Fem Simulation Study For Ultrasonic Guided Wave Evaluate The Defects Of Rail Head

Rail head defect is responsible for many railway accidents. Critical surface crack detection in the military is a major challenge for the railway industry. Conventional testing methods have been proven not to be sufficiently reliable in this case, so the purpose of this work is to develop an alternative or complementary screening method. The pulse-echo method is to scan the low-frequency surface wave probe deployed along the track. Dispersion curves and defect propagation characteristics of this study guided wave detection in the flat, and compared with the experimental results, the transmission characteristics of a particular work is as follows:First, this paper describes the current situation at home and abroad guided wave testing, introduces the guided wave theory, visually guided wave propagation studies and group velocity of the steel rail head dispersion phenomena.Secondly, the use of guided wave propagation board basic processes explained in this article ABAQUS simulation and finite element analysis to the flow chart, the guide plate finite element simulation of wave propagation in the view that a simple exposition of the contents of each step, especially reward selection problem, we choose Harming window signal, can effectively improve the degree of recognition of the simulation results, and to prepare for the numerical simulation results back.Then, this paper by the two-dimensional finite element modeling, and elaborate on the specific parameters of board guided by numerical simulation of wave propagation. We analyses the guided wave dispersion phenomenon and the product of Frequency and the thickness range of10MHZ-mm simulation results, and by calculating the size of the group velocity, and with the finite element simulation fastest mode of comparative analysis of the results of the theoretical results. Wave group velocity relative error of0.66%, to verify the accuracy of the finite element simulation. Then, We conducted a finite element simulation of defective board structure defects were defective and non-defective compare models and analyze the impact on board guided wave propagation from defects affected. Used in the defective board guided wave propagation encountered flaw echo to determine the location of the defect. Position accuracy of0.54%. Finally, at the rail head made specific parameters elaborated dimensional finite element numerical simulation of wave propagation modeling and guided, including meshing time step and determine, and we analyzed the phenomenon of guided wave dispersion, is the product of20kHz frequency simulation results and analysis of the fastest modes of finite element simulation results by the size of the group velocity, and the results were compared with theoretical calculations, wave group velocity relative error of4.19%. We then conducted a structural finite element simulation of defects in rail head, were defective and non-defective compare models and analyze the impact of the rail head guided wave propagation in from defects affected. Used in the defective board guided wave propagation encountered flaw echo to determine the location of the defect. The location accuracy is4.6%. And research the frequency of the rail head model optimization selection, when exploring the spread characteristic of the rail head model, the best choice is greater than20KHz and less than40KHz. When in the presence of defects, the comparison between the rail head model20KHz excitation signal is the most beneficial to computation and observation, Guided wave in the rail head with defect model of defect position selecting excitation signal center frequency of50KHz, can get the most accurate observations.