钉脚张开度对自冲铆构件机械内锁刚度的影响

Effect of the degree of rivet opening on the rigidity of the interlock in self-piercing riveting joints

关键词:  自冲铆机械内锁  铆钉张开度  刚度  图像分析  有限元建模

Key words:  mechanical interlock in SPR joints  degree of rivet opening  rigidity  image processing  finite element modeling

摘要:

利用数字图像分析技术研究了铆钉张开度对自冲铆接头机械内锁结构刚度的影响.借助材料性能试验机对具有不同铆钉张开度的5052铝合金板自冲铆接头进行单向静拉伸试验，加载过程中利用CCD获取自冲铆机械内锁结构形变的图像序列，利用图像相关分析计算不同载荷水平下铆钉脚与底板的滑移错动量，建立滑移-载荷曲线，并据此评估结构件刚度大小；建立自冲铆接头有限元模型，对比分析不同钉脚张开度的自冲铆机械内锁的失效过程.结果表明，在受载状态下，自冲铆接头存在一个临界滑移启动载荷值，当外载荷小于此临界值时，机械内锁结构保持相对完整，处于弹性变形阶段；大于此临界值时，滑移错动量明显增大，结构发生塑性大变形，并最终呈现脱离失效模式.其次，钉脚张开度对自冲铆构件的强度和刚度影响较大，提高钉脚张开度有助于增大构件整体刚度.

Abstract:

The effect of the degree of rivet opening on the rigidity of the interlock in 5052 a-alloy self-piercing riveting joints was analyzed by using image processing method. Two type joints with different rivet opening were tested in the proper test machine. The CCD with digital microscope was used to capture the images of the interlock deformation in the loading process. The relative slip between the rivet tip and the bottom sheet was calculated by using correlation analysis method, and the amount of the slip was defined as a measure of stiffness of SPR joints. Finite element models of two type joints with different rivet opening were established to simulate the deformation process of the interlock in tensile test. The results show that a critical value of slip-loading exists in the loading process. When the load value is lower than the critical value, the structural integrity of the interlock is kept and no apparent slip in the interlock can be detected. When the load value is greater than the critical value, the slip in the interlock can be observed and it increases with the increasing of the loading, and the rivet is pulled out, which is named pull-out failure model. The open degree of rivets has a large effect on the strength and rigidity of SPR structure, and high rivet degree can increase the stiffness of SPR joints.