高速列车S38C车轴外物致损模拟与疲劳性能研究

Fatigue Behavior Analysis and Simulation of Foreign Object Damage on S38C High-speed Railway Axle

外物致损是造成高速列车车轴疲劳失效的典型因素之一。采用立体显微镜分析CRH2系列高速列车S38C车轴表面的损伤,借助轻型空气炮向取于S38C车轴表面的四点弯曲疲劳试样发射多种角度、速度的球形和正方形钨钢弹体,模拟外物致损。采用逐步加载法来确定损伤试样的疲劳强度,在场发射扫描电镜下观测损伤特征和疲劳断口形貌。结果表明,车轴表面的损伤大部分是刮擦,少部分是缺口。球形弹体垂直冲击损伤随着速度的增大变得逐渐恶劣,材料缺失和微裂纹分布在损伤边缘,底部出现绝热剪切带引发的裂纹;球形弹体斜冲击损伤出射区主要以形变和剪切作用下的掉块为主;方形弹体冲击损伤形态各异。不考虑损伤形成的工况,试样疲劳强度随着损伤深度的增加而降低,深度作为损伤评价参数具有可操作性,本研究为车轴外物致损检修标准的制定提供参考。

Foreign object damage(FOD)is one of the typical issues leading to fatigue failure of high-speed railway axles.Morphologies of the damage on S38C high-speed railway axles were observed by stereomicroscopy.FODs were simulated by firing tungsten steel spheres or cubes under different velocities and incident angles to the outer surfaces of specimen extracted from S38C axle.Step-loading method was employed to determine the four-point bending fatigue strength.Morphologies of damages were investigated by scanning electron microscopy(SEM),and also the fracture surfaces.Statistics of surface damages on S38C axles show that a large fraction of damages are scratches and the percentage of notch is small.Damage volume of normal impact by spherical projectiles increases with improvement of impact velocity.Material losses and microcracks appear in the crater rim and cracks initiated by adiabatic shear band can be found on the floor.Chipping due to deformation and cutting is the feature of damage by incline impact.The shape of impact damage by tungsten cube is various.Regardless of the impact condition,fatigue strength declines with increase of damage depth and it is feasible to assess impact damage by depth alone.The results provide guidance to the maintenance of S38C railway axles subjected to FODs.