Experimental investigation of aluminum tube bulging using a rubber-pad on different loading curves

Nowadays, one of the very important issues in the aerospace and automotive industries is reduction of weight of structures and preventing the corrosion. The use of aluminum alloys could help a lot to produce lighter components, resulting in reduced fuel consumption. In this project, the process design and producing of a sample part using rubber-pad bulging process was done. Aluminum alloy used for the production of aluminum pipes was AA1050A alloy and polyurethane rod with Shore A 85 hardness was used as rubber. Mechanical properties of aluminum and polyurethane were obtained from mechanical tests. Experimental tests were conducted to produce sample part on the hydroforming machine. In the experimental tests, only the punches of the machine were used to apply both internal pressure and axial feeding. Applying different loading curves was possible with changing the initial tube length and using a urethane rod with a constant initial length. By varying the length of initial tubes and thus change in the onset of applying axial feeding, production of sample parts without fracture was possible. It was shown that with a beneficial wrinkling in first forming step, it is possible to produce a sample with higher bulging ratio and lower maximum thinning. Samples produced using the modified loading curve, had the maximum bulging ratio of 24.83 percent and maximum thinning of 6.5 percent.