中文摘要：

为了分析车轮纯滚动接触作用下的钢轨表面裂纹扩展机制,建立含表面裂纹的轮轨滚动接触疲劳计算模型,获得15t轴重作用下钢轨表面裂纹长度由0.1mm扩展到2.0mm全过程的裂纹尖端应力强度因子变化规律.基于复合型断裂准则和Paris疲劳扩展理论,分析钢轨表面裂纹扩展规律.分析结果表明：在微裂纹扩展至可见裂纹阶段,钢轨表面疲劳裂纹属于Ⅰ-Ⅱ复合型裂纹;随着裂纹长度增加,应力强度因子K_Ⅰ先迅速增加,然后逐渐减小,而KⅡ在裂纹扩展全过程中呈增加趋势;裂纹萌生与扩展初期以张开型为主,随着裂纹长度增加,其扩展形式向滑开型转变;当裂纹扩展至0.3~0.5mm间时,倾向于向上扩展导致剥离掉块,该扩展趋势与现场服役钢轨剥离路径较为一致.

英文摘要：

In order to analyze the propagation mechanism of micro crack on the rail surface under pure rolling contact, the calculation model of wheel/rail contact fatigue with rail surface crack was estab- lished, and the stress intensity factor of crack tip with the crack length of 0.1 mm to 2.0 mm was ob- tained under the axle load of 15 t. Based on the mixed fracture criterion and Paris fatigue cracking the- ory, the mechanism of spalling on the rail surface was analyzed. The results show that in the propaga- tion process from micro crack to macro crack, the mixed mode crack located on rail surface includes o- pening and sliding modes. The stress intensity factor K1 increases rapidly and then decreases gradual- ly with the increase of crack length, but the KII increases during the whole propagation process. The main failure mode of crack is opening during the initial stage and then transforms into sliding mode with the increase of crack length. The crack tends to extend upward and leads to spalling when the crack length is between 0.3 mm and 0.5 ram. The calculative path is basically identical with spalling path of the actual rail.