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Broken gap is an extremely dangerous state in the service of high-speed rails,and the violent wheel-rail impact forces will be intensified when a vehicle passes the gap at high speeds,which may cause a secondary fracture to rail and threaten the running safety of the vehicle.To recognize the damage tolerance of rail fracture length,the implicit-explicit sequential approach is adopted to simulate the wheel-rail high-frequency impact,which considers the factors such as the coupling effect between frictional contact and structural vibration,nonlinear material and real geometric profile.The results demonstrate that the plastic deformation and stress are distributed in crescent shape during the impact at the back rail end,increasing with the rail fracture length.The axle box acceleration in the frequency domain displays two characteristic modes with frequencies around 1,637 and 404 Hz.The limit of the rail fracture length is 60 mm for high-speed railway at a speed of 250 km/h.