凹坑形貌对喷丸应力场的影响

Influence of dimple morphology on stress field of shot peening

为消除残余应力及材料硬化等因素对弹丸撞击响应的影响,结合有限元模拟与试验分析,以2024-T351航空铝合金为研究对象,采用铣削制造了初始凹坑,又利用压头冲击进行了喷丸加工,研究了初始凹坑形貌对后续喷丸加工效果的影响规律。结果表明,凹坑原位单弹丸撞击后,凹坑变深,其深度变化随初始凹坑尺寸的增加而逐渐变小,凹坑中心位置残余应力随初始凹坑尺寸的增大而逐渐变大,并趋于稳定值。单个凹坑(凹坑投影半径r0)相邻位置单弹丸撞击时,撞击表面位移及残余应力与偏移量s(撞击位置到凹坑中心的距离)密切相关,当s=r0时,表面位移较大,但残余应力较小;当sr0时,随着偏移距离增大,距离较小时,表面位移小幅度减小,残余应力小幅度增大,距离较大时,变化都很小,基本可以认为保持不变;当撞击位置远离初始凹坑时,凹坑对弹丸撞击响应的影响逐渐减弱。两个凹坑相邻位置单弹丸撞击后,弹丸撞击响应主要受到近处(s≤r0)凹坑的影响,较远距离(s>r0)的凹坑则对弹丸撞击响应影响较小。

To eliminate the influence of residual stress and material hardening on the shot impact response,combining with finite element simulation and test analysis,the 2024-T351 aircraft aluminum alloy was taken as the research object,the initial dimples were fabricated by milling,and then the indenter impact was used for shot peening.The influence laws of the initial dimple morphologies on the subsequent shot peening were studied.The results show that after single shot impact of the in-situ dimple,the dimple becomes deeper,the depth variation decreases gradually with the increase of initial dimple size,and the residual stress at the center of the dimple increases gradually with the increase of the initial dimple size,and tends to a stable value.When single shot impacts at the position adjacent to single dimple(dimple projection radius r0),the displacement and residual stress on the impact surface are closely related to the offset s(the distance from the impact location to the center of dimple).When s=r0,the surface displacement is large,but the residual stress is small.When s<r0,the surface displacement decreases and the residual stress increases with the decrease of the offset distance.When s>r0,with the increase of the offset distance,the surface displacement slightly decreases and the residual stress slightly increases.When the distance is large,the changes are small and can be considered to remain unchanged.When the impact position is far away from the initial dimple,the impact of dimple on the shot impact response is gradually weakened.When two dimples are adjacent to each other after single shot impact,the shot impact response is mainly affected by the near dimple(s≤r0),while the dimples at large distant(s>r0)have little influence on the shot impact response.