Numerical Simulation Of Rotation Friction Pressing Riveting And Drill-pressing Riveting Of Light Metal Sheets

Due to the requirement for energy conservation and environmental protection, lightweight vehicle structures are targeted for the automotive industry. In order to reduce the weight of vehicle structures, the general efforts have been made to increase the use of lightweight metal materials such as magnesium alloys and aluminum alloys. Joining technology is a key technology required for expanding the use of lightweight metal materials. Traditional joining technologies include welding, mechanical connection, electromagnetic riveting and so on. However, existing joining technologies are not very suitable for joining lightweight metal materials due to the characteristics of the materials. For this reason, the researchers of the materials physics laboratory of Zhengzhou University developed two types of mechanical joining processes for lightweight metal sheets, they are:rotation friction pressing riveting (RFPR) and dill-pressing riveting (DPR). Experimental studies showed these two joining processes could be used to join various lightweight metal sheets, and provide the joints with superior mechanical properties. To study RFPR and DPR processes further and analyze the experimental results, the author of this paper simulated and studied the two joining processes with ANSYS finite element analysis software. The main studies and results are summarized as follows:(1) The realistic simulation analyses of RFPR and DPR processes showed that ANSYS finite element analysis software could be used to study and simulate the two joining processes.(2) The numerical simulation analyses of the RFPR operation of AZ31magnesium alloy sheet were performed, which gave the mesh change in the riveting forming process, the displacement, stress and strain vectors distributions in the pressing process and the stress and strain distributions in the sheet material around rivet. The effect of the punch pressure on the interlock of the simulation joints was also analyzed numerically. And the simulation results were compared with the experimental results. The results showed that riveting forming process and the cross-section of the simulation joints were basically consistent with the experimental results. With the increase of the punch pressure, the interlock of the simulation joints increased. However, the upsetting of the rivet could be observed when the excessive punch pressure was applied. This phenomenon and the quantitative analysis result of the interlock of the simulation joints were in agreement with the experimental results. The stress presented in the material around the rivet was compressive stress, and the compressive stress in the bottom sheet was obviously bigger than that in the top sheet. This compressive stress distribution could reasonably explain the fatigue test results of the RFPR joints. The simulation results provided the theory references for the further studies of RFPR process.(3) The DPR operation of6063wrought aluminum alloy sheet was taken as the object of study, the simulation analysis of the forming process of DPR joints was performed, which gave the forming process and cross-section of the simulation DPR joints. Through comparing the simulation results with the experimental results, it was found that both results were comparable. The simulation results also showed that the punch pressure had a significant influence on the mechanical interlock of the simulation DPR joints. The change trend of the mechanical interlock of the simulation joints with the punch pressure basically agreed with the experimental results, but the simulation values were a little smaller than the experimental values. The stress and strain distributions obviously existed in the sheet material around the rivet. Therefore, it could be inferred that the DPR joints should show good fatigue property. And the experimental results confirmed this judgment.(4) The numerical simulation analysis of the DPR operation of A356cast aluminum alloy sheet was performed. Although the alloy material has higher brittleness, the simulation analyses showed that the forming process, cross-section of the simulation DPR joints and the effect of the punch pressure on the mechanical interlock were all similar to the simulation results of the DPR operation of6063wrought aluminum alloy sheet and also in agreement with the experimental results. Therefore, DPR process can also be applied to join brittle metal sheets.