| With the rapid development of high-speed railway,CWR has been widely used,which puts forward new demands for real-time and detection efficiency of fracture state detection of the rail.The detection methods existing are not able to meet the testing requirements.Ultrasonic guided wave can propagate long distances well in rail,can cover the entire cross-section of the rail,and is not affected electrical parameters,which is very suitable for the fracture detection of the long-distance rail.But when ultrasonic guided wave is used for the rail state detection,having multi-modes,dispersion,attenuation characteristics,which will affect the judgment and recognition of ultrasonic guided wave signal detecting,so study the propagation characteristic of ultrasonic guided wave has important significance.A large number of experiments found to have a greater attenuation of ultrasonic guided wave propagating in the rail.It is not only concerned with the propagation distance,but also the external environment factors such as temperature,humidity and so on,which is not conducive to the detection of the rail of long distance fracture state using ultrasonic guided wave.Therefore,this paper mainly,from the propagation distance,temperature,focuses on investigating the attenuation characteristic of ultrasonic guided wave propagating in the rail.By using the characteristic frequency method through ABAQUS/Standard analysis module within the frequency range of 0 to 5000 to study the dispersion characteristic of guided wave in the rail,the study finds mainly to have horizontal bending,vertical bending,torsion,extension and other typical vibration modes.We draw the phase velocity dispersion curve which is consistent with the dispersion curve solving of using semi-analytical finite element method.In this paper,we do simulation of the attenuation characteristic of ultrasonic guided wave,using the ABAQUS/Explicit analysis module.A single audio signal modulated hanning window is selected as ultrasonic guided wave excitation signal,using the method of experimental validation,and we do a detailed study of the attenuation characteristic of ultrasonic guided wave propagating in the rail.Compared simulation results with experimental results showing the ones are basically consistent,so we verify effectively the correctness of the model.The study finds that the peak to peak of the ultrasonic guided wave signal varying with the increasing of propagation distance in the rail exponentially decay and obtain the function of the peak to peak of ultrasonic guided wave signal with the propagation distance.The premises of propagation distance and the form of incentive determined,ultrasonic guided wave signals have smaller attenuation in the rail when the frequency of the excitation signal at 20 kHz and 35 kHz.The premise within a certain temperature range and propagation distance determined,with the external ambient temperature increasingly,the peak to peak of ultrasonic guided wave signal received is greater,the smaller on the contrary.We have access to the function of ultrasound guided wave signal peak to peak with the external environment temperature changing.In view of the attenuation of ultrasonic guided wave propagating existing in the rail,the circuit of ultrasound transducer excitation is improved,and we discover the excitation circuit can effectively enhance the size of signal transmitting,which effectively extends the propagation distances of ultrasonic guided wave,while is conducive to recognition and judgment the signal of the receiving end detecting. |
