Experiment Research On Nondestructive Testing For Wire Ropes Based On Weak Magnetic Flaw Detection

The weak magnetic inspection of wire ropes flaw is to detect the leakage magneticfield in the defects when the wire rope is magnetized to the left of the maximumpermeability point. The characteristics of weak magnetic inspection are high detectionspeed and high sensitivity of sensor. It is possible to make monitoring on reality. It is oneof the latest techonology in the field of magnetic testing and a hot topic in the world.Basedon the analysis of advantages and disadvantags of the existing methods of wire ropestesting, this paper presents a weak magnetic inspection program. In order to confirm thefeasibility of the method, some theoretical analysis and a great deal of experimentialstudies are done in this paper.According to the theory of analysis of magnetic charge, the magnetic dipole modelsare built. Based on the weak magnetic inspection,the method of magnetic circuit magneticpermeability is adopted to calculated the parameters of the experimental platform for wireropes nondestructive testing. The experimental platform based on virtual instrument isbuilt, the program for data acquisition is compiled. On the platform,the wire ropes withmany broken wires whose diameters are30mm and8mm and specification is6×19S+SFare detected. The measured curves which are identical with defects are acquired. Theresults further demonstrate the feasibility of weak magnetic detection technology.According to the theory of orthogonal experiment, the orthonogal test table L16wasused to study the impact on the test result when the experimental factors are in differentlevels. The best parameters of magnetic circuit system are obtained for the testing wireropes.Based on wavelet analysis technique, the program for data analysis is written bycalling Matlab in LabVIEW with Matlab script node. In order to extract the abnormal dataeffectively, the amplitude super threshold algorithm is used to analyze result files.According to the theory of magnetic dipole, by extracting the peak to peak value, thenumber of broken wires is calculated. By camparing the results and scrap standard of wireropes, whether the wire rope should be replaced is determined.In order to make the data acquisition and processing done by a test system, an interface for wire ropes NDT is written based on LabVIEW2010. It includes dataacquisition, reading and analysis. It can record and analyze data, form experimentalreport and other function with some simple operation.The feasibility of weak magnetic inspection and the reliability of test result areproved further by inspecting a scrap wire rope with some fatigue broken wires whosediameter is25.4mm. The research achievement provides in this paper some scientific basisfor the design of the testing instrument.