The role of high positive friction (HPF) modifier in the control of short pitch corrugations and related phenomena

Vibration and noise from wheel–rail corrugations reduce the life of vehicle and track components and bring great discomfort to passengers and residents living in close proximity to the tracks. Roll–slip (stick–slip) oscillations are involved in a number of corrugation initiation and formation mechanisms, especially in systems that exhibit a high level of friction, and negative friction characteristics. HPF friction modifier has demonstrated the ability to change the negative friction characteristic of the wheel–rail interfacial layer to positive, and reduce and control friction to levels consistent with braking and traction requirements of the system. Depending on the circumstances of the system involved, HPF can always reduce top of rail noise by at least 3–4 dB and in some instances by as much as 25 dB.