Abstract
The deep drawing height of an aluminum alloy sheet on a truncated conical shell using the hydraulic counterpressure is determined by the intersection of the body wrinkling limit line occurred in the lower zone of blank holding force with the fracture limit line occurred in the higher zone. When applied the hydraulic counterpressure, the fracture limit line can be raised and the depression effect of body wrinkling is achieved, therefore, the limit height of deep drawing is increased compared to that in the conventional drawing method. Particularly, the nearer the ratio of head- and bottom diameters approaches 1 in a truncated conical shape, the greater the effect of hydraulic counterpressure is. In a shape of which ratio of head and bottom diameters is small, a method is effective to pressurize with an auxiliary pump from the initial stage of stroke. However, when the value of initial hydraulic pressure is too high, fracture may occur due to an excess bulged deformation. Accordingly, there exists an appropriate value of hydraulic pressure. The hydraulic counterpressure method is effective for the deep drawing of aluminum alloy sheet on the truncated conical shell. Compared to the conventional drawing method for the SPCD sheet, the height of deep drawing can be obtained a similar height in the shape in which the ratio of the head- and bottom diameters is 0.4, heights 1.22 times in the ratio of 0.6 and 1.96 times in 0.8.
