Abstract: The high-speed running stability and curve negotiation performance of rail vehicles lead to a significant contradiction in the demand for the primary longitudinal positioning stiffness of bogies, while the variable stiffness of solid-liquid coupled arm joints provides an effective solution. First, the structural characteristics and operating mechanism of the solid-liquid coupled arm joint for a specific type of rail vehicle are introduced, and its dynamic performance data is acquired through bench tests. Moreover, a lumped parameter mechanical model is established by considering the rubber-liquid coupling effect and nonlinear factors of the joint, and the corresponding simulation program is developed, with further verification conducted through experiments. Finally, a vehicle-joint co-simulation dynamic model is developed to analyze the influence of the solid-liquid coupled arm joint on the high-speed running stability and curve negotiation performance of the vehicle. The research results indicate that the dynamic stiffness of the solid-liquid coupled arm joint increases with the excitation frequency below 4 Hz and then tends to stabilize; when the excitation amplitude exceeds 0.5 mm, the dynamic stiffness rises with the increase of amplitude, while the dynamic stiffness under the 0.5 mm amplitude condition in the frequency band above 4 Hz is slightly greater than that of the 1 mm and 2 mm amplitude conditions at the same frequency. Furthermore, a displacement-related local stiffness increase phenomenon occurs under the superimposed excitation of high frequency and large amplitude. The established model can well reflect the nonlinear characteristics of the arm joint’s local stiffness increase, and the deviation between the calculated dynamic stiffness values and the test results is within 2 kN/mm, which verifies the model’s accuracy. Compared with traditional constant-stiffness arm joints, the solid-liquid coupled arm joint can improve wheel-rail interaction and reduce wheel-rail wear when the vehicle passes through curves. The smaller the curve radius, the more significant the advantages of the solid-liquid coupled arm joint become. Although the vehicle’s critical instability speed decreases slightly, the safety margin remains sufficient.

Key words: railway vehicle, solid-liquid coupled arm joint, physical modelling, experimental verification, dynamic simulation