The Research Of Numberical Simulation For Elastic Waves In Rails With EFIT

With the continuous improving of railway operating speed, the safety of trains’oprating is also an increasingly important issue, where the detection of track defectis a very important aspect. During the crack propagation in the tracks, the acousticemission signals will produce. Detecting the track defect with the information ofacoustic emission can achieve real-time monitoring without damage to the track.For non-destrucive testing, the numerical simulation of elastic waves is essential.Elastodynamic finite integration technique (EFIT) is a numerical method whichP.Felling proposed in1995. EFIT has high flexibility in complex geometricmodeling and boundary handling. Thus it is suitable for the simulation of elasticwave in the rail.The application of EFIT in the simulation of elastic waves in the rails isstudied in detail. The details of2D-EFIT and3D-EFIT are elabatated. Firstestablished the PDEs of the particle motion in the rails according the relevantknowledge of elastodynamics, and then get the discretzation of the PDEs. Theminimun time and spatial step for the stability conditions are given.Two models with analytical solution and one without analytical solution arepresented. As to the model without analytical solution, the EFIT results arevalidated with finite element method (FEM) software Abaqus.The boundary issues encountered in the elastic wave’s simulation inside therails with EFIT are studied:As to the actual boundary of the rails, stress-free boundary is used. The EFITalgorithm is modified according to the central difference. The simulation andverification of a2D model and a3D-model are implemented. A2-D simplifiedmodel of rail section is presented.The rail line can reach a length of up to several kilometers. Sometimes Acoustic emission information required are involved in only one section, and thenumerical simulation can only simulate finite grids.As to this point, an absorbing boundary treatment is designed. Add some‘absorbing grids’ around the simulation model, with gradual attenuation for themagnitude of speed, stress and other variables in these ‘absorbing grids’, assumingthat the waves and its energy are propagated to infinity through the treatment. Thesimulation proved the treatment achieved the effect of Abaqus, and the value ofgrids near the boundary is closer to the real value.The rail is geometrically axisymmetric. According to the symmetry andantisymmtery of the wave propagation, the processing of symmetric andantisymmetric boeder was designed and implented. Simulation verified the requiredstorage space and time are greatly reduced.