Experimental Investigation Magnetic Flux Leakage Signal Detection Of15kg/m Rails Under Impact Loading

Metal magnetic memory technology proposed firstly by Doubov, a Russian scientist, is a new technology of nondestructive testing,. Compared with the traditional electromagnetic nondestructive detection methods, it is of many advantages, for example the faster detection speed; unnecessary for external excitation; more compact testing equipment to carry, especially the higher sensitivity to testing stress area.Rail road is major technical equipment to guarantee the safe operation of the railway. In recent years, accompanying with the advancement of high speed and overloading, the problem of rail damage is increasingly serious, thus it puts forward higher request to the nondestructive testing to rail road. Most of the traditional nondestructive testing technology can only detect the damage, besides its accuracy and detecting speed are difficult to meet the demand of the current situation of railway’s development. Metal magnetic memory testing method, as the only effective method to early injury, increasingly draw people’s attention to the application of the steel rail flaw detection.This article explores the rail magnetic memory signal characteristics under the impact load, and we take the proposed damage criteria applied in the preliminary inversion of the impact point location on the rail. Detailed contents are as following:There are specimens of15kg/m rail for the single-point impact and multipoint impact experiments, and after the impact, the magnetic flux leakage signals of the specimen surface was tested. By analyzing the various characteristics of magnetic flux leakage signals, it is proposed the method to the peak signal of normal magnetic flux leakage signals and the gradient peak of tangential magnetic flux leakage signals can be used as the criteria for judging the location of rail impact point. Compared with the magnetic flux leakage signals on the rail surface under impact load and static load, it is found that the signals under impact load is obviously different with signals under static load, besides, to the magnetic flux leakage signals the influence of the background magnetic field and the magnetic field of ferromagnetic loading indenter is greater than the influence of force. It can determine the impact point location even without demagnetization by comparing the signals under conditions of demagnetization and non-demagnetization. By compare the magnetic flux leakage signals, this paper discovered the orientation of measurement has little influence on locating the impact point.Applying metal magnetic memory testing technology to position inversion of impact points on rail surface, it can accurately judge the impact multipoint position. Analysis a variety of signals were used to analyze, proving that metal magnetic memory testing method was qualified to judge the feasibility of locating impact point location, and it is concluded that normal magnetic flux leakage signal peak value is superior to the peak value of tangential magnetic flux leakage signals gradient in judging the impact point of the plane position.