The Method Of Wheel Defect Detection By Electromagnetic Acoustic Phased Array

With the rapid development of china’s operating railways,there are also higher requirements for the quality of train wheels.Timely and effective detection of train wheels can detect hidden dangers in train driving as soon as possible and eliminate accidents in the bud.Electromagnetic ultrasonic phased array detection technology overcomes the shortcomings of piezoelectric ultrasonic detection requires couplant,and can control the deflection and focus of the sound beam,the detection speed is fast,and the internal defects of wheel rupture can be detected in a timely and efficient manner.However,the electromagnetic ultrasonic phased array focused sound field has more influencing parameters,the design is difficult,limiting the development of EMAT phased array technology,in view of the above problems,the impact parameters of the focused sound field are theoretically analyzed,and a 16-channel EMAT focused phased array is simulated and designed.Aiming at the problem of low energy transducer efficiency of electromagnetic acoustic transducer,the size and arrangement of permanent magnets are optimized by establishing multiple sets of permanent magnet magnetic field simulation and comparative tests.A two-dimensional finite element simulation model of a 16-channel electromagnetic acoustic phased array is established,and the influence of deflection angle,working frequency,focus depth,and array elements width on the directivity of the focused beam is studied by using multiphysics simulation,and the parameter optimization scheme of the transverse wave electromagnetic acoustic phased array transducer is given accordingly.On this basis,in order to overcome the shortcomings of beam directivity and signal amplitude reduction when detecting wheels with large curvature,the focusing effect of electromagnetic acoustic phased array in different curvature specimens is studied,and the curved zigzag transverse wave phased EMAT is optimized and designed to improve the beam directivity.Finally,based on Matlab software,the processing and imaging method for electromagnetic acoustic phased array wheel detection array echo signal is designed.Through the filtering of the echo signal,denoising and detection,the characteristic values of the electromagnetic acoustic phased array wheel defect echo signal are extracted.The B-scan RF sampling imaging algorithm was used to image the positioning of 1×5mm air defects inside the train wheels,and the final results proved that the average error of the B-scan imaging algorithm for the detection of 1×5mm rectangular air defects inside the wheels was 4.37%.