喷丸对预腐蚀后铝合金疲劳性能的影响

目的分析喷丸对铝合金腐蚀损伤构件疲劳性能的影响,为飞机构件的维修提供有效指导。方法以未喷丸、三面喷丸、三面喷丸腐蚀后再三面喷丸3类不同表面状态的7075铝合金试样为研究对象,改变Na Cl溶液质量分数、时间、温度,获得两种程度不同的腐蚀损伤,通过疲劳寿命、断裂位置、断口形貌,分析表面喷丸状态对铝合金疲劳性能的影响。结果腐蚀损伤较轻时,喷丸试样的疲劳寿命为未喷丸试样的7.84倍,喷丸试样腐蚀后若再喷丸处理,疲劳寿命是不再喷丸试样的1.62倍。未喷丸试样的断裂位置位于截面突变颈部区域,另两类喷丸试样的断裂位置则在夹持段前端。未喷丸试样的裂纹在断口表面的边缘位置形成,喷丸试样的中心区域形成光滑平整的稳态扩展区。腐蚀损伤严重时,喷丸处理仍然会提高铝合金的疲劳寿命,但3类不同表面状态试样的疲劳寿命差距会缩小;从试样断裂位置、断口形貌看,3类试样的差异也会弱化。结论铝合金腐蚀损伤件若腐蚀前进行表面先喷丸处理,疲劳性能会有明显提升;若腐蚀后再喷丸处理,疲劳性能还会进一步提升;喷丸处理还会削弱铝合金外形截面突变处的应力集中,抑制疲劳裂纹在构件表面的萌生及延伸。

Effects on Anti-corrosion Fatigue Property of Aluminum Alloy after Shot Peening

Objective To analyze the influence of shot peening on fatigue performance of aluminum alloy components with corrosion damage so as to guide the repair of aircraft components. Methods The 7075 aluminum alloy samples with three types of different surface states, which were treated with un-shot peening, shot peening on three surfaces and shot peening for twice on three surfaces, were selected as the research subjects. The corrosion damage of two different degrees was obtained by changing the corrosion parameters such as NaCl concentration, temperature and time, and the fatigue property of aluminum alloy on shot peening surface state was analyzed according to fatigue life, fracture location and fracture morphology of aluminum alloy. Results At a mild corrosion damage, the fatigue life of shot peening on three surface was 7. 84 times longer than that of un-shot peening, and the fatigue life would be further improved by 1. 62 times if the eroded sample after shot peening was peened again; the fracture position of unshot peening sample was located in the abruptly changed area of cross section, and the fracture position of the other two types of shot peened samples was in the front of clip. According to observation of the fracture morphology, fatigue crack of un-shot peening samples showed that on the edge of the fracture surface, the central regions of shot peened sample formed a smooth and straight stable-extended area. At a serious corrosion damage, shot peening processing still could improve the fatigue life of aluminum alloy, but the fatigue life gap would be reduced on three kinds of different surface samples. According to observation of the fracture position and the fracture morphology, the gap was also narrowed between three kinds of samples. Conclusion The fatigue performance would be improved obviously, if the aluminum alloy corrosion damage components were shot peened before pre-corrosion treatments; and the fatigue performance of materials would be further improved, if the eroded sample after shot peening were peened again; besides, the stress concentration would be weaken on the abruptly changed area of cross-section, and production and growth of fatigue crack would be restrained on the component surface when the aluminum alloy component was shot peened.