Keywords : Bulge
Engineering and Technology Journal,
2016, Volume 34, Issue 2, Pages 245-256
This study aims to establish the forming limit diagrams of tubular material by bulge test.The bulge test applies internal (hydraulic) pressurewith and without applied axial feeding on tubularspecimen causing tube expansion, undergoing plastic deformation until bursting occurs.
In order to investigate bulge test, a hydraulic bulgetool has been designed and manufactured with insert dies having profile die radius (10)mm. the fixed bulgeand the bulge with axial feeding can be fulfilled by this tool.Axial feeds applied to tube ends were (1, 3, 5, 7) mm. The process has been carried out using aluminum alloy (6063) tubes with dimension of (d_°=50 ,t_° =1.7,L_° =150) mm before and after annealing.
Before doing the bulge test, tubes were annealed at temperatures of (425) ᵒC with holding time of two hours and then cooled in the furnace. Square grids have been printed on all tubes wall with dimension (5x5)mm. The grid was printed by screening method to calculation major and minor strain. A commercially available finite element program code (ANSYS11.0), was used to perform the numerical simulation of the bulge test.
Maximum bulge height without axial feeding that can be obtained from tubes annealed at 425ᵒC was (4.62)mm with bursting pressure of (7.5)Mpa and final tube thickness of (1.42)mm.When applying axial feeding the max bulge height is(4.95)mm with bursting pressure of(9.5)Mpa and final tube thickness of (1.55)mm these results obtained from axial feeding(5)mm,wrinkling occurs when applying axial feeding(7)mm.
Straincalculation wasperformed using software program (Matlab). The strain value was obtained by measured grid dimension before the bulge test and grid dimension after bulge test fortubes at all annealed temperatures and applied axial feeding.
It is noted thatgood agreement between experimental and numerical results, the maximum error is 5.2%.