Numerical Investigations on the Influence of Radius and Track Gauge on Wheel-Rail Contact in Narrow Curves

The conference contribution by Dominik Rudisch, M.Sc., and Prof. Dr.-Ing. Stephan Freudenstein, presented in June 2026 at the 12th International Conference on Bearing Capacity of Roads, Railways, and Airfields in Ljubljana, Slovenia, is now available at the following link:
doi.org/10.5281/zenodo.20662584

Abstract:

Narrow curves are common in metro systems worldwide, even though the conventional rolling-radius steering becomes ineffective in them. Due to the small radius, an angle of attack occurs instead, steering the bogie under high dynamic forces through the curve, which often results in vibrations and increased wear. Field measurements along curves at the Milan Metro have indicated that the leading axle mainly drives gaugewidening effects. Based on these findings, this research aims to enhance the understanding of wheel-rail contact in narrow curves by conducting a simulation-based parameter study on the influence of curve radius and track gauge. A multibody simulation model was developed in SIMPACK and extended by Vtech CMCC’s user subroutine CONTACT for full rolling contact theory. Simulations were performed with a radius varying from 200 m to 900 m, and in one scenario, with additional track gauge widening of 5 mm and 10 mm. For each scenario, the speed was chosen to fully compensate centrifugal acceleration for the constant superelevation, ensuring a balanced load distribution across all scenarios. The simulation results show that in narrow curves, large angles of attack result in flange contact at the outer wheel, leading to significant lateral creep forces. With an increasing curve radius, these lateral forces decrease — particularly on the outer rail — while longitudinal creep forces rise until roll-radius steering seems to become effective again. The maximum contact pressure trends differ: on the outer rail, pressures initially decrease and then increase with larger radii, likely due to changes in contact shape, position, and patch distribution. In contrast, maximum pressures on the inner rail remain high and largely independent of radius. Gauge widening primarily affects the inner contact by shifting it toward the rail center, causing lower pressure through a more favourable elliptical contact, while the outer contact remains mainly unaffected. Overall, moderate gauge widening of a softer fastening system implies that it can reduce pressure-related wear on the inner rail from a quasi-static perspective.