Dynamic impact of sleeper unsupported defects on the heavy haul locomotive-ballasted track coupling system

In this study, a dynamics analysis framework combining the multi-body dynamics method (MBD) and the discrete element method (DEM) capable of accounting for sleeper unsupported defects is proposed. Different sleeper hanging defects (e.g., number of unsupported sleepers and the hanging height) is an input for an analysis of the heavy haul locomotive dynamic behavior and related ballasted bed degradation in terms of ballast particle wear. Simulated results indicate that the sleeper hanging defects dramatically increase the average contact stress underneath the well-supported sleeper adjoining the sleeper hanging area and the corresponding ballasted bed stress, indicating that the unsupported height should be suppressed within 5 mm even if only there exist single or two consecutive unsupported sleepers. When occurring minor sleeper unsupported defects and not being maintained in time, the vibration acceleration and dissipation energy of the ballasted bed will further increase sharply, which will aggravate the wear of the ballast particles and may change the particle size distribution of the ballasted bed or even pollute it.