Influence of P2 resonance of metro wheel-rail system on fatigue failure of rail fastening clips

Fatigue fracture of rail fastening clips is a common failure in metro. In order to clarify the prevailing factors, on-site experiments and simulations are conducted on a metro line in China to reveal the relationship between wheel-rail resonance and the failure of fastening clips. To reveal the failure mechanism of the fastening clip in the installed state, a vehicle-track coupled dynamics model is created together with a refined finite element model of the fastening system. Rail irregularities are measured to account for the actual track excitations. The results show that both the wheel-rail force and the rail displacement increase significantly when the excitation frequency of the rail corrugation is close to the P2 resonant frequency of the vehicle-track system. At the P2 resonance frequency, the drastic increase in the amplitude of stress cycles of the clip leads to a significant reduction in the fatigue life of the clip. To remedy this situation, the influence of different corrugation depths on the fatigue life of the clip is investigated and a limit value for rail grinding is proposed, which takes into account the rail corrugation and the vehicle speed on the line under investigation to ensure the operating condition of the rail fastening system. The comparison between the dynamic behaviour and the fatigue life of the fastening clips before and after rail grinding shows that timely rail grinding can extend the life of the clip and ensure the safe operation of the train.