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- A novel methodology to automatically include general track flexibility in railway vehicle dynamic analysesPublication . Neves Costa, João; Antunes, Pedro; Magalhães, Hugo; Pombo, João; Ambrosio, JorgeThe interaction between the rolling stock and the infrastructure plays a crucial role in railway vehicle dynamics. The standard approach consists of using a multibody formulation to model the railway vehicles running on simplified tracks. The track model can be rigid, if it comprises only a geometric description of the rail; semi-rigid, if it considers an elastic foundation underneath the rail; or a moving track model, if it comprises a track section underneath each wheelset traveling with the same speed of the vehicle. Despite their computational inexpensiveness, these approaches do not provide a complete representation of track flexibility and disregard coupling effects with the vehicle and among the track components. This work proposes a methodology to automatically generate finite element models of railway tracks comprising its relevant flexible components, i.e., rails, pads, fastening systems, sleepers, and ballast or slab. The finite element mesh is generated based on a parametric description of the track that allows an accurate description of its geometry, including curvature, cross-level, grade, and irregularities. The methodology is demonstrated with a case study in which a track with a complex geometry is loaded with two different approaches. The first approach prescribes moving loads, which is a typical approach used to design or analyze the infrastructure. The second approach applies loads retrieved from the dynamic analysis of a complete vehicle. The results show the benefits of this method and reveal that prescribed loading underestimates the forces resulting from the vehicle dynamics, which is an important issue on curved sections.
- A finite element methodology to model flexible tracks with arbitrary geometry for railway dynamics applicationsPublication . Costa, J. N.; Antunes, Pedro; Magalhães, Hugo; Pombo, João; Ambrósio, J.The dynamic analysis of railway vehicles requires an accurate representation of the vehicle, the track geometry and structure, and their interaction. Generally, flexible track models with curved geometries represent the rails with straight beam elements, which results in a piecewise linear representation of the rails. Consequently, the wheel-rail contact mechanics are not properly captured, and the wheel-rail contact forces present spurious high-frequency oscillations. This work proposes a novel approach to model flexible railway tracks with arbitrary geometries, in which the correct geometry in the wheel-rail contact mechanics is assured by modeling the rails as Timoshenko curved beam elements. This approach improves both the geometric representation of the rails and the accuracy of the wheel-rail contact forces calculation. A realistic operation scenario in which a multibody model of a railway vehicle runs on a flexible track with a curved geometry is used here to demonstrate the novel aspects of this work and then discuss the improvements over the conventional approaches. The results show that the proposed methodology greatly improves the computation of the wheel-rail interaction forces and prevents spurious oscillations from propagating to the vehicle.