高速道岔曲尖轨疲劳裂纹成因分析

Cause of Rolling Contact Fatigue Cracks in Curved Switch Rail of High- speed Turnout

摘要:

根据高速铁路18号单开道岔的基本轨-曲尖轨设计廓形和实测廓形数据，采用车辆-道岔动力学模型，分析了列车逆向-侧向过岔时轮载位置的转移、基本轨和尖轨上的接触斑法向应力和疲劳裂纹指数，提出了高速道岔曲尖轨疲劳裂纹形成的原因。研究发现：高速道岔基本轨和尖轨实测廓形显示尖轨降低值存在不足，使得同一转向架1、2位轮对的外轮轮载转移分别过早和过快，且随着车轮和钢轨廓形磨耗，这种情况进一步恶化。由此造成曲尖轨受到较大的法向接触应力，特别是1位轮对的外轮对曲尖轨轨肩和轨距角疲劳裂纹的形成贡献度最大。曲尖轨最早出现裂纹的区域在其顶宽20~50mm范围内。

Abstract:

According to the designed and the measured stock and curved switch rail profiles of the No. 18 high-speed single-way turnout， a vehicle-turnout dynamic model was established to analyze the wheel loading position transfer， normal contact stress in the stock and curved switch rails and their fatigue damage indexes during train passing turnout along reverse and side direction. The reason that the fatigue crack in curved switch rail was presented. The results show that the switch rail machined depth to the stock rail was not as enough as the standard one which made the loading position transferred early and rapidly for the outer wheels of both the front and rear wheelsets in the same bogie respectively. With the wear’s coming into being between the wheel and rail profiles， this situation got worse. Then， large normal contact stress occurred in the curved switch rail especially by the outer wheel of the front wheelset in the bogie which contributed the most to the rolling contact fatigue crack at the gauge shoulder and corner of the curved switch rail. The fatigue crack would appear first in the curved switch rail with the top width of about 20 ~ 50 mm.