The experimental investigation of pre-bulging type on deep drawability

Deep drawing is the process in which flat sheet materials are formed into seamless cup geometry. To increase the drawing ratio and regulate sheet material flow into the die, drawbeads are added to the die in the classical deep drawing processes, while pre-bulging is applied in hydroforming. In this study, the pre-bulging process, which can only be applied by hydroforming methods, could be carried out mechanically by using innovative deep drawing dies designed with different entrance angles. In the experiments, DC01 sheet, forming speed (10 mm/s) and constant blank holder forces were used as input parameters, and drawing ratio, thickness variation, and energy consumption were also interpreted as output parameters. In experiments, a limit drawing ratio (LDR) of 2.2 can be achieved in a single operation in a 0-degree classical die, while 2.4 LDR was obtained in an innovative 15-degree design and the forming force was reduced by 1.35% compared to the 0-degree die. In the innovative 30-degree design, 2.5 LDR was obtained and it was observed that the forming force decreased by 11.36% compared to the classical deep drawing die. It was observed that the greatest thinning of 21% in the deep drawn parts occurred around the punch contact area of the sheet material.