航空铝合金自冲铆接接头微观失效研究

Microscopic failure study on self-piercing riveting joints for aviation aluminum alloys

采用自冲铆接技术实现了2A12和6061航空铝合金薄板材料的有效连接,通过进行拉伸-剪切测试,从宏观层面分析了接头静失效形式,从微观层面研究了接头拉脱失效和基板断裂失效机理。结果表明:航空铝合金自冲铆接接头的主要静失效形式为拉脱失效,并有接头伴随纽扣脱落现象,同时有上板断裂和下板断裂的失效形式出现。对拉脱失效机理进行分析,从宏观上发现接头有明显的刮蹭和大幅的塑性形变;从微观上发现,上板的断裂失效机理为沿晶断裂和局部显微孔洞聚集,下板的断裂失效机理为板材上下边缘区域以剪切断裂为主、靠近试样厚度中心区域以微孔洞聚集型正断为主。

The effective connection of 2A12 and 6061 aviation aluminum alloy sheet materials was realized by self-piercing riveting(SPR) technology, and a tensile-shear test was conducted. Then, the static failure form of joint was analyzed from the macroscopic level, and the failure mechanisms of joint pull-out and substrate fracture were studied from the microscopic level. The results show that the main form of static failure for aviation aluminum alloy SPR joint is a pull-out failure, and there is a phenomenon of joint pull-out with button-off. At the same time, there are failure modes of upper sheet fracture and lower sheet fracture. The pull-off failure mechanism was analyzed.From the macroscopic point of view, it is found that the joint has obvious scratches and large plastic deformation. From the microscopic point of view, it is found that the fracture failure mechanism of the upper sheet is intergranular fracture and local microscopic hole aggregation, the fracture failure mechanism of the lower sheet is dominated by shear fracture in the upper and lower edge areas of sheet, and the normal fracture of the microscopic hole aggregation type is mainly in the area near the thickness center of specimen.