Numerical and Experimental Study on the Effects of Expansion Ratio, Corner Fillets and Strain Rate in Warm Hydroforming of Aluminum Tubes

Due to the strict emission standards and fuel consumption restrictions, automotive industry is greatly interested in warm tube hydroforming of aluminum and magnesium alloys. The main shortcoming of these alloys is their inferior formability at room temperature, which can be improved by forming at temperatures below the crystallization temperature. Because of the complex nature of forming at high temperatures, the proper determination and control of forming parameters are very important in fulfillment of the process. In this paper, the effects of tube geometry, bulge height, corner fillets and strain rate are investigated on optimal internal pressure and axial feeding loading paths, which are required for successful hydroforming of annealed AA6061 tubes at 300 °C. A new method based on simulated annealing algorithm is developed for optimization of pressure and feed loading paths. Numerical results are discussed, verified and validated by experiments. A good agreement is observed between numerical and experimental results.