泡沫金属夹层板自冲铆接头的疲劳性能及失效机理

Fatigue Properties and Failure Mechanisms of Self-piercing Riveted Joints in Metal Foam Sandwich Structures

对铝合金自冲铆接头及泡沫金属夹层结构自冲铆接头进行疲劳实验,通过三参数经验公式采用S-N曲线拟合法绘制接头的F-N曲线,分析接头的疲劳寿命及泡沫金属夹层对自冲铆接头疲劳性能的影响;采用扫描电子显微镜对接头的疲劳失效断口进行观测,分析其微观失效机理。结果表明:泡沫金属夹层缩短了自冲铆接头的疲劳寿命,不同泡沫金属夹层对自冲铆接头疲劳性能的影响具有差异性,在高疲劳载荷下泡沫铜夹层接头疲劳性能更优。三组接头疲劳失效形式都为下板断裂,在高疲劳载荷下裂纹易在铆扣区域萌生,在中低疲劳载荷下裂纹萌生于下板一侧,沿铆扣区域下侧向板材另一侧扩展。

Fatigue experiments were carried out on the self-piercing riveted（SPR）joint of aluminum alloy and the foam metal sandwich structures.Based on the three parameter empirical formula,S-N curve fitting method was used to draw the F-N curves of the joints.The fatigue life of the joints and the influence of the metal foam interlayers on the fatigue properties of the SPR joint were analyzed.The fatigue failure fracture of the joints was observed by scanning electron microscope（SEM）,and the microscopic failure mechanism was analyzed.The results show that the metal foam interlay reduces the fatigue life of the SPR joint,and different metal foam has the different influence on fatigue performance of SPR joint.Under the high fatigue load,the copper foam sandwich joint has better fatigue performance.The fatigue failure modes of the three groups of joints are the lower sheet fracture,and the cracks easily occur in the locked region under the high fatigue load.The crack initiates at one side of the lower sheet under the low fatigue load,and extends to the other side of the sheet along the underside of the locked region.