Hydroforming is a metal forming process in which the required forming force is provided by a fluid media like water. Tube hydroforming is a relatively new process and thus in this thesis hydroforming of a car rear axel was studied. At the beginning, various tube hydroforming methods were explained and their advantages and disadvantages were discussed. Then computer simulation procedure of the process and its implementation was explained in detail. In these simulations the known parameters were material properties of the tube and geometry of forming dies. Unknown parameters which had to be determined by these simulations were the initial diameter of tube and the pressure path during the forming process. An important question in the design of process is the appropriate type of tube hydroforming to produce that particular part. In other words Low Pressure Hydroforming, High Pressure Hydroforming or Pressure Sequence Hydroforming(PSH). To find the answer of the question, these different types of hydro-forming were simulated and compared and it was concluded that the best method to produce this part was PSH which caused the best thickness distribution. After choosing PSH, tube diameter was optimized. To find the best diameter, upper limit of outside diameter has been determined. There is a maximum tube diameter because larger tube sizes will not fit in the die. A good choice to produce the axel was the largest outside diameter that fits in the die. However some wrinkles were made in transition zone near the end of tube. Simulation results showed that these wrinkles could not be removed even at pressures more than 7000 bar. Although the geometry of transition zone was not as important as middle zone, it was preferred to have a more accurate geometry and lighter part. Then the tube diameter range was reduced to avoid wrinkles in the transition zone. On the other hand small tubes needed very high pressures to be formed and in many cases the tube could burst. So an appropriate diameter was chosen and PSH was designed to produce the part using pressures under 500bar. It was also important to have an acceptable thickness distribution. Therefore low pressure and pressure sequence hydroforming were combined to obtain an optimum tube diameter. Then die and gripper forces were estimated using simulation results. A hydroforming industrial tool was also used to validate simulation results. Thickness distribution had been compared between simulated part and a real part that showed good agreement between them. At the end, sealing methods of tubes were discussed and two-dimentional stress simulation of dies was also performed. Keywords: Metal forming, tube-hydroforming, tube-sealing, die
