Research On Formation Mechanism Of Contact Fatigure Crack Of High Speed Rail Steel

With the fast developing of national economy, there is no way to avoid the high speed of train. And the fatigue damage of rail is more and more serious due to the development of the high speed railway. Therefore, it has important significance for the safty operation of high speed railway to study on the fatigue crack growth behavior of the rail.In this paper, two kinds of methods are used in the study of fatigue crack growth behavior of the rail, respectively test and numerical simulation. The test is finished by using JD-1rail-wheel simulating machine, and the numerical simulation is carried out by ANSYS and LS-DYNA software. According to the results of test and numerical simulation, main conclusions are drawn as follows:1. The width of the pre-crack has great influence on the growth behavior of fatigue crack when the length of crack and other parameters are identical. The pre-crack with greater width is easier to grow and has a faster growth rate in the crack propagation. In fact, the width of crack is much smaller than the length, so using the appropriate processing method to get the pre-crack with the width which is as small as possible in order to simulate the actual growth behavior of fatigue crack in the condition of the laboratory. At the same time, studying on the growth behavior of fatigue crack, especially the remaining life prediction, the result of calculation is safer using the width which is greater than the actual condition.2. There is the stress concentration at the tip of the pre-crack, the maximum equivalent stress and strain at the pre-crack tip and its both sides where the crack intitiates usually. The direction of the growth is not the same with the pre-crack, it’s easy to change or even branch when the growth arrives at a certain extent.3. The results of the simulation of the crack growth show that, the direction of the growth is different from the pre-crack whether in the two-dimensional or the three-dimensional simulation, and the crack propagation is at a certain angle, although it has the symmetrical structure and boundary conditions.4. Compare the results of test with numerical simulation, the crack growth path is almost the same. Because the test is influenced by the external factors and there are some assumptions in the theoretical calculation, a few of subtle differences exist. Using numerical simulation technology can do some research and anslysis on the crack growth behavior, not relying on the experimental results and relevant experience completely. It has some certain significance for saving research cost and providing guidance for the further study.