木村 真晃

The joint strength and its improvement of AA5083 Al alloy joints fabricated by friction stud welding method were investigated. The diameter of the work and stud side specimens were 32.0 mm and 12.8 mm, respectively, and those were friction welded. The appropriate welding condition for obtaining high tensile strength was established as follows: a friction speed of 17.5 s⁻¹, a friction pressure of 80 MPa, a friction time of 1.6 s, and a forge pressure of 360 MPa. However, all joints fractured between the initial weld interface and the work or stud sides, i.e. the fracture did not occur in the base metal. It could be considered that the initial oxide film on the weld faying surface of the work side was not exhausted as the flash during the welding process. To obtain the joint having the fracture in the base metal, the suitable shape at the weld faying portion of the work side specimen was suggested as the groove shape. The inner diameter of the groove corresponded to the same diameter of the stud side, and that had a groove width of 3.0 mm with a groove depth of 1.0 mm. As a conclusion, AA5083 friction stud welded joint, which had the tensile strength of the base metal and the fracture in the base metal, could make with the appropriate welding condition. Furthermore, the weld faying portion at the work side should be in the suitable shape that urges the extrusion of the flash from this side.

To reduce weigh of the transportation machines, joining of the FRP and the light metal is considered as important technique. In this study, the punching rivet method was applied to make joints between a GFRP sheet and an aluminum alloy A6061 sheet and joint strength was examined. The punching rivet method is possible to join the sheets without drilling by using a rivet and a rivet holder. The punching-out process of the sheets using a rivet shank as a punch and the joining process of the sheets using the rivet and the rivet holder are continuously performed. From the experimental results of joining of the GFRP sheet and the A6061 sheet, the joints made by the punching rivet method had no large crack and out-of-plane deformation of the joints was suppressed. From the results of the joint strength tests, the joints made by the punching rivet method had almost the same joint strength as the bolted joints which were tightened by regulated torque. In addition, the fatigue life of the joints made by the punching rivet method was longer than that of bolted joints. It could be confirmed that the punching rivet method was effective to join the GFRP sheet and the A6061 sheet.