Qun Ma, Wei Wei, Yuan Yao, Jiawen Sun
On China's Baoshen Railway, 10,000-ton heavy-haul trains navigating continuous steep grades and sharp curves are frequently plagued by violent longitudinal surge, repeatedly leading to coupler breakage. Traditional macroscopic models have limitations in revealing the multi-scale coupling mechanism of this phenomenon. To the end, a multi-scale coupled simulation model was established, bridging train longitudinal dynamics, multi-body locomotive dynamics, and real-time adhesion control. The analysis indicates that train surge is intimately linked to the nonlinear dynamic instability of the wheel-rail adhesion interface. The impact of locomotive configuration is highly conditional: under constant per-locomotive tractive effort and high adhesion-utilisation conditions, adding locomotives amplify the longitudinal surge response, increasing the maximum coupler force by 41.2% in a 4 + 0 consist compared with a 3 + 0 consist. However, distributing the same traction demand across more locomotives reduces the adhesion utilisation of each locomotive and improves the longitudinal dynamic response. Moreover, although adhesion control effectively caps peak transient loads (yielding an 18.4% reduction in maximum coupler force), its frequent torque adjustments introduce repeated low-frequency traction disturbances into the train longitudinal system. This strengthens the coupling between adhesion-control intervention and longitudinal coupler-force fluctuation, exacerbating the surge tendency and driving a severe 58.4% surge in coupler force fluctuation amplitude.