The influence of clearance and edge shape of a punch on the dynamic behavior of a low- cost die in shearing of an extruded alminum alloy sheet is investigated. In experiments, the dynamic behavior was visualized using a high-speed camera. It
was found that the punch shifted from the die accompanied by the deformation of the low- cost die. As a result, the dynamic
clearance was 1.5- 5.5 times of the static clearance. This dynamic behavior is minimum when the static clearance is 10% of
thethicknessofasheet.Thedynamicbehaviordecreasespunchenduranceanddie-setiigidity.The dynamic behavior,the
shearing droop and the burr of a sheet were decreased by using a punch with an edge angle. The dynamic behavior was decreased to 15% by using a punch with the shear angle of 7 , to 40% by using a punch with the bill angle of 45 , and to 20%
by using a punch with both the shear angle of 7 and the bill angle of 45. It is possible to achieve high working accuracy
of a sheet and high accuracy of shearing using the low-cost die.
Keywords:shearing, visualization, dynamic behavior, aluminum alloy sheet, die-set clearance, edge shape of punch.
Effect of Degree of Corner-Bending Imposed on Round Welded Steel Pipe in
Expanding Type Pre-Forming Process on Cross-Sectional Shape of
Square Pipe Formed by Extroll-Forming
(Received on December 18, 1995)
Yoshitomi ONODA, Takuo NAGAMACHI,
Sadao KIMURA and Takeo KITAWAKI
In order to improve the cross-sectional shape (outer curvature, inner curvature, wall thickness change it comer
zones, flatness of sides) of a square steel pipe (150mm wide) formed using an extroll-fomiing mill, an expanding
type pre-forming process is introduced to impose peripheral bending under tension on the portions of a round pipe
(190.7mm in outer diameter, 4.6m- m in wall thickness) that correspond to the comer zones of the finished product.
Characteristics of the cross-sectional shapes of the formed square pipes are investigated with respect to the degree
of comer-bending of the pre-formed pipes and compared with the results obtained by conventional extroll-forming.
The outer and inner curvatures of the comer zone increase and the depth of the hollow along the cross-sectional
profile of the side decreases with increase in the degree of comer-bending in the pre-forming. The increase in wall
thickness of the comer zone which is caused by the forming rolls is greatly affected by the degree of comer-bending
in the pre-forming. This wall thickness change at the comer zone can be reduced by imposing an appropriate degree
of comer-bending on the round pipe in the pre-forming process.
Keywords:roll forming, tube forming, extroll-forming, pre-forming, round welded steel pipe, square pipe, nondriven roomed rolls.