The effect of geometric features on multi-axial fatigue behaviour of aluminothermic rail welds

Aluminothermic rail welds typically exhibit a variable and often inferior performance when compared with flash butt welds. Fatigue failure as a result of surface defects or harsh geometric features in the presence of high axle loads and tractive forces gives rise to the so-called straight break and horizontal split web fractures. In this study, the reduction of fatigue performance due to geometric irregularities is investigated using a multi-axial high cycle fatigue criterion based on the critical plane concept. A thermo-structural finite element model of a track containing an aluminothermic weld is linked with a developed computer code to perform fatigue crack initiation analysis. Two geometrically different aluminothermic welds, one of which is widely used in Australian heavy haul railways, are investigated in terms of fatigue probability, to facilitate a better insight into the effect of weld collar shape and geometry at the edge of the weld collar on fatigue behaviour. The results confirm that the amount of fatigue damage is critically dependent on the geometric features of the collar edge, especially at the underhead radius which undergoes severe fatigue loading under some operational conditions.