Abstract: Fatigue fracture caused by tooth root cracks under high-cycle stress conditions is one of the main reasons for the strength failure of transmission gears in rail vehicles. In order to analyze the influence patterns and action mechanism of shot peening residual stress and tooth root bending stress coupling on the stress intensity factor of tooth root cracks of transmission gears of rail vehicles, a 20-node singular element 1/4-node displacement method was secondly developed based on the finite element method, aiming at the random characteristics of projectile positions during actual shot peening. A finite element method-discrete element method (FEM-DEM) coupled shot peening model and a three-dimensional single-tooth tooth root crack model were jointly established, and a set of multi-step joint numerical simulation method was formulated. The variation of stress intensity factor of tooth root cracks under the combined action of internal residual stress field and external loads was analyzed. The research results show that the residual compressive stress field introduced by shot peening reduces the stress intensity factor at the crack tip by approximately 12%, effectively suppressing fatigue crack propagation. The inhibitory effect of shot peening on crack propagation is most obvious on the surface and near surface areas and weakens as crack depth and external load increase. The stress intensity factor corresponding to residual stress is independent of external loads and only related to the initial stress state.

Key words: vehicle engineering; shot peening; fatigue crack propagation; residual stress; numerical simulation; stress intensity factor

摘要： 高周循环应力工况下齿根裂纹所引发的疲劳断裂是轨道车辆传动齿轮强度失效的主要原因之一。为了分析喷丸残余应力和齿根弯曲应力耦合下对轨道车辆传动齿轮齿根裂纹应力强度因子影响规律与作用机制，针对实际喷丸过程中弹丸位置的随机特性，基于有限元二次开发了20结点奇异元1/4结点位移法，联合建立了FEM-DEM (有限元-离散元)耦合喷丸模型和三维单齿齿根裂纹模型，制定了一套多步骤联合数值模拟方法，并对齿根裂纹应力强度因子在内部残余应力场和外部载荷共同作用下的变化进行了分析。研究结果表明：喷丸强化引入的残余压应力场使得裂纹尖端应力强度因子减小约12%，有效地抑制了疲劳裂纹扩展；喷丸对裂纹扩展的抑制作用在表面与近表面区域最为明显，随着裂纹深度和外加载荷的增大而减弱；残余应力对应的应力强度因子与外载荷无关，仅与初始应力状态有关。

关键词: 车辆工程；喷丸强化；疲劳裂纹扩展；残余应力；数值模拟；应力强度因子