The Research Of Metal Magnetic Memory Technology In The Flaw Identification Of Mining Steel Rope

Steel rope is a kind of flexible space spiral structure ferromagnetic products and it is widely used in the fields of towing operation, support structure and payload transportation and so on due to its advantage of strong carrying capacity, nice bending flexibility and smooth motion without noise. In the process of coal mine production, steel rope is used in monkey cars, winch and hoists. In the process of long-term operation, steel rope is often affected by uncertainties alternating stress, environmental corrosion, mechanical impact and friction which often result in broken wires, wear, corrosion, stress concentration and other damages of mining steel rope. Coupled with the steel rope itself special structure and the special application status, once the fracture failure of the wire rope comes into being, it will result in serious accidents of mine damages and deaths, and it seriously affects the normal production and life safety of mining workers. So for the accurate identification of broken wires of steel rope and the stress concentration zone, and to avoid and reduce mine accidents, it has important social significance and significant economic benefits.The broken wires and stress concentration are the major reasons of the failures of steel rope. Nowadays, the usual detect method of broken wires is Magnetic Flux Leakage Testing(MFL), but the reasons of the failures of steel rope are extremely complex and involve multiple disciplines and so it is difficult to illustrate the existence of broken wires only according to the relationship between the magnetic field intensity and the damage degree of the steel rope. Thus it has failed to form a complete and effective detection method and detection theory so far, and various existing wire rope testing instruments have been proved low efficiency, poor reliability and poor versatility from the actual testing in the process of coal mine safety production.The paper takes broken wires, the greatest harmfulness and the most common failure form of mining steel rope as the major research object based on a new test method of ferromagnetic material which is called Metal Magnetic Memory(MMM) testing technology. The paper has studied the theoretical distribution of the magnetic field of MMM in the mining steel rope broken wires zone, the denoise method of MMM signal, the design of the detection about sensor circuit and device, the design of the detection about software and the identification of the number of broken wires of the steel rope in the field of theory and experiment respectively.Employing magnetic charges as the model of magnetic dipole, The paper worked out and simulated the distribution of the magnetic field of MMM in the mining steel rope broken wires zone, and simulated the effect figures of broken wire diameter and broken wire quantity for MMM signals. Three methods to judge the damage zone of steel rope has been summarized depend on the literature which has been read.The MMM signal acquired by Eddysun Metal Magnetic Memory Testing Instrument EMS-2003 has been denoised. MMM test technology belongs to the weak magnetic field detection, the acquired signal contains a lot of interference which distorts the real signal. So the paper proposed a improved Ensemble Empirical Mode Decomposition(EEMD) to denoise the signal which filters high-frequency component of the signal. Compared with wavelet transform(WT) denoising method, the EEMD has a high Signal to Noise Ratio. The proposed method is more suitable for MMM signal denoise.To suppress the interference(like outside interference and self shake) of the signal and improve the accuracy of the test of steel rope with the metal magnetic memory technology, a new difference array sensing device has been made by magneto-dependent sensors and the design principle of the circuit and chip selection has been introduced. After using the designed differential array sensor device for the signal acquisition of a self-made broken wires of steel rope. Then the tested data was classified by one-against-one Support Vector Machine to obtain the broken wire quantity, and the result is as good as magnetic flux leakage testing technology and other broken wires identification method.A QT program has been designed for lower computer which employs ARM11 processor and embedded Linux Operating System. The program is used for showing the data of the signal which acquired by the designed sensing circuit, alarm and setting relevant parameters.