Eddy Current Testing Research And Application In Railway Equipments Crack Defect

The railway transportation has the vital significance to the national economy development. During the improvement of the railway transportation ability, and speeding up the railroad speed, we must safeguard the railway transportation safe operation. Crack and the welded joint flaw is one of breakdowns which often occurs in the railroad equipment parts, should use the advanced technical method and carry on highly effective and the reliable examination to it, achieve prevention from accidents before they occur.The eddy current testing is one of five normal Non-destructive testing methods. In comparison with the others, it is easily to implement, can test in higher speed, is extremely sensitive to the surface and the near surface defect, as well as needs not remove the superficial coating, and so on, therefore it is specially suits to detect the defects of parts under the bad working conditions. Considering problem of the railway crack flaw, the eddy current testing method for crack defect is researched in the paper.Firstly, several method of testing crack defect are put forward and compared. Considering of configuration and using characteristic crack, we get the result that the crack defect can be only detected by portable testing instrument. Secondly, the principle of eddy current test is introduced. Based on electromagnetic field theory, some important formulas are deduced. Impedance analytical method is presented, through which we analyze some factors that alter testing coil impedance's value. Then, characteristic frequency of laid test coil is calculated, it is important to select the test frequency.As for the sensor design, a sensor with high performance is designed through modification based on some sensors with better performance. Various factors that influence the sensor performance are analyzed through experiment to optimize the size of coil. Finally used the orthogonal experiment design method, we designated the parameters with reasonable combination, and completed the design of sensor system.As for hardware design, in signal converter, in order to improve the sensitivity, the parameter of signal converter is gotten though math illation. excitation circuit, signal converter circuit, single chip system, demonstration, and alarm part are all given particular analysis and design. As for software design, the software ismodularized, and every module is designed, then each flow chart is given.Portable testing instrument is successfully applied to railway equipments as well as expected. At last, the author summarizes the main conclusions and proposes possible future research directions.