Influence of rivet hardness on self - piercing riveting technology
Release：网站管理员
Browse：609Second
Time：2019/9/3 15:16:20
Effect of rivet hardness on self - piercing riveting. Rivet hardness has a great influence on the morphology and mechanical properties of rivet joint.
Under the action of the same aluminum plate, 40kN sub-bullet with impact force and rivets in different annealing states, the morphology of the different impact self-piercing riveting joints obtained is shown in figure 5. It can be seen that the rivet legs in the original state of no. The rivet with no. 2 annealing for 10min can be well formed. The rivet legs are curved and open, and the upper aluminum plate is finally broken in the middle of the rivet trunk. Under the action of no. 3 annealed rivet 20min, the rivet legs were in good shape apart, but due to insufficient rivet hardness, the legs were seriously pier and thickened, making the upper aluminum plate finally disconnected in the lower part of the rivet trunk. The lower aluminum plate was only a small part of the rivet leg stuck, so the joint's cross tensile strength was low.
A sharp Angle is formed at the junction, which leads to serious stress concentration under the action of fatigue load and significantly reduces fatigue strength. However, under the condition of impact self-piercing riveting, the rivets Pierce the first layer of aluminum plate, and the aluminum plate around the rivets and the upper and lower layers are in smooth contact, which will not produce large stress concentration. In addition, the aluminum in spot welding joints after melting and recrystallization transformation, molten aluminum due to the rapid heat dissipation of aluminum plate is prone to shrinkage defects, the heat affected zone of the weld also because of high temperature and rapid cooling and performance is reduced, and the self-piercing riveting joints are mechanical fastening, no metallurgical process. The analysis shows that the fatigue performance of self-piercing riveting joints is higher than that of spot welding joints because of these reasons.
