Effect and mechanism of wheel–rail adhesion on torsional vibration and stability of the braking system

A high-speed train braking system with the disc–pad sliding friction pair and the wheel–rail rolling friction pair is a classic torsional system. By adopting a developed braking system torsional dynamics model, the influences of dry and wet rail surface conditions on system dynamic responses were investigated. Further, the system stability under different disc–pad friction and wheel–rail adhesion characteristics was explored and the interaction mechanism between the disc–pad and the wheel–rail sub-systems was revealed. The results indicated that the wheel–disc torsional vibration was more complicated under the wet rail surface condition. Moreover, the braking system had worse stability when the negative slope characteristics of disc–pad friction and wheel–rail adhesion were interacted.