喷丸强化对异物致损车轴钢疲劳性能的影响

Influence of Shot Peening on Fatigue Strength of Railway Axle Steel Subjected to Foreign Object Damages

高速铁路车轴长期服役中形成各种损伤,严重破坏了结构完整性。为此,首先采用喷丸处理(SP)对车轴钢试样进行强化,运用空气炮装置预制异物损伤(FOD),基于X射线衍射和纳米压痕仪得到喷丸强化试样表层的残余应力和微观硬度分布,开展高周疲劳试验分别获得未强化光滑试样(UnSPed+UnFODed)、强化处理的光滑试样(SPed+UnFODed)、未强化处理的FODed试样(UnSPed+FODed)和强化处理的FODed试样(SPed+FODed)的疲劳S-N曲线,同时考虑疲劳寿命数据的分散性,引入C95R95的概率评估方法得到上述各类试样的疲劳P-S-N曲线。最后,建立了伤损车轴材料的修正Kitagawa-Takahashi图。研究发现,异物损伤过程将会显著降低车轴钢试样的疲劳强度和寿命,然而由于残余压应力和硬化层的存在,喷丸强化能够有效提高受到FOD冲击试样的抗疲劳性能,具有重要的工程应用价值。

During the long-term service of high-speed railway axles,various kinds of external damages were generated,which seriously destroyed the structural integrity.To avoid such failure,the surfaces of railway axle steel specimens were treated by using the shot peening(SP),and by using a compressed-gas device,foreign object damage(FOD)was then prepared on the surface treated specimens.The residual stress and microhardness of shot peened layer of the specimen were obtained by X-ray diffraction and nano indentation.Thereafter,the fatigue S-N curves of UnSPed+UnFODed,SPed+UnFODed,UnSPed+FODed and SPed+FODed specimens were acquired by high cycle fatigue experiments.In view of the disperision of fatigue life,the probability evaluation method of C95 R95 was introduced to fit the fatigue P-S-N curves of the above specimens.Finally,a modified Kitagawa-Takahashi diagram of damaged axle was established.It was found that the fatigue performance of railway axle steel specimens would be significantly reduced by foreign object damage.However,due to the introduction of residual compressive stress and the presence of hardened layer,shot peening can effectively improve the fatigue resistance of the FODed specimens,which provides important engineering application value.