Colloquia

Samenvatting

Train rails are highly susceptible to surface damage and surface defects such as wear and rolling contact fatigue (RCF). Due to this damage, it is of great importance to maintain rails before critical defects arise. The Whole Life Rail Model (WLRM) is a model that can be used as a tool to predict rail damage based on the wear number for a certain situation. The WLRM is formed by a function for wear and RCF, which together show the Damage Index, a theoretical measure indicating rail damage. As the WLRM is completely built upon field results at specific locations, it is not possible to use it everywhere. In this study, it is tried to design a numerical model that can describe the RCF function of the WLRM, such that WLRM's can be developed for each location. 

The fatigue crack formation can be divided into crack initiation and crack propagation. In this study, propagation was mainly investigated. Using an XFEM model, crack growth rates were obtained to determine the Damage Index for certain situations. These Damage Indices were used to reconstruct the RCF curve of the existing WLRM. Results for various situations also showed the influence of different parameters, such as rail radius, train speed, or friction coefficient. It was shown that variation in these parameters changed the RCF curve. Either the threshold or the slope of the curve would change. This made it difficult to set up a single RCF function for a theoretical case. It is however shown that calculation of the Damage Index could be used to determine the dominant failure mechanism and show in which damage regime the selected case can be placed.