Friction is the bond linking the tangential and normal forces at the wheel-rail interface. Modeling friction is the precondition for the wheel-rail adhesion calculation. In this work, the critical role of friction in the calculation of wheel-rail adhesion is discussed. Four types of friction models (Coulomb model, linear model + Coulomb model, rational model and exponential model) which are commonly used for the calculation of wheel-rail adhesion are reviewed, in particular with regard to their structural characteristics and application state. The adhesion coefficients calculated from these four friction models using the Polach model are analyzed by comparison with the measured values. The rational model and the exponential model are more flexible for defining the falling friction, and the adhesion coefficient calculated by these two models is highly consistent with the measured one. Though the rational model and exponential model describe the falling friction well, the existing friction models are not applicable for calculating adhesion after considering more realistic factors, such as thermal effect, contaminants and so on. Developing a novel and practical friction model to accurately describe the wheel-rail friction behavior is still an essential but challenging and significant task. This review provides a reference for the selection of existing friction models and generates fresh insights into developing novel and practical friction models.

摩擦力是将轮轨界面上的切向力和法向力联系在一起的结合。建模摩擦是计算轮轨附着力的前提。在这项工作中，讨论了摩擦在轮轨附着力计算中的关键作用。综述了轮辋附着力计算中常用的四种摩擦模型（库仑模型，线性模型+库仑模型，有理模型和指数模型），特别是其结构特性和应用状况。通过与测量值进行比较，分析了使用Polach模型从这四个摩擦模型计算出的附着系数。有理模型和指数模型在定义下降摩擦时更加灵活，由这两种模型计算出的附着系数与实测值高度一致。尽管有理模型和指数模型很好地描述了下降摩擦，但考虑到更实际的因素（如热效应，污染物等）后，现有的摩擦模型并不适用于计算附着力。开发一种新颖实用的摩擦模型以准确描述轮轨摩擦行为仍然是一项必不可少但具有挑战性的重大任务。这篇综述为选择现有的摩擦模型提供了参考，并为开发新颖实用的摩擦模型提供了新的见解。考虑到更现实的因素（例如热效应，污染物等）后，现有的摩擦模型不适用于计算附着力。开发一种新颖实用的摩擦模型以准确描述轮轨摩擦行为仍然是一项必不可少但具有挑战性的重大任务。这篇综述为选择现有的摩擦模型提供了参考，并为开发新颖实用的摩擦模型提供了新的见解。考虑到更现实的因素（例如热效应，污染物等）后，现有的摩擦模型不适用于计算附着力。开发一种新颖实用的摩擦模型以准确描述轮轨摩擦行为仍然是一项必不可少但具有挑战性的重大任务。这篇综述为选择现有的摩擦模型提供了参考，并为开发新颖实用的摩擦模型提供了新的见解。