钛合金自冲铆接头微动磨损机理及疲劳性能

Fretting wear mechanism and fatigue behavior of titanium alloy self-piercing riveted joint

关键词:  钛合金  自冲铆  微动磨损  疲劳特性  扫描电子显微镜

Key words:  titanium alloy  self-piercing riveting(SPR)  fretting wear  fatigue behavior  scanning electron microscope(SEM)

摘要:

对钛合金同种TA1-TA1（TT）及异种TA1-Al5052（TA），TA1-H62（TH）自冲铆接头进行疲劳试验，用扫描电子显微镜对断口及微动区进行观测研究其微动磨损机理，并研究下板强度对接头疲劳寿命和失效形式的影响.结果表明，断口裂纹萌生区即为微动磨损区.微动磨损导致微动区亚表面产生微裂纹并逐步扩展为宏观疲劳裂纹导致接头最终失效；微动磨屑在微动磨损过程中主要起减轻磨损作用.总体上TT接头具有最优疲劳性能，疲劳载荷较高时TA接头疲劳性能优异，疲劳载荷较低时TH接头疲劳性能优异.两板强度相当且疲劳载荷较高时失效形式主要为铆钉断裂，疲劳载荷较低时失效形式主要为下板断裂；而下板强度与上板强度相差较大时，疲劳失效形式为下板断裂.

Abstract:

Fatigue test of self-piercing riveted joints of TA1 titanium to itself (TT), TA1 titanium to 5052 aluminum alloy (TA), TA1 titanium alloy to H62 brass (TH) was performed. The fretting wear mechanism of the joints was analyzed by using scanning electron microscope (SEM) to observe the fracture surface and fretting domain. The influence of the strength of bottom sheet on the fatigue behavior and failure mode of the joints was investigated. The results show that crack initiation area on fracture surface located in the fretting wear domain. Micro cracks were generated from the sheet of fretting domain and gradually propagated and became macro fatigue cracks, which led to the final failure of the joints. The main function of fretting debris was to relieve wear in fretting process. In general, TT joint has excellent fatigue behavior; TA joint possesses superior fatigue behavior under high fatigue load; TH joint presents superior fatigue behavior under low fatigue load. As the upper and bottom sheets possess similar strength, the dominating fatigue failure mode of the joints is rivet fracture under higher fatigue load; the fatigue failure mostly occurred through the bottom sheet under lower fatigue load. As the strength of bottom sheet is lower than that of upper sheet, the fatigue failure mainly occurred through the bottom sheet.