Wheel Rim Defects Detection Based On Frequency Domain Synthetic Aperture Focusing Algorithm

Train wheel rim is an important component for train operation.During the production and operation of train,the wheel rim would cause a lot of defects,so the detection of wheel rim is very important.In this paper,the defects in the wheel rim are positioned and quantitatively detected.Based on the study aim,this paper uses the beam synthesis of virtual source technology to enhance the detection energy,and combines the phase shift migration algorithm to study the non-destructive detection of the wheel rim.The typical defects imaging of wheel rim are studied by phase migration algorithm in cylindrical coordinates.The coordinates of refraction points are obtained by Snell theorem,which makes the imaging of double-layer media has better signal-to-noise ratio.This paper mainly studies phase migration algorithm and virtual source technology.Firstly,the model of conventional phase shift migration algorithm is established by solving wave equation,and the simulation,experimental imaging of single-layer and doublelayer media are carried out.Secondly,the phase shift migration algorithm of phase array sector-scan virtual source is proposed.The phase shift migration algorithm model in cylindrical coordinate system is analyzed by using the wave equation in cylindrical coordinate system.At the same time,the virtual source technology of phased array probe is analyzed.The focusing model of sectorscan virtual source is analyzed.The A-scan data is obtained by phased array sector-scan,and the beam synthesis is carried out by using virtual source model.Phase shift migration algorithm in cylindrical coordinates is used to focus image,which greatly improves the speed of the second stage of focusing image and the resolution of imaging.Finally,Field ? simulation and the experiment by Multi2000 are used to verify the effectiveness of the proposed algorithm.Finally,the phase shift migration algorithm of virtual source with wedges is proposed to study the propagation of wave in double-layer media.The first critical angle is used to eliminate the influence of longitudinal wave in the second layer media.The Snell law and the shortest path are used to establish the refraction model,and the coordinates of refraction points are obtained by Ferrari method.After obtaining the coordinates of refraction points,the Ascan data are synthesized by using the theory of beam synthesis in virtual sources and high resolution lines are obtained.In the second stage,coordinate correction is used to make the phase shift migration algorithm applied to the two-layer media with wedges.The effectiveness of the algorithm was proved by the experiment.The algorithm has better signal-to-noise ratio was proved by quantitative analysis.