钢轨轨底裂纹扩展影响因素分析

Analysis of Factors Affecting the Growth of Rail Bottom Cracks

【目的】为分析钢轨材质、残余应力、温度应力在钢轨使用中的内外因对轨底裂纹扩展的影响开展研究。【方法】基于断裂力学理论结合轨底伤损实测,建立钢轨轨底裂纹扩展模型,对轨底伤损扩展失效时的临界裂纹尺寸、裂纹平均扩展速率、剩余寿命等指标进行量化分析。【结果】结果表明:钢轨材料断裂韧性与轨底初始伤损扩展的剩余寿命存在正相关关系,U95Cr H材质钢轨的轨底裂纹扩展剩余寿命小于U78CrV H材质小于U75V H材质;以某线路实际使用的钢轨材质U78CrV H为例,轨底残余应力由0增加至300 MPa,轨底裂纹扩展的临界尺寸增长约2.5%,剩余寿命下降约6%;残余应力为200 MPa时,温度应力由0增加至200 MPa,轨底裂纹扩展的临界尺寸变化不大,在1%内。【结论】研究结果可为轨底裂纹扩展研究和养护维修提供参考。

【Objective】In terms of the rail material,residual stress,temperature stress and other factors,work conditions are respectively designed to explore the influences of rail bottom crack expansion.【Method】Based on the theory of fracture mechanics,combined with rail bottom measurement,the model of rail bottom crack expansion has been established and indicators such as critical crack size,average crack extension rate as well as remaining life has been quantified.【Result】It is found that there exists positive correlation between the fracture toughness of rail material and the remaining life.The remaining life of U95Cr H is less than U78CrV H,which is less than U75V H.Taking U78CrV H,used in the line under test,as an example,when the residual stress grows from 0 to 300 MPa,the critical crack size grows by about 2.5%and the remaining life decreases by about 6%;and when the residual stress is 200 MPa,with the temperature stress from 0 to 200 MPa,the critical crack size does not change much and is within 1%.【Conclusion】The research results of the article can provide reference for the research and maintenance of rail bottom crack propagation.