Characteristics of material flow in friction stir spot welding tools in consideration of cutting tools

Abstract

ABSTRACT This paper investigates the material flows in A5052/A6061 lap joints when friction stir spot welding tools with cutting edges and rake angles similar to a cutting tool are used. In this study, several kinds of modelling experiment were used to visualize the material flows during the friction stir spot welding. The majority of the material flows in A5052/A6061 lap joints was diagonally upward from the lower sheet, whether the rake angle of the probe with the cutting edge similar to a cutting tool was negative or positive. When the tool shoulder failed to contact the upper sheet surface, the stirring ability of the probe alone was to an extent high with a negative rake angle and very low with a rake angle of 0° and with positive rake angles. However, when the tool shoulder came into contact with the upper sheet surface and the chips generated by the probe were clogged, the stirring abilities of the tool with a rake angle of 0° and with positive rake angles were very high. In addition, in the tool with a rake angle of 0° and with positive rake angles where the discharge of chips was smooth, the lower sheet material moved upward as the chips were stirred and produced new material flows. From these results, when these tools are used, it is suggested that the generation, the discharge and the stirring of chips affect the material flow upwards, which is crucial, and also downwards, in A5052/A6061 friction stir spot lap joints.