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Abstract:In the past, the reprofiling intervals of railway vehicle steel wheels have been scheduled according to designers' experience. Today, more reliable and accurate tools in predicting wheel wear evolution and wheelset lifetime can be used in order to achieve economical and safety benefits. In this work, a computational tool that is able to predict the evolution of the wheel profiles for a given railway system, as a function of the distance run, is presented. The strategy adopted consists of using a commercial multibody software to study the railway dynamic problem and a purpose-built code for managing its pre and post-processing data in order to compute the wear. The tool is applied here to realistic operation scenarios in order to assess the effect of some service conditions on the wheel wear progression.

In order to develop more durable wheel materials to cope with the new specifications being imposed on wheel wear, a greater understanding of the wear mechanisms and transitions occurring in wheel steels is needed, particularly at higher load and slip conditions.The aim of this work was to draw together current understanding of the wear mechanisms, regimes, and transitions (particularly with R8T wheel material) and new tests on R7T wheel material; to identify gaps in the knowledge; and to develop new tools for assessing wear of wheel materials, such as wear maps, that can be used to improve wear prediction. Wear assessment of wheel materials, as well as wear rates, regimes, and transitions, is discussed.Twin disc wear testing, used extensively for studying wear of wheel and rail materials, has indicated that three wear regimes exist for wheel materials: mild, severe, and catastrophic. These have been classified in terms of wear rate and features. Wear rates are seen to increase steadily initially and then level off, before increasing rapidly as the severity of the contact conditions is increased.Analysis of the contact conditions in terms of friction and slip has indicated that the levelling off of the wear rate observed at the first wear transition is caused by the change from partial slip to full slip conditions at the disc interface. Temperature calculations for the contact showed that the large increase in wear rates seen at the second wear transition may result from a thermally induced reduction in yield strength and other material properties. Comparisons made between discs and actual wheels have provided some support for the theories relating to the transitions observed.Wear maps have been produced using the test results to study how individual contact parameters such as load and sliding speed influence wear rates and transitions. The maps are also correlated to expected wheel-rail contact conditions. This improved understanding of wheel wear mechanisms and transitions will help in the aim of eventually attaining a wear modelling methodology reliant on material properties rather than on wear constants derived from testing.

Twin disc tests are commonly used to study wear in railway materials. In this work the implementation of a numerical model of the twin disc arrangement is given, which reproduces the distribution of tangential forces over the contact patch between the two discs. Wear is subsequently calculated by relating the forces and creepage between the two discs using three different wear functions found in the literature. The resulting wear rates are compared with experimental data for discs made of common railway wheel and rail steels. This allows a comparison and assessment of the validity of the different wear algorithms considered.

To improve the efficiency and competitiveness of railway transport, passenger and freight trains should travel faster and have increased payload, without losing the necessary levels of running safety and ride comfort, as well as assuring low aggressiveness on track and minimising the life cycle costs. Hence, the manufacturer’s challenge consists of improving the dynamic performance of the railway vehicles and reducing the loads on the track as well as on the rolling stock components. These objectives can be achieved through optimizing the design of the vehicle, while taking into consideration that the characteristics of the vehicle and of the track may change over time and space, and that they depend on the maintenance conditions of the vehicle and of the infrastructure. This work proposes a computational methodology to study how the varying vehicle component characteristics, on normal and degraded conditions, impact on the vehicle/track interaction loads and on the track damage. The purpose of this study is to trace a path towards a realistic definition of a load mission profile for the structural fatigue dimensioning of the vehicle components. The assessment criteria and the evaluated quantities are defined according to the EN14363 regulation.