Analysis On Wheel-Rail Contact Models And Wheel Wear

Up to now, there are few numerical procedures which can be used to predict the wheel and rail wear reliablely. However, with the rapid development of computer technology, vehicle/track coupled dynamics, wheel/rail contact dynamics and tribology, it is possible to apply numerical simulation to predict wheel/rail wear. The main objective of this thesis is to present a numerical procedure to simulate the wheel profile evolution due to uniform wear. Such a tool is also useful for the wheel maintenance and parameter optimisation of wheel/rail system. More specifically, this method can be used to estimate wheel reprofiling frequency, optimize wheel-rail profile and running gear suspension parameters, and identify the effect of wheel profile variation on the vehicle dynamic responses.The main research included in this thesis is as follows:1. The recent studies on wheel-rail interaction and wear in China and abroad are reviewed, and the ways and simulation methods for studying wheel wear are introduced.2. The vehicle dynamic modeling method using SIMPACK and the parameters related to wheel wear volume are discussed, which is the preparation work for solving the wheel/rail contact forces later on.3. The calculation methods of wheel/rail contact forces are extensively studied, that includes Kalker linear theory, Vermeulen-Johnson theory, Shen's theory, Kalker simplified theory (FASTSIM), Zhang and Knothe theory, and Polach's theory. The differences between these theories under given conditions are studied, and the reasons of the resulted differences are analysed in order to find out the features of oneselfs and the application scopes.4. The semi-Hertzian contact theory is investigated, in which the contact zone is determined based on the the method of virtual penetration between wheel and rail. This method is indroduced according to Hertzian theory and can be used for non-Hertzian contact force calculation. The formula of the normal and tangential forces is given, and the calculation time is shortened due to the non-iterative calculation. At the same time, the calculation accuracy is maintained comparied with FASTSIM. 5. Several wear models are studie. The characteristics of different wear models are analysed.6. The wear volume distribution in the contact area after the wheel rotating one cycle is given. Incorporating the vehicle dynamic model, wheel/rail contact force model with the wear model, the wheel wear profile after several ten thousands kilometers' operation is simualted. Finally, it is trying to pursue the measures to reduce wheel wear.