Dynamic behavior of railway Vehicle-Ballasted track system with unsupported sleepers based on the hybrid DEM-MBD method

In order to understand dynamic effect of the unsupported sleepers on railway substructure at the meso-macroscopic scales, this paper develops a dynamics analysis framework combining the discrete element method (DEM) and the multi-body dynamics method (MBD). Firstly, a DEM model of ballasted tracks is built by the PFC software (The full name is Particle Flow Code, which is based on the general discrete element (DEM) framework and code software) for capturing meso-macro mechanical behavior, while a MBD model of electric locomotive is presented for simulating accurately dynamic wheel loads. A numerical simulation program is compiled by the FISH Language to implement two-way coupling calculation between the DEM model and the MBD model. Then, experimental validation is carried out by comparing the dynamic response results obtained from the ShuoHuang Heavy-haul Railway Line field dynamics test with the simulation results adopting a hybrid DEM-MBD model and the classical railway vehicle-track hybrid dynamics model (VTCD model) known as Zhai’s model. Finally, the hybrid DEM-MBD model is used to simulate dynamic responses of the locomotive and ballasted tracks considering 0 ∼ 5 pieces of unsupported sleepers. Simulated results show that the acceleration of 1st and 2nd wheelset begin to increase when running to the position of one sleeper-space in front of hanging area and increase to the maximum when running to the edge of hanging area. In addition, it is necessary to pay attention to the variation of acceleration amplitude near the characteristic frequency excited by the distance between bogie pivot centers. The contact stress in well-supported area adjacent to both ends of hanging area increases greatly when the number of unsupported sleepers is greater than 3.