A novel approach to estimate wheel-rail contact forces considering wheel flats and out-of-roundness

Abstract

The vehicle-track interaction plays a role in railway dynamics, since the developed wheel-rail forces are responsible for supporting and guiding the vehicle. However, the existence of high wheel-rail contact forces or abnormal contact conditions typically leads to several surface degradation mechanisms like wheel flats. Hence, wheels and rails with defects on their contacting geometries tend to amplify the vehicle-track interaction forces deteriorating other railway components from both the vehicle and infrastructure. Multibody system dynamics methodologies allow simulating vehicles negotiating a given railway track at specified operating conditions, which can be of interest to determine the causes and consequences of certain defects. In these studies, the computation of wheel-rail contact forces is not only fundamental to accurately and efficiently analyze the vehicle’s dynamic response, but also for assessing the development of degradation phenomena, such wear, rolling contact fatigue or plastic deformation. This work proposes a methodology to deal with the contact detection between rails with constant profile and wheels with variable profile (i.e., with flats and out-of-roundness) in order to take into account the wheel defects on the vehicle’s dynamic response. Both wheel and rail potential contacting surfaces are parametrized. The wheel is divided into strips, and the contact is evaluated between each strip and a locally straight rail close to the wheel. With this methodology, it is obtained the virtual penetration for each strip along the contact patch which allows a better characterization of the effective contact area and apply a non-Hertzian contact force model. The proposed approach is applied to a running scenario in which one wheel of the vehicle is defective. The defect is artificially manufactured by cutting the wheel with a rail profile, which leads to material removal in the tread and transition zone. Further studies must be performed to completely assess and validate the methodology.