Research On Quantitative Magnetic Detection Technology Of Multi-scale Defects Of Steel Wire Rope

Wire rope multi-scale defect detection is defined as the identification of different types of damage and the analysis of quantitative indicators such as the loss,location,distribution,and corrosion level of the damage,whose purpose is to provide more accurate quantitative parameters for the assessment of wire rope strength.At present,there are the problems of difficult quantitative detection of small-scale defects(e.g.localized flaw and narrow width defects)and difficult identification of complex scale defects(e.g.internal defects and corrosion),which severely restrict the development and application of wire rope non-destructive testing.The thesis adopts multi-sensor fusion technology and designs a variety of quantitative algorithms to realize the quantitative detection of different scale defects based on the requirements of multiscale defect detection and the problems in the existing detection technology.Main flux-Magnetic flux leakage(MF-MFL)fusion method is proposed to improve the low quantitative accuracy of localized flaw,discover the mechanism of the influence of the width of local defects,which effectively decouples the width of the defect from the quantitative measurement,and improve the quantitative accuracy of the important parameter of defect measurement loss.The requirement of excitation width for wire rope magnetic flux leakage detection limits the width of localized flaw.The width of the defect is the main factor,so it is difficult to accurately quantitatively analyze the cross-sectional loss of localized flaw.With the method of axial magnetic leakage compensating main magnetic flux,the effect of defect width is eliminated,and more accurate cross-sectional loss is directly obtained.A quantitative algorithm for the cross-sectional loss of MF-MFL fusion method is proposed based on the main magnetic flux signal and magnetic leakage signal collected by the induction coil and Hall array.Through the simple production of standard defects,not only the quantitative accuracy of section loss of local defects is improved,but also the universal detection of section loss of different types of wire ropes is realized.Radial and Axial Magnetic flux leakage-Main flux(RA MFL-MF)fusion method is proposed to realize the internal and external identification,the positioning of buried depth and quantitative detection of defects with a single incentive method.Internal and external defects are difficult to be distinguished and quantitatively detected because of the concealment of internal defects and the complexity of multiparameter solution.RA MFL-MF fusion quantitative algorithm and Local Binary Patterns(LBP)positioning algorithm are proposed based on the magnetic dipole model and the simulation model of the internal defects to analyze the effect that defect width,cross-sectional loss and burial depth has respectively on magnetic flux and leakage field.The quantitative accuracy of internal defects is improved by optimizing the method of designing the internal standard defects of wire rope.The quantitative accuracy of internal defects has been improved,and the internal and external identification of defects,calculation of buried depth,distribution positioning and quantification of cross-sectional loss have been realized.The magnetic probe detection method is proposed to improve the signal-to-noise ratio of narrow defect signal and solve the problem of difficult detection of narrow defects in wire ropes.It is integrated with MFL detection to realize the detection of defects with different width scales from narrow to wide.MFL detection cannot meet the requirements of narrow defect detection because of the weak detection signal of narrow defects,the influence of background noise,the limitations of existing sensor sensitivity,detection circuit accuracy and narrow defect detection in the MFL detection mechanism.The narrow defect signal is stronger with the detection advantage combined with magnetic tip effect and magnetic balance.By optimizing the structure,the magnetic probe detection is lighter and easier to be integrated with MFL detection equipment.A defect signal extraction method based on Hilbert transform is proposed to eliminate the effect of noise,improve the signal-to-noise ratio of narrow defect signal,realize the detection of narrow defects and reduce the risk of missed detection.The fractal dimension detection method is proposed to distinguish corrosion and achieve the quantification and localization of corrosion.Although the sectional loss detection algorithm can analyze the sectional loss of defects such as broken wires,wear,and corrosion,corrosion cannot be distinguished separately,and it is difficult to evaluate the degree of corrosion through the cross-sectional loss.The corrosion signal characteristics of the wire rope can be obtained through analyzing the distribution,frequency and amplitude of the MFL signal.The special attributes of corrosion are studied with the perspective of fractional dimensions and mathematical methods.Quantitative analysis of corrosion degree by fractal dimensional value and corrosion quantitative detection method of fractal dimensional are proposed to eliminate the influence of detection noise and other defect signals,distinguish corrosion separately,quantify corrosion levels,and locate corrosion positions.