A novel non-keyhole friction stir welding technique was proposed to weld the butt joint of 6061-T6 aluminum alloy with the thickness of 6 mm. A sound joint was obtained by this technique, simultaneously eliminating the flash, shoulder mark and keyhole defects. The sleeve directly affected zone (SDAZ) and the sleeve indirectly affected zone (SIAZ) were divided into the joint according to the plunging position of the hollow sleeve. The lack of root penetration defect was avoided when the plunging depth of the hollow sleeve was only 4.2 mm, because the hollow part inside the sleeve improved the material flow below the sleeve. An S-shaped line was left at the SIAZ, and the height of it had the minimum value of 1.47 mm at 20 mm/ min. Whether the failure location of the joint was in SIAZ/SDAZ or the heat-affected zone (HAZ) depended on the height and bonding strength of the S-shaped line. The joint fracture location changed from the SIAZ/SDAZ at 35 mm/min to the HAZ at 20 and 30 mm/min. The maximum tensile strength of 224.3 MPa was obtained at 30 mm/min which was 73.7% of that of the base material. The fracture surface morphology exhibited the typical ductile fracture.
Die-less spinning has high flexibility in aeronautics, aerospace vehicles and other manufacturing fields; however, the wall thickness of the workpiece is hard to control in die-less shear spinning. A flexible control method of wall thickness distributions on the truncated cone shape is attempted using double-sheet shear spinning. The fundamental approach entails the adjustment of original thickness during forming. In double-sheet die-less shear spinning, two aluminum disk blanks arranged concentrically are formed for truncated cone. The cover thicknesses of the spun workpieces are smaller than the value that conforms to the sine law using the same blank thickness. The wall thicknesses of base spun workpieces are bigger than the sine law value under the same circumstances. The theoretical mechanics analysis of the double-sheet shear spinning process is carried out through mechanics and finite element analysis.
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