| Summary: | 碩士 === 國立屏東科技大學 === 車輛工程系所 === 96 === In this thesis, the life of rail fatigue crack initiation under multi-train braking condition is explored using the elastic-plastic finite element model. The kinematic hardening behavior of the rail steel is employed throughout the numerical simulations. The temperature-dependent material properties and friction coefficients are also considered in numerical analyses. Numerical simulations are performed to explore the effects of the braking speed, number of cars, axle load and distance between wheelsets. The results show that the crack initiation occurs on rail surface and is located at the maximum value of fatigue parameter, FPmax. The results also indicate that the life of fatigue crack initiation decreases rapidly with increasing number of trains and then gradually approaches to a constant value. The life of fatigue crack initiation decreases as the braking speed increases. Based on the numerical results, a curve-fitted equation is proposed to predict the life of rail fatigue crack initiation, 2Nf , using the number of trains for various braking speeds. The life 2Nf for braking speeds of v=60, 120, 180 and 360 km/h predicted from the results of three trains are only 30%、11%、16%and 35% of the one train situation, respectively.
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