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

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 a few 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. Results are presented as plots of stress intensity factor around crack fronts for single- and multiple-crack situations, for which crack growth rates are predicted. The work focuses particularly on the degree to which single-crack models may be misleading when dealing with a rail containing multiple cracks. The work has application in improving the modelling of crack growth in rails, leading to improved asset management and risk assessment.