Numerical simulation of crack propagation and wear in rails

Licentiate thesis, 2010

This thesis is concerned with rail deterioration due to Rolling Contact Fatigue (RCF) and wear. Focus lies primarily on numerical modelling and prediction, with the long-term objective of developing tools to be used for specifications and planning of rail maintenance. In the first paper, a framework for the simulation of crack propagation is proposed and various aspects of it are discussed. The formulation sets out from the concept of material forces. Within the framework three different crack propagation strategies are suggested, all derived from a common crack propagation model. These strategies are evaluated in two numerical examples, where it is shown that they produce similar results and are robust with respect to time discretization. In the second paper, a numerical procedure for calibrating a wear model, based on results from a wheel--rail test rig, is presented. The procedure is capable of accounting for profile change due to both plastic deformation and wear. Besides Finite Element (FE) simulations of rail deterioration, the suggested procedure also includes simulations of wheel--rail dynamics using Multi Body Simulation (MBS) software in order to find contact locations and relative movements between rail and wheel. Quantitatively good agreement is obtained between simulations and experimental results in terms of worn-off area and shape of the worn profile. It is also shown how the conformal contact between the rail and the wheel gives a high sensitivity regarding how often the rail profile needs to be updated in the MBS simulations.