Comparative Study of Continuous Versus Discontinuous Numerical Models for Railway Vehicles Suspensions with Dry Friction

Dry friction dampers are widely used in railway vehicle suspensions due to their simplicity, robustness, and cost-effectiveness compared to hydraulic alternatives. However, accurately modelling their behaviour remains challenging because of the discontinuous nature of friction forces. This paper presents a comparative study between two modelling approaches: continuous (regularized) models, which smooth out discontinuities, and discontinuous (switch-based) models, which explicitly capture stick–slip transitions. Using a two-degree-of-freedom suspension system, both models are implemented and analyzed under steady-state and transient conditions. Results show that while continuous models are easier to implement and integrate numerically, they fail to capture key physical phenomena such as zero relative velocity intervals and force discontinuities. In contrast, discontinuous models offer superior physical fidelity and significantly better computational efficiency, especially during static friction phases. This study highlights the trade-offs between modelling simplicity and accuracy, providing valuable insights for the simulation and design of railway suspension systems. The findings support the use of discontinuous models in safety-critical simulations and suggest avenues for hybrid modelling strategies.