基于近场动力学的裂纹扩展及轨面剥离掉块成因机理

Crack Propagation and Rail Surface Spalling Mechanism Based on Peridynamics

建立了态基近场动力学钢轨表面滚动接触疲劳裂纹扩展模型,研究钢轨疲劳裂纹的扩展以及由此引起的轨面剥离掉块形成过程。结果表明,轨面单裂纹或裂纹间距>1.5mm情况下,随着通过总重的累积,裂纹扩展的路径逐渐转向钢轨内部,且扩展速率随着通过总重累积和裂纹长度的增加逐渐降低;轨面多裂纹情况下,通过总重增量低于8.8 Mt时,裂纹在荷载作用下主要发生沿长度方向扩展。通过总重增量超过8.8 Mt后,裂纹之间的次生损伤形成;而且,这种情况在轨面多条裂纹间距≤1.5 mm时较为显著,裂纹间距>1.5mm时,裂纹间的相互影响减小;轨面多条裂纹同时存在且裂纹间距≤1.5 mm时,通过总重增量达到一定程度(>10.0Mt),裂纹间的次生损伤形成剥离掉块,剥离掉块深度约为裂纹深度的1/2以上。

Rail surface rolling contact fatigue(RCF)crack propagation model based on state peridynamics was established to research the propagation of RCF crack and the formation process of spalling.It was found that the crack propagation path gradually turned towards into the internal rail with the accumulation of traffic tonnage in the case of single crack or cracks with distance longer than 1.5 mm between each other.The propagation rate gradually decreases with the increase of traffic tonnage and crack length.In the case of multiple cracks,the cracks propagated along their length direction below traffic tonnage of about 8.8 Mt.After the traffic exceeded 8.8 Mt,the secondary damage between cracks was formed especially between the cracks which their distance was less than 1.5 mm.If the distance between cracks was longer than 1.5 mm,the interaction among cracks was reduced.In the case of multiple cracks with adjacent distance less than 1.5 mm,the spalling occurred from the secondary damage when the increment of traffic tonnage reached a certain amount(>10.0 Mt).At that time,the spalling depth was about over 1/2 depth of the crack.