Investigating the Effects of Cold Bulge Forming Speed on Thickness Variation and Mechanical Properties of Aluminum Alloys: Experimental and Numerical

In this work, cold bulge forming of an Aluminium-Magnesium (Al-Mg) sheet with a solid bulging medium is experimentally and numerically performed. Mechanical properties and thickness variations of Al-Mg sheet are evaluated before and after the forming process. The results indicated that the Al-Mg sheet has taken the desired shape without necking using the cold bulge forming process. Also, the experimental results showed significant improvements of 13 and 9.7% in yield and ultimate tensile strengths of Al-Mg sheet after bulge forming. It is proved that the maximum thickness reduction of Al-Mg blank is less than 6% after cold bulge forming. Numerical simulations of cold bulge forming of Al-Mg sheet are conducted using Abaqus finite element software. For this purpose, many numerical models were created and analyzed to investigate the effects of bulge forming speed on the blank thickness variation for different Aluminium alloys. In these simulations, four different speed of 1, 5, 15 and 25 mm/min are used as forming speeds. Numerical results of bulge forming of Al-Mg sheet were compared with experimental measurements and good correlation, less than 2.6% difference at critical zone, was observed between the results. Moreover, obtained results from numerical simulations for different Aluminium alloys showed that the thickness variations of formed Al-Mg sheet are more uniform by reducing the forming speed. Note also that, the less strength of material, the more uniform thickness variation is achievable along longitudinal direction of metal sheet.