轮对蠕滑条件下钢轨疲劳裂纹萌生寿命预测

Rail Fatigue Crack Initiation Life Prediction Under Wheelset Creep Condition

摘要:

采用多体动力学与三维弹性体非赫兹滚动接触理论，得到不同轨底坡、超高、摩擦系数与曲线半径等多种轨道条件下的轮轨蠕滑状态，将接触力分别施加于钢轨有限元模型的接触斑位置，分析轨头应力应变响应，得到所有节点的疲劳参量.研究疲劳参量的组成类型，若剪应力与应变部分占主要组成部分，则采用剪切型裂纹萌生预测公式，否则采用拉伸型预测公式.分别预测导向轮与非导向轮作用下的曲线外轨疲劳裂纹萌生寿命，结果表明，外轨疲劳裂纹主要由导向轮作用产生，非导向轮对其影响很小；裂纹萌生寿命随曲线半径的增大而延长，随摩擦系数的增大而减小；设置1∶20轨底坡可以延缓外轨疲劳裂纹萌生，尤其是在半径较小的曲线上效果更明显；过超高能延缓曲线外轨疲劳裂纹萌生；当摩擦系数大于0.3时裂纹萌生于曲线外轨表面，而小于0.3时裂纹萌生位置则逐渐向轨头内部转移.

Abstract:

Multi body dynamics and three dimensional elastic bodies Non Hertz rolling contact theory were used to obtain wheel rail creep states in several tracks which include different rail cant, superelevation, coefficients of friction (COF) and radius. Pressure and tangential force distribution were loaded to the contact patch of rail finite element model. Then the fatigue parameters of all nodes in the railhead were obtained by stress/strain response analysis. Composition of fatigue parameter was analyzed to decide the prediction formula. If the share stress/strain part was dominating, the share type prediction formula should be used, otherwise the tensile type formula was used. Rolling contact fatigue (RCF) crack initiation life in the leading and trailing wheel was predicted separately. The result shows that the high rail RCF crack is caused by the leading wheel, the influence of the engaged wheel is little. High rail RCF crack initiation life increases with the augment of the curve radius or superelevations, and it decreases with the augment of COF. It can delay high rail RCF crack initiation to set the cant of 1∶20. When COF is over 0.3, the high rail RCF crack is initiated on the surface of railhead; when COF becomes smaller than 0.3, the location of RCF crack initiation transfers to the inside rail head gradually.