Fatigue crack is one of the most common defects in railway system. Fatigue crack growth may lead to wheel and rail failure and damage to other components. In this paper, by applying the including service conditions of the railway system, first, a 3D nonlinear stress analysis model has been applied to estimate stress fields of the rail under the influence of periodic overloads. For this purpose, an UIC60 rail with accurate geometry using finite element method (FEM) is studied. Next, the results of this model are used for fatigue crack growth and also to estimate the fatigue life in rails using boundary element method (BEM). In this regard, first, the types of cracks and the corresponding factors which cause them were analyzed. In addition to performing stress analysis for different positions of the wheel, different values of the stress intensity factors (SIFs) were also obtained. Using these stress intensity factors, two characteristics of fatigue crack propagation namely, crack growth and direction of its development, were obtained. In this study, Paris Equation is used as a criterion of fatigue crack growth rate and the maximum tangential stress was considered as the crack growth direction. The numerical analysis results showed that the effect of periodic overloads on the fatigue life in rails was significant and could not be ignored.

疲劳裂纹是铁路系统中最常见的缺陷之一。疲劳裂纹的扩展可能会导致车轮和轨道故障以及对其他组件的损坏。在本文中，通过应用铁路系统的包含服务条件，首先，使用3D非线性应力分析模型来估计周期性超载影响下的铁路应力场。为此，研究了使用有限元方法（FEM）具有精确几何形状的UIC60导轨。接下来，将该模型的结果用于疲劳裂纹扩展，并使用边界元方法（BEM）估算轨道的疲劳寿命。在这方面，首先，分析裂纹的类型和引起裂纹的相应因素。除了对车轮的不同位置进行应力分析外，还获得了不同的应力强度因子（SIF）值。利用这些应力强度因子，获得了疲劳裂纹扩展的两个特征，即裂纹扩展及其发展方向。在这项研究中，巴黎方程被用作疲劳裂纹扩展速率的准则，并且最大切向应力被视为裂纹扩展方向。数值分析结果表明，周期性过载对钢轨疲劳寿命的影响是显着的，不能忽视。使用巴黎方程作为疲劳裂纹扩展速率的标准，并且最大切向应力被视为裂纹扩展方向。数值分析结果表明，周期性超载对钢轨疲劳寿命的影响是显着的，不能忽视。使用巴黎方程作为疲劳裂纹扩展速率的标准，并且最大切向应力被视为裂纹扩展方向。数值分析结果表明，周期性过载对钢轨疲劳寿命的影响是显着的，不能忽视。