城市轨道交通钢轨磨耗和裂纹萌生分析与选型建议
Analysis on rail wear and crack initiation and recommendation on rail selection in urban rail transit

分析了基于能量密度法和临界平面法的滚动接触疲劳裂纹萌生预测理论与Archard法的磨耗预测理论,提出了城市轨道交通钢轨滚动接触疲劳裂纹萌生和磨耗共存发展预测模型; 针对城市轨道交通常用的U71Mn热轧、U75V热轧和U75V热处理等3种不同硬度的钢轨,预测其表面滚动接触疲劳裂纹的萌生寿命、相应的钢轨型面变化和磨耗发展率; 分析了3种硬度钢轨的疲劳裂纹萌生和磨耗发展特征; 基于安定极限理论,结合城市轨道交通常见坡度和常用ER9型车轮,从轮轨硬度匹配的角度提出了城市轨道交通的钢轨选型建议。研究结果表明:随着硬度的增大,钢轨滚动接触疲劳裂纹萌生寿命延长,磨耗发展率降低,U75V热轧和U75V热处理钢轨的磨耗发展率分别比U71Mn热轧钢轨低3.2%和12.1%,裂纹萌生寿命分别比U71Mn延长14.8%和31.1%; 在城市轨道交通常用坡度情况下,3种不同硬度的钢轨材料都处于弹性安定极限范围,但随着坡度增大,钢轨材料趋向于塑性安定极限; 考虑与ER9车轮的硬度匹配情况,建议钢轨踏面较车轮踏面的硬度高些,ER9车轮与U75V热轧钢轨和U75V热处理钢轨的轮轨硬度比分别为0.87～1.04和0.71～0.84,这2种钢轨均适合于中国的城市轨道交通系统。
The theory of rolling contact fatigue(RCF)crack prediction based on the energy density method and critical plane method, and wear prediction theory based on the Archard method were analyzed, a prediction model of the coexistence of RCF crack initiation and wear growth in rails of urban rail transit(URT)was presented. The RCF crack initiation life, corresponding rail profile evolution and wear growth rate were predicted for three kinds of the rails with different hardnesses, named U71Mn as-rolled, U75V as-rolled, and U75V heat-treated rails that were commonly used in URT. The development characteristics of the fatigue crack initiation and wear growth were analyzed. Based on the shakedown limit theory, according to the common gradients and type ER9 wheel, the rail selection suggestion for URT was proposed considering the hardness match between the wheel and rail. Analysis result shows that the RCF crack initiation lifes of the rails prolong and the wear growth rates reduce with the increase of the rail hardness. Compared with those of U71Mn as-rolled rail, the wear growth rates of the U75V as-rolled and heat-treated rails reduce by 3.2% and 12.1%, respectively, and their crack initiation lifes prolong by 14.8% and 31.1% respectively. The materials of three kinds of rails with different hardnesses are all within the elastic shakedown limit under the common gradients condition in URT, but they will tend to the plastic shakedown limit with the increase of the gradient. Given the hardness match of the ER9 wheel, it is recommended that the hardness of the rail surface should be higher than that of the wheel tread. The wheel-rail hardness ratios are 0.87-1.04 for U75V as-rolled rail and ER9 wheel, and 0.71-0.84 for U75V heat-treated rail and ER9 wheel, respectively. Both U75V rails can be adapted to the URT system in China. 2 tabs, 8 figs, 26 refs