Rail vehicle impact analysis: A critique of the suitability of the rigid wall model and the assumption of symmetrical behaviour

Abstract

This paper studies the accuracy of rigid-wall (stonewall) and symmetric models in rail vehicle impact stability. The investigation is based on modelling results and theoretical analysis. The theoretical investigation consists of a mechanical description of the conservation of energy transformation and instability of train impact due to irregular structural collapse and loose coupling patterns. It is shown that an unstable response is a common consequence in vehicle impacts and the corresponding stiffness amongst cross-sections has a strong effect on collapse stability. The modelling investigation summarises impact simulations of a cab vehicle. This illustrates the pitfalls of the rigid-wall and symmetric models as follows: firstly, using a rigid wall in modelling could mask irregular deformations and lead to overestimated crashworthy performance behaviours; and secondly, symmetric impacts could lead to asymmetric deformations resulting in crucial irregular responses of rail vehicles being missed. This paper explores the irregular responses of rail vehicles in train collisions and highlights the relevant issues which might be overlooked when conventional static approaches are used in dynamic scenarios. It is anticipated that the paper will provide increased insight into impact mechanics of rail vehicles and promote a rethink about the influence of characteristic behaviours in dynamic responses resulting in a more accurate representation.

Evaluation of coupled finite element/meshfree method for a robust full-scale crashworthiness simulation of railway vehicles

“…The observation of the underframe deformation is one of the criteria to assess the reliability of a simulation result. According to the analysis method of a rail vehicle impacting with a rigid wall proposed by Xue et al, 7 the underframe in our model should produce a deformation of bending downward in the predefined scenario due to friction force of contact area and the downward pitch moment of the leading vehicle. The underframe deformations of three cases with both methods are shown in Figure 10.…”

“…7 Instead, a full-scale vehicle model is constructed by removing some components that have very little influence on the simulation results, including underframe equipment, weld parts, cowcatcher and so on from the complex computeraided design (CAD) model. Some key components related to impact absorption, such as car body, energy absorber, draft sill, side sills and so on, are retained so that the model can yield reliable simulation of a real crash performance.…”

“…MB is generally used to simulate the dynamics of rigid bodies and can only provide limited accuracy for complex structures such as rail vehicles, while FEM can simulate the nonlinear large deformation in the case of vehicle crash, offering detailed analysis of different models and accurate simulation results. [6][7][8] However, the accuracy of the FEM strongly depends on the quality of the meshes. 9 In order to improve the accuracy of simulation results, conventional approach is to increase the mesh density of the input model.…”

Development issues for impact safety of rail vehicles: Robustness of crashworthy designs, effect of structural crashworthiness on passenger safety and behaviour characterisation of vehicle materials

“…This section targets the two types of questions from the reviewers of the previous two papers 10,11 on the effects of the parameter variations of vehicles and scenarios. One is the robustness of the simulation result when vehicle configuration is changed.…”

A data-driven dynamics simulation framework for railway vehicles

“…Taking the complexity of the whole train into consideration, although using the FE method can build a detailed model for each substructure and reach a high accuracy [16][17][18], it is inevitable that the FE method demands for a large amount of time, especially for those involved in an iteration and optimisation process for designing train's structures. Moreover, when it comes to the highly nonlinear dynamic problems (e.g.…”