E.G. Vadillo

A linear model to explain short pitch corrugation on rails

Abstract In the present paper a linear model to predict the corrugation formation on railway rails is described. A feedback process between the structural dynamics of wheelset and track, coupled by the contact mechanics, interacting with a wear mechanism, is proposed to explain the features of short pitch corrugation on rails. The wheelset and brake discs are modelled using the finite-element method with solid-types elements. For the track, the discretely supported model developed by Gry is used. This model, based on wave propagation, combines the finite-element method for describing accurately the rail section and periodic structures analysis to consider the support. In this model, rail section strains are allowed. The track and wheelset dynamics are introduced into the global model by using receptances. The forces’ variations at the wheel–rail contact are assumed small compared with the quasi-static forces and creepages, which are obtained through a theoretical model for bogie curving. A transfer function between the initial wheel and rail roughness and the wear spectra in the contact patch is presented. Finally, the study uses the model described above to explain a specific kind of short pitch corrugation that had shown up on low rail in sharp bends on certain section of railway in the Bilbao area. Antiresonances in the vertical structural dynamics together with high values in the lateral dynamics were identified as the main corrugation formation mechanism.

A Comprehensive Method for the Elastic Calculation of the Two-Point Wheel-Rail Contact

This work shows the method developed to solve the wheel–rail contact problem via a look-up table with a three-dimensional elastic model. This method enables the introduction of the two contact-point effect on vehicle movement using three-dimensional analysis of surfaces, including the influence of the angle of attack. This work presents several dynamic simulations and studies the impact that the introduction of the two contact points on three dimensions has on wear indexes and derailment risk against traditional bi-dimensional analysis. Furthermore, it studies advantages and disadvantages of using a look-up table against an on-line resolution of the problem.

Influence of creep forces on the risk of derailment of railway vehicles

The derailment mechanism in a railway vehicle is a complex mechanical phenomenon which has been, and still is, the subject of intense research activity due to the serious consequences it can entail. Since Nadal deduced his well-known formula, many researchers have put forward alternative equations which all attempt to move closer to the data obtained experimentally. This paper provides a summary of the best known and draws up a new formulation based on the theoretical 3-D study of creep forces emerging from the contact patch of the wheel likely to derail. It also provides an in-depth analysis of the role played by spin creepage, including its effect on obtaining theoretical derailment limits, which are more realistic than those obtained using Nadals formula. Finally, a new derailment criterion is proposed. This new criterion leads to less conservative values than Nadals equation for zero yaw angles. When the yaw angle is high enough, the results obtained are coincident with those predicted by Nadals equation.

Design of an optimised wheel profile for rail vehicles operating on two-track gauges

This article sets out an optimum synthesis methodology for wheel profiles of railway vehicles in order to secure good dynamic behaviour with different track configurations. Specifically, the optimisation process has been applied to the case of rail wheelsets mounted on double-gauge bogies that move over two different gauges, which also have different types of rail: the Iberian gauge (1668 mm) and the International Union of Railways (UIC) gauge (1435 mm). Optimisation is performed using Genetic Algorithms and traditional optimisation methods in a complementary way. The objective function used is based on an ideal equivalent conicity curve which ensures good stability on straight sections and also proper negotiation of curves. To this end, the curve is constructed in such a way that it is constant with a low value for small lateral wheelset displacements (with regard to stability), and increases as the displacements increase (to facilitate negotiation of curved sections). Using this kind of ideal conicity curve also enables a wheel profile to be secured where the contact points have a larger distribution over the active contact areas, making wear more homogeneous and reducing stresses. The result is a wheel profile with a conicity that is closer to the target conicity for both gauges studied, producing better curve negotiation while maintaining good stability on straight sections of track. The article shows the resultant wheel profile, the contact curves it produces, and a number of dynamic analyses demonstrating better dynamic behaviour of the synthesised wheel on curved sections with respect to the original wheel.

Modelling rail corrugation with specific-track parameters focusing on ballasted track and slab track

The objective of this paper is to compare three types of track (high-performance ballasted track, STEDEF and AFTRAV) from the corrugation growth point of view. This work has considered different vehicle speeds and track radii, and the results have taken into account the four wheels of a bogie. These tracks have been studied using finite elements with Nastran–Patran and RACING, a tool developed in Matlab by the authors, which estimates the corrugation growth tendency. The tracks are studied using the finite strip method and the periodic structure theory. Lateral and vertical receptances for track and vehicle have been obtained, as well as the corrugation growth functions. In the paper, the tracks are ranked according to the corrugation development.

Optimization of Track Parameters, Considering Their Physical Dispersion, to Minimize Rail Corrugation

In this paper, the influence on corrugation and therefore on the noise levels, of the most significant track parameters has been examined. After this parametric study, the optimization of the track parameters to minimize the undulatory wear growth has been achieved. Finally, the influence of the dispersion of the track and contact parameters on corrugation growth has been studied. This work is based on the computer application RACING (RAil Corrugation INitiation and Growth) which has been developed by the authors to predict rail corrugation features.