Experimental comparison of the effects of superimposed axial and bending ultrasonic vibrations on friction stir welding process

چکیده مقاله

True application of ultrasonic vibrations improves the solid-state process of friction stir welding. This study focuses experimentally on the effects of axial (along the tool axis) and bending ultrasonic vibrations on material stirring process of friction stir welding process. First, in ABAQUS software , an especial friction stir welding tool set geometr y was designed containing two types of axial and bending vibrations in different frequencies. Resonance frequency of the tool set, in axial and bending modes, occurred at 19.8 and 23.8 kHz, respectively. The use of a unique set of friction stir weld-ing insert tools as well as its ultrasonic transducer which was equipped with half-ring piezoelectric actuators, due to the identical tool set iner tia, made the comparison of the ultrasonic vibrations in different modes to become possible . Then, the tool was manufactured and some experiments were designed to join aluminum 6061-T6 plates as working material. Finally, to investigate the effects of vibrations on the quality of the weld, hardness, tensile strength, temperature and axial force were measured. Regarding the obtained results, in spite of welds, which were created with axial vibrational mode and without vibration states, superimposing bending vibrations, because of its better capability of material stirring pat-tern, resulted in a higher weld quality, whereas the tool axial forces were enlarged.