| The fatigue of wheel/rail contact is the problem which the micro cracks form in the surface or sub-surface of rail due to the effect of cyclic force between wheel and rail. The micro cracks extend and lead to large pieces of stripping or rail fracture. With the increase of railway traffic volume and train speed, wheel/rail contact fatigue damage is becoming more and more serious, especially in high speed heavy lines. Therefore, by studying the rail surface crack can understand the mechanism of fatigue and fracture more clearly, improving the rail fatigue resistance, prolonging the service life of rail. This can reduce not only the operating cost but also the risk of operation.The finite element software ANSYS was used to study the fatigue problems of rail with surface crack in this article. The two-dimensional finite element model of rail was established. Firstly, the principle of ANSYS to calculate the factor K was studied and the correctness of the calculation result was verified. Then the influence of different factors on the propagation of crack was analyzed. The factors included axle load, friction, friction coefficient, crack angle and so on. The following main conclusions were got in this paper.1.The accuracy of K calculated by ANSYS can reach99.9%in the linear elastic range. When the yield area of the crack tip is very small, the effect of plastic area may be ignored.2.The contact pressure from Hertz theory has the following defects, such as narrow scope of application, larger result and error accumulation when analysis of wheel/rail contact fatigue problems. The finite element method is an effective method to solve the complex contact fatigue problem of wheel/rail.3.The crack of wheel/rail contact includes sliding mode and opening mode. The crack is closed when the contact area is on the crack, and the crack is open when the contact area approaches or keeps away from the crack. The most dangerous location of opening mode crack is at the edge of the contact area.4.The stress intensity factor KⅠ increases with the increase of axle load. In the fraction free state, KⅡ accounts for5%of KⅠ. In the pure rolling state, KⅡ accounts for20%of KⅠ. In the full sliding state, KⅡ accounts for55%of KⅠ. The fatigue of wheel/rail contact increases significantly with the effect of the friction, but the influence of friction is based on axle load. 5.The major damage of crack is opening mode when the crack angle is greater than75°. The major damage of crack transforms into the mixed mode including sliding mode and opening mode when the crack angle is30°~75°. With the increase of the crack angle, the stress intensity factor KⅠ increases, but the KⅡ decreases. The rate of crack propagation with60°angle is the fastest. |
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