Investigation on the effect of use of movable die in sheet hydroforming with die on formability

Abstract

In this study, effect of use of movable die has been numerically investigated on thinning of sheet metal parts in sheet hydroforming with fixed die process using finite element analysis and analyses have been verified experimentally in fixed die. Both of sheet hydroforming processes with fixed and movable die has been modeled by using the same coefficient of friction, blank holder force and pressure curves so as to compare thinning of flat cylindrical part. SS 304 was selected as material. As results of conducted analysis, while maximum percentage of thinning of the part analyzed by using sheet hydroforming processes with fixed die is about 17%, in case of using movable die maximum thinning occurs about 9%. In the other words, maximum thinning of the part analyzed using the hydroforming with movable die is about 8% lower than that's of the fixed die. Moreover, when the strains on the part is evaluated on the forming limit curve, while there is risk of crack on the part analyzed with fixed die, there is no risk of crack on that's of with movable die. Less percentage of thinning of the part analyzed by using sheet hydroforming processes with movable die can be explained by friction duration between sheet metal and die is less than that's of fixed die during the process. Because of less friction duration between sheet metal and die, sheet hydroforming with movable die process, resistance of the sheet metal against to thinning increases