DP780/AA6061薄板自冲铆接头微动损伤特性

Characteristics of Fretting Damage in Hybrid DP780/AA6061 Self-piercing Riveted Joints

对高强钢DP780与铝合金AA6061薄板的异质自冲铆接连接工艺进行研究,并分别制备了不同搭接顺序的DP780/AA6061(SA)和AA6061/DP780(AS)接头。对两组接头进行了高周疲劳试验,对比分析了两组接头的疲劳性能与失效行为,并进一步利用微观检测技术较系统地分析了两组接头的微动损伤机理。结果表明:AS接头的疲劳性能明显优于SA接头,且两组接头疲劳失效模式依次为铆钉断裂和下板断裂。SA接头和AS接头的上板近端与下板末端接触区域、上板近端与下板远端接触区域和铆钉与下板近端接触区域均发生微动磨损。微动磨损会导致SA及AS接头的铆钉和下板近端均出现疲劳裂纹,由于板材性能的差异,裂纹在铆钉和下板上的传播路径和扩展速率不同,最终导致接头失效模式存在差异。

The self-piercing riveting(SPR) processes between the high strength steel DP780 and aluminum alloy AA6061 sheet are studied. The DP780/AA6061(SA) and AA6061/DP780(AS) joints with different combinations are fabricated respectively. The high-cycle fatigue tests are carried out and then comparative analysis about the fatigue properties and failure behaviors are conducted. Further, the fretting damage mechanism of the corresponding joints are discussed systematically using the micro detective methods. The results show that the fatigue strength of the AS joints is significantly better than that of the SA joints. The SA joints fail in locked sheet and the AS joints fail due to the rivet fractured. The fretting wear mainly exists in the contact surfaces between the proximal end of pierced sheet and the distal end of locked sheet, the proximal end of pierced sheet and the far end of locked sheet, as well as the rivet and the proximal end of locked sheet. The fretting wear can result in the fatigue cracks to initiate in both the rivet and the locked sheet of the SA and AS joints. However, due to the different material properties between the high strength steel and the aluminium sheet, the propagation path and rate of the fatigue crack on the rivet and the proximal end of locked sheet are affected, which finally bring the different fatigue failure modes.