Simulation Study On Growth Behavior Of Rail Tread Oblique Crack

As a type of rail defects, rail tread oblique crack has been paid extensively attentions in recent years. It will cause rail transversal failure and endanger the traveling safety if it severely develops. Several accidents resulted from rail transversal fractures caused by tread oblique cracks have already taken place at home and abroad.With large finite element software ANSYS, the solid model of typical rail tread oblique crack has been built according to its characteristic observed in field, and the influences on growth behavior of rail tread oblique crack under various load cases, including three-dimensional contact force, contact position, axle load, wheel / rail frictional coefficient, steel strength, travel velocity, etc, have also been simulated and analyzed.Useful results have been obtained: Vertical force mainly affects all three types of stress intensity factors K, lateral force strongly affects II, III types of K, and longitudinal force chiefly affects II type of K. In the range of a quarter of sleeper spacing from the oblique crack along longitudinal direction of rail, the wheel load affects crack growth outstandingly, while the rest can be ignored. Deviated from the centre of rail head less than 4.5mm along transverse direction, the wheel load affects crack growth inconspicuously, while crack growth becomes rapid between 4.5 to 7.5mm and enormously expedites beyond 7.5mm; loaded car affects crack growth much more obviously than empty car; different axle loads affect crack growth similarly; lower wheel / rail frictional coefficient, higher steel yield strength and travel velocity accelerate crack growth. In addition, two typical field cases including straight line and 800m radius curve of the outside rail have been calculated; the growth behavior and mechanism of rail tread oblique crack has been explained, and bend shear stress is pointed out as the main factor of controlling rail tread oblique crack to propagate and turn around.These study results are helpful for qualitatively mastering and quantitatively evaluating the growth behavior and influencing factors of rail oblique crack. They can also give maintenance and safety monitoring of rail theoretical instructions.