## 1 Introduction
Most of the previous scholars studied the train dynamic response just considering the single-vehicle dynamic model and did not consider the longitudinal dynamics between vehicles. Or, they only considered the fixed connections (without IVS) between vehicles to study entire-train dynamics, which may ignore the influence of IVS on train movement, especially the vibration acceleration of the car body. [PERSON] et al. [15] established a 3D dynamic model of a high-speed train coupled with a flexible ballast track and considering nonlinear couplers and inter-vehicle dampers, and the linear tight-lock vestibule diaphragm was established to simulate the effect of the end connections of neighboring vehicles on dynamic behavior; it was found that inter-vehicle connections have an important influence on the dynamic behavior of high-speed vehicles. [PERSON] [16] studied the longitudinal dynamic behavior of high-speed trains under variable speed by establishing an eight-vehicle train model considering the IVS. However, he did not take into account the curve-passing condition and the influence of crosswinds. Therefore, it is necessary to study the dynamic response and safe driving standards of high-speed trains considering  
Figure 1: High-speed train running on the Lanzhou–Xinjiang high-speed railway under crosswinds. the real IVS characteristics in complex operating environments. It would be advantageous to incorporate the actual IVS characteristics into the vehicle-dynamics model as a nonlinear force element and to evaluate the safety properties of the train under various radii and operating conditions such as traction and braking. Therefore, based on the above engineering background requirements and related research, we established a three-vehicle-dynamics model considering the IVS by using the multi-rigid body dynamics method. The dynamic response of the vehicle when accelerating and decelerating through a curve track under crosswinds with different speeds was studied. The vibration acceleration of the three carriages with or without IVS during traction and braking was analyzed. The physical model of the vehicle, the setting of boundary conditions such as the multibody dynamics model and traction braking force, as well as the validation of the multibody dynamics model of the vehicle, are all in Section 2. Whether to consider IVS for the simulation of high-speed train dynamics under different wind speeds, vehicle speeds, and track radius conditions is discussed in Section 3. The conclusions are drawn in Section 4. In this study, we studied the safe speed and dynamic response of the CRH2 train considering IVS devices in a complex environment. At the same time, the vibration responses of different carriages during the frequent speed changes of the train, as well as the influence of the IVS, are obtained. This provides an important reference for studying the safety of high-speed trains in complex operating environments and provides a more realistic safe operating speed. It can also help researchers to better understand the role of IVS devices in the process of train speed change and provide truer references for the safety basis of the curve passing of the train under crosswinds.