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利用气动式喷丸机对7A09超高强铝合金试样进行喷丸强化,对喷丸强化前后试样小孔两侧残余应力分布进行测试,探讨了喷丸时间对7A09铝合金疲劳寿命的影响,分析机械喷丸强化前后铝合金试样疲劳断口。结果表明,机械喷丸强化后,7A09超高强铝合金表层分布高幅值残余压应力,表层残余压应力分布显著地降低了疲劳裂纹扩展速率,疲劳寿命明显提高;通过扫描疲劳断口,发现未处理试样的疲劳裂纹源位于孔壁上表面的尖角处,而机械喷丸强化试样的裂纹源逐渐转移到强化层以内,在最终断裂区内分布大量韧窝,且韧窝形态随喷丸时间的延长而增大,并且韧窝尺寸更深,说明机械喷丸改善了最终断裂区的塑性。
The peening of 7A09 ultra-high strength aluminum alloy was carried out by pneumatic shot blasting. The distribution of residual stress on both sides of the small holes before and after shot peening was tested. The effect of shot peening time on the fatigue life of 7A09 aluminum alloy was discussed. Analysis of mechanical shot peening before and after fatigue fracture aluminum alloy specimens. The results show that after the mechanical shot peening, the high-amplitude residual compressive stress and the residual compressive stress distribution in 7A09 ultra-high strength aluminum alloy significantly reduce the fatigue crack growth rate and significantly increase the fatigue life. By scanning the fatigue fracture, it is found that untreated The source of the fatigue crack in the sample is located at the sharp corner of the upper surface of the hole wall. However, the crack source of the shot peening specimen is gradually transferred into the strengthening layer, and a large number of dimples are distributed in the final fracture zone. The increase of time and deeper dimple size indicate that mechanical shot peening improved the plasticity of the final fracture zone.