Crack Testing Technology Based On Lamb Wave & Time Field Method And Its Application In Rail Transit

In recent years,rail transit train accidents often occur,threatening the safety of people’s lives,and even bring huge losses to the country and society.Bogie frame and rail are very important infrastructure in rail transit system.The bogie carries the weight of the whole vehicle itself,as well as the weight of passengers or goods,and it is also the running part of the vehicle running along the track.Rail is the main component of railway track,which guides the vehicle forward and bears the weight of the whole vehicle and the huge impact pressure during operation.If the cracks in the bogie and rail are not handled in time,it may cause serious traffic accidents.Therefore,aiming at these two important parts of rail transit system,this paper proposes a non-destructive crack detection method based on Lamb wave time field method(1)The basic principle of Lamb wave and the principle of time distance curve related to time field method are studied.The time distance curves of surface wave and reflection wave with arbitrary interface shape are analyzed.Three signal processing methods of Fourier transform,wavelet transform and Hilbert transform are compared and analyzed;(2)Based on ABAQUS software,the finite element simulation analysis method of the welding seam structure of steel pipe girder of bogie frame is studied.The finite element simulation model of steel pipe girder weld based on Lamb wave is established to analyze the propagation of Lamb wave in the structure and the characteristics of reflected wave.The velocity of each mode in the signal is calculated,and the consistency between the simulation value and the theoretical value is verified.The fatigue crack damage is simulated in the model,and the damage and non-destructive signals are compared and analyzed to verify the effectiveness of Lamb wave in the damage detection of steel pipe girder weld structure.(3)The damage identification method based on Lamb wave time field method is studied.Firstly,the horizontal boundary of the steel plate is analyzed,and the Lamb wave received signal is obtained.According to the time distance curve,the interface occurrence elements are obtained by the time field method.Then the inclined damage is simulated,and the occurrence factors of inclined damage are obtained,which verifies the applicability of time field method.(4)A time field method based on Hilbert transform is proposed.Different types of damage are simulated in the weld structure of steel pipe girder and rail damage detection experiments.The Lamb wave signal of each path is fully used to obtain the arrival time of reflected wave energy peak value by Hilbert transform method,and the damage location is realized according to the proposed time field method.