Numerical Simulation Analysis of FSPR Joint Forming for Steel/Al Alloy Hybrid Body-in-White

Key words:  flush self-piercing riveting(FSPR)  joining  die-casting Al alloy (DCAA)  thermo-formed steel sheets(TFSS)  two or three-layer plate

Abstract:

The development and application of large Die-Casting Al Alloy (DCAA) parts and Thermo-Formed Steel Sheets(TFSS)in Body-in-White (BIW) have created higher demands for the joining technology of high-strength steel/Al dissimilar materials. As an emerging technology, Flush Self-Piercing Riveting(FSPR) is still in the experimental phase and undergoing small batch equipment verification. This paper focuses on the joining methods for DCAA and TFSS in BIW, investigating the joining mechanisms, technical features, and forming principles of FSPR for steel/Al dissimilar materials with two-layer or three-layer plate combinations. Considering the TL4225/C611/CR5 sheet combination as a subject, the forming mechanism of high-quality joints was studied, and a physical and mathematical model was established to depict the relationship between the filling amount of the arc-gap and die dimensions, as well as the extrusion amount. This model effectively illustrates the relationship between the filling amount of the flowing metal in the arc-gap and critical parameters, such as die dimensions and feeding amounts. By simplifying the process of selecting joining parameters, it significantly reduces both the time and experimental workload associated with parameter selection. This provides a technical foundation for the application of DAAA and TFSS parts in BIW, enabling the rapid choice of appropriate joining parameters to meet the requirements for obtaining high-quality joints. The model can be effectively utilized to investigate the relationships between key parameters, including arc-gap radius, plate thickness, rivet arc radius, nail head radius, groove width, and feeding amount, while keeping other parameters constant. This approach provides a theoretical foundation for the design of Friction Stir Processing (FSP) joints and aids in the selection of optimal parameters.