| The coal mine steel wire core conveyor belt is used as the main transportation equipment for coal mining.Under long-term high-load operation conditions,the steel wire rope at the joint of the conveyor belt is usually prone to twitch,causing the belt joint to break and causing serious economic losses.Magnetic flux leakage detection is widely used in the non-destructive testing of steel cord conveyor belts for its unique advantages,but there are still many deficiencies in the detection of conveyor belt joints.Therefore,studying the law of the distribution of magnetic flux leakage in joints of steel cord conveyor belts and quantitatively evaluating joint twitching has important theoretical significance and application value for the quantitative detection of magnetic flux leakage in coal mine steel cord conveyor belts.Firstly,in order to solve the research problem of the distribution law of leakage magnetic field in conveyor joints,the structure of the joint of the wire rope core of the coal mine,the process of joint breaking and the nondestructive testing principle of the joint magnetic leakage were analyzed,a reasonable magnetic flux leakage magnetic dipole model was established.The theoretical analysis of the distribution of the leakage magnetic field of the first-order joint and its influence on the factors has been conducted.The theoretical distribution characteristics of the first-order joint leakage magnetic flux and its variation with joint structural parameters and related detection parameters have been obtained.Secondly,aiming at the huge bulkiness of the steel cord conveyor belt equipment and the inability of the internal joint structural parameters to be controlled,an automatic three-dimensional magnetic flux distribution detection system was designed to explore the leakage flux distribution of joints.The system includes a joint flux leakage detection system and a three-axis motion control system.The joint flux leakage detection system uses a high-precision Hall sensor and a digital high-accuracy CH-3600 Gauss meter to measure the leakage magnetic field of the joint with high accuracy.The three-axis motion control system uses the multi-axis motion controller SMC6480 to precisely control the positioning and movement of the sensor probe during scanning.Labwindows\CVI software was used to develop the superordinate control software.The automation of space domain acquisition of joint leakage information was realized,which provided a good precondition for the experimental study of joint leakage flux distribution.Thirdly,according to the possible difference between the theoretical analysis of joint leakage and the magnetic flux leakage of the actual joints,experimental joints were made,and the positions of the probes,joints and coordinate directions during the experiment were specified,so that the experimental results were intuitive and reliable.By testing the leakage distribution of the first-order joints,the conclusions in the theoretical analysis of joint leakage are verified,and the complex multi-stage joints are tested experimentally to obtain the leakage magnetic distribution of multi-stage joints.Finally,in order to solve the quantitative evaluation problem of the magnetic flux leakage detection joint twitching of the conveyor belt,according to theoretical analysis and experimental test leakage magnetic distribution of the joints,a joint leakage magnetic peak spacing feature extraction method was designed,and the effective feature extraction of the peak distance between the magnetic flux leakage component Bz of the experimental joint is carried out.According to the correspondence between the length of the joint and the peak spacing of the magnetic flux leakage signal,a quantitative method for the magnetic flux leakage of the joint twitching was developed.Through the quantitative evaluation of the magnetic flux leakage of the experimental joint,the results are compared with the direct measuring distance of the joint twitching.The error distribution range of the quantitative evaluation of the magnetic flux leakage of the joint twitching is obtained.The validity of this method for the quantitative assessment of magnetic flux leakage in the joint and the correctness of this study were verified. |
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