Surface Defect Detection Of Bearing Rollers Based On Laser Diffraction Measurement Technology

At present,most of the bearing production enterprises adopt artificial visual method,magnetic particle detection,eddy current testing,acoustic vibration detection,ultrasonic testing,and machine vision inspection for surface defect detection of bearing rollers.Each method has its own advantages,but there are also some disadvantages.For example,these methods have limitation in the detection of micro defects.Aiming to provide a practical method for the defect detection of high-precision bearing rollers,a bearing roller surface defect detection system based on laser diffraction measurement technology was investigated in the thesis.According to single slit Fraunhofer diffraction theory,the proposed system realizes the amplification of micro surface defects of rollers by transforming the changes of the roller appearance to obvious changes in fringe spacing,which can solve the difficult problem of detecting this kind defects,and greatly improve the detection accuracy.The developed system mainly includes the light source,lens,CCD camera,and the mechanical structure module.It can be applied to implement surface defect detection of different type rollers,making it have wide applications.According to the testing environment of the system and the defect features shown in the diffraction fringes,a standard of denoising quality was proposed,which requires removing the noise in the diffraction images and detailed edge features of stripes but retaining the fluctuation characteristics of diffraction stripes.After comparing some denosing algorithms,the method based on anisotropic diffusion equation was adopted to filter the original images.The method not only could filter the noise,but also could remove the useless information formatted by the surface roughness of rollers,which may influence the detection result.In this thesis,a method by extracting and analyzing the fluctuation characteristics of the 3-th dark stripes in the images collected by the CCD camera was adopted to recognize the surface defect of rollers.According to the light intensity distribution characteristics of Fraunhofer diffraction field,a 2D derivative-sign binary image method was used to obtain diffraction fringe center lines.The boundaries of the binary fringes in derivative-sign binary images are center lines of original fringes.This method can avoid the influence of uneven illumination to the result.In order to filter the isolated noise points and noise holes,a new method was proposed to denoise the derivative-sign binary images.It can,to some extent,eliminate the effect of noise on the subsequent separation of skeletons.Meanwhile,a new method was presented to detect the edge of the derivative-sign binary images.This algorithm has the advantage of fast execution,and the separated edge curve is single pixel width that there is no need to do follow-up processing.Finally,the detection of the surface defects of bearing rollers can be achieved by separating the center lines of the 3-th dark fringes and analyzing their fluctuation characteristics.In order to realize the detection and recognition automatically,a user control interface based on GUIDE function of MATLAB was developed.It not only can control the entire detection progress,but also can display the testing results.The measurement resolution of the developed system can theoretically reach 0.05?m.Therefore,it is very suitable for micro surface defect detection of bearing rollers.The types of rollers which can be detected include cylindrical rollers and tapered rollers.Research on surface defect detection system of bearing rollers based on laser diffraction measurement technology provides a reliable and effective tool for bearing production enterprises to detect and evaluate the surface defects of bearing rollers.