The tool breakage at the friction stir welding of 35-mm-thick AA5056 sheets.

The paper is devoted to the study of friction stir welded samples, in which the special high-speed steel tool has been broken during the process of their production. The thickness of the samples is equal to 35 mm. It has been observed that after the tool breakage, the pin section separated from the tool remains in the weld. Around the pin, there is the structure modified by the severe thermomechanical action, which made it possible to estimate the size of the material fragmentation zone in the area ahead of the tool. After the breakage, the tool fragment itself has been deformed by the remaining part of the tool, including the shoulders. It resulted in the layering of the upper part of the pin fragment and the crack propagation into the central part of the pin. Based on the data obtained, it was considered that the tool breakage was caused by the excessive axial force, which resulted in the high tangent loads in the area below the shoulders. [ABSTRACT FROM AUTHOR]