Experimental and Numerical Investigation of Die Filling and Thickness Variation at Two Step Box Copper Tube Hydroforming Die with Movable Bushes

Recently, tube hydroforming had been developed in many industry. Prediction and prevention of possible defects such as wrinkling and failure are the major issues when it comes to hydroforming technique. These flaws are directly dependent on the initial and ultimate pressures and axial feed in this method. Thus, selecting an appropriate pressure path in a proper correlation with axial feed is crucial. In this paper, a new die capable of producing two-step box shaped pure copper specimens is presented by experimental test and finite element simulation. Compared with conventional hydroforming dies, it consists of four moving bushes to produce completely filled steps. Moving bushes can be considered as one of the advantages of the new die. When feeding, the movement of the specimen is accompanied by the movements of the bushes which results in elimination of friction. Also, sliding between the die and the specimen decreases to zero, so the produced specimen has filled and complete corners. Besides low forming pressure, simple die structure and cheaper machining costs as compared with conventional hydroforming dies can be considered as other advantages of the proposed die.