外物损伤对25CrMo4合金车轴钢疲劳性能的影响

为研究外物损伤（FOD）与25CrMo4钢疲劳性能的关联，采用空气炮装置开展高铁车轴钢试样的FOD模拟试验. 首先于试样表面预制FOD缺陷；其次，通过旋转弯曲疲劳试验获得光滑试样和含FOD试样的应力-疲劳寿命（S-N）曲线；同时，基于有限元方法估算不同缺陷试样的应力集中系数，结合Peterson公式预测疲劳缺口系数（FNC）和疲劳极限. 研究结果表明:FOD车轴钢试样的疲劳性能明显低于光滑试样，冲击速度越高，疲劳性能越低；其中边缺陷的疲劳缺口系数最大为1.52，面缺陷最小，约为1.14，但疲劳寿命分散性较大；与试验结果相比，仿真模拟和理论计算可获得更低（偏于保守）的疲劳强度估算值. 

Influences of Foreign Object Damage on Fatigue Strength of 25CrMo4 Axle Alloy Steel

To study the correlation between the foreign object damage (FOD) and the fatigue strengh of alloy steel 25CrMo4, the simulated test for FOD of high speed railway axle steel specimens was carried out by a compressed-gas gun device. Firstly, the FOD defects were simulated on railway axle steel specimen surfaces. Secondly, the fatiuge S-N curves of smooth and FOD specimens were obtained from rotating bending fatigue tests. Furthermore, the stress concentration factor was evaluated for different types of defects by elastic finite element method (FEM). The fatigue limit and fatigue notch coefficient (FNC) of FOD specimens were calculated based on Peterson formula. The results show that the fatigue performance of FOD specimens is considerably lower than that of smoothed ones, the higher the impact velocity, the lower the fatigue performance. The FNC of edge defect specimens is the largest (about 1.52) while the smallest (about 1.14) for plane defect specimens, thus leading to a larger dispersion in lifetime. Compared with the experiments, theoretical evaluation and FEM method can obtain relatively conservative results in fatigue strength.