选择4组轻合金自冲铆进行疲劳实验,用扫描电子显微镜和能谱仪对其断口进行微动磨损机理分析,并系统地研究了接头疲劳寿命和失效形式的影响因素.结果表明,下板与钉腿区的微动磨损是导致下板沿纽扣断裂和铆钉断裂的主要原因,两板间的微动磨损是导致上板靠钉头断裂的主要原因;微动磨屑主要成分为金属板材氧化物,并对微动磨损起缓冲作用.增加板厚可提高接头疲劳寿命,且疲劳载荷较大时寿命提高更为显著;增加板强可提高接头疲劳寿命,且寿命提高程度受疲劳载荷影响较小.增加板厚使失效形式从上板断裂变为下板断裂,增加板强使失效形式从板材断裂变为铆钉断裂.
Four groups of self-piercing riveting (SPR) of lightweight alloys were chose to perform a fatigue test.Scanning electron microscope (SEM) and energy dispersive X-ray spectrum (EDX) were adopted to observe the fracture surface and analyze the fretting wear mechanism further.The impact factors of fatigue life and fatigue failure mode of the joints were also analyzed systematically.Results exhibited that bottom substrate fracture along the button and rivet fracture were mainly caused by fretting wear occurred in an interface between bottom substrate and rivet leg,upper substrate fracture close to rivet head was primarily caused by the fretting wear occurred in a riveting interface between two sheets.The main composition of fretting debris was the oxide of metal substrate,and the debris had buffering effect in fretting wear process.Increase substrate thickness could enhance fatigue life,especially when fatigue load was high.Augment substrate strength was able to improve fatigue life,and the increase of fatigue life was influenced barely by fatigue load.The fatigue failure mode changed from upper substrate to bottom substrate owing to increase of substrate thickness,fatigue failure mode transformed from substrate fracture to rivet fracture due to augment of substrate strength.
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