轮轨黏着特性是影响列车牵引和制动的重要因素，轮轨黏着特性的研究对于列车安全平稳运行、减少轮轨疲劳和表面擦伤，以及降低脱轨风险都具有重要意义。轮轨之间的黏着特性主要体现在黏着系数上，影响黏着系数的因素很多，例如蠕滑率、速度、润滑介质特性、轮轨表面粗糙度和表面形貌取向等。

本文主要研究激光毛化形成的车轮表面形貌取向对水润滑和冰润滑条件下运行的高速列车轮轨黏着特性的影响。根据弹流润滑理论，对于水作为润滑介质的情况，将轮轨接触按混合润滑情况处理，基于统一Reynolds方程方法计算了车轮表面具有纵纹、横纹、菱形三种形貌以及无激光毛化处理的随机形貌的黏着系数随蠕滑率、速度而变化的规律；对于零摄氏度以下，冰作为润滑介质的情况，首先计算了具有随机形貌的轮轨接触区压力分布，根据冰的相图和压力融化原理，将接触区分为混合润滑区域和固体（冰-钢）接触区域，在混合润滑区仍然用统一Reynolds方程进行计算，而在冰-钢接触区域，用退化的Reynolds方程，即Hertz方程进行计算，总的黏着系数是两个区域黏着系数之和。最后，计算了蠕滑率为0.02条件下纵纹、横纹、菱形三种激光毛化形貌车轮表面在0~-21℃温度范围内的黏着系数。

本文主要结论是：

    （1）在水润滑条件下，激光毛化形貌有明显的增粘效果，其中，菱形分布增粘效果最明显，横纹优于纵纹；

    （2）对无量纲压力和膜厚的计算显示，载荷比是影响黏着特性的主要因素，载荷比表示固体承担载荷的比例，激光毛化技术可以有效提高载荷比；

    （3）冰润滑时，在相同的蠕滑率和速度条件下，黏着系数比水润滑情况更低，随着温度升高，冰润滑的黏着系数逐渐增加；

    （4）激光毛化形貌在冰润滑的条件下也有显著的增粘效果。

关键词：高速列车，黏着系数，形貌取向，混合润滑

 

Adhesion property has a key effect on traction and brake of train running. It is important to maintain safety and stability reduce contact fatigue and surface scratching, and low the risk of derailment of trains. The adhesion property between wheel and rail is mainly reflected by adhesion coefficient. There are many factors that affect the adhesion coefficient, such as slip rate, speed, lubricant characteristics, surface roughness and roughness orientation of wheel/rail.

In this paper, the effect of laser texturing wheel surface orientation on adhesion properties of wheel/rail of high-speed train under water lubrication and ice lubrication were studied. According to the theory of elastohydrodynamic lubrication, the wheel/rail contact could be treated as a mixed lubrication under water lubrication. The variation of adhesion coefficient with slip ratio, speed was computed based on the unified Reynolds equation method, where the wheel surface was wih and without laser texturing patterns, i.e., longitudinal, transverse, rhombus, and random pattern. For minus temperature with ice lubrication, the dimensionless pressure distributions with random pattern of wheel surface were computed at first. Then the contact area was divided into mixed area and solid area, i.e. steel-ice area, based on the phase diagram of ice and the theory of pressure melt. In the mixed area it was still computed by unified Reynolds equation method, while in the steel-ice area it was computed by degraded Reynolds equation, i.e. Hertz equation. The total adhesion coefficient was the sum of the two adhesion coefficients of the areas. Finally the adhesion coefficient with three laser texturing wheel patterns, such as longitudinal, transverse, rhombus was computed under the conditions of 0.02 slip ratio and 0~-21℃ temperature region.

The conclusions of this paper were the following:

(1) Under the condition of water lubrication, the laser texturing patters have apparently effects on increasing adhesion. The adhesion coefficient of rhombus pattern is the most one, and that of transverse is better than that of longitudinal;

(2) The calculation of the dimensionless pressure distribution shows that the load ratio is the main factor to affect adhesion property. The load ratio is the ratio of asperity contact pressure to the total pressure. Laser texturing could effectively lift up the load ratio;

(3) Under the condition of ice lubrication, the adhesion coefficient decreases significantly with the same slip ratio and speed. The adhesion coefficient increases with the increase of ice temperature;

(4) The laser texturing patterns still enhance apparently on adhesion coefficient under the conditions of ice lubrication. 

Key words: High-speed train, Adhesion coefficient, roughness orientation, Mixed lubrication