Optimization of sanding application parameters based on the wheel-rail adhesion restoration effect and surface damage

Sanding with hard particles is an effective method to improve wheel-rail adhesion under low-adhesion conditions. However, the lack of unified standards for sanding parameters necessitates further investigation into their optimization. This study examined the effects of sanding application parameters on adhesion restoration and surface damage using a twin-disc wheel-rail rolling contact testing machine. The results showed that particle distribution density as the most critical factor influencing adhesion restoration, outweighing the effects of particle size and material. With the increase in particle distribution density, the wheel-rail adhesion coefficient (adhesion restoration amplitude), wear rate and material damage increased sharply at first and then stabilized after surpassing a threshold (approximately 0.607 g/m). Additionally, the restoration duration (adhesion coefficient remained in a proper amplitude) increased almost linearly with an increase in particle distribution density. The influence of particle size on adhesion restoration amplitude depended on particle distribution density, affecting the sensitivity of the adhesion coefficient to density changes. While Alumina exhibited better adhesion restoration effect (restoration amplitude and duration) than Silica sand, it resulted in significantly greater surface damage. Furthermore, to facilitate field applications, an empirical equation was developed to evaluate adhesion restoration amplitude. Based on this equation, a graded control strategy for sanding amounts (0.6–2.2 kg/min) was proposed, related to train operating speeds ranging from 20 to 120 km/h.