11 - Force and torque in friction stir welding

Abstract

Forces in friction stir welding, as well as torque and power, induced by welding input parameters, including tool shape, material and process parameters, play a key role in welding. Forces and torque in FSW can be considered as online indicators of weld quality, in which their values during processing should be in a safe range to obtain defect-free welds. While processing for a given set of tool and material characteristics, changes in process parameters result in force variation in traverse and axial directions, as well as torque around the tool axis. These values can be monitored and controlled by welding parameters adjustment, in order to avoid defective welds. Hence, forces and torque measurements and understanding their relationship with welding parameters are highly important in successful FSW, which are the focus of this chapter. Presented empirical and analytical models could also be successfully employed to predict welding forces and torque values used for instrument (e.g. fixture) design.