铝合金自冲铆接头疲劳性能及失效机理

自冲铆是轻量化材料的有效连接技术，为促进该技术的广泛应用，文中基于两组铝合金自冲铆接头，采用疲劳测试、统计方法、断口分析和X-射线能谱仪元素分析，获得接头疲劳特性和断口典型部位微观组织特征，从而对铝合金自冲铆接头疲劳性能及失效机理进行研究。结果表明，随着疲劳载荷降低，接头疲劳寿命稳定性和相对滑移量下降。由于多铆钉接头有效减小了应力集中，其疲劳强度比单铆钉接头提高了31.36%~23.14%，且多铆钉接头的疲劳寿命稳定性较高。多铆钉接头中存在首要和次要承载顺序，疲劳断裂表面为首要承载顺序所在位置。接头疲劳宏观失效模式均为下板断裂，疲劳裂纹主要萌生于铆钉管腿与下板接触部位，微振磨损区域自铆钉管腿底部向铆钉头方向生长。减缓该部位的摩擦作用，可有效延迟疲劳裂纹萌生和减缓裂纹扩展，从而提高接头疲劳寿命。

Fatigue properties and failure mechanisms of self-piercing riveted joints in aluminium alloy

Self-piercing riveting (SPR) is an effective joining technology for lightweight materials. In order to promote the application of SPR technology widely, two groups of SPR joints in aluminium alloy were selected to obtain the fatigue properties and the microstructure characteristics of typical failure surface of joints by the fatigue test, statistical methods, scanning electron microscopy and energy dispersive X-ray. Results show that with the reduction of fatigue load, the fatigue life stability and relative slip value of joints decline. As the stress concentration in the SPR joints with multiple-rivet (MR) is reduced effectively, compared with SPR joints with single-rivet (SR) joints, the fatigue strength of MR joints is improved by 31.36%~23.14%, and the fatigue life stability of MR joints is favorable. The primary and secondary load bearing sequences are found in MR joints, and the fatigue fracture surface is the location of primary load bearing sequence. Macroscopic fatigue failure mode of all joints is the fracture of lower sheets, and fatigue crack initiation is located at the interface between the rivet shank and lower sheet. The fretting damage region spreads from the bottom of the rivet shank toward the rivet head. Deceleration of friction function can delay the initiation and slow down the propagation of fatigue crack to improve the fatigue life of joints.