Effects of die corner radius and temperature on the formability of AA7075-T6 alloy

Abstract

This study focused on the formability of aluminium alloy (7075-T6) sheets through hydroforming route. Formability of these sheets was tested using a warm forming setup at three different temperatures and four different die corner radii. Forming limit diagrams (FLD) were generated by measuring the grids of the sheet formed. The results show that the forming limit of AA7075-T6 can be significantly improved when the blank was heated to 140-250 • C. It was also observed that as the temperature increases above 140 • C, dome height began to decrease. Also the results indicated that both the die corner radius and temperature have a significant effect on the stress-strain curve and warm forming of AA7075-T6 sheets. Thus, with the temperature increased from room temperature (RT) to 140 • C, the flow stress decreased and the strain increased, hence, the formability is enhanced. However, further increase in temperature causes decreases the flow stress and strain. Similar changes of the flow curve were seen in die corner radius. Decreasing the die corner radius decreases the flow stress and increase the strain. Moreover, an equation was obtained by establishing correlations between the experimental parameters and their results. In this way, it became possible to make predictions.

The verification of strains obtained by grid measurements using digital image processing for sheet metal formability

“…1,2 Formability is the capability of sheet metal to undergo plastic deformation to a predetermined shape without defects. 3 Formability is evaluated through different methods: mechanical tests, 4 simulations, 5,6 limiting dome height, 7,8 and forming limit diagrams (FLDs). 9 Grid marking, advocated by Keeler, 10 is usually practiced in sheet metal formability tests to calculate strain in principal axis.…”