An innovative numerical model of friction draft gears for heavy-haul trains

A precise model for the dynamic impedance characteristics of draft gears is essential for studying the longitudinal dynamic behaviour of heavy-haul trains. To achieve accurate predictions, this paper establishes a modified viscoelastic impact numerical model of draft gears based on the impact collision characteristics of draft gears and elastic collision theory. To establish the new numerical model, we first construct a 3D finite element draft gear model and derive static impedance force characteristic curves using static pressure simulations. Subsequently, we simulate and analyze the frictional energy dissipation behaviour of the internal components of the draft gear under various initial compression velocity impact conditions, thereby clarifying and establishing the functional relationship between two critical parameters: the energy recovery coefficient and speed ratio coefficient. Finally, by integrating the static impedance force characteristics with this functional relationship, a modified viscoelastic impact numerical model that can effectively describe the dynamic impedance characteristics of draft gears is developed. The modified model, developed through an in-depth investigation of internal component interactions, enables reliable calculation of dynamic impedance characteristics from the essential friction energy dissipation mechanism of draft gears, unlike traditional approaches that focus mainly on external performance. The model’s validity is verified by drop hammer tests.