Prediction of bulge height in warm hydroforming of aluminum tubes using ductile fracture criteria

Warm hydroforming is used widely to increase the formability of aluminum and magnesium tubes. Prediction of forming limit is a vital problem in designing the warm hydroforming process of tubes. In this paper, bulge height of aluminum tubes AA6063 is predicted using ductile fracture criteria at high temperatures. Ductile fracture criteria were calibrated by performing several uniaxial tensile tests at different temperatures and strain rates. Fracture strain and work functions were obtained based on Zener-Holloman parameter. Free bulging process of tubes was simulated using finite element method and different loading curves were used to bulge the tubes. Prediction of ductile fracture was compared with the experimental results measured on a warm free bulging set-up. The comparison shows that Ayada ductile fracture criterion is able to predict the bulge height of aluminum tubes at high temperatures.