A Study On Wheel/rail Creep Theory By Using Finite Element Method

The development tendency of the railway construction in the world today is serving high speed trains and csirrying heavy load. With the development arise some problems of the wheel/rail performance, the requirement of the train traction for the adhesion of wheel/rail will become more and more strict, and rail corrugation of wheel/rail, rolling contact fatigue and derailment will become more and more serious. The solution to the problems will have direct effects on the railway development. Although the investigations in the problem are concerned with many disciplines, they are all based on the theory of wheel/rail rolling contact, in which the transmission process of wheel-rail contact force is the core.The performance of wheel/rail is the most elementary and most complicated problem of locomotive and vehicle and rail system. It is a 3D rolling frictional contact problem. Some experts and scholars with Kalker as a representative have contributed a lot to the development of wheel/rail rolling contact theory. But their theory hasn't broken the limit of Hertz contact conditions and elastic-half-space assumption, which cannot be used to make further investigation in the problem of, complicated wheel/rail reaction.Lots of engineering applications demonstrate that the finite element parametric quadratic programming method (FEPQPM) is an advanced and efficient method in solving 3D contact problems. In this paper, the wheel/rail 3D elastic and elastoplastic contact problem is analyzed and solved by using FEPQPM, which is based on the parametric variational principle. And the multi-substructure technique is also used. The model is built according to the actual geometric relation. The Hertz assumption and the elastic-half-space assumption in the classical analytical or half-analytical method are completely avoided.In this paper, the 3D FEM models of cone-tread and worn-tread locomotive and vehicle wheels are firstly established, which come into contact with the rail of standard size. There hasn't been any more refined 3D FEM computation model of wheel/rail up till now. The elastic effect of crosstie and roadbed is also considered. Lots of the elastic contact problems and elastoplastic contact problems are computed. A lot of data such as the wheel/rail contact force; contact status and wheel/rail stress distribution are obtained. After detailed analysis of the computation results, some lawsIIIare obtained on how the structures of locomotive and vehicle and some applied parameters affect the performance of wheel/rail contact.The computation model of two-point contact (for cone-tread) and conformal contact (for worn-tread) resulting from wheel flange close to rail is firstly established in this paper. A detailed analysis is made of the wheel/rail contact force, contact status and wheel/rail stress distribution on the different action of tractive forces and transverse forces. We draw some important conclusions, one of which is that the locomotive adhesion performance will decrease with the increase of transverse forces between wheel and rail.The method of computing creep using displacement of wheel periphery and the length of contact surface is applied. The curves of wheel-rail longitudinal creep forces and creepages are drawn for different load case factors. The effect on wheel-rail longitudinal creep forces and creepages of friction coefficients, axle loads, transverse forces, wheel/rail geometry surface, the relative position of wheel/rail and plastic deformation is also studied.The research here is a fundamental and complete application of FEM to wheel/rail 3D elastic contact and elastoplastic contact problems. The results show that this research work is not only feasible, but it also has some advantages over the classical methods. It will have a greater development prospect.