Abstract
The process reduction by the forming limit improvement is demanded from the economy of drawn shell. Influence of hydraulic counterpressure on the limiting total drawing ratio in direct redrawing method for forming cylindrical shells is investigated. Thin sheets of A1100-O and A5052-O are applied. Because of the restraining of the material movement at the radius part and side wall of punch and better lubrication between the blank and die surface by hydraulic counterpressure, the limiting drawing ratio is improved. Limiting total drawing ratio improves in all the methods when hydraulic counterpressure is applied to first deep drawing and redrawing. The improvements of the limiting total drawing ratio are 1.25–1.60 times in A1100-O, and 1.22–1.58 times in A5052-O. The improvement ratio of limiting total drawing ratio by intermediate annealing of A5052-O is 1.12 times. Therefore, the effect of hydraulic counterpressure in redrawing is more excellent than that of intermediate annealing.
