Dynamic responses under wheel–rail irregularities: Experimental analysis

Wheel out–of–roundness (OOR) and rail irregularity represent two typical geometric defects in urban rail transit, whose combined excitation significantly affects the service performance of the vehicle–track system. To further reveal the actual influence of this combined excitation, this study primarily relies on field measurements, supplemented by model–based validation. Wheel OOR and rail irregularity are incorporated as key variables into a vehicle–track coupled dynamic model developed based on measured data to investigate the amplification mechanism of their combined excitation on system responses. This model supports the interpretation and validation of experimental results. Static tests indicate that the wheels generally exhibit mild to moderate wear, with 5.9% exceeding the severe threshold. Short–wavelength energy concentrations at 6mm and 13mm are identified in severely worn sections. Dynamic tests demonstrate that the combined excitation markedly amplifies vibration amplitudes in the vehicle–track system, with the vertical response being the most critical. Compared with wheel OOR, rail irregularity exerts a more pronounced influence on vibration responses. These findings provide a valuable reference for future investigations of vibration mechanisms in the vehicle–track system.