# Research on Response Postures of Subway Train in Straight Line Collision
## 1 Introduction
They obtained the different dynamic response and analyzed the derailment mechanisms during the collision process, including the behaviors of pitching, yawing, and overturning of the vehicles. [PERSON] et al. [17] used a combined simulation method of nonlinear finite element analysis and multi-rigid body dynamics to analyze the climbing behavior of a three-car train collision. They found that factors such as train mass, center of gravity height, and pitching frequency significantly affect the climbing behavior in a collision. [PERSON] et al. [26] established a multi-body dynamics 3D computational model of a twenty-car train to study its collision behavior. They discovered that when the train collides with rigid obstacles either head-on or at an angle, the train exhibits climbing, arching, and lateral buckling behaviors. In recent years, some researchers have begun to focus on the response postures of trains under asymmetric collision scenarios. [PERSON] et al. [27] analyzed train collisions at railway-road intersections and pointed out that derailments are more likely to occur on curves with smaller radii. [PERSON] et al. [28] used a 3D model of a four-car train to analyze the collision process of coupled trains with an inclined rigid wall, proposing that different collision angles affect the damage modes of coupled trains. [PERSON] et al. [29] took a metropolitan subway train as the subject and analyzed the influence of the initial state at the single-car level on the collision response under four typical geometric attitudes using a three-dimensional head-on collision model of a four-car train. However, the aforementioned studies simplified the entire or most of the train cars as rigid bodies or mass points, which improves computational efficiency but neglects the energy dissipation of the carriages during asymmetric collisions at higher speeds. Based on the extensive research results of projects such as SAFETRAIN and SAFETRAM, the EN15227 standard \"Requirements for the Collision Resistance of Railway Vehicle Bodies\" [30] has been developed. This standard is primarily referenced and applied in Europe and Asia. It specifies the general methods for testing railway vehicles, definesthe characteristics of the reference obstacle models used in collision scenarios, and outlines verification methods to confirm whether the vehicle's passive safety performance meets the standards. The British standard [31] requires that the collision-resistant structural design of all railway vehicles must comply with EN15227. The three-collision scenarios defined in the International Union of Railways (UIC) standard system under UIC660 [32] also overlap with the content of EN15227. In contrast, the Japanese JIS E-series standards do not provide clear provisions on collision scenarios. The U.S. standards for evaluating the collision resistance of subway trains are similar to EN15227 [33], but with speed requirements of 24 km/h and 40 km/h. For locomotive vehicles, the impact conditions involve collisions with different types of obstacles, head-on and at an angle [34]. The Russian standards for passenger locomotive collision scenarios differ from EN15227, as they specify impacts with rigid walls and do not differentiate between vehicle types [35]. The collision scenarios for subway vehicles in the aforementioned standards all involve head-on symmetrical impacts. However, with the frequent occurrence of accidents involving side impacts and collisions with obstacles (such as civil defense doors, construction cranes, etc.) during subway operations, such asymmetric collision scenarios, which are more likely to cause derailments, should also receive attention. Based on the above studies, this paper establishes a numerical model of a six-car metro train using ABAQUS/CAE 2021, considering the elastic-plastic deformation of the carriage and the weak nodes of the train front. A one-dimensional dynamic theory model was established to verify the rationality of the numerical model.