This research focused on developing a novel Friction Stir Riveting (FSR) technique, viz., Friction Stir Blind Riveting for pre-drilled holes (FSBR-pH), to improve the mechanical performance of hard-to-access aircraft joints. This objective is realized through a hierarchal four-pronged experimental and numerical analysis approach. Firstly, the existing FSBR process was evaluated where the existing process was found infeasible for pre-drilled holes. The existing process was then modified to develop good quality joints in case of pre-drilled holes. In the second step, a process window was created for FSBR-pH joints through (a) microscopic analysis of joint cross section to observe the presence of any defects/gaps and (b) numerical simulation. Microstructural and mechanical characterization (i.e., tensile strength and microhardness) of the optimized joints were performed in the third step where the presence of dynamic recrystallization was found responsible for the formation of submicron-sized grain in the stir region. The strain-hardening phenomenon was observed in the stir region which occurred due to extensive stirring at high spindle speeds. Finally, a comparison of the developed joints was drawn with existing Blind Riveted (BR) joints in terms of failure modes and tensile strength where the FSBR-pH joints performed better than their existing counterparts.
