| With the increase of rail speed and traffic, the speed of rail flaw detection requirements are also raising, thus the previous static rail flaw detecting method needs to be improved. At the same time, the rail defects on high-speed railway mainly appearance as slash-like contact fatigue cracks, and a series of similar crack often emerged at the same place which became the main factor to the safety of railway. Compared with other non-destructive testing technology, Magnetic Flux Leakage (MFL) is non-contact and easy to realize online testing, it becomes a feasible way for rail crack detection. Therefore, high-speed rail MFL testing research is of great importance.Firstly, the paper describes the significance of high-speed rail non-destructive testing research, and the common rail detection methods are also discussed. Compared with other rail testing methods, MFL has the advantages on high speed on line rail defect detecting. Based on the domestic and international non-destructive rail testing and magnetic flux leakage detection research, the paper focus on the simulation and experiment, including the theory, system modeling, numerical simulation and experimental analysis and so on.Based on the electromagnetic fundamental theorem and Maxwell equation, the paper discusses the speed effect on magnetic flux leakage testing. In the system modeling, the paper introduces the finite element method and Ansoft Maxwell software. During the transient simulation, the paper divide simulation into geometric modeling, material selection, exciting loading, boundary condition choosing, dynamic simulation realize, meshing and post-processing analysis seven steps to build high-speed rail magnetic flux leakage model.In numerical simulation, system parameters such as yoke shape, lift-off distance, magnetic yoke and rail distance and sampling interval are optimized. The paper focus on the study of speed effect of MFL testing and oblique crack detection, including speed effect on MFL signals and crack depth and width detection, the difference between the rectangular and oblique crack, oblique crack depth and width detection, continuous multiple oblique crack detection. Based on the research above, the basic crack identify methods are also discussed.Finally, the paper discusss the experimental platform building and the crack specimen designing. Through the crack depth, width and inclined crack detection experiments, we obtained the same conclusion with simulation results, thus verify the correctness of the simulation analysis and feasibility of high-speed rail MFL testing. |
