Theoretical modelling of a vehicle-slab track coupled dynamics system considering longitudinal vibrations and interface interactions

Traction or braking operations are usually applied to the motor cars or locomotives for acceleration and deceleration, especially in perilous mountain high-speed railways that have complex and large gradient sections. Under such a circumstance, the wheel-rail longitudinal interactions may become more intense, which could induce longitudinal impact on the track structure. In this paper, some new concepts are introduced to account for this rarely concerned issue. Two typical interface interactions for a slab track system are fully considered, involving the longitudinal resistance between the rail and rail pad based on the Dahl friction model, and the longitudinal cohesive force between the prefabricated slab and CA (cement asphalt) mortar layer based on the bilinear cohesive zone model. By introducing system longitudinal vibrations and implementing the interface interactions into the classical vehicle-track system, a novel vehicle-slab track vertical-longitudinal coupled dynamics model is established, and investigated under the combined excitation of rail irregularities and polygonal wheel wear in traction conditions. Results indicate that the developed model is capable of capturing the longitudinal interactions between the track structures and enables considering initiation or evolution of the damage at the interface between the track slab and CA mortar subjected to complex train dynamic loads.