Sub-scale simulation and measurement of railroad wheel/rail adhesion under dry and wet conditions

The adhesion characteristics of railroad wheels against rails were simulated using a sub-scale wheel/rail configuration. The apparatus consists of a small roller to simulate the locomotive or rolling stock wheel and a large roller to simulate the rail. The scale of the wheel/rail profiles, relative to full size, is 1:4. Results indicated that this laboratory test can be used to adequately simulate and evaluate the adhesion behavior of the wheel/rail interface under various conditions. Under dry conditions, the adhesion coefficient of wheel/rail has a sharp initial increase of between 0% and 1.5% as creep ratio increases, and then a slight reduction of up to 5%. The presence of water or oil markedly decreases the adhesion coefficient of wheel/rail. With an increase of speed and due to the water volume in the wheel/rail surface, the adhesion coefficient drops. With an increase of lateral force, the adhesion coefficient of wheel/rail increases. Axle load has no obvious effect on the adhesion coefficient in the presence of water. Tree leaves have an important effect on the adhesion coefficient and should be cleared away from the contact surface of wheel/rail if water is present. Further work on improving adhesion and damage of wheels on rails should be studied and explored under a range of low adhesion conditions.