水介质下打磨磨痕对钢轨疲劳损伤的影响

采用棕刚玉砂纸在钢轨试样表面处理得到不同角度打磨磨痕，利用MMS-2A轮轨摩擦磨损试验机研究了水介质下不同角度打磨磨痕对钢轨疲劳裂纹扩展的影响。结果表明：水介质条件下打磨磨痕与运行方向夹角在0°～45°范围内时，钢轨表面粗糙度略高，高于夹角为70°、90°打磨磨痕区域表面粗糙度；相比没有打磨磨痕的光滑区域，0°～45°打磨磨痕将加速钢轨接触疲劳裂纹的扩展，20°磨痕区域的裂纹扩展尤为严重，出现了许多分支裂纹；而70°、90°的打磨磨痕一定程度上会减缓疲劳裂纹的生长，90°打磨磨痕区域基本只存在表层裂纹；打磨磨痕角度由0°向90°增大时，裂纹扩展深度先变大后变小，而裂纹扩展角度呈现出逐渐减小的趋势。

Effects of Grinding Marks on Fatigue Damage of Rails under Water Conditions

The object herein was to investigate the effects of different grinding marks directions on the rail fatigue crack propagations under water medium conditions using a MMS-2A wheel/rail friction wear testing apparatus. And the different grinding marks angles to the running direction were manufactured on rail specimens by brown corundum sand. The results indicate that the surface roughness of rail specimen with the grinding marks angle of 0° ～45° to the running direction is higher than that with the grinding marks angle of 7°and 90° under the water medium conditions. The grinding marks with the angle of 0°～45° to the running direction may accelerate the fatigue crack propagations compared with the smooth area on rail specimen without prefabricated grinding marks. And the crack propagation is particularly serious on the rail specimen surface with the angle of 20° grinding marks which has a lot of branch cracks. The growth of the fatigue cracks slows down for the rail specimen with the grinding marks angle of 70°, 90°, and there are only surface cracks on the rail specimen with the angle of 90° grinding marks. With the angle of grinding marks increases from 0° to 90°, the crack propagation depth of rail specimen increases firstly and then decreases, and the crack propagation angle tends to decrease gradually.