EA4T动车组车轴疲劳性能评价影响因素研究

Study on Influencing Factors in Evaluating the Fatigue Performance of EA4T Axle

动车组车轴的疲劳强度与寿命是关乎动车组走行部安全服役的重要参数。随着运行速度的提高,在轴颈部位应力集中区域的疲劳裂纹萌生、扩展行为与结构的设计强度和材料在缺口效应下的疲劳极限的关系愈发密切。针对动车组常用车轴钢EA4T的疲劳强度与裂纹扩展行为,利用有限元计算和疲劳试验方法研究了毫米/微米级短裂纹、表面粗糙度及不同程度缺口效应等因素的影响。结果表明:利用单点疲劳法确定疲劳加载应力幅后,升降疲劳法获得的疲劳强度极限变异系数可低于15%,同时,工作载荷方向对轴颈部位应力集中的影响较小。在轴颈的应力集中位置,浅裂纹长度越长,则张开型裂纹的应力强度因子及其增量越大,当短裂纹深度在0.1~0.2 mm之间时,应力强度因子陡增。当车轴钢在疲劳应力超过400 MPa左右时,其表面粗糙度对疲劳寿命极限的影响较小,但会导致疲劳失效模式转变为明显的多源疲劳断裂特征。

The fatigue strength and life of axle are vital to the safe service of high-speed EMU.With the increase of speed,the fatigue crack initiation and propagation behavior in the stress concentration zone of shaft neck are highly related to the strength design and the fatigue life limit of materials under notch effect.The influencing factors of fatigue strength and crack propagation behavior of axle steel EA4T were studied considering different scale or level notch,such as short crack and surface roughness.The results show that the variation coefficient of fatigue strength limit obtained by lifting method can be less than 15%by using single-point method to obtain fatigue stress amplitude.Meanwhile,the direction of working stress has limited influence on stress concentration at the shaft neck.At such stress concentration zone,the longer the shallow type-I crack length,the greater the stress intensity factor and its increment.When the depth of short crack is between 0.1~0.2 mm,the stress intensity increases rapidly.With fatigue stress reaches about 400 MPa,the surface roughness of axle steel has little influence on the fatigue life but will obviously cause change of fatigue failure mode from single-source into multi-source.