Analysis and testing of tread braked railway wheel — Effects of hot spots on wheel performance

To investigate the impact of localised heating phenomena in the form of hot spots on wheel performance in general and on wheel residual stress state in particular, a combination of experimental testing and finite element simulations of tread braked wheels has been performed. Using a newly established full-scale railway brake test rig, a wheel is exposed to prolonged drag braking applications at constant power levels to induce high temperatures on the wheel tread. The distribution and evolution of the temperature is studied using a high-speed, high-resolution thermographic camera in addition to traditional sliding thermocouples. Measured temperature data are then used in combination with a thermomechanically calibrated material model to simulate the wheel behaviour. For this purpose, a 3D finite element model representing a sector of a railway wheel is used. The experimental results show that the temperatures measured utilising sliding thermocouples provide insufficient information since they cannot resolve the uneven tread temperatures given typical response times. Non-uniform heating is found to have a significant effect on tensile residual stresses in the rim. Especially the case with global uneven temperatures is found to generate potentially hazardous residual stresses. The results presents future challenges for the analysis and development of the brake-wheel-rail system.