Investigation of metro wheel polygonal wear through vehicle-track coupling vibration and track modal analysis

Wheel polygonal wear is a critical degradation phenomenon in metro systems, causing intensified wheel-rail interaction, abnormal vibration, and increased maintenance requirements. However, its formation mechanism remains insufficiently understood, particularly regarding the role of track structural dynamics in the resonance-driven evolution process. This study investigates the mechanism of metro wheel polygonal wear through an integrated approach combining field measurements, wheel-rail coupling analysis, and vehicle-track coupling modal analysis. Field measurements were conducted on an operating metro line using four trains with different service histories after wheel re-profiling. The results reveal that polygonal wear develops progressively with mileage and is predominantly characterized by the 7–9th orders, with the 8th order exhibiting the highest amplitude. These polygonal components generate periodic wheel-rail excitation, leading to abnormal axlebox vibration mainly within the 50–70 Hz frequency range. Frequency-response analysis based on wheel-rail coupling models identifies a pronounced resonance peak near 63 Hz, corresponding to the wheel-rail P2 resonance mechanism. Furthermore, finite element models incorporating vehicle-track coupling were developed for three representative track structures, including steel-spring floating slab track (FST), conventional slab track (CST), and trapezoidal sleeper track (TST). Modal analysis suggests that the P2 resonance frequency increases with structural stiffness, ranging from 63.36 Hz for FST to 95.72 Hz for TST and 126.91 Hz for CST. The frequency coincidence between FST resonance and polygonal excitation promotes dynamic amplification. Based on these findings, a resonance-driven regenerative mechanism is proposed, involving periodic excitation, wheel-rail P2 resonance amplification, initial wheel irregularity formation, and feedback-induced wear growth. The results suggest that wheel polygonal wear may be governed by the interaction among wheel condition, external excitation, and track structural dynamics. The proposed mechanism provides theoretical guidance for integrated condition monitoring and preventive maintenance of urban rail transit systems.