Experimental Investigation On Low Adhesion In The Wheel-Rail Interface And Improving Adhesion Behaviors

Since the beginning of railway transportation, low adhesion of wheel/rail is one of the vital factors that has been restricting the traction and braking capabilities of rolling stock. Especially for poor environmental contaminants and complex track conditions, a higher adhesion coefficient of wheel/rail is required. When it comes to track ramp and rainy day, low adhesion phenomena occurs which easily results in the wheel slipping. Therefore, further understanding the low adhesion phenomenon of wheel/rail and improving the available adhesion force between the wheel and rail, is crucial to ensure the operation safety of locomotive.A testing fixture was designed to simulate different track gradient contacts of wheel/rail, and the effects of track ramp on the adhesion behaviors under third medium conditions were explored in detail using a JD-1 wheel/rail simulation apparatus. The experiments of improving adhesion were carried out under the water condition by means of a MMS-2A wheel/rail simulation facility. The effects of sand parameters and sand-alumina mixed mediums on the adhesion coefficient and damage characteristics of wheel/rail were analyzed. Furthermore, the improving adhesion mechanisms of sanding in the wheel-rail contact were discussed as well.Main conclusions are drawn as follows:(1) Compared with the level track, the adhesion coefficient of wheel/rail of ramp track has a significant fall under dry, water and antifreeze medium conditions. Furthermore, the adhesion coefficient shows a downward trend with the track gradient increasing and the loss of adhesion coefficient under the decent track is more than that of ascent track.(2) Compared with water medium, the antifreeze fluid is much easier to cause low adhesion phenomenon of wheel/rail. Moreover, with the speed and axle load increasing, the adhesion coefficient of wheel/rail presents a slight downward under the ascent track condition.(3) Under the wet condition, sanding plays a vital role in improving the adhesion coefficient of wheel/rail. With an increase in the particle diameter and feed rate, the adhesion coefficient increases. However, the surface damage of wheel/rail aggravates and the surface damage is dominated by spalling and pits.(4) With an increase in alumina proportion in the sand-alumina mixed mediums, the adhesion coefficient of wheel/rail increases correspondingly. Meanwhile, the damage type of wheel/rail rollers transforms from slight spalling to severe spalling, serious fatigue cracks and bulk material breaking.