Effect of Variation of Angle of Attack on Adhesion-Creepage Behavior Using Virginia Tech - Federal Railroad Administration (VT - FRA) Roller Rig

摘要

Angle of attack is one of the most important parameters affecting the distribution of creep forces at the wheel-rail contact patch, in turn, affecting the lateral stability of the car body. This study reports the experimental testing conducted using the one-fourth scale VT - FRA roller rig to evaluate the rolling contact and slip dynamics at the wheel/rail contact patch. The Rig consists of a wheel and roller in a vertical configuration and is equipped with positioning systems for controlling the angle of attack, cant angle, lateral displacement and normal load. The contact is between a flat cylindrical wheel and a roller machined to US-136 rail profile. Baseline study with 0° angle of attack is compared with 2° angle of attack study. The adhesion-creepage behavior of the wheel-rail contact in the longitudinal and lateral directions are discussed. Creepage is introduced at the contact patch by changing the wheel velocity with respect to the roller velocity. Measurements are carried out from 0% to a maximum of 6% creepage. Creep forces are measured quasi-statically at each creepage point. Shape of the contact patch and its pressure distribution are discussed. A peak adhesion coefficient of 0.26 was measured on the roller rig. A consistent testing methodology and experiment design was used for conducting the experimental studies to obtain results in an accurate and repeatable manner. The report also elaborates on the algorithms developed in MATLAB to automate the data processing.