考虑材料塑性变形的高速道岔心轨裂纹萌生预测

Rolling Contact Fatigue Crack Initiation Prediction in Nose Rail of High-speed Railway Turnout Considering Plastic Deformation

摘要:

根据高速铁路18号单开道岔钢轨设计廓形，考虑车轮逆向-侧向通过翼轨?心轨时轮载转移引起的冲击荷载和材料塑性变形，将心轨塑性变形结合到裂纹萌生和磨耗共存发展预测方法中，预测了心轨裂纹萌生。分析发现，心轨顶宽35~40 mm为承受轮载转移的最不利位置；该位置的表面材料在冲击荷载下发生塑性变形，其应力应变明显降低，直至在一定轮载次数下达到稳定状态，这时的最大塑性变形量为0.087 5~0.092 5 mm，延缓了疲劳裂纹的萌生；心轨疲劳损伤最大值位于轨头亚表面，顶宽35和40 mm处的裂纹萌生区域分别在心轨表面垂直向下1.2和1.5 mm、从轨顶中心水平向工作边一侧4~5 mm和1~2 mm的位置。疲劳裂纹萌生寿命分别为1.63×10⁶ t和3.97×10⁶ t。

Abstract:

According to the designed profiles of wing and nose rails at the No. 18 high-speed single-way turnout， the rolling contact fatigue （RCF） crack initiation in nose rail was predicted by the coexistence prediction method of RCF crack initiation and wear growth considering the impact load and material plastic deformation caused by the wheel load transfer from wing rail to nose rail when the train passes the turnout to side and reverse direction. The analysis shows that the worst position at the nose rail is the part with a top width of 35~40 mm at which the impact load caused by wheel load transferring is the largest. There would be plastic deformation at rail surface of this part under impact load which would reduce the material stress and strain obviously until the plastic deformation reaches a stable state with a certain number of wheel cycles. At that time， the maximum plastic deformation is 0.087 5~ 0.092 5 mm， which would prolong the （RCF） crack initiation. The maximum fatigue damage in the nose rail is at the rail subsurface. The RCF crack initiation positions for the nose rail at top width of 35 mm and 40 mm are 1.2 and 1.5 mm below rail surface vertically， 4~5 mm and 1~2 mm from rail center towards gauge side horizontally respectively. Moreover， the RCF crack initiation life are 1.63 ×10⁶ and 3.97 ×10⁶ tones at these two positions respectively.