铝锂合金T型自冲铆接头疲劳特性及失效机理

为研究T型自冲铆接头的疲劳特性,以铝锂合金(AL1420)同种及其与铜合金(H62)和不锈钢(410)异种组合制备的AA、HA和SA三组T型自冲铆接头为研究对象,基于其静力学试验采用正弦波进行拉-拉加载疲劳试验,用二参数威布尔分布对所得疲劳数据的有效性进行验证,采用最小二乘拟合直线得到拟合的F-N曲线,并采用SEM扫描电镜对各组典型疲劳失效断口进行微观分析。结果表明:SA组疲劳寿命对载荷变化最敏感,并且疲劳寿命随相对滑移量的增加而减小;由三组T型接头失效形式可看出接头薄弱环节有由铆钉向板材转移的趋势;从微观分析疲劳断口可知裂纹萌生区多为形貌特征较为平坦的准解理,裂纹瞬断区形貌更加突出,多为沿晶断裂或韧窝形貌。

Fatigue Properties and Failure Mechanisms of Self-piercing Riveted T Joints in Aluminum-Lithium Alloys

In order to study the fatigue properties of self-piercing riveted(SPR) T joints, three sets of T joints (1420 aluminum-lithium alloys joined with itself (AA joints), with H62 copper alloys (HA joints) and with 410 stainless steel(SA joints)) were prepared. Fatigue test were conducted on the basis of peeling test. The effectiveness of test data was analyzed by two-parameter Weibull distribution, and the equations of fatigue load-fatigue life curves were calculated by least square method. Scanning electron microscope was adopted to observe the appearance of the joints fracture. The results show that the fatigue life of SA joints was the most sensitive to the load fluctuation which were loaded on joints, and fatigue life decreased with the increasing relative slippage. The weak point of the joints transferred from rivets to sheets. From micro-view, the fracture features of crack initiation region is flatter than the fracture features of crack transient zone which are mainly the intergranular fracture or the dimple.