Compressed stability analysis of the coupler and buffer system of heavy-haul locomotives

This paper develops a locomotive dynamic model to study the coupler compressed stability and locomotive running safety under severe longitudinal compressive forces, taking into account a new model of the flattened pin coupler and buffer system employed by heavy-haul locomotives. In this new model, the arc surface contact friction element is built up for the first time to simulate the compressed contact friction process between the arc surfaces of the coupler tail and the following plate. An improved nonlinear mathematical model of buffers and a coupler rotation angle stop element are also included. After validating the presented locomotive dynamic model by comparing its calculated results with test data, simulations are carried out to analyse the influences of the coupler-tail arc surface and locomotive secondary suspension parameters on the coupler compressed stability and locomotive running safety. Results indicate that the friction coefficient and the arc radius of the coupler-tail arc surfaces have a remarkable influence, and that the locomotive secondary lateral stop and lateral stiffness also have a significant effect. Optimising these parameters could significantly improve the coupler compressed stability and locomotive running safety. Finally, a real example of Chinese heavy-haul trains is shown to confirm the importance of the coupler-tail contact friction action.