Wheel-rail adhesion utilization in the presence of wide-wave track irregularities

In railway vehicles, wheel-rail adhesion utilization follows a static design with redundancy, yet its dynamic characteristics under realistic operating conditions remain poorly understood. This study quantifies adhesion utilization in the presence of track irregularities by developing a high-speed train-track coupled dynamics model and a wheel-rail transient contact finite element model. Mid/long-wave irregularities are simulated using power spectrum density, while short-wave irregularities are considered as the critical rail corrugation, rail weld and wheel flat. The analysis focuses on operations on the tangent track under dry and wet conditions, with speeds up to 400 km/h during full-acceleration traction or urgent braking. For single-type irregularities, adhesion utilization remains below 0.3 under dry conditions but can reach 1.0 under wet conditions, indicating occurrences of low adhesion (LA) or dynamic low adhesion (DLA). This is attributed to irregularity-induced normal unloading, axle load transfer, or the mismatch between high adhesion demands and low adhesion coefficients. The maximum allowable operating modes are further determined to avoid LA and DLA. Additionally, adhesion utilization is analyzed in scenarios involving the coexistence of mid/long-wave and short-wave irregularities, as well as on typical curved and sloped tracks, and with the use of adhesion design limits.