DYNAMICS OF WHEEL SET ON RAIL-TRACK

Abstract

The stability of the fast moving trains is the major issue for the dynamics of the rail vehicle systems. The dynamics of rail vehicles is associated with the dynamics of the wheel-sets. In this dissertation, one wheel-axle set is taken into consideration for the study of its dynamics. When the wheel and rail come into contact the load is distributed over a small area of contact. The method of calculating the shape and size of contact patch is based on the well known llertz's theory. As the wheel rolls, it simultaneously generates forces tangential to the plane of contact, known as creep t'orces. Because contact between the two bodies is assumed to occur on a plane, the normal pressure distribution is independent to this tangential force. As a result, for any given material, the dimensions of the contact patch depend only on the load and the curvatures of the wheel rail. When wheel rolls on rail, the steady-state velocity difference occurs between wheel and rail. These are known as creepages. The relationship between creepages and creep forces are given by diflcrcnt wheel rail contact theories. In this dissertation, two wheel rail contact theories, Kalkcr's linear theory and Ilcuristic non-linear theory are applied to determine the creep forces. Creep forces determined by Ileuristic noii-linear model is more than the creep forces determined using Kalkcr's linear theory For the same given conditions. It is therefore considered better to apply Ileuristic theory, which includes two note-linearties, for the creep forces determination and is expected to give the better results. U When wheel set rolls on the rail, it has three type of displacements, lateral displacement, roll displacement and yaw displacement. In this dissertation equations of motion of wheel set are developed using Newtons law. The variation of creepages, longitudinal creepage, lateral creepage and spin creepage for the left wheel and right wheel respectively w.r.t. time are obtained. These variations are useful to get the creep forces at any specific time. These equation are solved by numerical method. 7'hc method which is used here is Runge-Kutta fourth order method. The lateral motion path, yaw motion path, roll displacement path is obtained with respect to time. It is found that all these three motions are oscillatory. iv