目的 研究不同喷丸工艺处理EA4T车轴钢的疲劳性能和破坏行为，并分析表面影响层性能，尤其是表面残余应力对疲劳强度的影响机理。方法 采用传统喷丸（CSP）和微粒子喷丸（MSP）工艺分别对EA4T车轴钢进行处理，对不同喷丸处理后的试样进行表面性能分析，然后采用旋转弯曲疲劳试验机进行疲劳试验，获得疲劳S-N曲线和残余应力松弛过程，并通过扫描电镜对发生疲劳失效的断口进行观察。结果 与CSP相比，MSP可以引入更高的表面硬度和残余压应力，同时又可以有效地减小表面粗糙度。喷丸可以有效地提高试样的疲劳性能，CSP和MSP分别提升了试样疲劳极限的25%和33%。所有喷丸试样残余应力松弛与循环次数（10≤N≤107）之间存在线性关系，这个线性关系可以用经验公式定量描述。在相同加载应力下，CSP试样的残余应力松弛过程比MSP试样更快，当试样在疲劳加载过程中发生残余应力松弛后，剩余的残余压应力高于初始值的80%时，疲劳失效不会发生。所有试样的疲劳裂纹均萌生于表面，喷丸没有改变试样的疲劳断裂机制。结论 与CSP相比，MSP可以引入更优的表面影响层，在相同加载应力下有更加缓慢的残余应力松弛过程，从而可以进一步提高试样的疲劳性能。另外，残余压应力、表面完整性是影响疲劳极限提升的主要因素。

The work aims to study the fatigue properties and failure behavior of EA4T axle steel treated by different shot peening processes, and to analyze the properties of the surface affected layer, especially the mechanism of influence of surface residual stress on fatigue strength. The EA4T axle steel was treated by the traditional shot peening (CSP) and micro-shot peening (MSP) respectively. The surface properties of the specimens after different shot peening treatment were analyzed and then the fatigue test was carried out by a rotary bending fatigue machine to obtain the fatigue S-N curve and residual stress relaxation process. The fatigue fracture surface was observed by scanning electron microscopy (SEM). Compared with CSP, MSP could introduce higher surface hardness and compressive residual stress, while effectively reducing surface roughness. Shot peening treatment could effectively improve the fatigue performance of the specimens and CSP and MSP increased the fatigue limit of 25% and 33%, respectively. There was a linear relationship between the compressive residual stress relaxation and the number of cycles (10≤N≤107) for all shot peened specimens and the linear relationship could be quantitatively described by the empirical formula. The CSP specimens showed a faster compressive residual stress relaxation process than MSP specimens at the same loading stress amplitude. When the compressive residual stress of the specimens after residual stress relaxation process during fatigue loading was higher than 80% of the initial value, fatigue failure did not occur. All the fatigue cracks were initiated on the surface and the fracture mechanism was not changed by shot peening treatment. Compared with CSP, MSP can introduce a better surface influence layer and have a slower compressive residual stress relaxation process at the same loading stress amplitude, which can further improve the fatigue properties of the specimens. Moreover, compressive residual stress and surface integrity are the primary factors affecting the improvement of fatigue limit.