Examination of rails on which large rolling contact fatigue cracks have developed, either at the gauge corner, or on the rail head, typically reveals that the cracks have not developed in isolation, but occur at intervals along a length of track. Individual cracks are typically separated from one another by around 5 millimetres, although the reasons for this spacing between the cracks are not yet understood. This paper presents an investigation into the interaction between adjacent long cracks (tens of millimetres) that are at the beginning of their bending stress driven propagation phase. Based an a boundary element model of a rail in bending (the primary driver of long cracks in rails) it has been found that stress intensity factors are reduced to between 40% and 55% of the value predicted for a single crack when multiple cracks are considered. Using a crack growth law developed for mixed mode loading of rail steel, this translates to a reduction in crack growth rate to around 27% of it value for single crack models. This reduction is large enough to have a significant effect on the predictions of integrated rail wear and crack growth models. The majority of the stress intensity factor reductions predicted can be found by looking at the central crack of a three or five crack model, but at the expense of increased computing time some refinement was produced by enlarging the model to include 7 cracks. Further investigations will concentrate on the effect of crack inclination angle and different crack separations, multiple cracks at the gauge corner and on multiple cracks in ratcheting and contact stress driven crack growth.


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    Title :

    Growth of multiple rolling contact fatigue cracks driven by rail bending modelled using a boundary element technique


    Contributors:
    Fletcher, D.I. (author) / Hyde, P. (author) / Kapoor, A. (author)


    Publication date :

    2003


    Size :

    8 Seiten, 8 Bilder, 1 Tabelle, 20 Quellen


    Type of media :

    Conference paper


    Type of material :

    Storage medium


    Language :

    English