Abstract: AA6061-T6(1 mm) and AA6022-T4(2 mm) aluminum alloy sheets are fabricated by three friction stir blind riveting (FSBR) processes with different rivet penetration mechanisms. It is found that the rivet penetration force of FSBR-III with the penetration mechanism of extrusion, is 33% and 83% respectively higher than the other two FSBR processes (i.e. FSBR-I and FSBR-II), where the penetration mechanism is a combination of extrusion and cutting. For the penetration process of upper plate, the relationship between material removal rate and the penetration force is discussed in terms of the penetration mechanism and the influence of frictional heat. It is found that the penetration force at the same material removal rate is larger when the proportion of extrusion is dominated in the rivet penetration mechanism, and the penetration force is more sensitive to the frictional heat. In addition, by observing the cross-sections of joints, it is found that the FSBR-II joint possesses the smallest gap between upper and lower workpieces due to superior cutting performance of the rivet, and FSBR-I and FSBR-II produced chips during the penetration process, while no chips were generated in the penetration process of FSBR-III.

Key words: aluminum alloy, friction stir, penetration force, rivet structure