of wind power tower weld,the optimized imaging signal-to-noise ratio is improved,the defect depth positioning error is less than 0.1 mm,and the average transverse positioning error is 0.5 mm.The defect identification scheme can eliminate false defects.