Keywords: multibody dynamics, contact force, lookup table, exponential fitting, worn wheels, friction.

In real-time simulations of railway vehicles, accurate but computationally efficient methods to solve wheel-rail contact problems are needed. In this work, three constraint-based contact methods are compared for modelling wheel–rail of interaction within the framework of railway multibody dynamics. The first method employs a lookup-table approach, in which wheel–rail contact information is interpolated from precomputed tables during the dynamic simulation. The second method uses analytical exponential functions to represent the wheel–rail contact geometry, allowing the contact information to be evaluated analytically during the simulation. The third method simplifies the contact geometry by using constant parameters, such as equivalent conicity, throughout the dynamic simulation. These approaches are implemented on a dynamic model of a wheelset on a tangent track with irregularities, and the results are compared against commercial software Simpack. Both new and worn wheel profiles are considered. The results show that the approaches based on lookup tables and analytical exponential functions are able to model the variations on vertical-lateral wheel-rail contact forces, while constant parameter approach underestimates this. % However, none of these approaches capture the abruptly varying longitudinal contact friction force and normal contact force, while the low frequency variation is captured.

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