Punchless Piecing Process of Aluminum Tube Wall by Impulsive Water Pressure

Piecing of the aluminum alloy A6063-T6 tube was attempted with the help of impulsive water pressure in the tube caused by the impact of drop-hammer. The availability of this approach was investigated. Shapes of the die hole were circular, square and long rectangle. The outer diameter was 40 mm, and the wall thickness was 1 mm. The maximum impact velocity was 10 m center dot s11. The pressure at the occurrence of crack was almost same for different impact velocity of the drop-hammer. However, if the number of holes was increased from 2 to 4, all the holes could not be pierced. The circular hole with a diameter of 10 mm and the square hole with an edge length of 10 mm were successfully created. When the size was doubled, the material did not partially separate. The water pressure rapidly increased and crack occurs at around 1 ms depending on the impact velocity. The effect of positive strain-rate sensitivity of the material was observed in comparison with the quasistatic experimental result. Profile of the hole edge was tapered. Burr formation was not observed, which is a significant advantage of this process.