ISSN   1004-0595

CN  62-1224/O4

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基于表面微织构纹理的U75V钢轨表面增摩特性研究

Friction-Enhancing Properties of U75V Rail Surfaces Through Surface Micro-Texturing

  • 摘要: 轮轨黏着系数是描述轮轨间摩擦特性的重要参数,它直接关系到列车的牵引力和制动性能. 而低黏着状态的出现极易诱导轮轨表面擦伤、剥离和扁疤等损伤. 为提高钢轨材料表面摩擦系数,本文中采用飞秒激光技术在U75V钢轨材料表面上制备了波浪形织构纹理,考察了水介质环境下不同波浪形角度和织构面积率对钢轨材料波浪形织构纹理表面的增摩效果,证实了参数优化后的织构纹理表面兼具增摩抗磨性能,进一步揭示了波浪形织构的增摩机理. 研究结果表明:优选的波浪形织构纹理表面,其织构角度θ≥120°可达到增摩目的,且θ=150°时增摩效果显著;而织构角度θ=150°条件下,面积率为30%时摩擦系数最高,可达0.57,相比光滑表面增摩性能可提升42.5%. 同时,表面增摩效果好的波浪形织构纹理有更优异的亲水特性,其中纹理参数(θ=150° @ η=30%)试样表面的亲水性出色且呈现各向异性,在沿垂直摩擦方向易呈铺展趋势. 因而,第三体介质在摩擦副间的成膜能力下降,赋予了摩擦副间的增摩性能提升. 这项研究工作可为抑制轮轨界面低黏着问题提供理论支撑.

     

    Abstract: The wheel-rail adhesion coefficient is a crucial parameter that describes the friction characteristics between the wheel and rail, directly influencing the traction and braking performance of the train. When the adhesion between the wheel and rail becomes insufficient to meet normal traction or braking requirements, it is referred to as a low adhesion state. This condition can lead to wheel spinning, slipping, and result in damage such as scratches, peeling, and flat spots on the wheel-rail surface. To enhance the surface friction coefficient of rail materials, this paper employed femtosecond laser technology to create wavy textures on the surface of U75V rail materials. The study investigated the effects of different waviness angles and texture area ratios on the friction enhancement of the textured surface in aqueous environments. It was confirmed that the optimized textured surface exhibited both improved friction and anti-wear properties, further revealing the friction enhancement mechanism of the wavy texture. The research results indicated that as the wave angle gradually increased, the average friction coefficient initially rised and then decreased. Similarly, as the area ratio increased, it followed a comparable trend of first increasing and then decreasing. The optimal wavy textured surface could effectively increase friction when the texture angle θ was greater than or equal to 120°, with a particularly significant effect observed at θ = 150°. In contrast, at smaller wave angles (θ = 60° and 90°), the friction coefficient of the sample surface tended to decrease. Furthermore, under the condition of texture angle θ=150°, the maximum increase in the friction coefficient reacheed 0.57 when the area ratio was 30%, resulting in a 42.5% improvement in friction performance compared to smooth surfaces. Under the same friction conditions, the wear damage of the non-textured sample was more severe, exhibiting numerous deep ploughing grooves and plastic deformation protrusions that were higher than the original surface due to friction shear. Additionally, a significant number of pitting and delamination features appeared locally on the worn surface. The surface wear of the wavy textured sample (θ=150° @ η=30%) was slight, and the height of the wear marks did not significantly decrease. The worn surface featured a substantial area covered by a local adhesive layer, which contributed to the potential for adhesive wear. Overall, surface texturing treatment effectively reduced the wear volume of the friction surface. The wear volume of the wavy textured sample (θ=150° @ η=30%) was V=220.5 μm3, which was larger compared to other parameters of textured texture. However, compared to the non-textured surface (V=272.1 μm3), the wear volume could still be reduced by 19.1%. This indicated that while ensuring excellent friction performance, the wavy texture could still store wear debris and lubricating media, reducing the probability of abrasive wear and oxidative wear between friction pairs. This successfully achieved the dual objectives of enhancing friction and providing anti-wear benefits. At the same time, the wavy texture that enhanced surface friction exhibited improved hydrophilic properties. Among the various texture parameters, the configuration with θ=150° and η=30% demonstrated excellent hydrophilicity and anisotropy on the sample surface, tending to spread along the vertical friction direction. This suggested a reduction in the film-forming ability of the third-body medium between the friction pairs, which contributed to improved friction performance. This research provided theoretical support for addressing low adhesion issues at the wheel-rail interface.

     

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