Research On Welding Rail Detection Based On Barkhausen Effect

Low-alloy steels,including rails,are widely used,but vary widely from different conditions such as applied load,fatigue wear,and service temperature.The service condition of the material is closely related to its mechanical properties,so it is necessary to pay attention to the information such as load,hardness,and microstructure.Magnetic Barkhausen Noise(MBN)method was used to improve the characteristics of traditional testing.As a non-destructive testing method,it does not cause damage to specimens and the signal strength is closely related to material parameters.Therefore,the MBN signal is used to indirectly reflect material properties.This paper mainly carried out three contents:(1)Based on the pre-built detection platform,the variation in MBN signal-pull stress of DC01 steel under elastic deformation was quantitatively studied.The influence of static load on domain wall motion was qualitatively analyzed from the microscopic point in combination with magnetic domain and magnetization theory.The results show that the tensile stress growth of the elastic range is approximately linear with the growth of the MBN signal.Compared with the peak signal,the RMS signal fluctuation interval is smaller and the linear fit are higher.(2)Based on the wavelet packet decomposition and reconstruction method,the change of MBN signal-hardness of different hardness samples is analyzed from the energy point of view.It is concluded that compared with the traditional wavelet soft threshold denoising,the global threshold partial reconstruction denoising method for Barkhausen distribution has better denoising effect,with an increase of 4.1dB.MBN signal and material hardness change linearly.The greater the hardness of the material,the smaller the corresponding MBN signal;The total energy,energy combination(W2-W4)and energy combination(W2-W8)showed a decreasing trend with increasing hardness and a greater rate of change in the low hardness range.This indicates that the energy distribution is more sensitive to changes in hardness over a relatively low hardness range.(3)The hardness distribution of the surface of welded rail was studied and characterized by MBN signal.Experiments show that the incomplete global pearlite area in the heat-affected zone causes the hardness of the material to change,and the difference in the size of the pearlite structure contained in the base metal,weld and heat-affected zone is also the reason for the inconsistent hardness distribution.