United States Department of Transportation
i
Quantitative Evaluation of Effect of Top of Rail Friction Modifiers on Reducing Wheel and Rail Wear
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2021-10-01
[PDF-4.30 MB]
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Edition:Final Report
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Abstract:This study provides a detailed experimental evaluation of wheel-rail interaction for railroad vehicles, using the Virginia Tech Federal Railroad Administration (VT-FRA) Roller Rig. Various contact dynamics that emulate field application of railroad wheels on tracks are set up on the rig under precise, highly controlled and repeatable conditions. For each set up, the longitudinal and lateral traction (creep) forces are measured for different percent creepages, wheel loads, and angle of attack. The tests are performed using quarter-scaled wheels with different profiles, one cylindrical and the other AAR-1B with 1:20 taper. Beyond the contact forces, the wheel wear and the deposition of worn materials are measured and estimated as a function of time using a micron-precision laser optics measurement device. The change in traction versus amount of worn material at the contact surface is analyzed and related to wheel-rail friction. It is determined that the accumulation of the worn material at the contact surface, which appears as a fine gray powder, acts as a friction modifier that increases friction. The friction (traction) increase occurs asymptotically. Initially, it increases rapidly with time (and worn material accumulation) and eventually reaches a plateau that defines the maximum friction (traction) at a stable rate. It is estimated that the maximum is reached when the running surface is saturated with the worn material. Prior to the saturation, the friction increases directly with increasing amount of deposited material. The material that accumulates naturally at the surface—hence, referred to as “natural third-body layer”—is estimated to be a ferrous oxide. It has an opposite effect from the Top of Rail friction modifiers (TOR) that are deposited onto the rail surface to reduce friction in a controlled manner.
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