Analysis of sanding deterioration and braking performance in subway vehicles

To address the low adhesion issue caused by contaminants such as water or oil entering the wheel-rail interface, high-speed rail vehicles utilize sanding devices to improve adhesion. This method effectively mitigates most low-adhesion conditions. However, subway vehicles currently lack sanding devices, leading to extended braking distances, wheel slip, and even collisions under low-adhesion conditions. This paper systematically investigates the wheel-rail adhesion change and the braking performance under the influence of sanding, aiming to explore the necessity of adding sanding devices to subway vehicles. Laboratory tests were conducted using a 1:4 circumferential test rig, which mimics the field lines, establishing an equivalence between the actual vehicle and laboratory conditions. The study also analyzed the deterioration of the sanding effect between Axles under three conditions: water, oil, and an oil/filings mixture. A subway braking/anti-slip simulation platform was developed, incorporating sanding deterioration, to evaluate the train braking performance under different sanding amount. Finally, the paper provides reasonable recommendations for the optimal installation positions of sand devices on subway vehicles.