Shattered Rim Failure Modeling in Railroad Wheels

Shattered rim cracking, propagation of a sub-surface crack parallel to the tread surface, is one of the dominant railroad wheel failure types observed in North America. This crack initiation and propagation life depends on several factors, such as wheel rim thickness, wheel load, residual stresses in the rim, and the size and location of material defects in the rim. This paper investigates the effect of above mentioned parameters on shattered rim cracking, using finite element analysis and fracture mechanics. This cracking is modeled using a three-dimensional, multi-resolution, elastic-plastic finite element model of a railroad wheel. Material defects are modeled as mathematically sharp cracks. Rolling contact loading is simulated by applying the wheel load on the tread surface over a Hertzian contact area. The equivalent stress intensity factor ranges at the subsurface crack tips are estimated using unimodal stress intensity factors obtained from the finite element analysis and a mixed-mode crack growth model. The residual stress and wheel wear effects are also included in modeling shattered rim cracking.