Extruded joining elements manufactured by friction stir forming: an investigation of the process parameters

Aluminium sheets (EN AW-1050) have been worked by a friction stir process to allow forming pins to be used as joining elements, in a clinching-type solution, for assembling multi-material components. Two lines of pins of diameter 4 mm and 6 mm, respectively, have been formed experimentally at various process conditions. A process control, using the force-trend distribution, has been pursued for a full comprehension of the forming steps. The strength of the pins has been tested aiming at understanding the influence of all the analysed process parameters thoroughly. Additionally, a numerical model has been developed and compared with the experimental evidence. This model has been employed to investigate the material flow during the pin formation. The results demonstrate the feasibility of this innovative method and highlight the significance of the main parameters that have to be set carefully for an optimised implementation of friction stir forming based joining technique. Graphical abstract