Analytical and Numerical Analysis of Free Bulge Tube Hydroforming

Free bulge hydroforming simulation was analysied to investigate the biaxial behavior of extruded aluminum tubes. A finite element model was constructed to simulate the hydroforming process and asses the influence of friction between die walls and tube, tube material properties and springback of formed tube. It was found that material hardening coefficient had the most significant influence on formability characteristics during bulge hydroforming, the simulated model also revealed that die radius and tube thickness had great effects on springback and hence changed tolerances of formed tube. Also an analytical model for free bulge forming was proposed and it was shown that for P = -0.5(P = £2/£i), good correlation between experimental and analytical model was obtained. It was also shown that for P = (-1), formability of tube increased and lower pressure is needed for forming the tube.