Research On Eddy Current Detection Of Broken Wires On Wire Rope Surface

Rope is one of the most important bending components and is widely used in key industries.Due to the special environmental conditions in which the rope is used,surface damage is unavoidable,and its primary damage wire breakage is an important factor affecting the safe use of the rope.However,existing methods of nondestructive testing of ropes do not take into account the unique spiral structure of the rope surface.To solve this problem,this paper analyzes and investigates the surface damage of broken ropes based on the eddy current detection principle,using the 6×19+IWS rope model as an object of study to achieve effective detection.Firstly,to cope with the difference between standard skin depth and actual skin depth in eddy current detection,a neural network model was built to predict the actual skin depth based on BP and GA-BP.A finite-element model of eddy current detection based on MATLAB was built to accurately determine the actual skin depth.Based on this,the influence of the coil conductor parameters on the actual skin depth was analyzed using gray correlation analysis to establish a nonlinear relationship.Three quantitative measures and three different materials confirmed the feasibility of the model and laid the foundation for improving the accuracy of disconnection detection.Secondly,the unique characteristics of the alternating peaks and troughs on the cable surface were then qualitatively and quantitatively analyzed for their effect on the eddy current response signal and helix morphology.In order to clearly characterize the influence of the helix shape,a differential bridge scheme was developed.A Comsol-based finite-element model of the coaxial differential probe was developed,and the same intact cable was linearly scanned with two different medium-diameter probes.This was confirmed experimentally,and a detailed analysis using ensemble empirical mode decomposition to extract reliable information from the test scan signal effectively confirmed that the probe type was affected by the helical shape of the rope surface,which was consistent with the simulation results.Finally,to eliminate the influence of the eddy current response signal due to the helical shape of the cable surface,an axisymmetric differential probe was developed using the central symmetry of the cable to detect the cable break surface.Using Comsol,different degrees of cable break detection were obtained.To create a surface simulation model,the results show that the probe through the undamaged position of the cable surface,the voltage amplitude tends to be around 0 V,and after the defective position,the peaks and troughs of the cable in the detection results effectively "M" type variation,eliminating its effect.To verify this,a test apparatus was constructed and three different probes with different degrees of detachment were selected to detect the rope strand surface,and the detection signal showed a variation of "M" at the detachment location,similar to the simulation results.By observing the presence or absence and amplitude of the "M" oscillations in the detection signal,the position and degree of disconnection can be accurately determined.To eliminate the oscillations caused by the increased level of the detection signal,the test scan signal was decomposed and recovered by continuous wavelet transform to obtain three different disconnection degrees corresponding to signal oscillation levels of 18.8%,50.09%,and 16.69%,and to achieve accurate identification of the disconnection degree.