预腐蚀和交替腐蚀作用下航空铝合金多轴疲劳行为及寿命预测

飞机在腐蚀环境下服役时，损伤形式为地面腐蚀与空中疲劳交替过程。依据该工况特点，研究了预腐蚀和交替腐蚀作用对2024-T4和7075-T651两种航空铝合金多轴疲劳行为的影响规律。结果表明：等效应力恒定时，随着预腐蚀时间增加，试样表面蚀坑数量和密度增加，腐蚀影响权重增大，2种铝合金多轴疲劳寿命均降低；交替腐蚀-多轴疲劳试验中，单位加载周次恒定时，单位腐蚀时间增加导致多轴疲劳寿命下降，试验过程中随着交替级数的增加，试样表面腐蚀程度加剧；基于Miner模型和预腐蚀疲劳寿命数据，提出修正的损伤累积模型，进行交替腐蚀-多轴疲劳寿命预测，寿命预测值基本位于2倍分散带内。

Multiaxial fatigue behavior and life prediction of aerospace aluminum alloy under pre-corrosion and alternate corrosion

When aircraft is in service in a corrosive environment, its damage mode shows an alternate process of corrosion on ground and fatigue in air. Based on the characteristic of this working condition, the effects of pre-corrosion and alternate corrosion on multiaxial fatigue behavior of 2024-T4 and 7075-T651 aerospace aluminum alloys are studied. Under the same equivalent stress amplitude, with the increase of the pre-corrosion time, the number and size of pits on specimen's surface augment, indicating that the weight of corrosive influence increases and the multiaxial fatigue life of the two alloys decreases. When the unit loading units hold constant, the unit corrosion time increases, decreasing the multiaxial fatigue life. With the augmentation of the alternate stage, corrosion on the surface of specimen tends to be more severe. Based on the Miner model and life data from pre-corrosion fatigue tests, a modified accumulative damage model is proposed, which shows fine results within 2x scatter bands in alternate corrosion-multiaxial fatigue life prediction.