Flexible Joint Design for Tube Structure 2007-01-0456

Increasingly stringent requirements for auto safety, fuel consumption and environmental friendliness require lightweight and efficient vehicle designs. Advanced High Strength Steel (AHSS) tubes, including hydroformed tubular parts, are one of the key enablers used today. However, conventional tube joint designs, in general, are difficult to utilize with spot welding processes, a preferred and commonly used assembly process in North America's automotive industry. This is particularly true for light gauge tubes. In this paper, a new tube joint design is proposed and this new proposed joint is applicable for spot welding, adhesive bonding, and other joining methods. From a performance perspective, this joint design utilizes the advantages of the box joint, which distribute load more uniformly through the whole joint structure, and thus it provides better stiffness and stability to the vehicle structure. Furthermore, this new proposed joint offers the flexibility to meet various assembly, manufacturing and geometry requirements. In the design, special mating surfaces, flanges and access holes are carefully developed to satisfy assembly requirements using spot welds. Six joint variants including applications for hydroformed and rollformed tube have been investigated. To demonstrate the joint performance, a FEA model was generated and analyzed. The FEA results show that the new joint design is four times stiffer in bending mode and more stable in torsion loading condition than conventional tube joint designs.