Study on the hydroforming process for automobile radiator support members

Tubular hydroforming was used to manufacture radiator support members that support radiator components such as a radiator and a cooling fan, which is placed in front of car body. New tool design concept named mechanical cam sliding system was introduced for the pre-forming process in which a starting tube was simultaneously pre-bended and narrowed to approximately fit the part shape. Since irreversible wrinkles appear at the bended region during pre-forming without internal pressure, pre-forming was performed after internal pressure (∼150 bar) was added into the tube. From hydroforming tests, it was known that radiator support members were hydroformed at the internal pressure ranging from 420 to 780 bar. However, radius (20R) of the corner at rectangular section of the parts showed larger than design specification (10R). In order to investigate the strain hardening effects of the hydroformed parts, tensile properties of the parts hydroformed at 420 bar were compared to those of starting tubes. Through this investigation, it was revealed that tensile stress of hydroformed parts was increased by 22.1%, whereas elongation of these parts was reduced by 49.7%. Concerning the function of this part, it is believed that the sectional shape and these tensile values are enough to assemble and support the radiator members.