预腐蚀对夹层结构自冲铆接头疲劳特性的影响

Effect of Pre-corrosion on Fatigue Performance of Sandwich Structure Self-piercing Riveted Joint

探究了周期浸润环境下以AA5052-O铝合金为基板的夹层结构自冲铆接头的耐蚀性能,并对不同预腐蚀时间下的试样进行了疲劳性能测试,依据三参数经验公式采用S-N曲线拟合法拟合出各试样的S-N曲线,分析了预腐蚀对接头疲劳寿命的影响规律;此外,采用扫描电子显微镜对接头的疲劳断口进行观测,研究了接头的损伤特性和微观疲劳失效机理。结果表明:预腐蚀会使接头产生多个疲劳源并加速裂纹的扩展,接头疲劳裂纹易在预腐蚀缺陷处萌生;腐蚀损伤和机械损伤存在竞争关系,预腐蚀显著影响了接头在低应力水平下的疲劳寿命,总体来讲,接头的疲劳寿命随预腐蚀时间的延长而缩短;接头疲劳失效形式有铆孔区下板断裂和铆孔区一侧的下板断裂,接头疲劳源区断口呈现准解理特征。

The corrosion resistance of sandwich structure self-piercing riveted joint with AA5052-O aluminum alloy as substrate in periodic immersion environment was explored,fatigue performance tests were carried out on samples under different pre-corroded time.According to the three empirical parameters,the S-N curves of samples were fitted by S-N curve fitting method,and the influence of pre-corrosion on the fatigue life of joints was analyzed.In addition,the fatigue fracture was observed by scanning electron microscopy to study the damage characteristics and the micro fatigue failure mechanism of the joints.The results show that pre-corrosion can cause multiple fatigue sources on the joint and accelerate the crack pro-pagation,fatigue cracks of joints are easy to initiate at the defects caused by pre-corrosion.There is a competitive relationship between corrosion damage and mechanical damage during the tests,pre-corrosion significantly affects the fatigue life of joints at low stress levels.In general,the fatigue life of the joint decreases with the increase of the pre-corrosion time.Fatigue failure patterns of the joint include the fracture of the lower plate in the riveting region and the fracture of the lower plate on side of the riveting region.The fatigue source fracture of the joint emerges the characteristics of quasi-cleavage fracture.